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another '90 CR250R rebuild

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Hi Guys,

I'm finally getting around to completing the rebuild of my 90 CR250R. I've owned the bike for about 7 years and bought it as a project. So far I've stripped it out and had the lower frame rail dents repaired and had the frame powdercoated back to white. I'll upload some photo's in the next couple of days.

Look forward to getting some feedback and advice 

Cheers

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The frame lower rails were rusty and dented, so we weld repaired them after sandblasting the frame.
Once that was finished off to powdercoating. I'm pretty happy with how it's come out.

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Nice. Really like the white frame. 


Thanks, yes it looks so clean. I'm looking at frame guards to keep it looking good for as long as possible
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Pulled the top end off today, the head has seen a bit of action, not sure what I'll do about the damage marks yet. The cylinder has some scoring and obviously the piston is toast. Not great, but not the end of the world either.

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Those " damage " marks in the head will be fine. If it was my head I would 100% run it no problem. 

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Just heard back from my machinist, cylinder has a sleeve which has cleaned up with a hone. We'll fit an oversized Wossner piston and call it good. Stoked it's only costing half the price I budgeted...

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I've picked up the barrel from my machinist, came up well with a hone. I went with a Wossner piston and will drill the exhaust face (photos of that to come).
Picked the other obvious parts: gasket set and small end rod bearing.
There's a set of new fasteners for the bike as well, to add a bit of detail to the rebuild.
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Oh yeah, the sleeve in the barrel has some pretty rough grinding marks where the PO ground it to fit. I'll tidy them up with a dremel before a final clean up.

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I'm starting to think ahead a little and need some advice about suspension. The '90 forks have a terrible rep for being harsh, so I'm keen to hear from anyone with experience on improving the handling.

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Progress today with the recommended modifications to the Wossner piston. Measured and drilled with 2mm holes facing the exhaust bridge.
Deburred and tidied up the steel sleeve and casting marks in the intake port.

IMG_1162.JPGIMG_1157.JPGIMG_1161.JPG

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Progress today with the recommended modifications to the Wossner piston. Measured and drilled with 2mm holes facing the exhaust bridge.

 

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Why did you drill the holes?

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My machinist, who runs a well known 2-stroke race engine shop here in Brisbane recommended the holes. There's a thread here on TT about it somewhere too that I read up on, helps cooling of the exhaust bridge which they say is the hottest part of the engine. I figured the holes are small and I've deburred them, so it's not going to do any harm...IMG_1163.JPG

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I guess I could try it when I eventually do a rebuild


I'll definitely post if there's any issues with cracking etc once there's a few hours on the motor
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