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'10 250r not idling after cam chain replacement

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I bought a '10 crf250r a couple months ago from a guy that just had the top end rebuilt with a cylinder works top end kit. It was hard to start, i assumed it was due to my not riding for a few years and needed to relearn a couple of things. took it out to our local MX park and was riding some trails. about 2.5 hrs into it, I heard loud slapping in the top end. I immediately rode it back and loaded it up.

Upon inspection, the cam chain was stretched and incredibly loose. Ordered a new Hot cams cam chain and manual tensioner. when I broke the engine down, got it to TDC and looked at the cam, it was 180 degrees off. I assume due to the amount of slack in the cam chain it allowed itself to spin out of timing. replaced cam chain, installed manual tensioner to manufacturer recommended specs, reinstalled the cam to coincide with TDC, checked valves, which were in spec. 

After putting everything back together, torqued according to the service manual, i tried to start it. it was still really hard to kick over, had a couple of back fires and once started, would not idle. With the high idle knob pulled out, it was idling at what i would consider normal idle speed and when high idle pushed in, it would not idle on its own. i would have to rev it up. took it for a spin, kept having to keep it revved up and when pulling back into shop it died on its own, due to low idle. 

Pulled the spark plug, it was badly fouled out and was rusted around the exterior. So when he rebuilt the top end, he kept the same plug and did not change the cam chain. Replaced the spark plug with a new factory one. Starts up a little easier, however the idle issue is still there. i tried turning the idle knob, but did not notice any real difference until i took it for a ride around the shop parking lot. it was pretty much the same thing until i pulled in the clutch to turn around. it would idle up high like it should when the high idle knob is out but would go back to normal when i let the clutch out and gave it throttle. it did that a few times, but i did not ride long as i was in a hurry to leave. 

I would appreciate any ideas anyone can give me on this topic. i cleaned the throttle body and the IAT sensor, but have not had a chance to try it since then. Thanks.

 

Attached is a picture of how loose the cam chain was.

22017 resized.jpeg

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I would think a chain that loose is, literally, impossible. Are you sure he didn't install an incorrect timing chain? Is that the right cylinder and cylinder head for that bike? Something is off.

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12 hours ago, Eddie8v said:

I would think a chain that loose is, literally, impossible. Are you sure he didn't install an incorrect timing chain? Is that the right cylinder and cylinder head for that bike? Something is off.

Thanks for the reply. I double checked the part numbers on the box i was given that the parts came in, and it is the correct parts. As you can imagine, the cam chain was slapping really loud. When I get it running, it sounds like it should, just wont idle on its own since i replaced the cam chain. I plan to mess around with it after work today. I havent had a chance to try since i tore it down and cleaned the TB and IAT sensor, which was filthy. 

Would using too much oil on the air filter cause this?

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Ive never seen a cam chain that loose when the tensioner was installed correctly, given correct parts anyway. Does it still look like that after you installed the new one?

Btw the cam rotates once for every two rotations of the piston, it cant be 180° off, that just means that you were at tdc on the exhaust stroke instead of the compression stroke.

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If you ran it with the chain that loose there's a pretty good chance the chain skipped timing and is now off.

And your valves have probably become intimate with the piston

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On 5/18/2017 at 5:06 AM, CRFRida1605 said:

Ive never seen a cam chain that loose when the tensioner was installed correctly, given correct parts anyway. Does it still look like that after you installed the new one?

Btw the cam rotates once for every two rotations of the piston, it cant be 180° off, that just means that you were at tdc on the exhaust stroke instead of the compression stroke.

The new one was nice and tight. had a little trouble getting it on. Maybe so on the cam rotation. However see below....

 

On 5/18/2017 at 9:53 AM, nesc103y said:

If you ran it with the chain that loose there's a pretty good chance the chain skipped timing and is now off.

And your valves have probably become intimate with the piston

I did change the cam chain and installed a manual tensioner, I didnt get that deep into the head, but the valves were in spec and didnt notice any warpage or damage...

 

Follow up...For the moment the problem appears to be fixed. I took it back apart, rechecked the timing, noticed it was 1-2 teeth off, put it back correctly. Here's the part I'm unsure of. And if so, I'm an idiot. When i re-assembled it the first time, I did not reconnect what the manual calls a stopper wire (which is a small piece of cable with two loops on the ends) to the small bracket that connects to the bottom of the fuel pump. When i re-assembled everything this time, i attached it. It started up in 5 kicks, which i attribute to disconnecting the fuel line. Idled up perfectly, was able to adjust the idle when the high idle pushed in. Tried it out yesterday afternoon again just to make sure it wasnt a fluke, 3 somewhat generous kicks and it fired right up, idled like it should and felt great to ride.

So in conclusion, not sure if that small piece of cable doubles as a ground for the fuel pump, But it is running to my expectations as of right now. Thanks for the replies and feedback.

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