hey team

i have just purchased a brand new os tr r spec
awesome engine i bought it for backup as im already using one.

i thing i wanted to ask was why does the crankshaft move back and forth slightly ? meaning i can hold the engine by the crank case and pull the crank shaft back and forth a fraction. say about 1-2mm of movement

ive owned many engines and ive never seen this. i took off the engine backplate and all seams normal inside.

should this be ok ?

thanks
John

mrgsr... It's one of 3 things... Worn bearings, worn out con-rod or a worn crank pin... Check these 3 things out and see which one you should change... Best bet would be to change all 3 if the piston and sleeve are in good condition... Remember, over time, everything in the motor will wear out and need replacement...

Rc_Alan

He said in the original post it is a NIB engine. I would think it has a dud bearing. Take it back to the shop you bought it from for warranty.

Same thing with mine. Relatively new, only run about 2litres through it. And I thought by bearing was a gonner... apparently not...

Hey John, you have 2 of the same engine right? Does this happen with your first engine as well?

the engine is brand new i removed it from the shrink wrapping and packaging myself.

no my other engine does not do this, how can i inspect the bearing ? im pretty sure its not the other pics as its just the crank that moves back and forth.

thanks guys
john

tolerance too big between bearing and crankshaft. it usual happen on the bearings. check the size of your two crankshafts. if they have the same size,then just replace new bearings. You need a digital caliper.

i wonder if this movement will go away when i put on the flywheel and tighten up the clutch set up ??

ill strip the engine apart later tonight and then ill get one of the racers at the track tomorrow to check it out.

thanks guys
will keep u all posted

So it is important when you put on the flywheel cone,you need to make sure the crank stay at the forefront place. After you tighten up the flywheel nut,you can check again.

msgsr,

This crankshaft movement is completely normal. By design the crankshaft has movement until the flywheel is installed and the torque applied to the flywheel nut pulls the crank up against the large bearing. The only thing stopping the crank from moving inward when the flywheel is removed is the crank pin touching the back plate. Basically the movement you are feeling is the clearance between the crank pin and the backplate, If this clearance is inadequate, then you will get con rod rubbing on the back plate, (you still may though, due to the fact that the con rod is basically a floating unit). I hope this answered your question, and relieves your worries.

By the way, if you have crank movement after installing the flywheel and torqueing it down then you prabably have either bearing or crankcase issues.

BK

Yes,a little movement is normal. But I have seen some engine that when you rotate the crank,the bearing does not rotate at the same time. When it happen I will replace a new bearings.

Dino, Yes I to have seen this. Usually when this happens the crankshaft is slightly undersize where it contacts the inner race of the bearing. I would replace the crank in this situation. However, very rarely, the bearing race is suspect. But on average a little in and out play on the crankshaft with the flywheel off is normal, even desireable.

BK

You are right,Brian. But he said it is a new engine so I'm try to explain how and why. That is why I asked him to check the crank size of his two cranks.
Most engine manufactory produce all parts except bearings.(of course I knew some manufactories produce bearings self) Most of them just buy bearings from big bearing manufactories or bearing suppliers. Engine manufactories can control all the sizes except bearings. Sometime it is hard to control the bearing size. Maybe this batch it comes with 7.00mm inner ring,but next batch is 7.02mm inner ring. If your crank is 6.98mm designed for 7.00mm inner bearing ring,but you got a bearing which has 7.02mm inner ring? With a 0.04mm tolerance you will feel it loosely. But if the tolerance is too small,it is hard to assemble.

Dear Valued Customer:

Thank you for your Email. We are the O.S. service center in North
America.

If you have nothing mounted to the engine (flywheel, clutch, etc), then
it's normal for the crank to move in and out of the bearings. When you
get the flywheel/clutch assembly properly-mounted, there should be
virtually no fore-and-aft movement of the crank.

We hope you find this information helpful. Should you have any further
questions or concerns, please do not hesitate to contact us at this
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Anyway i installed my clutch setup and their is no more movement. problem solved
thanks to everyones input