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Disturbing noise after turning engine w/ cam chain at the bottom.

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So the bike had the camshafts taken out to adjust the tight valve clearances and at the same time a used FCR 39mx was swapped into the project. The camchain was left sitting at the bottom of the engine one night, after a few too many shots... long story short the engine was turned over through a couple strokes and the cam chain bundled up at the bottom. Cam chain was recovered and bike was put back together with new shims, clearances were triple checked and new (used) FCR 39mx was installed. Bike struggle like hell to run, had to turn up idle adjustment screw quite a bit. Only jet that is different from the standard DRZ FCR jetting happens to be a potentially lean size 42 pilot jet. Gaskets in fcr are all new, midbody wasn't touched.

Anyways there is a gnarly clanging sound coming from the bike, especially at the end of the video when the revs slow down before it dies. Could that be from the carb, or could it be that the cam chain or valves have an issue? I tore it down and rechecked the clearances after running it for about 5 minutes, everything was right in the middle of the range. I went ahead and rebuild the mikuni paperweight, so I can always test and see how the bike runs with that. First I would like to see if anyone has an opinion based on the sound of this video, i'm tired of taking the fcr out and putting it back in so many times with all the bikes I maintain for my family. You'd think I would get faster at it, and sure that's true but my eczema skinned hands hate it the most!

Does it sound like the noise is from the top end of the motor?? Thanks for any input.

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Mostly sounds like your carb is screwed up ,leaking choke/wrong choke plunger, missing o-ring somewhere ect.... The sound at the end was just the starter at shutdown . As the motor stops it hits the last compression stroke and stops abruptly so there can be that noise . I have 2 different bikes that do that , both high comp with no autodecomp system .

 

Are you absolutely sure the timing is correct ?

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Edited by jjktmrider

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13 hours ago, jjktmrider said:

Mostly sounds like your carb is screwed up ,leaking choke/wrong choke plunger, missing o-ring somewhere ect.... The sound at the end was just the starter at shutdown . As the motor stops it hits the last compression stroke and stops abruptly so there can be that noise . I have 2 different bikes that do that , both high comp with no autodecomp system .

 

Are you absolutely sure the timing is correct ?

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I agree that it sounds like the carb is messed up, I will go ahead and pull it out for a closer look. I'm pretty positive the timing is correct, i've checked it a couple times now. 

 

9 hours ago, ohiodrz400sm said:

That clanking is the slide in the carburetor. Mine will do it too some times at really low idle.

I was wondering if it could be the slide, maybe I put it in backwards :o (apparently it goes in either way and i suppose that would explain the poor performance.)

Thanks for the evaluations, time to get to work. Would much rather fix a carb issue than something from the top end. 

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The doubt the slide is backwards. I'm not sure if it will physically fit backwards but the vacuum release plate would be a dead give away during assembly. That is something that gets put in upside down from time to time.

 

 

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Havent replaced the timing components on any bike,but have on plenty of ohv cars aND overall the setup seems similar,  (crank sprocket,  guides, tensioner,  and cam sprockets). If you turn the crank on most cars without some kind of tension on the top of the chain,  the chain will jump teeth on the crank sprocket. You won't be able to tell just from looking at the cam sprockets. 

Maybe somebody wit bike experience can chome in, but seems like a possibility to me. 

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One tooth off on the crank would put it quite a ways off on timing , it probably wouldn't even run and possibly bend a valve , but I haven't really tried it to find out . Should be equivalent to 2 teeth off on the cams .

 

 

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Edited by jjktmrider

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Its the carb slide on idle. If there is any more doubt. Take off the intake boot and watch it jiggle with the idle until its held in place by pulling on the throttle. Id guarantee that noise goes away once its all back together. Well mostly.

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Mission accomplished! So the hunch about the vacuum release plate having been installed backwards was correct (I called it the slide like a dork, I know lol.) 

I installed it backwards and although the bike fired up, it would never run right until I corrected it. Thanks for the advice and i'll post pictures so that way anyone else who is dealing with this problem might understand the simple mistake that can cause a huge headache. 

 

Snapchat-652188164.jpg

Snapchat-1343571067.jpg

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Man does that sound familiar. My problem was only a surging idle though. 

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