Jump to content
Are Project Bikes Even Worth It? Read more... ×

I didn't know there was a spring under the plunger for the cam shaft and lost it

Recommended Posts

Hi,

First time working on my XR400, took off the head and cover. I removed the plunger that fits into the head which runs up against the cam shaft but did not know there was a small spring underneath it. I spent an hour sweeping the floor looking for it, its gone. Can I use a spring of similar diameter? Am I screwed.

Thanks, Terry

Share this post


Link to post
Share on other sites

Its the manual decomp. You (should) have an auto decomp. You might not even need it but it's nice to have especially if you dump the bike riding. Here's what I'd do. Put it back together without it. See it you even need it. Its not a 600, but its not the 250 either. Sometimes anything to make a pig a better starter is totally wanted. But what I'd worry about more is if it fell into the motor. But its nothing that'll cause excessive damage. Maybe some scratches but it'll get chewed up. But yeah, put it back together and ride. Save up for #4,5 and decide if you need it. When you do and have it, just pop the hood and throw em in. An hour with many beer sips minimum.
Always best to work with schematics. If you had been looking at a schematic 100x a day everyday while waiting for parts, before even loosening one bolt...you'd be covered. Another way to CYA is BUY A MANUAL...an (OEM) manual is just as important a "part" as anything in the motor.
This mistake is in the dollars...

Share this post


Link to post
Share on other sites

It's not a part of the manual decomp system. It's part of the auto decomp system. It acts upon the decomp cam on the camshaft. It prevents the auto decomp mechanism from continually dumping cylinder compression. Unless the decomp cam is pressed off of the camshaft and removed completely, the spring and plunger have to be installed for the engine to start and run. Don't waste your time putting it back together without it.

When I drop tiny things like that on the floor, I go over it with a magnetic sweeper. Saved my but a few times. But I don't see why one couldn't come up with another compatible spring that would do the job.

Edited by Trailryder42

Share this post


Link to post
Share on other sites

Apologies. I was backwards. Its the auto decomp.

And I disagree, all Ive done is not have the spring or plunger in and fill that hole. I dont like auto decomps. I take them off and only use the manual. But I have a Webcammed hi comp xr628r and it has no decomps. Sure it's tougher to start than my stock rebuilt xr600r with stock bore and stock cam with manual decomp still there/auto removed... but if you understand comp and motors then you'll save yourself 100 kicks!

 

Good call on a magnet.

 

 

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:


×