Well after a year of nothing but trouble with my daughters athena YZ144 conversion I gave up and it's going back to an OEM 125. Can no longer stand the blown head gaskets, replating cylinders, expensive gasket kits and towing her back to the pits. having spent over 1500.00 on top end parts in the last eight months not counting the 680.00 for the big bore kit i ordered a new OEM cylinder $377.00, New OEM head $81.00, power valves $220.00,Piston $89.00, Gasket set $31.00 Worst decision I ever made on bike mod to do the 144 kit. Hopefully return to the orginal relability with the OEM top end in 125cc

Sorry to hear that. Good luck with the 125

What brand 144? my son has a Athena GYTR 144 and it is as reliable as my other sons stocker, ran both all last year no issues.

The Athena kit is really tempting, but I've read so many accounts of problems with head gaskets that I won't buy one.
On the other hand, I've heard as many or more reports of excellent reliability.

They must have some kind of quality control issue, or a design flaw.
I've heard that some Athena kits are two piece heads and some are one piece?

Does anyone actually know the differences and the actual cause of the problems?

Well ours is one piece using a metal fibre gasket. It refuses to stay water tight more than an hour. If you do a cross country race odds are high the bike will sieze. This results in a replating new piston and Athena over priced gasket set. Also the added expense of running racing gas has to be caculated too. We should have just stuck to her gas gas 125 but she wanted more juice for MX tracks even though we primarly race woods.

Athena parts are a lot of money and often you are left hanging waiting for a new batch of pistons to be manufactured. Last time I cracked my 490 piston I waited 8 weeks for them to fabricate a batch of pistons before they shipped it to me.
Head gaskets are a fortune. I myself have never had any reliability issues with my kit, but that is apples to oranges.

The Athena YZ parts are readily available , and not much more than stock, I rode our 140 miles in one day on single track near Temple Mountain Utah, on a red trail. I only run 93 pump gas , and the bike never whimpered or seeped or skipped a beat. There must be something worng with your set up? Jetting? surface of the sealing area? Dont have an answer, except to say, the Anthea setup we have rips, will pull 250fs in a drag race and a light weight racer.

ncc, on 08 February 2012 - 07:46 AM, said:

Hmmm what type of racing do you do most? When we do 2 hour or more XC races you can count on head gasket failing. Jetting seems spot on and no signs of detonation as long as you run 100+ octane. Funny the Wiesco 125 piston hit the front porch while I was typing this. now if motosport will get me the cylinder before the 17th we can make opening on her YZ. If not looks like she is back on her KX100 for a bit

With all those issues I tend to agree, there has to be a set up issue.
Jetting, crank seal, squish, warped head, something which is fixable.
After all it is mechanical.

gruberyz, on 08 February 2012 - 07:55 AM, said:

What type of riding do we do? You do know a "red" trail is the most difficult ? and 140 miles in one day is quite a bit more tan a two hour XC race.
We also motocross it every other week during spring , summer and fall, race indoors during the winter, all in the desert, plus ride right from our house down the street to two local tracks three to four times a week. I dont waste money on 100 octane gas, just 93+., This bike takes a beating and keeps on coming back for more . I am just thinking there is something else going on with your setup?

Hey gruber i have issues with my athena head gasket also. New cylinder and head, head machined flat as a pancake as is cylinder. New studs that i dont think are moving. Torqued to specs by OCD man. And it will still leak upon startup. I have found the only way to get it to seal is to apply several coats of copper gasket spay stuff. Which seems like a geto way to fix a $45 gasket. FWIW, once i get it sealed i can beat on it and it doesnt leak until i tear it down. But i only have 40 hrs and 3 teardowns so far.
You dont have to use athena piston, btw.
I have no idea why athena went away from the oem o-rings, they are awesome and cost about $3. If i had to do it again, i wouldnt go near an athena kit, not in a million years. Bore your stocker guys.

I bought a athena 144 cyl off of Erric Gorr with his majik done to it, and his power valve in it and he modded a stock head for it (pump gas 91oct) bolted on to it,and I topped it off with a HGS 144 pipe. I couldnt ask for a more reliable ,easy to tune in set up,had this set up for about 3yrs now ,rock solid. Erric G and a 144 pipe is the way to go!

john484, on 09 February 2012 - 05:42 AM, said:

Yeah the longest it ever went without blowing water was when I doped it up heavily with copper coat. Except when it did let go the radiator had copper coat floating around in it. I'm hoping to have all the OEM parts here this week to get Amanda started on the 2012 XC season.

Have not notice anyone stating their squish measurement or if they were running leaner jetting?

I think it is the metal malish stickers personnaly

BRM, on 12 February 2012 - 02:44 PM, said:

Hey she won those as part of her swag after a MX series. I can garuntee I would never have bought them. Still have the ones that go on the airbox and fenders if you need them

So is the 144 kit for sale?

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 way to do it is to send off the OEM cylinder and get it bored by one of the big name guys

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.