Jump to content
Sign in to follow this  

CRF450 crank plug?

Recommended Posts

Can anyone tell me what the plug is for in the flywheel side of the crank. Is it maybe a check valve for oil flow? It's in the oil flow circuit from the filter/pump but i don't see how the oil gets by it.  I pushed it in by mistake using a 3 legged puller. .

Share this post


Link to post
Share on other sites

 I pushed it in by mistake using a 3 legged puller. .

Forget the valve for now, did you use that puller on the flywheel? Becuase if you did, you probably destroyed the crankshaft. Look at the carburized end of the crank and see if it is now smashed in/mushroomed

 

It is a relief valve. If the valve got smashed in you will need to extract it. Try do do so with care. If you have to destroy something to get it out then destroy the valve as they are only about 12.00 US to replace

Edited by mrmoto35

Share this post


Link to post
Share on other sites

Forget the valve for now, did you use that puller on the flywheel? Becuase if you did, you probably destroyed the crankshaft. Look at the carburized end of the crank and see if it is now smashed in/mushroomed

The end of the crank is OK. I tried the puller with a small amount of force to see if the flywheel would come easy. It wouldn't so i stopped.

Share this post


Link to post
Share on other sites

It is good that you stopped. If you do a search you'll find many people destroyed their cranks using anything but a CRF specific flywheel puller

Share this post


Link to post
Share on other sites

I drilled and tapped it and used a 6-32 screw to pull it out. It is just an orifice to control oil flow. I put it back in.

Share this post


Link to post
Share on other sites

If you drilled and tapped it, it is now a larger orifice. I would assume that some other oiling circuit would now be starved of oil if you run the bike with a larger flow area there.

Share this post


Link to post
Share on other sites

Yes it controls the oil flow. If you have made the hole bigger, the pressure will drop as a consequence. If you continue to run the motor like this, you risk oil starvation and a very big repair bill down the track. Bite the bullet and buy a new crankshaft. It will be cheaper in the long run. Its an expensive lesson, but you are hardly the first.

Share this post


Link to post
Share on other sites

Depending on how much bigger the hole was drilled it might not be a problem.

These motors run basically 0 psi oil pressure.

And flow oil primarily to keep the parts cool and lubricated.

The only place requiring pressure is the case jet under the piston.

I don't know any way to measure the pressure or flow there.

I remember reading a post from Ron Hamp where he was experimenting with enlarging the oil feed hole at the end of the crank, with the goal of extending the lower bearing life. .

Share this post


Link to post
Share on other sites

Thanks for the good info. I drilled and tapped only about 2/3 of the way through. I still have the original orifice bore in tact.

Interesting about the oil pressure. I wondered how to check the pressure at the top of the engine. After a rebuild I run the engine a few min and then check to see if I have lots of oil at the camshaft.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×