Tapping noise coming from top end...

Started by lfg929, September 06, 2003, 06:51:36 PM

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lfg929

I have a tapping noise coming from the top end of my motor. I pulled the valve cover off and checked valve clearances but they are within spec. I only have one valve that is off of optimal clearance but it is still within specified tolerances of the shop manual.

So, anyone have some suggestions where else I might look? The cam visibly looks fine (no visible marks on it from excessive wear). The bike is a '00 929 and I know lots of people have complained about cam chain noise on the CBRs, but I am not sure if that is the source of my noise.

The tapping speeds up with RPM and is can easily be heard standing 10-20 feet away from the bike. It isn't as bad when the motor is cold, but definitely gets louder once the engine is hot. I don't notice it above 7000RPM or so, but it is probably just being drowned out by the exhaust noise. It does it from idle on through the RPM range.

Any suggestions on what it might be, or things to do to help isolate it to a particular area would be helpful. This is my first time tearing into the top end of a 4-stroke so I am learning as I go. I used to tear my quads 2-stroke motor apart all of the time, but haven't spent any time playing with cams, timing, and valves at all.

Thingy

Is it an exhaust leak coming from where the headers seal up against the head?  I would look into this if you have had the headers on and off a few times.  You might have to replace these gaskets.
-Bill Hitchcock
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'01 Ducati 748

Tuck your skirt in your panties and twist the throttle!

lfg929

That is a possibility. I have not had the exhaust off since I installed it a couple of years ago, however, when I tore into the top end I did notice some soot around the header for cylinder 2. There isn't much soot so I don't think the leak is very big, but it is there.

Xian_13

can you feel the noise on the head?...
Meaning, if you move your hand around on the head, can you feel the vibration that might be causing the noise?

there is a million differant things that can cause this noise, fron a tapping valve, to bad rod bearing (bad rod bearing lets the piston hit the head on upward travel)
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lfg929

I have to put the motor back together to start feeling for the tapping. I have gotten some other suggestions that maybe it is the cam chain tensioner.

As for rod bearings... Honda is known for its bullet proof motors. Mine only has 12,500 miles on it, more than half of which was street time. My valves are spot on for the most part so unless I just got a bad bearing to begin with I would find it hard to believe that would be the first thing to go in the motor (it could happen, but I would think the odds would be low). I might go ahead and pop the top of the head off though just to inspect the pistons. If that is what is occuring then it should be easy to spot.

Thanks all for the suggestions so far!

tcchin

PAIR valves...? Kinda hard to say without hearing the noise in person.

lfg929

PAIR valves were removed over the winter so that isn't it.  ;D

Super Dave

Larry, did you come up with anything yet?

Get a better location for the noise?
Super Dave

lfg929

Not yet. I got the motor put back together a few days ago. I will finish getting everything else on there tonight and will try to isolate the noise to a specific part of the motor.

Super Dave

So, there wasn't anything specific that was broken or anything.  

Does seem like Honda hydraulic cam chain adjusters do die over a period of time.  Never had one go on my old F2 years ago, but I think everyone else's did.
Super Dave

lfg929

Most people I know with 929's that either have a lot of miles in general or have a lot of track miles have either replaced the cam chain adjuster with a manual one or have gotten it replaced by the dealer several times.

tcchin

Dave,

Honda uses a mechanical cam chain adjuster on the 929, as it did on the F2 and F3. Suzuki is the only manufacturer that uses hydraulic adjusters on their bikes, at least from my limited experience. As for the longevity of Honda adjusters, it seems as though they're sensitive to crash loads, often requiring replacement after geogravitational experiments of considerable scope and magnitude.

Super Dave

F2s mechanical?  I remember we had to put it in oil and pump it up.  Nothing exteral to work with.  Don't know.  I know they failed.

The Suzuki...what do you call it.  I think the hydraulic part is only to initially tension it, then the mechanical teeth take over from there.  The teeth strip.  That's the problem there.  Had one let loose just enough, but I was able to cut up an allen wrench to put inside to make sure that the racheting mechanism stayed put.  Was good enough to win a team challenge race last year and some other weekends until we got the manual one.
Super Dave

Litespeed

And everyone says two-strokes are high maintenance :).  You may also want to run a compression check on the cylinders as this may indicate a slightly bent valve or some other sort of problem.  Other than that, I hope whatever it is is a simple and inexpensive fix for you.