isolating a sound

Lately while riding the commando I have started to hear, the best I can describe, a hollow metal PLONK sound coming from somewhere, but I can't isolate it while going down the road and it is also an intermittent PLONK. If I could guess it is coming from the tranny area, but I really cannot tell. Anyone have an idea of what to check?

Tim

Tim

Could be your centre stand bouncing against the frame, mine does it a bit. Someone did give me a detailed explanation (which typically I can't find at the moment !) that it was something to do with the stand attachment pivot/bushes wearing, and that it is quite common. It is one of those jobs I need to do (in the winter!). I don't think that it is something to overly worry about

Now if it is the kick start lever snatching back/forwards whilst on the move, then you should check the gearbox layshaft immediately & IS something to worry about :shock:

I'll check the kick start lever as you say. I thought about the center stand as the problem, but it really sounds like it may be coming from the tranny. Sometimes when on the move and during shifting the transmission makes a similar sound when the tranny engages gears. I was/am a little concerned if this is the case, but wouldn't know where to look.

Can we assume it's not a Mk111 Electric Tart ? They make all sorts of 'orrible noises from the primary case.

Have you checked primary chain tension and that everything that rotates there is tight ? I would pay particular attention to clutch location circlip, clutch centre nut etc.

I have a sound like that once in a while caused by the gas tank hitting the frame tube. It sounds like a drum sometimes at various RPM's , just adjust or add the rubber pads that should be around the tube. Sometimes tightning the front hold downs help.

Bruce MacGregor said:

I have a sound like that once in a while caused by the gas tank hitting the frame tube.

Click to expand...

Just a tip....I ignored my tank hitting the frame, and ended up with a crack in the tank, right in the rear, where it meets the seat...pain in the butt to silver solder it closed, tank has to be full of water, etc.....not to mention the unpleasantness of coming home from a fast run down the autobahn (at three in the morning) and finding out the reason I felt kind of uncomfortable and cold...wasn't the wind or air temp...but rather the couple of quarts of petrol that had soaked my leathers in the area we all find so important. Smelling and itching like that...doesn't do much for the love life...if you get my drift. Fix your rattling tank.

To some this will be very obvious ~ but~

An old trick of the trade is to take a largish screw driver, (long shafted) preferably one with the steel shaft extends right through the plastic handle , and hold this on/ against the frame or engine while the engine is running or in this case "rattling" .

Of course.. you then put your ear up to the opposite end ~ IE ; the outer end ~ you will be impressed with the actual effectiveness..

Essentially this is amplifying the noise in a concentrated point~!

But be warned if you start to check over your engine while it is running you may well be horrified as to the rattles and clatters you can actually hear!!

This will overall isolate the region of the problem very quickly.

The catch is that if for some strange reason the rattle is NOT mechanical then it will not be heard...:shock:

There are in fact specific tools made for this purpose, but essentially any thing will do the job... but a metal shaft is far more effective~

In my book NO rattle is good news.. it may seem be insignificant ~ but if it not normal ~ then is not right and~ will end up in some degree damage some where ~

As for tank/s hitting the frame/s ~ this is fairly easy to locate ~ again with the engine running and the rattle audible.. simply press down on your fuel tank or lift the edges.. this will stop the rattle and or you will be able to feel the rattle ~ I've had the same deal in the past `/ `

It isn't the tank. I go through the tank rattle thing about three or four times a season as the foam padding breaks down and that is a very obvious sound and much different. I tried to isolate it again today with my wife on the back. She thinks it is from the chain/guard area and I think it sounds like it is in the tranny. It only does it once and then it may not occur again for 5 minutes or an hour. no reason for the sound, but it does or at least is only audible at very low speeds as in plodding along the country road with my wife at 25-35mph. It is as though something is hanging up or binding and then lets loose. It doesn't sound like chain bind though. I am going to investigate in the morning. Crap, this is the only classic I have running right now. 650 Triumph is down for a total rebuild and one of the Tridents is also down for a total strip down. Ol norty can't be going bad yet and I don't want to rely on the new Hinckley triumphs for the rest of the year

Tim
Did you check the kick start lever? cos it will make a plonk as it returns, and is more likely to do it at lower speeds just as the tranny loads up.

What about the cush drive or rear brake torque arm?

Cash

I have a feeling this one is going to remain a mystery until A) something breaks and I can see where the problem is or B) it just isn't anything critical and eventually through time and wear I will replace what is causing the sound :?

britbike220 said:

Lately while riding the commando I have started to hear, the best I can describe, a hollow metal PLONK sound coming from somewhere, but I can't isolate it while going down the road and it is also an intermittent PLONK. If I could guess it is coming from the tranny area, but I really cannot tell. Anyone have an idea of what to check?

Tim

Click to expand...

What about your chain guard? It is still attached? Mine broke off at the from mount tonight and made a funny sound.

Sure your forks aren't topping out? I know it's at the opposite end of the bike but it's amazing sometimes where you think sounds are coming from and where they actually are. I thought my front brake was rattling and it actually ended up being my battery tray.

Possiblities.
1. Loose horn mount. Particularly the single bolt holding the horn to the double plates.

2. Cracked or broken centerstand. This will thump the swingarm if broken or bent. Can even hit the chain and remove the masterlink leading to spitting the chain out on the road. DAMHIK!

3. Bad transmission layshaft bearing. Watch that moving kickstart!

4. Rubber missing from rear frame to fender mounting clip.

5. ???

Process of elimination-
Get a handfull of zip ties. Pick a suspect. Zip tie it securely so it does not move. Ride. Either it continues or it don't. Repeat until you find the loose item. This should do it if it's something loose banging around. At lease it'll tell you what it ain't and you can diagnose from there.

HTH
Mike
Kansas, America