ATC 185s Big Bore problems, halp!

[BenATC185S]

Hey guys in bit of a conundrum as to whats wrong, hope you can help!


my ATC 185 with a 65.50mm Bore Wossner Piston kit in it has gone through its second head gasket, I say gone through they both just seeped oil and let the odd puff of smoke out of the right side between the cylinder and the head - compression is very good. the first time I rebuild it it was with regular whatever OEM gasket off of ebay, second one was a NOS oem. i heard you used to be able to get copper gaskets but i have searched high and low for them but no joy. torqued correctly to 14 ft/lbs like the manual says. stumped.

anyway going to wait a while and think of all avenues before i rebuild it again. please help, thank you very much!

Regards, Ben

[ATC-Eric]

Could have a warped head. I have an issue with my current 200 with the o-ring for the oil passage. The head gasket I used looked like it had a built in "seal" for that passage. I know an o-ring went there from the factory, so I threw it in. Well now the damn thing is leaking because of it.

But I would start with checking the head for warpage.

[BenATC185S]

Could have a warped head. I have an issue with my current 200 with the o-ring for the oil passage. The head gasket I used looked like it had a built in "seal" for that passage. I know an o-ring went there from the factory, so I threw it in. Well now the damn thing is leaking because of it.

But I would start with checking the head for warpage.

Thanks for the reply Eric. yeah I put the o ring your talking about on too, top left i think isnt it? when i got the engine is had never been apart before and there was one there so im sure its meant to be there no? not 100% but i dont think the head is warped but i could be wrong, will add it to the list the next time in take it apart. thank you.

[HairyJR]

Like Eric mentions check for warped head and cylinder. A mistake I've seen people make is using American sized style O-rings instead of metric sized. Torquing head with 3 or 4 equal step up torque values to final torque. There is a difference in torguing lubricated or non lubed nuts. Lastly another option is using a copper head gasket, use a sealer on sides of gasket faces. Contact a fellow member "Jwheeler" on here think he may have gasket you can purchase.

"HJ" 250772 :beer

[BenATC185S]

Like Eric mentions check for warped head and cylinder. A mistake I've seen people make is using American sized style O-rings instead of metric sized. Torquing head with 3 or 4 equal step up torque values to final torque. There is a difference in torguing lubricated or non lubed nuts. Lastly another option is using a copper head gasket, use a sealer on sides of gasket faces. Contact a fellow member "Jwheeler" on here think he may have gasket you can purchase.

"HJ" 250772 :beer



Maybe, it has blown in the same spot twice now so it could be the issue, gasket is visably saturated aswell. i just shot him a message. thank you hairy! :)

[yaegerb]

I will echo a lot of comments here. Use a copper head gasket and I would blue dykem the mating surfaces and hand lap to see if it is warped.

[shortline10]

Here’s the copper head gasket .
https://www.ebay.com/itm/Honda-ATC-185s-200s-1981-1985-Big-Als-Top-End-Gasket-Set-NOS-Aftermarket/162901554416?hash=item25edb074f0:g:hdMAAOSwmSdaZ8I Z&vxp=mtr&redirect=mobile