Jump to content

Best head mechanic for 4 strokes?

Recommended Posts

Hello. I recently bought an 08 crf250r out of Colorado and it's having a lot of problems. The previous owners raced it and installed lots of aftermarket parts but didn't maintain it near as well as they should have. I just put in a high compression cylinder and piston thinking it would fix my compression problem after re shimming twice and figuring out that the rings had been installed wrong and rubbed a groove in my cylinder. I am now thinking I need my head fixed up but I'm on a limited budget. Anyone have ideas on who is good but won't send me into the poor house. Thanks

Hayden

Share this post


Link to post
Share on other sites

I used MXTime in Indiana with great results and quick turn around.
What is makes you think you need head work? If youre trying to figure out where the issue is find someone to do a leak down check, that will tell you if it rings or valves causing the low compression.

Share this post


Link to post
Share on other sites
3 minutes ago, CRFRida1605 said:

I used MXTime in Indiana with great results and quick turn around.
What is makes you think you need head work? If youre trying to figure out where the issue is find someone to do a leak down check, that will tell you if it rings or valves causing the low compression.

Thanks for the suggestion, I'll check em out. I just put a brand new high compression cylinder in it so I know there's no problem with the rings. We put lapping compound on my valve seats and made them good and smooth we thought, but I'm still only getting 27 ish psi when I need 57. The previous owners didn't take good care of it at all so I'm not surprised that all these problems came up. 

Share this post


Link to post
Share on other sites

How are you testing to get 27 psi reading? That doesn't make much sense to me. 27psi of leak down vs 57? 27psi of static compression vs 57? Neither makes sense. Has the head been checked for warp or resurfaced?  We're the valve guide checked for wear? 

Edited by HappyAndy

Share this post


Link to post
Share on other sites
1 minute ago, HappyAndy said:

How are you testing to get 27 psi reading? That doesn't make much sense to me. 27psi of leak down vs 57? 27psi of static compression vs 57? Neither makes sense.

We are just using a regular old compression gauge. We did kinda a half ass leak down test but the only test we've done besides that is just sitting there kicking it and we can only get 27 psi. Before taking it to the shop, we could get 49 out of 57 so the shop screwed up somewhere when they were diagnosing it.

Share this post


Link to post
Share on other sites

Fastheads

BigBoreThumpers

Both reputable and quick turn around. You should not of lapped the valves. If the valve to seat contact was wrong, the seats should of been cut and the valve stem milled to account for the seat cutting.

Share this post


Link to post
Share on other sites

27psi of static compression is virtually no compression. Does it feel like no compression when you kick it?

Share this post


Link to post
Share on other sites
1 hour ago, William1 said:

Fastheads

BigBoreThumpers

Both reputable and quick turn around. You should not of lapped the valves. If the valve to seat contact was wrong, the seats should of been cut and the valve stem milled to account for the seat cutting.

There wasn't anything wrong with the valve seat contact, we lapped them to make sure the surface was smooth and everything came together good.

Share this post


Link to post
Share on other sites
1 hour ago, HappyAndy said:

27psi of static compression is virtually no compression. Does it feel like no compression when you kick it?

It feels like it has compression, just like it had last year when it started and ran. The only problem is it doesn't start, and I am completely sure everything got installed right

Share this post


Link to post
Share on other sites
4 hours ago, HancockMX546 said:

There wasn't anything wrong with the valve seat contact, we lapped them to make sure the surface was smooth and everything came together good.

Did you lap the intake and exhaust valves? Or just one set?

Share this post


Link to post
Share on other sites
2 hours ago, Eddie8v said:

Did you lap the intake and exhaust valves? Or just one set?

We did intake and exhaust with 400 grit lapping compound. We didn't lap it hard, just enough to get it smooth

Share this post


Link to post
Share on other sites
1 minute ago, HancockMX546 said:

We did intake and exhaust with 400 grit lapping compound. We didn't lap it hard, just enough to get it smooth

If the intake valves were the stock titanium valves, they are now compromised as the lapping process removes a hard-coat layers from their sealing surface. They'll wear very fast after lapping. They need to be replaced and I would have the intake seats touched-up to ensure a proper seal.

Share this post


Link to post
Share on other sites
10 minutes ago, Eddie8v said:

If the intake valves were the stock titanium valves, they are now compromised as the lapping process removes a hard-coat layers from their sealing surface. They'll wear very fast after lapping. They need to be replaced and I would have the intake seats touched-up to ensure a proper seal.

Oh that's not good haha. The guys I bought it from said they put the kibblewhite stainless steel valves but the bike hasn't even run since December. I took it to the shop to have it diagnosed and they did a terrible job. They didn't clean the carb as I requested and there was lots of varnished fuel in it, which was part of the problem. I was getting 49 psi before we took it in so the shop definitely had some dummies back there doing something wrong. The one flaw in your logic I see is that it held 27 psi so the seals aren't bad.

Edited by HancockMX546
Left out info

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:


×