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Does this sound like a connecting rod issue?

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The bike probably had about 175 hours on it when I changed the top end. Cam chain yes, tensioner no. I can hear what sounds like a tapping noise, but not like the ticking of valves.

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It's hard to say.  It's sounds louder on the left side.  A mechanics stethoscope would help narrow it down, but you'll need to tear it apart to find out what the problem really is.  Doesn't sound bad, but it does sound like something ticking that should not be.

 

I think I'd start by:

 

1. Draining the oil and looking for bits of metal.

 

2. Popping the valve cover and checking that the decompression system is working correctly and not binding.   There were problems with the actuator pins in 2008/2009 breaking.  If partially bound, idle alone might not be enough to push the pin all the way in.

 

3. Also while your there, check for tension on the cam chain and visually inspect the guides for wear.

 

If that bears no fruit, then I'd pull the crankcase covers and look for anything.  If it really is a rod,  you're going to end up taking them off anyway.

 

Nothing there, then of course the head and jug come off next and you'll find out real quick what the problem actually is.

 

Jim

Edited by Jim Dettman

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Can you post a vid of you holding it on the rev limiter for 60 seconds? That would really sort things out quick and we could all try our turn at internet troubleshooting.

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  I had forgotten about that video....man the front of that case really exploded.

 

Jim.

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Thanks for the step by step sugestions. A quick ride up the coast tomorrow and then into the garage, I'll be back with findings. Thanks, Stephen

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In case no one noticed the heat shield on the head pipe is loose, or at least it looked like it. Right at the end of the video when he revs it a big you can see it shaking as the engine returns to idle.

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i see the loose shield too, but sounds more mechanical... a more disturbing question is what is with all the fuel lines, does it have a back up tank somewhere?

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Any chance that it's the balancer shaft bearings? The sounds in the vid has a vibration that goes with it, feeling any extra vibration through the foot pegs?

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What I CAN tell you, is that it doesn't sound like piston slap. Had two bikes with worn pistons and cylinders, so I know it well.

 

The tapping sounds more like a valve or chain issue.

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It sounds like valvetrain noise. Loose valves to be specific. I would at least pull the valve cover and inspect and check clearances.

I had a crf250r that sounded just like that. The rocker arm roller ate itself and made for a huge exhaust valve clearance.

Just pull the valve cover and it will prob be pretty obvious.

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Thanks guys,

 

I'll check valves first. I was probably foolish not to repleace the chain guides and perhaps the tensioner, as well, when I redid the top end. The cam chain is new.

 

Is there a way to determine if the tensioner is pushing enough? Any kind of specs?

 

Thanks again.

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To test the tensioner there are a few things you can do.

First off you need to remove the one centre 8M bolt on the retainer housing to insert a small flat blade screw driver and retract the tensioner plunger. Count the number of turns it takes for the plunger to retract in full. 1 turn or less is a good sign that the tensioner is putting the right amount of pressure on the Cam chain.

Now to test the tensioner itself. You need to remove it completely. With it removed make sure it is fully extended. Holding the tensioner in hand press against the plunger fairly hard to see if it move back or collapses. You can also hold it and smack it against the palm of your other hand to try and get it to retract / collapse inward.

Also check the tension plunger for play, it should not rattle or have any excessive play.

If none of the above is happening I'd say the tensioner is fine.

With the Cam Chain guides you would have easily seen if the were worn when you did the top end. Worn guides end have having similar wear patterns as thw chain guide on the swing arm.

Edited by Van Wick

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