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machman

XR650L gasket question with 101mm piston kit

18 posts in this topic

Hey guys,

Going to a 101 JE 10.5:1 piston. Do the OEM head and base gaskets still work?

probably getting sick of my replies(LOL) by now but are you saying to reuse the originals? i would say inspect very closely and if you see nothing wrong, go ahead and reuse.

if you have the extra cash, replace.

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I'm not sick of any replies! Just happy to have valuable input:thumbsup:

No, I've already got a new gasket in my possession. It's just 100mm OEM size instead of 101mm like my new piston, and soon to be cylinder.

I'm just wondering if I should buy a couple new gaskets from Cometic for the 101mm size.

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i just looked at xr's only and the only 2 listed(that i can find) are the cometic 102.5 and 103 gasket kits. they have different part numbers, so i'm ASSUMING that the 100 and 101 sizes would have different part numbers too. making me think to buy the 101 kit.

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I'm sure that the base gasket is OK since the sleeve goes inside it. However this is not the case with the cylinder head. You don't want the head gasket to be intruding into the combustion chamber. If the hole in the gasket is smaller than the bore then get the larger gasket.

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Hey guys,

Going to a 101 JE 10.5:1 piston. Do the OEM head and base gaskets still work?

I won't use a Cometic gasket again, both the head and base gaskets leaked after a few months. I tried to re-torque the head but it still leaked. I check the flatness of the head and cylinder, both fine. I installed an OEM head gasket and all is well. The OEM head gaskets are far superior to the Cometic junk. Cometic may work for some, didn't work for me.

MGS

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I didn't use a oversized piston, I went with a 100mm Wiesco and just honed the cylinder as the motor only had a few thousands miles on it.

MGS

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1. Try annealing a cometic gasket and install with yamabond. 2. or machine a groove in the sleeve and use a stainless steel wire for a fire ring. 3 get some 9mm studs made that seemed to fix everything but they are about 10 bucks a piece without the nuts. Finnaly got the big bore to seal with all three of these ideas.

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Machman, great question. The 102.5 should be used with the 101mm thats size will fit for both. Replace your gaskets when you do your head work dont keep the old ones.

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I've got new OEM size gaskets. I'm thinking I'll just cut out the extra 1mm with an exacto knife using the new piston as a template.

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I just completed my top end rebuild and I used a new stock gasket with a 101mm JE PISTON.

This tread never really came to a firm decision whether this is okay or not?

When installing it I did not notice the gasket encroaching into the cylinder space. However I did not examine it up close. There was nothing obvious.

Any firm definitive info as to whether this is okay or nay?

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I used the stock gasket with a 101mm piston for a couple thousand miles without issue.

I replaced it with a thicker copper gasket to reduce compression and combat detonation.

The stock gasket looked fine when I removed it.

If you measure a stock gasket, I think its around 101mm

The cometic gaskets look pretty cheap to me, i wouldn't use them...

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Thanks I will keep it on unless someone gives me a reason to change it. So far it seems to run great. Thanks for the reply. If any one else has anyother info please let me know.

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I used a stock OEM gasket on my 102.5 bore. I was a little worried about size so I mounted it carefully in a vise with jaw protection and used a hone to re size it. It didn't take long and was perfectly round. Finally found a use for my hone after all these years of sitting on a shelf.

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