Setting compression after CC'ing heads.

[billbuilds]

   It is unreasonable to expect a shop that CC'd my heads and supposedly decked them .030 to be able to tell me what the new volume of those heads is?

[hrdtail78]

I don't think so.  Seems they would of been cc'd after to make sure they were the same.

[billbuilds]

     I really thought that that was part of what i was paying for. The round trip ride alone was close to $70. I will not go on a bash as it's not allowed but I have to say that we should all be able to expect a little better from someone who hangs his shingle out here.

[Ohio HD]

I guess it depends on what you asked for. If you asked for a specific amount to be removed, like the 0.030". That's what they would do.

If you said to them, I want heads to be 82cc, then they would machine and check cc to get that amount.

Maybe there was unclear communication as to what was expected?

[tdrglide]

Purchase a burette. I always like to double check. No matter who cc'd or decked the heads

[billbuilds]

      We did a fair amount of talking, initially via email then via phone. He knew what cam I had, we discussed the compression ratio we agreed to shoot for. Did he actually measure and mill the heasd or did he just slap the 10.25-1 pstons in and call it good? If he can't tell me the volume of my heads then how did he "set the compression" as he put it? From what I've learned here I really need to know the deck height to be able to "set the compression" via thickness of head gasket or milling of bottom of jug.
     Furthermore, when he called to tell me that the parts were ready I asked him  how much he milled off the heads to get the the agreed upon comp ratio and he clearly said thirty thou. I mean, if he knew how much he milled off my heads how can he not know what the resulting volume is?  I did not pay good money to play guessing games.

[Buglet]

   Bill that's must be the new way of doing business, talk in circles. That being said he should of being able to tell you what CC's he was shooting for. It came up a while back about head porters of who keeps track about the heads they do. To my surprise I think there was only one head porter that said. In todays world get it out the door worry about it later if it comes up.       

[billbuilds]

Purchase a burette. I always like to double check. No matter who cc'd or decked the heads

     Thought about doing that before I even sent them out the door and I should have listened to my gut.

[Don D]

You need a class A glass burette, preferable 100cc. They are not easy to find and are expensive. The two classes are Class A and Class B. Class A pipettes are manufactured to precise tolerances, or "error limits". Class B are allowed twice the error limits of Class A. The class specification or serial number of Class B are not marked.

[hbkeith]

I guess it depends on what you asked for. If you asked for a specific amount to be removed, like the 0.030". That's what they would do.

If you said to them, I want heads to be 82cc, then they would machine and check cc to get that amount.

Maybe there was unclear communication as to what was expected?

I agree , and if you had to ask how much was milled off after the work was done , you didn't discuss enough before hand

[Buglet]

  How far off is the class B say at 80cc?

[Buglet]

  I would thing if someone takes of .030 they should know what they were expecting for how many CC's they were aiming for. Or do you just take .030 of and call it good with out checking.

[Don D]

How far off is the class B say at 80cc?

The standard, +/- .004% VS .008%
For further clarification, if wanted, read up on ISO 102 and DIN 12664
We are assuming the burette carries a class rating at all. I threw away a few plastic burettes when I tested them with a known standard that exceeded class A, a digital bottletop dispenser I borrowed.
Many of the off brand plastic burettes are not rated.
In my experience a knockoff plastic burette can be a full CC or greater off at 80cc
Today I use a 120cc class A burette after I went through the weeds with cheap junk. It also has a glass valve that can be cleaned.

[Ohio HD]

Bill you can get a 100ml class A Burette and stand for about $70. It won't be heavy duty, but for once and awhile use, it will do. 

Amazon has several style to pick from.

[Don D]

A good value for occasional use. Pyrex is my preference.

[PoorUB]

We did a fair amount of talking, initially via email then via phone. He knew what cam I had, we discussed the compression ratio we agreed to shoot for. Did he actually measure and mill the heasd or did he just slap the 10.25-1 pstons in and call it good? If he can't tell me the volume of my heads then how did he "set the compression" as he put it? From what I've learned here I really need to know the deck height to be able to "set the compression" via thickness of head gasket or milling of bottom of jug.
     Furthermore, when he called to tell me that the parts were ready I asked him  how much he milled off the heads to get the the agreed upon comp ratio and he clearly said thirty thou. I mean, if he knew how much he milled off my heads how can he not know what the resulting volume is?  I did not pay good money to play guessing games.

Personally, if I had CC'd the heads my answer might be I wasn't certain, but around .030". I asked a local shop if they would mill and CC my heads and got a blank stare. I could have sent them away, but I wanted it done ASAP. I ended up CC'ing the heads and making a guesstimate of how much material to remove and surprisingly they came back perfect. I was prepared to send them back if they needed more taken off.

[Buglet]

  Thanks Don That's good to know I have to check mine out to see how far off it is.

[billbuilds]

Bill you can get a 100ml class A Burette and stand for about $70. It won't be heavy duty, but for once and awhile use, it will do. 

Amazon has several style to pick from.

      Brian, I'm lookingat a 50ml on Amazon that is .1ml graduatons and .05ml tolerance

Bill you can get a 100ml class A Burette and stand for about $70. It won't be heavy duty, but for once and awhile use, it will do. 

Amazon has several style to pick from.

    Looking on Amazon now. See a Schellbach glass 100ml class A burette by Eisco labs. It's got 4.5 star rating and is only $34.09. I would magine that it would be wise to buy a stand to hold the thing? 

[billbuilds]

A good value for occasional use. Pyrex is my preference.

    Thanks. Any idea how borosilicate glass compares to Pyrex?. When I search Pyrex 100ml burettes the borosilicate ones show near the top of the list.

[Ohio HD]

Looking on Amazon now. See a Schellbach glass 100ml class A burette by Eisco labs. It's got 4.5 star rating and is only $34.09. I would magine that it would be wise to buy a stand to hold the thing? 

Yes, they have some moderate priced stands in about the $35 to $40 range. If you can buy one with duel mounts instead of a single mount for the tube, they're more steady. What I mean is teh glass tube will stay located over the plexiglass plate better.

You also need one of these.
Clear Plate

Or you can get the entire kit.
Summit Racing

[PoorUB]

Bill you can get a 100ml class A Burette and stand for about $70. It won't be heavy duty, but for once and awhile use, it will do. 

Amazon has several style to pick from.

      Brian, I'm lookingat a 50ml on Amazon that is .1ml graduatons and .05ml tolerance

Bill you can get a 100ml class A Burette and stand for about $70. It won't be heavy duty, but for once and awhile use, it will do. 

Amazon has several style to pick from.

    Looking on Amazon now. See a Schellbach glass 100ml class A burette by Eisco labs. It's got 4.5 star rating and is only $34.09. I would magine that it would be wise to buy a stand to hold the thing? 

I didn't buy the stand as I rarely use it and I have enough stuff to store away. I did have something that worked with some rubber bands holding the burette. I had a scrap piece of plexiglass laying around so I cut a square out of it and drilled a hole and put a large chamfer for a "funnel".

[billbuilds]

     Thanks, poorUB. I've got all kinds of stuff laying around to make someting out of. I don't want to cheap out but I'm not exactly awa$h in it.

[FXDBI]

Go to a vet supply store and buy a 100cc syringe, the hardware store for piece of plexiglass. Drill a hole in the plexiglass and test each one a few times to check repeatability. Its accurate enough for what your doing. I have also used a syringe to check valve pocket totals on flat top pistons. The calculations have worked for me using this method and the bigboyz calculator. No ISO standard but then I am building my own not providing a service. My heads came in @ 83cc just has the porter said. He also used to stamp the heads and keep a full report of the work done. The syringe cost me like $10 back then, now a days most hydroponics shops also carry them.  Okay you all can flame me now...but its cheap and it works for me.   Bob

[billbuilds]

     That's not a bad idea Bob. We have a Tractor Supply and a Blue Seal Feed & Needs store on the outskirts of town. Thanks for mentioing, Bill

[PoorUB]

Also, if you cut a piece of plexy to make a cover for the cylinder head, drill the hole way off center and prop the head up at a slight angle with the hole up at the top edge of the chamber. A bit of grease to seal the plexy and fill'er up! any air can escape the hole. Other wise you end up fighting air bubbles.

[Don D]

On the fluid to use. I like windshield washer fluid. It does not bubble when filling and has less meniscus than plain water. Cheap and not toxic.

[kd]

On the fluid to use. I like windshield washer fluid. It does not bubble when filling and has less meniscus than plain water. Cheap and not toxic.

    Learning to read the meniscus is key and critical.  In a tube it must be perpendicular to the graduation marks too.

[FXDBI]

On the fluid to use. I like windshield washer fluid. It does not bubble when filling and has less meniscus than plain water. Cheap and not toxic.

I think the " meniscus" effect is neutralized with the use of a syringe. All entrapped air is removed before use and none should re-enter with proper use. The measurement will be close enough for the home guy not selling his services has a professional. Not a ISO standard but why complicate things, a little food coloring in the water works well. I use the KISS method same way the engine is designed simple. No disrespect to anyone just what has worked for me.   Bob

[kd]

I guess it wasn't clear but I used the tube as an example for reading a meniscus line only and the need for it to be perpendicularly square.  The colored washer fluid works well in both rather than clear.

[billbuilds]

On the fluid to use. I like windshield washer fluid. It does not bubble when filling and has less meniscus than plain water. Cheap and not toxic.

    Learning to read the meniscus is key and critical.  In a tube it must be perpendicular to the graduation marks too.

     Thanks for that info kd and HD Street Performance. I got my plexiglass cut and hole drilled. Did a bunch of running around yesterday that I would usually ddo on the weekend so hopefully I can lay low for the storm. I'd seen where Summmit Racing had recommended a 50/50 mix of rubbing alcohol and water then add food coloring. I found some rubbing alcohol at the CVS Pharmacy that has a green tint. It was getting late yesterday afternoon and I wanted to start fresh this morning. Let's see how this goes. 

[billbuilds]

     I used a 60cc and a 12cc syringe because they were handy and cheap. Did each head three times and I found the front one to be about 78.5cc and the rear to be about 79.5cc.

     I ran the Big Boyz caclulator for 98" using 80cc as head volume, putting the pistons .0005 in the hole, pistons having a 10.40 dome volume and S$S 570's. With an 045 head gasket it shows a corrected compression of 10.15:1 and 215.8 ccp. Is that a little high or should it be ok seeing as I was a little conservative with the actual head volume figure in my figuring?   

[kd]

Actually you weren't conservative with the head volume Your measurement shows a smaller volume which relates to higher compression than you calculated.  Rerun the numbers at 79 CC and you'll see what I mean. Then run it again with a .030 head gasket. The .045  head gasket isn't favorable to controlling detonation like a .030 is either.) With a good tuner and tuning device you may still be OK but the head gasket size may be better at the .030 for control of pinging.

[Ohio HD]

I really depends on how you wish to use the motor. If a cruiser, the compression may be a little high. If a lighter bike, and will be a play bike, less issues. It also depends on if there is ample 93 octane in your area. 

I'm calculating about 10.40 corrected compression. That's pretty high. If you're at a higher elevation then that helps reduce the cylinder pressure.

[billbuilds]

Actually you weren't conservative with the head volume Your measurement shows a smaller volume which relates to higher compression than you calculated.  Rerun the numbers at 79 CC and you'll see what I mean. Then run it again with a .030 head gasket. The .045  head gasket isn't favorable to controlling detonation like a .030 is either.) With a good tuner and tuning device you may still be OK but the head gasket size may be better at the .030 for control of pinging.

     Yes, I meant that I rounded up the head volume number because I had an idea that the corrected compression and ccp were going to be on the high side anyhow. If I plug in the .030  head gasket, even with the 80cc head volume number, it's where I don't even want to try it - 10.5:1 compression and 225.3ccp.   

[billbuilds]

I really depends on how you wish to use the motor. If a cruiser, the compression may be a little high. If a lighter bike, and will be a play bike, less issues. It also depends on if there is ample 93 octane in your area. 

I'm calculating about 10.40 corrected compression. That's pretty high. If you're at a higher elevation then that helps reduce the cylinder pressure.

     No, it's not a lighter bike, it's a Road King. This was made very clear to the shop. No, you can't always find 93 octane around here sometimes the high is 91. Really don't want to play that game. When the guy at Campbell Industriestold me the compression of these CP pistons my immediate thought was "ping monster". The bike is carbed.
     This really bums me out because I went over exactly who did these 06 heads of mine before I shipped them down to him so that he could measure them, clean them up and install new springs in them. He knew that they weren't stock. It's pretty obvious that he did not bother to measure the chamber volume but just spun them up and shaved the .030 off of them. They'd obviously had some taken off before.
     I really thought that he was going to give me the 9.5:1 pistons seeing as the Rev Perfs were 9.5:1. There was a difference in valve pocket size and we spoke in detail about that. It was left that he'd measure the heads and make the decision. Ok, I'd better stop or I'm going to get this thread locked. Thanks, Bill

                                       

[rigidthumper]

IMO, Flat tops and those 570s would make an easy to tune/no drama build. If there's enough meat on those pistons, chuck em up in a lathe, remove the domes, and get er done...

[Ohio HD]

I assume these are the CP Bullet style pistons? I think they're designed to allow a flat top if milled down.

You might see about talking to someone at CP, explain what you have, and ask them how much less compression or rather cc's you have when milling every 0.010" off the piston dome. And ask if they can be milled flat if desired.

[Ohio HD]

As calculated, a flat top would give you about 9:1 or 182ccp. A flat top you have to calculate negative dome for the valve reliefs. A 2cc dome you would have about 9.45:1, or 193ccp.

Just estimates on the ccp of course.

[billbuilds]

I assume these are the CP Bullet style pistons? I think they're designed to allow a flat top if milled down.

You might see about talking to someone at CP, explain what you have, and ask them how much less compression or rather cc's you have when milling every 0.010" off the piston dome. And ask if they can be milled flat if desired.

     Yes, they're the Bullet style though the one descrepancy between the spec sheet that I got and the list that you included in your reply to my piston question thread is that my spec sheet shows dome hieght as 10.40 whereas the listing shows dome height at an even 10. I'll call Campbell Industries tomorrow morning as they're three hours ahead of CP Carillo time zone-wise. If they're not sure I'll just have to wait and call Cali.  Thanks, Bill

[Don D]

The deck must remain .200 thick at all points. If there is under deck milling often times the amount that can be cut is minimal. There are also limits even when the deck is thick enough. The forging can distort.

[billbuilds]

The deck must remain .200 thick at all points. If there is under deck milling often times the amount that can be cut is minimal. There are also limits even when the deck is thick enough. The forging can distort.

      Thanks for the reply. I had an idea that there would be limits to how much material could be safely shaved off. I'm no machinist but I did work in a machine shop for several years. I would guess that the optimal way to shave that material off would be in a lathe, a high tech lathe that has cutting/cooling fluid being directed onto the tool/part contact area. That's not going to be a cheap procedure. 

[Buglet]

   Make sure either way you do it is that you have a good way to hold the piston so it don't get distorted either on a lathe or a mill is most important.

[billbuilds]

     I just got off the phone with CP-Carillo and the guy I spoke with said no, can't turn these into flat tops as they'd be too thin. Houston, we have a problem.

[kd]

It's beginning to look like all of this heart wrenching problem solving will be best addressed with a new set of pistons with more appropriate specifications.  The ones you have may be sold or repurposed in another build.

[cheech]

It's beginning to look like all of this heart wrenching problem solving will be best addressed with a new set of pistons with more appropriate specifications.  The ones you have may be sold or repurposed in another build.

My thought from the get go.

[billbuilds]

It's beginning to look like all of this heart wrenching problem solving will be best addressed with a new set of pistons with more appropriate specifications.  The ones you have may be sold or repurposed in another build.

    With my cylinders already bored to supposedly fit these pistons what are the chances that newer, lower compression pistons will fit to spec?

[kd]

If too tight, that's adjustable.  If too loose, coatings are showing a lot of promise.  That's 2 options I see.

[billbuilds]

     I'm shelving this project or now and going another route to seek a "soution". I've got way too much money invested in this already to start throwing good money after bad. Thanks to all for the help, Bill

[harpwrench]

If it were mine I would install a mackie 598 with a -4 crank sprocket, and enjoy the power

[billbuilds]

If it were mine I would install a mackie 598 with a -4 crank sprocket, and enjoy the power

     That's 11.57:1 static and 9.85:1 corrected. Wouldn't it be pushing thing with a nearly 208ccp?   

[harpwrench]

I figured it with a .040" gasket at my elevation

You cannot see attachments on this board.

[Buglet]

   I'm throwing this out there if this would be a option. I know this is going backwards but couldn't he open out the chamber in the heads to get his cc's back.   

[billbuilds]

I figured it with a .040" gasket at my elevation

You cannot see attachments on this board.

     Correct me if I'm wrong but I don't see where you figured for the -4 degree cam gear. Also, it's my understanding that you leave the **intake close at zero if you've selected a cam. Am I missing something?

[harpwrench]

I didn't select a cam, then entered the 54 intake close for the 598 retarded 4 degrees instead. You'd leave that box at zero if just using a selected cam installed straight up. Another option is the S&S 625, but the exhaust opens a lot earlier which might kill the torque. Depends on the head porting and pipe

[tdrglide]

I would be looking at sending cylinders out to check fit for new flat top CP pistons, Manufacturers are pretty consistent and tight with their own piston tolerances. Worst-case scenario you have to find some take off cylinders and bore. I was able to swap pistons before with no issues.
0.030 mls head gaskets. Leave heads as is. It's a carb bike isn't it.

[billbuilds]

I would be looking at sending cylinders out to check fit for new flat top CP pistons, Manufacturers are pretty consistent and tight with their own piston tolerances. Worst-case scenario you have to find some take off cylinders and bore. I was able to swap pistons before with no issues.
0.030 mls head gaskets. Leave heads as is. It's a carb bike isn't it.

    Yes, it's a carbed bike and I was thinking along the lines of what you suggested, having really wanted to go that route from the git-go but...

[billbuilds]

I didn't select a cam, then entered the 54 intake close for the 598 retarded 4 degrees instead. You'd leave that box at zero if just using a selected cam installed straight up. Another option is the S&S 625, but the exhaust opens a lot earlier which might kill the torque. Depends on the head porting and pipe

     OK, I see now. Thanks

     The heads have been massaged a bit with slightly larger intakes but I'm not sure that they're set up for the S&S 625's. I've been using the stock touring header pipes with the internal protruding portion removed and the older off road-only SE slip-ons.

[Ohio HD]

I would be looking at sending cylinders out to check fit for new flat top CP pistons, Manufacturers are pretty consistent and tight with their own piston tolerances. Worst-case scenario you have to find some take off cylinders and bore. I was able to swap pistons before with no issues.
0.030 mls head gaskets. Leave heads as is. It's a carb bike isn't it.

    Yes, it's a carbed bike and I was thinking along the lines of what you suggested, having really wanted to go that route from the git-go but...

Bill I think this is also the most reasonable method to resolve the problem. You can resell the pistons you have and recover almost 100% of the new pistons cost.

Staying with a CP piston, I would not worry that the pistons finished size would change. I've used a lot of CP pistons over the years. I measure them all, and they measure what the spec sheet says they are.

CP-Carrillo BHM98FT is a flat top pistons, use a piston cc of -1.6 and you'll see about 9.1 corrected compression. Roughly 184ccp.

Mechanical compression with the heads and 0.030" head gasket is 10.10:1.

 

[Don D]

Drag Specialties has a nice flat top JE piston, 0910-5936 3.937" nominal

[Ohio HD]

On the bottom of the piston there should be two numbers; the CP job number and the piston part number (assuming its a standard CP shelf piston). The CP 98" pistons have the following designations:

BHM98FT -1.6cc 9.5:1 compression
BHM98-3 +3cc 10.0:1 compression
BHM98-6 +6cc 10.25:1 compression
BHM98-10 +10cc 10.75:1 compression

Bill, this is the piston data that Jamie posted in the Question on CP 98" Pistons thread.

If it were me, I'd source the "BHM98FT -1.6cc 9.5:1 compression" and not look back. They'll measure the same as the pistons you have regarding the fit into the cylinder bore.

[billbuilds]

    Thanks Brian. It's sure reassuring to know that I can count on a good fit with CP's.     Bill

[billbuilds]

Drag Specialties has a nice flat top JE piston, 0910-5936 3.937" nominal

      Thanks. I tried to find some info on fit and did not find JE's website very user friendly. Why it won't let you search by 3.937 bore size eludes me.

[Jamie Long]

Each of the CP BHM-98 pistons use the same forging, and there is more than sufficient dome thickness to machine yours as necessary. If you determine your chamber volume and what you need for a piston displacement to help you out of this jam i'll machine them for you no charge. We have a dedicated machine & piston fixture and I can turn them around in a day, just pay the shipping back. Just send an email to jamie@fuelmotousa.com and ill send you an authorization code

[Ohio HD]

That's a generous offer.   

[kd]

    

[billbuilds]

Each of the CP BHM-98 pistons use the same forging, and there is more than sufficient dome thickness to machine yours as necessary. If you determine your chamber volume and what you need for a piston displacement to help you out of this jam i'll machine them for you no charge. We have a dedicated machine & piston fixture and I can turn them around in a day, just pay the shipping back. Just send an email to jamie@fuelmotousa.com and ill send you an authorization code

    Wow, Jamie, that is a indeed a very generous offer.    I think that I'll cc those head again twice to firm up the chamber volume number now that I have a better grip on how to do it. Also need to carefully remove those rings. I'll send you an email later today.
                            Thank you  very much, Bill

[Buglet]

   Jamie is the man, I guess CP look for the easy why out and make money. As far as the deck thickness goes it's easy to check.   

[Don D]

It is a simple rule, just don't cut the dome leaving less than .200 cross section. Weight and skirt changes are factors as well in extreme cases where high domes are flattened. I am not suggesting this is the case here and I agree this is a generous offer.

[Buglet]

  I agree on the weight but unless you redoing the flywheels them have it balance to those pistons then I would be concern about it. When you going big bore not many are getting there wheels rebalance. The other thing is he will be taking weight off and being there bigger piston it should get him closer to the original weight. The only real way to check it out is to check the weight on both pistons after taking the dome off. 

[Don D]

As the pistons grow in weight the pins are reduced, with a mind on allowable minimums for reliability. It is an attempt to keep the performance domed pistons as close to stock as possible unless you just have a very different configuration such as a 20 degree dome. Those are just way heavy up top. This is how builders can use S&S wheels by using their target weight stated. Correction factors go up and down according to loss or gain of weight and this is not make or break stuff unless you again go very much out of spec.

[billbuilds]

    I CC-d both heads twice once again for peace of mind and I get 79cc pretty much dead-on for the front head and about a half cc bigger for the rear head. According to the spec sheet these pistons presently weight 421 grams. The pin diameter is .927. I looked into Kramm-Loxx (great idea Brian) and this appears to be a very popular size, at least for CP. Hoping that lightening the pistos some may help a bit balance-wise but only time will tell.
                                                          Thanks, Bill

[Don D]

Bill
I think you missed my point a little. I don't know about your crank but when a crank is balanced by the shops they ask for a gross weight. Rings, pins, clips included. If you drop 27g per piston, a reasonable swag for -10cc, that is X2. That changes the balance factor. Early TC cranks were balanced (factory) for ~1200g later cranks, cold forged ~1050. When the cranks are balanced for a certain weight that changes things, you give the shop the gross weight, they decide the balance factor and start drilling or filling. Piston weights are juggled some by changing the pins' weight, in other words the ID, within reason. None of this is news to Fuel Moto, they get it.
This build seems to be handled so I will drop off.

[billbuilds]

     HD Street Performance,

     The crank is the stock 1999 first year Twin Cam crank with the factory balance. I undestand what you mean now about increasing pin weight to make up for lost piston weight, thanks for pointing that out. Bill   
     

[Buglet]

    Bill  Did you measure the weight of the stock piston the came out of the motor.

[billbuilds]

Bill  Did you measure the weight of the stock piston the came out of the motor.

     I thought about that, Buglet. I know that I still have them, just have to put my hands on them and slide the rings off. I bet I'll have to go after some button batteries too. Thanks for the reminder.

[Buglet]

  When you check the weight 100 %. You should check the pistons complete with all the rings, wrist pin and clips.   

[billbuilds]

      Somehow I thought that the number on the CP spec sheet was that for the bare piston so that's why I removed the rings and wrist pin. I really don't have an accurate gram scale for anything over 300. I have an 11lb spring scale and it looks like these bare stock 88" TC pistons weight about 415 grams. Adding on thw wrist pin and the rings they look to weight about 655 grams.

[Ohio HD]

Bill, the weight shown on the CP spec sheet is piston weight only. You do need to weigh the rings, wrist pin, and rails if included. Anything that mounts to the piston is needed x 2 to balance the crank assembly.

Someone on this site has to have weighted these 98" CP pistons with rings and pin before. Maybe someone will post. Or maybe someone local to you cab weigh them.

[billbuilds]

Bill, the weight shown on the CP spec sheet is piston weight only. You do need to weigh the rings, wrist pin, and rails if included. Anything that mounts to the piston is needed x 2 to balance the crank assembly.

Someone on this site has to have weighted these 98" CP pistons with rings and pin before. Maybe someone will post. Or maybe someone local to you cab weigh them.

     Thanks Brian, I see what you mean now, really do need totals since pin weight can vary as I've learned from HD Street Performance. The pistons are enroute to Fuel Moto. Pins and rings are still here so maybe I can weigh them on my 300 gram scale and add that figure to the piston weight. I will need to pick up a couple of 2032's later today.

[Ohio HD]

Bill, I can't speak to all piston manufactures in regards to wrist pin changes in weight. The CP Bullet series pistons that I've been using for 117" and 124" motors, this is not the case. The wrist pins always weigh the same. Example is below.


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As expected the pistons with a higher (thicker) dome weight more. The wrist pains always weigh the same. I would expect the same with the 98" CP bullet series pistons.

CP would need a lot of wrist pin part numbers (different size / weights) to cover all of the options a customer might want with a given piston bore size.

[Don D]

Brian, weights still are missing rings and clips, which are fixed across all the pistons of course. Then I assume from your other posts the cranks are balanced for the exact weight of your parts.

For reference to achieve the factories intended balance the gross piston weights must be 1200 grams piston reciprocating weight for the early twin cam engines. Guys juggle piston weights and don't seem to notice the "sweet spot" so to speak actually the balance factor is changing unless they change things pretty radically. The shops that balance the flywheels get gross weight of the pistons and actually correct the balance based on their decided balance factor which varies between shops.

[Ohio HD]

Yes the rings and wrist pin retaining rings are missing because they are the same weights. These pistons I indeed used with custom built crankshafts and balanced with weights of the piston assemblies in mind. I would not use these 4.125" CP pistons with an off the shelf S&S crank unless I were to have the crank rebalanced. For that matter or an OEM HD 4.375 crank in regards to a 117" motor without rebalancing.

My only point to Bill is the four pistons CP offers for the 98" motor most likely has the same wrist pin. I'm trying to keep the info relevant to what he is working with.

[billbuilds]

     The most accurate scale I was able to use today to weigh my stock 88" piston rings, pin and clips only went to the tenth of an ounce and no switch for gram weight. The 1 pound 4.9 ounces it read equals around 593 grams. Seeing as a tench of an ounce is 2.83 grams there's sure room for the actual figure to be closer to the 600 grams that HD Street Performance mentoned as being required for the early TC cranks.
     The 300 gram scale that I have shows down to tenths of a gram. The CP pin alone weighs 106.9 gramss. Add the two clips and full ring set I and I get 138 grams even. With the piston weighing 421 grams that's a total of 559 grams. So there's 80 grams of reciprocating weight less With thr forged CP's over the stock cast pistons. I can see where this would change the balance some but how much I've no clue. Thanks, Bill

[Don D]

So you will drop another 50 grams or so with a dome cut. A little lighter piston won't change the factor percentage significantly. The cranks are balanced with a higher percentage to achieve low rpm smoothness and a lower percentage to achieve smoothness at a higher rpm. If I understand this correctly installing a lighter piston will increase the balance factor percentage. How much and how significant or important a certain number grams equals a certain number increase of the balance factor and what the rpm the "sweet spot" changes to I do not know.
S&S does follow the stock scheme and weights. They used to balance flywheels to weights the customer specified but then lean manufacturing took over.

[Ohio HD]

Bill, rather than clog up your post with all of this flywheel balance estimation I started a new post in regards to that in General. Sorry for clogging up the post.

Crankshaft Balancing


I "think" the piston weight changes moves a 60% crank balance to 64%.

I think it's a good idea to weigh the pistons that came from the motor and compare them to the new CP values. Then you can see what if any differences there may be.

[billbuilds]

     Thanks Brian. I could well have misinterpreted the spec sheet concerning the weight of these pistons. I'll continue over in general. Bill 

[Don D]

CP pin is 927-2250-15CP1C, see if 927-2250-20CP1C will make up the weight. Might be the simple solution.

[billbuilds]

CP pin is 927-2250-15CP1C, see if 927-2250-20CP1C will make up the weight. Might be the simple solution.

     That would sure be cool. Thanks

[billbuilds]

     I just called CP and was told that the .015 wall thickness wrist pin is 106 grams and the .020 wall thickness wrist pin is 131 grams. Will that be enough?

[Don D]

We are talking .15 vs .2 wall. You are taking off about 54 grams piston weight and adding 50 grams back pin weight. I would move forward. 

[billbuilds]

We are talking .15 vs .2 wall. You are taking off about 54 grams piston weight and adding 50 grams back pin weight. I would move forward. 

    Ya, I goofed on typing the wall thicknesses, doh!


Sounds real good. Your help is greatly appreciated. 

[Admiral Akbar]

I'm a little confused here.   

Early 88 ci TCs had about a 600 gram for 1 piston assy. balance factor.  OP has pistons that are 559 grams that need 10ccs cut off so they loose 27 grams. The new pin adds 25 so the piston assy weights 557.  Isn't the balance factor still off by 43 grams?

Don seems to mention that the balance factor for 88 ci TCs changed when HD went to cold forged cranks which is mid to late 2004 models.  Didn't it really change in 2007 when HD went to the 4 3/8 stroke?

[Ohio HD]

Bill, I agree with what Max has above. I placed some additional info in the balance post in General.

The .250 wall pins should get you really close. But I recommend weighing the OEM parts, just to see what they are.

[Admiral Akbar]

I have a set of early Wiseco 10.5 95 ci pistons that came out of my 02 RK and weighed them.. They weigh 554 grams. Ran them for 60K miles without issue. Motor wasn't balanced to the pistons. Did not seem to vibrate too bad.  IIRC it still had the original from motor mount when I sold it at 80K.   

Did the same thing for my 2000 fxdx. It did seem to vibrate a little more but then different motor mounts and weight.

If I crank out the numbers the piston change works out to 54.6% balance factor the Wiescos.

I guess it's really how anal you want to get.

I'm doing an all bore 107 for the DX and the piston assys weight 540.  I rebalanced since the crank was out of the cases.

[djl]

Seems the OP is on a path but I thought I would share my experience with piston weights and how the affect crank balance.  It has been years since I built an all bore 107 motor with an Axtell "Mountain Motor Kit". The cylinders would not hold a true bore and after a .010" overbore and new pistons at my expense, Axtell offered no help.  The final solution was a set of MTC cylinders/pistons. After assembling, the motor vibrated so bad it was unrideable. It finally dawned on me that the MTC pistons (weight) might be the problem.  So, I pulled the top end down and compared the MTC piston assy weight to the JE piston assy weight (crank was Hoban Brothers balanced to the JE pistons).  The MTC pistons were about 15% lighter than the JE pistons; problem found.  I called John Dahmer and he pointed out that anything more than 10% +/- weight differntial in piston assy weight would affect crank balance; balance being more sensitive to lighter than heavier.  I checked the .010" JE pistons and they were in spec so I intalled them with new rings; problem solved; quiet, smooth running motor.

Fast forward to two years back when I decided to rebuild the 95" motor in my Deuce to 98" which required new CP pistons with a 6cc dome.  I weighed the SE cast flat top 95" piston, rings, pin and locks and that assembly weighd in at 593.5g.  The scale I used was Mike Lozano's (Lozano's Brothers Porting) digital scale he uses for that purpose in his shop; very accurate.  The CP piston, rings, .150" wall pin and locks weighed in at 554.5g which was about 8% lighter but not close enough for me.  I called CP and orderd a .230" wall pin which put the CP piston assy weight at 599.5g; good to go.

I can't find all my notes from that build but I did find the CP .230" wall pin PN 927-2250-23CP3C which is different from the PN Don previoulsy posted 927-2250-15CP1C.  The difference is the wall thickness and the material. The PN Don posted is for a chrome moly 5100 pin (1C)and the pin (3C) I used is made of 9310 steel. I don't know if chrome moly is lighter than 9310 steel but the .230" wall pin I used added 45g to the CP piston assy weight.  I wish I could find my notes wherein I had recorded the indivivual weights of the piston, rings, pin and locks but I can't.

This doesn't add much to what has already been posted but I thought there might be something of interest to others reading the thread.

[Ohio HD]

It's very good real information. I can see where John said that a little heavier wasn't as bad as lighter. Good folks at DH for sure, that know what they're doing.

[billbuilds]

     djl,
     Thanks for posting your piston and pin balance experience. I found that .230 wall pin p/n in the CP catalog but it does not list the weight. I know that the .5 wall pins that came with the pistons are 106 grams. I found some on the Summit Racing website with a .250 wall thickness made of H-13 tool steel. They're p/n H9272250250C and they weigh 153 grams. I was thinking of going with them but maybe I'll check with CP to get a weight on their 927-2250-23CP3C first. Bill 

     Edit: just called CP and was told that the 927-2250-23CP3C pins are 144 grams. I really need to go with the 153 grams pins.