Rebirth of a YZ125

baxterj787

baxterj787

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On the heels of Southside Honda's closure (aka Troy Racing): I picked up a locked-up 2003 YZ 125 from their "warehouse" for $400. The piston let go at very high RPM and took out the crankshaft and cylinder. I have a bottom end "kit" coming from a retiring kart racer for $170.

Now the BIG question: Do I go for an Athena 144 kit or go back to stock. Keep in mind I am doing my own work (Certified H, Y, S mechanic for many, many years) and I am a cheapskate. At least I'm honest.

Bike already has a PC exhaust, PC suspension, Hinson clutch basket and pressure plate and a VForce reed cage. Anyone have experience with the Athena bolt-on kits? Any other tips or pitfalls of this era YZ?
 
I woudent get the Athena from what I have read a lot of people were having problems with them. They were saying your better off sending it to gorr.
 
Athena kits now have an update solid head that has fixed the problem, I know because I just put the new design head on mine and problem solved. The 144 is the way to go, the power difference is worth it !
 
Cool. Thank you both for your feedback. I am familiar with Eric's work. Top notch in my book. I will strongly consider either route in the near future. Bottom end will be reassembled in the next week. This bike will be fun either way (125 or 144). First 125 I have owned since 1992.
 
yeah for sure go 144 i have one also and love it. But unless something elso has changed with the athena dont put the bottom end back together because you have to split the cases to install it. You have to grind something i thnik which is totally stupid to me that it does not just bolt on.
 
I was aware that I need to grind the cases for a 144 conversion. I put my foot in my mouth when I mentioned buttoning up the bottom end next week. I know they run a lot better as a 144, but I weigh in at 150 with gear and frankly the 125cc configuration from Yamaha runs pretty good. I may take the cheap way out and leave it stock displacement, as the bike will likely be ridden 6-7 times a year. Thanks again for the input.

I'll refrain from posting pics. The last thing anyone wants to see is a con rod that looks like a banana. Might give the 4t owners some cause for concern!
 
Since you're splitting the cases, why not go ahead and grind away the needed clearance on the cases anyway in case you get the 144 in the future?
 
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