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Do bad crank seals make a Cr250 hard to start?

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Bad crank seals, either stator side or clutch side, will affect the jetting and either make it run too lean (air leak stator side) or rich/sploogey (oil leak clutch side).  You may be able to check the plug and see if it is blac/sploogey or white and that should indicate which if either is bad.  You will be able to replace them without splitting the cases, but you will need a flywheel puller for the stator side,  and a new gasket for the clutch side. Exitable is correct that you will want to run a compression test and a pressure test prior to digging in to confirm the exact problems you will be facing.  Here is a link to pressure testing: http://www.thumpertalk.com/topic/432226-pressure-testing-a-2-stroke/

Edited by Iamcrakhed
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Most Cr series bikes access to the seals is easy, after removing all parts to them, the crank case is pressurized and no air leaks must be present, or bad running and performance will be the result, a good indicator is excessive smoking and fouled spark plugs, you can perform the task yourself, but you will need a flywheel puller, and some good shop tools and a torque wrench. good luck.

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How would i know if its the crank seals, not the top end

If top end is worn, it'd have a low compression reading.  To test, you'll need a compression tester

 

For crank seal testing ( also tests gaskets, etc ), you want to build a pressure tester.  You can read a how to, at the top of the Honda 2 stroke page.  Here:

 

http://www.thumpertalk.com/topic/432226-pressure-testing-a-2-stroke/

Edited by wykyd450r

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