05 CRF250R rebuild

I ended up with an 05 recently for $500. It was all there, just needed valves adjusted so the PO claimed. Yeah, right. Anyhow, it wasn't locked up, so I paid the fella and took it home. After taking off the valve cover, It was obvious that it had been apart and buttoned back up due to an idiot with tools. He broke the cam wheel trying to pry the chain off, rather than releasing the acct and sliding the bearing over for sufficient slack. But he was right about the valves as the right intake was zero clearance.

I found a new take-out cam from an 06 for $50. I got a ss valve & spring set, lapped them in, and put it all together with new gaskets and a cam chain. I know, I should have put a new piston in, but it actually looked really good as did the cylinder. I thought I'd chance it. I've got exhaust valves at .010 and intakes at .005 now. Cam lobes are facing the rear and all timing marks line up. I've got fuel, spark (new plug), and 65 psi of compression (throttle open, decompressor intact).

It won't even try to start. I took the valve cover off again & checked clearances, they're good. I'm not sure what to look for at this point. Any help would be appreciated.

Does it matter if the crank is on the correct stroke? I don't see how as the timing is set by the cam position.

I'm no pro, so take my word for what it's worth. I believe the crank position (rotation) does matter and I think I had this exact issue last time I did the top end on my CRF. Kicked it over 100 times with nothing more than a backfire or two. Pulled the cam out, spun the engine one rotation and put it back together. Started first kick.

On a four stroke the motor rotates twice to complete all four strokes, so you can be at TDC but if youre out one rotation of the crank the ignition will be firing after the exhaust stroke rather than after the compression stroke. Or maybe I'm totally out to lunch haha.

Edited by sjvmtb

I too wondered about that, but I figured that it was the cam position that determined which stroke it was on. I will try your suggestion tomorrow. Good to know that it solved your issue, so there must be something to it. Thanks for the info.

Btw, where in Alberta are you? I'm in northern Montana, so I've rode at the Raymond track quite a bit.


I think the ignition is based on the flywheel/stator and therefore controlled by the crank.

I'm in Calgary, familiar with the town of Raymond but never ridden the track. I mostly ride trails in the foothills along the Rockies. We've ridden at Kookanusa which you may be familiar with. Usually we go to Maclean Creek or Waiparpous which are just west of Calgary. Hundreds of trails and a lot of fun if you like hills and single track. PM me if you're ever up this way with your bike!


Edited by sjvmtb

Steve, right you were! I pulled the cam, rotated the crank 1 revolution, and it started first kick. That was sweet music considering I bought this knowing it did not run.

I have a buddy in Okotoks that rides at McLean Creek and an area I think he calls Indian Graves? I have also ridden in BC quite a bit at Jaffray & Tie Lake. I'll try to take you up on that offer if I get the chance.

Still needs a few little parts, but it runs well, looks great, and I've only got $1300 in it. I told my nephew he could have it for cost, as he's been looking for one. I'll prolly ride for the summer while he raises the cash.

Thanks again for the tip!



I was recently told my son's 04' CRF250R would not run 180 degress out. His starts really hard the first start of the day. Once going, it runs strong and starts easier. All the timing marks are correct.

You said you rotated the crank once. Just to be clear, from TDC to BDC to TDC?

Wondering now if we are 180 degrees off?


Nice work Jason, glad it helped. Sounds like you got a nice deal on the bike.

A few buddies rode at Indian Graves for the first time this weekend and said it was great. Got a new place to ride!

Jeff, I'd say that if the bike runs at all then the crank being off isn't the problem. It only sparks once per cycle so when it's off there isn't any spark to initiate the power stroke. Are you sure your valves are all in spec? The hard start when cold but good when hot sounds like a valve symptom...


Edited by sjvmtb


Left intake is .003, right is .004, left exhaust is .009 and the right is .011. The seats were cut when the valves were replaced about 10 hours ago.

The timing is good, new piston, rings and cam chain.

Is a leak down test something to try? I do have a fuel screw on the way. Maybe just need to wait for that.


Ah. I saw on your other post that (originally) it was cool out when you were having the trouble. I actually just did the top end on mine too and was having a similar problem - first start was hard but it started good when hot. It was also a little boggy around 1/8 throttle. I put a high comp piston in mine, did you? What I found was that it ran better on warmer days and that the fuel needs changed a bit with the rebuild (I assume b/c of the high comp piston). After some playing around, I ended up with the fuel screw 1/4 turn more open than before the rebuild and that's got it running good again. And I have to twist the throttle 5-10 times before starting when cold. I'd wait for your fuel screw to arrive and see if playing with it helps.

Or if you're antsy to try something, I use a flat bit in the adapter for one of those cheap multi-bit screwdrivers and it fits under the carb well enough to adjust the fuel screw without loosening the carb boots (the thing in the pic below).

ImageUploadedByThumper Talk1366682296.684019.jpg

Edited by sjvmtb

Jeff, just to confirm, I went one full turn on the crank & installed cam in same position. Like Steve said, I doubt it would run on the wrong TDC stroke or 180 degrees off on the cam.

Steve, thanks again for the help. Here is a shot of the finished bike. I bought a new chain, but it was too small for the larger sprocket. I will have to get a longer one, this one's just plain gross.


Create an account or sign in to comment

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

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now