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CRF 150 knocks

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CRF 150 knocks when running. It is slow at idle and gets faster as engine speed increases. Where do I start when trying to diagnose this problem? Bike starts and runs fine...except for the loud knocking. 

I am not a mechanic and have never worked inside an engine. Have worked on carbs and other pieces, but not the engine. Thanks in advance! 

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What is the history of the bike...........and the knock?  Is the oil up to the proper level?  Is there metal in the oil............may want to drop it into a clean pan and check?  Does the knock change when you put it in gear and let out the clutch loading the engine? 

Old School Al

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It's an 04.  Belongs to a friend and we share it to ride when our kids are riding. He picked it up from someone else for cheap. History is unknown. Bike has clean oil and up to level. Runs great other than the knock. When idling in neutral and then shifting to 1 and going slow the knock remains the same and speeds up and the speed increases. Doesn't seem to affect performance but can't possible be good for it.

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I'm not sure why but it played one time, I hit replay, and now won't play................my lack of computer skills?

I have no 150 experience, but from what I heard I'd check valve adjustment and cam chain slack to start with.  Would be looking for maybe say a valve tappet adjuster that hadn't been tightened properly and came loose. then fell out .................. or may a broken cam chain adjuster or bow.  The noise calls for attention for sure.  If you are going to look into this yourself, first thing you need to do is get a manual for a 150!:thumbsup:

Old School Al

PS: Not sure what I did but the video is playing again..............!

Edited by Old School Al

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I tested the link and it works multiple times for me. Maybe do a refresh of the browser window.

I would love to tear it down myself and use it as a learning experience, but between work, kids, and doing what my wife tells me to do it will probably end up at the mechanic. If anyone has any other suggestions please chime in. 

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On ‎5‎/‎8‎/‎2017 at 8:40 AM, wesatl said:

I tested the link and it works multiple times for me. Maybe do a refresh of the browser window.

I would love to tear it down myself and use it as a learning experience, but between work, kids, and doing what my wife tells me to do it will probably end up at the mechanic. If anyone has any other suggestions please chime in. 

Did you have a chance to get it checked out yet to find the problem.............?

Old School Al

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Search "Engine noise when hot" in the specific 150/230f forum.

The OP there had a sized piston.

I listened to the video and agree that the very first thing that I would recommend to do would be to properly adjust the valves (dead cold engine) then do a cylinder leak down test to pin point the problem if the noise is still there.

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I took the video to they guys at Atlanta Cycle and he thought it was the valves and could possibly include other problems such as cams, cam chain, tensioner, etc. His guess was that someone ran it low on oil for too long. Parts would be expensive unless I could find some used ones. I relayed this info to the guy that owns the bike and he is deciding what to do. 

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48 minutes ago, wesatl said:

I took the video to they guys at Atlanta Cycle and he thought it was the valves and could possibly include other problems such as cams, cam chain, tensioner, etc. His guess was that someone ran it low on oil for too long. Parts would be expensive unless I could find some used ones. I relayed this info to the guy that owns the bike and he is deciding what to do. 

I think that's a pretty good assessment of the noise..........one of my first questions was oil also.  Lack of oil (and dirty oil) will wear the rockers, cam, and cam bearings, which in turn drastically increases tappet clearance.  I've seen cams that were literally flopping around and still ran............with lots of hammering noise though.  Sadly this is caused by lack of maintenance and is the reason most motorcycles die way before their time.

Old School Al  

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