Rebuilding, I have some questions ???

1 reply to this topic
  • jasonmcc

Posted February 09, 2001 - 10:54 PM



I have ridden my 1999 wr400f for the last year just about everyweekend sometimes more and have decided to rebuild the topend of the motor.

I pulled it down and noticed a few things: There is no bush or bearing in the small end of the conrod ? have some small pitting on the piston pin and in the small end if the conrod. Is this ok i'll replace the piston pin. The next thing is the cylinder bore there is some really fine scratches/scuffing on the intake and exhaust sides of the bore and like wise on the piston skirt. Is this normal and ok. Is there any prepartion for the bore before reassembling. I have heard using scotch brite to lightly cross hatch it.

Next, it looks like it will be hard to get a torque wrench in to tighten up the camshaft cap bolts what should I do just tighten them up to what I think is ok. Also how can you torque the 4 external nuts that bolt the head on, they are so close to the cylinder you couldnt get a torque wrench and socket on there. And finally could someone explain the cam dot alignment to change to yz timing.

Thanks a lot !

Jason McCarthy

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  • Boit

Posted February 09, 2001 - 11:27 PM


there is no bushing at the small-end. Replacing the piston pin certainly won't hurt, but don't be alarmed by the small grooves(pits). Reassemble with good quality asembly lube...and just use a smear...not globs. Those globs will show up in the oil filter.

The scoring on the intake and exhaust side of the cylinder might be normal. However, changing the oil more often might help here.

Getting a torque wrendch on the cam caps is not that difficult. Just use the proper incremental wrench with a short extension, and you are there.


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