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2011 crf450 crankshaft play

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Just rebuilt my 11 crf450. New crank and bearings. I didn't notice when I took it apart but I have side to side play in the crank. Is that normal? I have the whole bottom end of the motor assembled accept covers and also notice the slightest up and down movement as well when I lift up on the flywheel.

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Just rebuilt my 11 crf450. New crank and bearings. I didn't notice when I took it apart but I have side to side play in the crank. Is that normal? I have the whole bottom end of the motor assembled accept covers and also notice the slightest up and down movement as well when I lift up on the flywheel.

 

The side to side play should be taken up as you tighten up on the drive gear bolt. Things should snug things up against the inner bearing race on the right side of the motor.

I have found up and down movement on the flywheel sometimes when new bearings are installed. I assume it's due to the left roller bearing design.

This bothers me because it means the whole crank, rod, and piston are floating around which in turn affects the rings ability to seal. And even though the lower end is newly freshened up its still "loose". Who knows maybe if it were tight heat related "bad things" would be happening.

 

Maybe someone here with background in thermo design engineering (if thats what its even called) can comment on what happens as things heat up.

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I found a little side to side movement to be normal and the service manual calls for crankshaft side clearance to be between .30mm - .55mm. I'm assuming this is due to the style bearing being used on the flywheel side.

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i have put new cranks in 2 of my 450s and there is some movement up and down. i changed main bearings,also, the roller bearings will have some movement they have too for oil and expansion from heat. it is normal to have this,

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The play in the left side roller bearing shouldnt be enough to allow a .001 feeler gauge inbetween the crank pin and the rollers. If you can hear the play but not feel it (in the main bearings) thats fine. Lateral run out isnt an issue. The crank is sandwiched between the main bearings. If there is a lot of slop laterally, there may be an issue with the rightside crank pin being undersized. You shouldnt be able to detect any play up and down in the right side. If you can, you need to investigate where its coming from (Bearing ID or crank pin OD) ideally this is a  press fit.

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