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deck height measured over the pin differant side to side?

Started by 1340evo, May 01, 2021, 11:12:11 AM

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kd

I know that crankcase halves sometimes are not perfect on the deck that the cylinders bolt down on.  That would cause a variance.  A straight edge may show that.  Also as a set of cases season it wouldn't be hard to believe the same deviance could occur.  A slight angle on the case deck over the length of a cylinder the tilt would grow at the other end too.  There are so many ways it can happen over time. 
KD

1340evo

Decks are nice (except the bit where the engine builder has used a rod through the small end to torque up the cam gear and indented it!) but there is no way I can check how true they are to the crank.
Unless they caused this in the re-con, I have to assume it was like this before and it worked well then.

Need to calc squish but think I need .015 off each head which I can do this week, then weekend its back together ;)

Hillside Motorcycle

Start by precision decking the cases, then insure the wrist pin C/L is perpendicular to the case deck, then both ends of the cylinders are machined to 90* to the bore C/L...............or assemble it and ride.
Then, the oil trapped in the flywheel balance holes??
Me thinks you are overthinking this.
Otto Knowbetter sez, "Even a fish wouldn't get caught if he kept his mouth shut"

1340evo

That's what I say, put it together and ride...
Need to work out the gaskets now..
My cc's are the same and squish is correct.... but what CR is best for a ev27 cam and how to work it out?

kd

I'm thinking around 10.5:1.  Some that have extensive background using that cam will be more helpful.  While you are waiting for a few answers try this calculator to see where you will be at with what you now know.
KD

rigidthumper

Quote from: 1340evo on May 05, 2021, 04:51:45 AM
That's what I say, put it together and ride...
Need to work out the gaskets now..
My cc's are the same and squish is correct.... but what CR is best for a ev27 cam and how to work it out?
EV27 has a 36° close, and I've found less issues setting the static CR to 9.5:1- can use the stock carb, and available fuel, any time, any where, without drama, and enjoy the ride. Add an adjustable ignition, if you feel the need.
Cometic .030" thick head gaskets, 74cc chambers, zero deck height, and Bob's your uncle :)
Ignorance is bliss, and accuracy expensive. How much of either can you afford?

1340evo

Well, not a lot of gaskets available right now, but if I got a
.036 head and a .016 base, that gives me .052, on average the pistons are .010 high, so that would equate to a .042 squish.
My heads are 81cc...

What I'm working to is advice from the engine guy saying don't go mad with the ev27. Knowing all of the above, he said using a .020 base and a .030 head was just about right?

kd

KD

1340evo

With who? The engine guy...

From your calculator, I get

8.51:1 static

And corrected for the cam ev27 gives

7.98:1   ? what ever that means?

If I shave heads to 74cc, I get 9.15 : 1
But would need to take .028 off the heads .. is this right

Or just but new gaskets to give .042 sqish

Or do I just build it with what I have....  .020 base gaskets and .045 heads?

Guess what I need to know is what it does to the drivabuility of the bike?

Whats the most important to get right... Squish or CR?

John D

Just for reference, our Darkhorse spec is +.002/-.002 at 2" from centerline of ConnRod, so essentially a 4" bore piston.  We have developed pins and ground surface with indicators to verify every connrod that comes through the door (Including brand new connrods). 

When we replace wristpin bushings they are sized with a TobinArp pin boring machine (1960's version) and then verified on our "rod checker" to make sure big end and small end are parallel within that same +/- .002" spec at 4"

The best way to resolve wristpin / rod alignment issues is before they are installed back into the crankshaft!

1340evo

Quote from: Darkhorse on May 05, 2021, 01:21:35 PM
Just for reference, our Darkhorse spec is +.002/-.002 at 2" from centerline of ConnRod, so essentially a 4" bore piston.  We have developed pins and ground surface with indicators to verify every connrod that comes through the door (Including brand new connrods). 

When we replace wristpin bushings they are sized with a TobinArp pin boring machine (1960's version) and then verified on our "rod checker" to make sure big end and small end are parallel within that same +/- .002" spec at 4"

The best way to resolve wristpin / rod alignment issues is before they are installed back into the crankshaft!

so if its +/- .002, does that mean overall it could be .004? (i know I'm 3.5 inch)

John D

At a 3.5" piston it should be less using our specs and tolerances

1340evo

So

what do I need to work on. I've ordered the new gaskets to get me the squish.. do I leave it or work on CR?

Squish I'll be at .042 so close enough, CR I'm at 8.5 : 1 using the calculator?

rigidthumper

Years ago, we would routinely take .050" off of EVO heads, and use thin gaskets to achieve a final quench distance between .030-.036.
Ignorance is bliss, and accuracy expensive. How much of either can you afford?

1340evo

Hi, well I'm at .042 quench and 81cc heads, 8.5 CR... and for problem free motoring, thats how its getting put back together. Built and in this weekend.

Thanks for all the input :)

98fxstc

Quote from: 1340evo on May 06, 2021, 12:42:27 PM
Hi, well I'm at .042 quench and 81cc heads, 8.5 CR... and for problem free motoring, thats how its getting put back together. Built and in this weekend.

Thanks for all the input :)

may be problem free motoring, but will be soft at that compression and less than efficient combustion
you have done a lot of work and missed an opportunity
go back and read advice from rigidthumper (both posts)

1340evo

Arrrg. so I have my squish at .042.
I can still mill the heads if it makes a big change.

Putting it back as I have it now is better than std though....

What gives a 'nice' improvement? 74cc maybe a bit too much ??






Hillside Motorcycle

Otto Knowbetter sez, "Even a fish wouldn't get caught if he kept his mouth shut"

Don D

Quote from: 1340evo on May 06, 2021, 11:28:48 PM
Arrrg. so I have my squish at .042.
I can still mill the heads if it makes a big change.

Putting it back as I have it now is better than std though....

What gives a 'nice' improvement? 74cc maybe a bit too much ??

Probably 10ft/lbs and half that on power if you follow the formula that I and others use.

tdrglide

Quote from: rigidthumper on May 06, 2021, 05:33:03 AM
Years ago, we would routinely take .050" off of EVO heads, and use thin gaskets to achieve a final quench distance between .030-.036.
That was the standard hop-up among me and many of my friends back in the late eighties and nineties. Along with the EV27 or EV3 cams

1340evo

Quote from: HD Street Performance on May 07, 2021, 05:44:49 AM
Quote from: 1340evo on May 06, 2021, 11:28:48 PM
Arrrg. so I have my squish at .042.
I can still mill the heads if it makes a big change.

Putting it back as I have it now is better than std though....

What gives a 'nice' improvement? 74cc maybe a bit too much ??


Probably 10ft/lbs and half that on power if you follow the formula that I and others use.

27 and 9.8?  without milling the jugs .042 is the best I can get.

so I can still change the CR.... don't want problems like starter won't turn it over, need a new carb, blows gaskets etc.. so on a 81cc head, how much to shave off to make it a nice Sunday ride if I don't take the sports bike out.. I'm not looking for anything great, just make it right :)

If I did mill .050 would I need adjustable rods.. want to keep the std rods ;)

jsachs1

Last 3 sets I did with EV 27 cams, 80". I set the chambers at 78 cc., 0 deck, .030" MLS gaskets, stock flat tops. No PMS, happy customers. :up:
John

1340evo

Quote from: jsachs1 on May 07, 2021, 03:04:49 PM
Last 3 sets I did with EV 27 cams, 80". I set the chambers at 78 cc., 0 deck, .030" MLS gaskets, stock flat tops. No PMS, happy customers. :up:
John

Hi John, thats interesting. I have .042 squish and I'm kind of stuck with it as no .030 MLS available in the UK right now. (.016 base and .036 head)... but 78cc is less of a shave of the heads.
so if I'm at 81cc now, how much do i need to take off?... and did they run std rods etc  ... 

no PMS?.. whats that?

cheers.

Ohio HD

Quote from: 1340evo on May 07, 2021, 03:24:51 PM

Hi John, thats interesting. I have .042 squish and I'm kind of stuck with it as no .030 MLS available in the UK right now. (.016 base and .036 head)... but 78cc is less of a shave of the heads.
so if I'm at 81cc now, how much do i need to take off?... and did they run std rods etc  ... 

no PMS?.. whats that?

cheers.

Your talked to three shops in this one thread that can send you the head gaskets. I don't understand the difficulty?     :emoGroan:

1340evo

If anyone is willing to send Gaskets to the UK, I'm all ears  :smiled:

It would get me another .006 off my squish taking it to .036"

then CC the heads maybe to what John says above or a tad more.

Want to stay with std bits like rods, carb, starter etc... :)