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Need help diagnosing a problem


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good idea to replace the crank. spin the rods around very very slowly on the lower end and look for cracks in the bearing races. about 1 out of 5 used cranks that are in "great shape" have this issue.

 

oem cranks are nicely built but its about the same to replace the crank as have it rebuilt with all new parts.

 

i'd suggest if your going to keep it for a long time to get a HOTRODS crank or a sstar crank ( ebay) or call andy at M+M and get one from them use a fully welded crank and use NEW OEM crank seals. the oem seals are built differntly adn will hold up much better. if your not looking for top performance and are on a budget just stay with a 350cc crank.

 

top end if your not really racing it any piston will work fine , i'd say namura, ART ( oem) vertex, if your going to be revving it a LOT and going to be hard on it i'd suggest forged pistons. like WOSSNER or wiseco. the wiseco's quality as of late has been questionable. if your going to keep it i'd also suggest an update to the clutch, the stock trans , and installing a clutch pusher bearing. do the motor right and assemble it correctly , then make sure its tuned right and the motor will last a long time.

 

clean clean clean the bottom end. spending a lil extra time and buying good parts now will go a LONG long way.

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that seal kit dosent look bad i think i have used those in th epast.

 

you can see in the 2 crank seals the added brown stuff(?) that is a harder material and takes the higher RPM of the cranks much better without burning up. i have seen some seals come through here and DONT have that in them these are also the seals that have leaked after just a few months and needed replaced. be particular on your crank seals !!! you dont want to have to remove the motor and split it all apart again for a set of 15.00 seals..

 

use yamahabond grey on the cases OR import grey from autoparts store i personally prefer the import grey its not as "stringy"

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