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99 Yz144 Big End Bearing Fix


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I have a 99 yz 125 fitted with an Athena 144 kit.

 

The thing is an absolute blast to ride (heaps more fun than my KTM 350) and the kit holds up well, but I have problems with not enough lubrication getting to the big end bearing and the crank seizing with all the plastic melted around it.

 

I read in Eric Gorr's book that it is a problem with the model (97 to 2000?) and that you need to bevel the plastic around the pinholes to allow more pre-mix to lubricate the area.

 

My question is whether a newer model YZ crank and bearing has metal instead of plastic covers and if it would fit the 99?

 

Any thoughts would be appreciated.

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1998 to 2000 are supposed to have

the same cranks. Have a 98 that has

been everywhere, including Glamis,

where it was pinned wide open all the

time, and never had any problems ?

Which oil / ratio are you using ?

Using Yamalube at 32:1.

Motul 8002T also has good oil

film strength.

Can get a complete aftermarket bottom

end rebuild kit these days for under $200

A couple different manufacturer part #'s

are WPC124, and 421-4035.

Or, Yamaha rod kit part #'s

4PE-11651-02-00 ...ROD, CONNECTING 1 66.99

3JD-11681-02-00 ...PIN, CRANK 1 1 36.99

90209-22071-00 ...WASHER 2 6.31 93310-522P7-00 ...BEARING 1 36.56

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I have a 99 yz 125 fitted with an Athena 144 kit.

The thing is an absolute blast to ride (heaps more fun than my KTM 350) and the kit holds up well, but I have problems with not enough lubrication getting to the big end bearing and the crank seizing with all the plastic melted around it.

I read in Eric Gorr's book that it is a problem with the model (97 to 2000?) and that you need to bevel the plastic around the pinholes to allow more pre-mix to lubricate the area.

My question is whether a newer model YZ crank and bearing has metal instead of plastic covers and if it would fit the 99?

Any thoughts would be appreciated.

Beveling the stuffers seems like a sound idea but no experience myself. Look into buying aftermarket metal crank stuffers which should help but don't think it will fix the lube problem.

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