If i remember correctly i have about .9 mm squish and jetted a skosh fat.
I loved the stock o rings. They didnt seem to know the difference between 15 and 25 ft/lbs of torque. They just sealed. I love the way my bike runs, but hate the suspense the head gaskets give me.

The athena 144 kit calls for 1.1mm not .9mm( is for the 125cc kit and race fuel ) that would be your issue right there. I had 50 hard hrs on athena 144 kit (old kit with orings and never had an issue ) always ran 1.1mm squish though. even ran leaner then stock jetting.

The athena 144 kit calls for 1.1mm not .9mm( is for the 125cc kit and race fuel ) that would be your issue right there. I had 50 hard hrs on athena 144 kit (old kit with orings and never had an issue ) always ran 1.1mm squish though. even ran leaner then stock jetting.

I dont know about that. All my issues are at startup immediately following rebuild. If the head will seal up then, it will stay sealed. We are talking about gaskets, not orings. I have no doubt the orings work better than the athena head gasket. The motor was built to run .8-.9 mm squish.

The oring kits were the original and the gasket came later due to issues costumers were having. My opion is assembly issues are th whole reason there were so many problems(noone reads the instructions) 1.1mm is the stated aquish in instructions if you are not running that how is it the kits fault

Well i know tightening up the squish would load the gasket more, but crap man i kinda thought a $45 gasket would handle it. I mean, the athena kits arent cheap, and they know people are gonne lean on them, its not like they are marketing them as industrial vacuum cleaner motors or something. And cwtoyota, no they do not give you more gaskets to alter squish, which seems lame if the one they give you is gonna pop if you cross the 1.1 mm barrier. So i stand by my comment that their head gasket=poop. Though i am curious as to what other folks are running as far as fuel and squish and timing, etc.

Tightening up the squish has nothing to do with squishing the gasket more. Squish is the crown to head clearance. Too much crown to head clearance leads to detonation. Detonation eats head gaskets.

Did someone on this thread suggest that they thought squish meant squishing the gasket more?

Remember, detonation kills head gaskets.

My 87 CR 250 eats aftermarket head gaskets. I get about 5 hours on the aftermarket gaskets. They are a pressed graphite gasket on a steel core with a steel fire ring. The gasket fails suddenly and catastrophically. The bike will be running fine and the next time you go to start it you'll push the water out the overflow on the radiator due to compression leakage. The fire ring is thin and splits. Probably due to minor detonation.

The factory Honda gasket is a multi-layer steel shim type. It's expensive at $20 but never fails. The Honda doesn't require you pull the head to do a piston so I'll run 3-4 pistons on a single head gasket on that bike.

Do the 125 Yamaha's run a head gasket? The 250's use o-rings.

I don't run aftermarket gaskets anymore. Even simple ones like cylinder base gaskets. I recently replaced a Moto Gasket brand base gasket on a cylinder that squeezed out after a rebuild. It was immediatly clear after disassembly (no loose bolts) that the gasket experienced a chemical attack from the fuel. The fuel wasn't the problem, it was the rubber binder in the gasket that failed.

So is the 144 kit for sale?