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base gasket exchange

23K views 26 replies 14 participants last post by  2wheelrider 
#1 ·
About to change heads , so is it imperative that base gaskets are replace as well? If so what is required (tools,piston ring compressor ect) Thanks inadvance Dukcarver
 
#3 ·
Anubisss Thanks for your reply, just curious have you tried this or are you speculating (as I am that reusing base "o"ring will be good). Of course I will not be disturbing cylinders, just installing head gaskets. Dukcarvr
 
#4 ·
dukcarver,

I have removed and replaced a cylinder head for repair without disturbing or changing the cylinder base o-ring. It's best to be careful not to disturb the cylinder and "break the seal". If the o-ring has been in there for long it will have flattened and you may not be able to get it to seal again. Why not replace them? All you really need is a ring compressor, a TC's cylinders are "unbolted" once the head bolts are off.
 
#5 ·
I have pulled the heads on my 117 w/o replacing the base gasket. My 117 does not have O-rings but cometic base gaskets. So far I have had no problems(leaks). I did not remove the cylinders and took great care not to disturb them wile the heads were off. If you do feel the need to replace the base gaskets or O-rings you can sometimes pull the ristpins out without pulling the piston from the cylinder depending on the compresson hight of the piston, to install a new base gasket. That way you don't need to worry about re honing or new rings.
 
#6 ·
I have always wondered why people say " if you remove the piston from the cylinder, you have to hone and replace rings "... Why? Why not just put it right back together with the same rings and same cylinders? I have done this on briggs v-twins with no problems...ever....
 
#9 ·
I also think that it would be possible to pull the pistons from the cylinders....most of the time. Maybe even every time. I not willing to break new ground in this area. Its just as easy to leave them in the cylinders.
 
#7 ·
Streetglidekirk I agree with you,if the piston is back in its original jug ( which it has too, to be correct) why would a hone & rering be needed! But I do like 2wheelrider's way of getting around that issue(leave the piston in the cylinder). This is getting interesting ! Any body pulled cylinders installed base gasket and not honed or reringed successfully ? dukcarvr
 
#10 ·
Yep, pulled the cylinders on an EVO for base gaskets and reinstalled w/o hone using the same rings about 85,000 miles ago. No problems or excessive oil consumption yet, but those damn base gaskets are seeping again.
 
#8 ·
I have pulled heads and changed only HG before. If you want to change the base o-ring, you can pull the cylinder up until you can remove the wrist pin. Then you can leave the piston in the cylinder. If it were me, just pull the head and change the head gasket and forget about it.
 
#11 ·
I talked to a buddy of mine that builds top fuel drag bikes. I asked him this question on the cylinder and piston ring deal. He said that it is possible to remove and reinstall the cylinders with the same rings, but to not let the rings rotate for best results. He said if he were to do it, he would do as mentioned above by leaving the piston in the cylinder and remove the wrist pin.
 
#12 ·
If you're not going to replace the heads immediately, get some 1/2" PVC couplings and use them with two of the head bolts to keep the cylinders in place until ready.

Roger
 
#13 ·
So lets say you just replace the head gaskets, then the 0-rings leak. It happened to me on both cylinders when the bike had about 5K miles on it and Harley covered it.

What are the costs for you to go back and redo the job to replace the O-rings if they leak? How many miles are on the engine since it was done? If it's a lot, then thats a lot of heat cycles. If I tried to cut this corner, they'd leak. But it's just the way things happen to me I guess. :whistle:

Chris
 
#14 ·
I've pulled heads on a couple with 20,000+ miles and never had any o-ring leaks. I have nuts made to screw onto the cylinder studs, I immediately install them and snug them down when I pull the head. As the_tunaman suggested PVC will get the job done also.

 
#15 ·
I myself would not hesitate to replace the 1.99c O ring, Its just too much hassel to go back in, but thats just me I guess.
 
#16 ·
I agree . ....$2.00 "O" rings VS leaking base gasket! Got to put the "O" rings in! BUT weather to hone & rering OR pull out wrist pin OR Remove piston from cylinder ,install "O" ring , then install piston in bore without honing or reringing ? I am leaning toward removing wrist pin with piston in the bore . I (we) Would like to hear from people who have attemped this "short cut" ! Any details or tips would be very helpfull. Also I am assuming thst no soecial tools are required & that after removing wrist pin "c" clip. Piston pin should easely push out while "buddy"or wife hold & support piston/cylinder assembly . I suspect that removing & reistalling 1 cylinder at a time might be wise . Any more thought or tips would be help full . Thanks for helping me now & some else in the future. Dukcarvr
 
#17 ·
The best tip I can think of is....After you raise the cylinder up a few inches, take a clean towel, and put in the cases around the connecting rod, to prevent ANYTHING ,ESPECIALLY A WRIST PIN CLIP,from winding up in a place where you do not want it to go. Have your manual handy and a torque wrench....Good luck..
 
#19 ·
I would do what every one else has said and I would do both cylinders at the same time..easyer to get the rear one out that way Also pin the rear jug down with the stud bolts and 1/2 in PVC couplers that way when you push the wrist pin out you can lower the rod out of the way by turning the motor over slightly. Also you will have to turn the jug with piston so the piston will clear the studs to remove it or... push the piston back up inside the cylinder to get it past the studs. Use new cerclips when reinstalling the piston on the rod. Make sure you have the back wheel off the ground to turn the motor over.
Good luck
 
#22 ·
A lot of people dont understand what the honing process is for. When you hone and leave the "cross scratches" , it leaves the cylinder like sand paper. This is what causes the rings to wear to cylinder, creating the right seal.... If you can find high compression pistons to fit your bore, then hone the cylinders to specs and install... But there is more to it than that. You need to know what the compression will be, how thick of head gasket to use, will the heads flow enough, will you need compression releases, etc.
 
#24 ·
Thanks to all for the input ! Yesterday I yanked the jugs as suggested by lifting just enough to push the wrist pins out. however when the cylinter was about 4-5/8" up the studs, I slipped 4 pieces of 1/2" PVC conduit cut 4-1/2" long with a slot about 7/16' wide cut . This formed a long "C" and then rested the cylinder safely on the 4 pieces of conduit. All went as predicted and today I got out for a 40 mile ride with my wife. She on her trike . By the way the weather here in Southern Ontario has been has "Great "for the last week. Tons of scooters out.
 
#25 ·
Yup, weather has been crazy, hasn't it. Got to break in the 120 and run some vtunes in the last week. Warmest March ever.
Ron
 
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