Cylinder base gasket leaking oil.

[JW113]

I have James Foam-met base gaskets in my otherwise stock '92. Bone dry at the cylinder bases. These new type of gaskets appear to be pretty forgiving of surface to surface imperfections.

According to my machine shop guy, who's worked on a ton of San Jose police bikes, police EVOs came from the factory with .050 off the heads. So I say go for it.

-JW

[thumper 823]

Some of the heads can have 0.075 ripped off from the factory as they are not very QC in that area..
Once we start dwn the road here...we could say CCing them might be a good idea...
BUT-
It is all too EZ to spin a web for someone that is not up to speed on this stuff.
If you up the CR, you will prolly have to go up a fudge on the carb depending on the pipes etc .

Next, the nodular iron jugs need no base gasket. 
This is especially helpful for getting for squish setting correct, as cometic will custom make you most any thickness you want.
Slippery slope.

[4DogsanaHog]

Cleaning the cylinders and heads to reassemble the engine, I noticed rubber O-rings on the 2 protruding oil passage pipes. Well I didn't notice them while buffing the top surface of one of the cylinders in preparation to reassemble the head to cylinder and tore them up. Are these O-rings really necessary?  Seems to me the head gasket would not allow oil to leak between the head and cylinder. The Harley dealer closest to me, 100 miles, has only one of these O-rings in stock. Are these O-rings really necessary? Can't I just leave them out?

[Ohio HD]

I wouldn't leave them out. 

[jamminhd2000]

Cleaning the cylinders and heads to reassemble the engine, I noticed rubber O-rings on the 2 protruding oil passage pipes. Well I didn't notice them while buffing the top surface of one of the cylinders in preparation to reassemble the head to cylinder and tore them up. Are these O-rings really necessary?  Seems to me the head gasket would not allow oil to leak between the head and cylinder. The Harley dealer closest to me, 100 miles, has only one of these O-rings in stock. Are these O-rings really necessary? Can't I just leave them out?

I believe Cometic and newer oem gaskets do not require the oring on top of cylinder. They are usually embossed around the dowel area. They fit snug up against dowel and there would be no room for oring...jimmy

[Ohio HD]

I believe he's using OEM gaskets.

[4DogsanaHog]

Yes, I'm using OEM gaskets. Just got some new O-rings and will put them in.

[D-1]

New OEM gaskets wont use the oring on the dowels. Put the gasket on the dowel, if there is no room for the oring, dont use one

[astropi]

if the plugs are running clean-not burning oil and your not up to a complete top end rebuild while apart, leave the piston in the cylinder. If you remove the piston it does need to be re-honed and new rings. Pull the front one also. Replace the cylinder studs and use the appropriate lock-tite, torque tool-CYLINDER STUD REMOVAL TOOL FOR EVOLUTION & TWIN CAM-, use metal base gasket sets for the cylinder base(cometic has served me well).

[Ohio HD]

If you remove the piston it does need to be re-honed and new rings.

This is incorrect. Many here including me have performed the operation of removing a cylinder and placing it back on the same rings without honing the cylinder with zero ill effects.

Do you think that HD replaced all of the piston rings and honed the cylinders of all of the  warranty Evo's that leaked base gaskets in the early 90's? You do more damage to the cylinder honing it by hand unless you have cylinder torque plates and a hone with a micrometer adjustable head.

[Scotty]

If you remove the piston it does need to be re-honed and new rings.

Pulled heaps and re-installed Evo & Twin Cam and no issues at all.
Internet myth this re-honing and new rings.
Never heard about it until I read it on the internet and can't for the life of me work out why I never had any problems 

[jsachs1]

if the plugs are running clean-not burning oil and your not up to a complete top end rebuild while apart, leave the piston in the cylinder. If you remove the piston it does need to be re-honed and new rings. Pull the front one also. Replace the cylinder studs and use the appropriate lock-tite, torque tool-CYLINDER STUD REMOVAL TOOL FOR EVOLUTION & TWIN CAM-, use metal base gasket sets for the cylinder base(cometic has served me well).

??.

[bobrk1]

Rear base leaking  is common , I  found  that  waiting  for  the  motor  to  warm  up  helped a lot .

[Ironheadmike]

If you pull the cylinder you should at the very least hone and new rings . The rings will not seat properly . You have to warm up an Evo before you ride . Not warming up the bike is the main cause of base gasket leaks . This is from over 40 years of wrenching on bikes . If you do a job, don't do it half assed or it will bite you in yours .

[Hossamania]

If you remove the piston it does need to be re-honed and new rings.

This is incorrect. Many here including me have performed the operation of removing a cylinder and placing it back on the same rings without honing the cylinder with zero ill effects.

Do you think that HD replaced all of the piston rings and honed the cylinders of all of the  warranty Evo's that leaked base gaskets in the early 90's? You do more damage to the cylinder honing it by hand unless you have cylinder torque plates and a hone with a micrometer adjustable head.

If you remove the piston it does need to be re-honed and new rings.

Pulled heaps and re-installed Evo & Twin Cam and no issues at all.
Internet myth this re-honing and new rings.
Never heard about it until I read it on the internet and can't for the life of me work out why I never had any problems 

If you pull the cylinder you should at the very least hone and new rings . The rings will not seat properly . You have to warm up an Evo before you ride . Not warming up the bike is the main cause of base gasket leaks . This is from over 40 years of wrenching on bikes . If you do a job, don't do it half assed or it will bite you in yours .

Or not

[Ironheadmike]

Yes you should use boring rings to hone . I never hand hone . Just because people don't hone doesn't make it right . Why do thing half asses . Harley have always done the cheapest and easiest thing possible . I personally have seen them reuse gaskets and seals . Sorry I don't gamble on anything .

[Ohio HD]

It's an Internet myth and an old wives tale to replace rings when pulling them from a cylinder.

Rings do in fact tend to move around the bore when the motor is running. So pulling them out and reinserting them changes absolutely nothing.


Piston Rings and Grooves by Wiseco

[Bagger]

I didn't see anyone mention leave piston in cylinder and remove wrist pin.

[JW113]

I guess that is a question of how many hands you have to do this. It is a real PITA to hold the cylinder, get those piston pin clips out, and then get the pins out of the pistons. But in my opinion, it's all moot. There is no need at all or any advantage to leave the pistons in the cylinders. Unless you don't have a ring compressor?

-JW

[Scotty]

If you do a job, don't do it half assed or it will bite you in yours .

40+ years as well and has not bitten me yet................

[kd]

Even without a ring compressor you can use a simple popsicle stick and your finger tips on each individual ring as you slide the barrel on.  You can stagger the ring gaps easily too.  A dowel of sorts under the piston allows you to slip the piston into the cylinder at a height that gives you plenty of room to work and see what you are doing.  It has worked so well for me that I have left my ring compressor in the drawer.  I now keep a few popsicle sticks in my tool box too.

[JW113]

Well I was kind of being a dick about the ring compressor remark, but now that you brought it up...

A popsicle stick? I'm trying to picture that one there kd. You have to hold the cylinder with one hand, so that leaves you with only one more to squeeze the rings into the bore. Hmm. Am I missing something? Please make a video of that next time you do it, love to see/learn how this is done.
 

OK... so do you cock the cylinder, start one end of the ring, and walk the popsicle stick around the piston until the other end is in?
 

I use one of those Rowe band type ring compressors, works perfectly.

-JW

[kd]

FWIW I am totally on board with you being a dick.    NO no just kidding.  I'm on side with the pull the barrel off and slip it back on method.    Wrist pin clips can disappear and in that situation and you'll neve know if it made it past that rag you have stuffed in your cases around the rod, stuck in the tread of your boot, under the bench or who knows where.   
 
Using the popsicle stick is pretty much as you envision it with the stick on the rings for reassembly.
Someone on here mentioned it years ago so I tried it. Dowels crossway on the piston skirt front and rear of the rod stabilizes the piston. Slide the barrel on up to the piston and feed it in to the first ring.  You no longer really have to hold it.  Remember that the spigot hole does not have a sharp edge in the bore so the ring will feed in.  One hand starts the ring in and the other gently coaxes the ring up to each end at the ring gap with the popsicle stick on the flat around the spigot until it slips inside. (it's helpful to have at least normal fingernails but the spigot depth and piston height gives plenty of finger room to start the ring)  The side of your hands by your thumbs and installed ring friction just naturally stop the barrel from dropping hard to the next ring.  Once there is a ring in the bore the friction is your friend. Rinse and repeat making sure the ring gaps are where you want them on each set before feeding them in. I found it so easy peasy that I am serious that the ring compressor is seeming to be more work.  Now, I can't say it would be a cake walk on a shovel or any other base mounted cylinder.  It sure works well with full length studs and the piston supported above the case deck.