Buzz in foot pegs

Hi,

Need the collective wisdom of this forum as my foot pegs started buzzing and I can't figure out why. I'm fairly certain this wasn't the case before but not sure when it started. I've become aware of it the last time I rode the bike.

It's a high frequency buzz that increases with the rpm and most noticeable in the foot pegs. It's also felt in the seat and to a lesser degree in the handlebar.

I'm convinced something is touching the sub-frame but can't figure out what.

Following things I've checked:
- Iso clearances. All around in spec.
- All engine and gearbox fasteners. Tightened a couple but no change.
- Head steady mounting. All tight but early 750 type with crack starting at the bend on one side. Only 5mm right now.
=> Hard to believe but could this be the cause?

- Checked all around for anything touching the engine or sub-frame. Can't find anything.
- Carbs synched with both showing equal vacuum
- Primary and secondary chain tension
- Exhaust mountings. Have S-Type exhaust and nothing is touching.
- No unusual noises
- Checked frame for cracks. Can't find anything and have no funny handling.

Bike is fairly smooth until 2500rpm. After that the vibes start in the pegs. No buzz when the clutch is pulled coasting.

Appreciate your input.

When you checked frame did you get real good look at battery tray with flashlight .... crack there will cause symptoms you describe...

Sounds like you have been pretty thorough looking for the problem,
But when you say the engine is smooth upto 2500 rpm that is completely at odds with all the commandos I have ridden it should start to get smooth at those revs !!
And really smooth by 3000 rpm
What type of ISOs do you have?
What have set them to?

Crack at head stay would be the a big cause for concern and could be a reason for that buzz, things don't crack unless something is wrong, look into it further.

Ashley

The early type headsteady was a huge piece of crap. It was followed up by the "box" headsteady which is slightly better for strength, but it's isolastic qualities are poor in comparison to either the production racer headsteady which is an actual isolastic mount or a heim joint headsteady...

Ditch the early headsteady, and get at least the box headsteady type. My original headsteady also had a stress crack in it. I replaced it with the box style headsteady, and then replaced that one with one of Jim Comstock's rose joint style headsteady. The originals all seem to crack.

As far as the vibrations go, try loosening your rear isolastics a bit and see if the vibration goes away. The suposed scuttlebutt on vibrations is that vibrations in the handlebars is too tight of a front isolastic, and vibrations at the footpegs are too tight of the rear isolastics. It should be simple enough to make some adjustments and go for some test rides. Personally, either I'm used to the way my commando vibrates and I'm oblivious to it, or everything is working as it should be and there isn't much vibration at all.

If your ISOs are original, they may be very near metal to metal, plus, when they sag they bring all kinds of metal items closer to the frame, which wouldn't necessarily touch unless the engine was running with a load. Have you checked your swingarm for looseness between it and the engine cradle? Is the center stand touching the frame?

Is it worse in gear or stationary... Why one wonders does pulling the clutch in resolve matters? Could it be that clutch centre nut is loose ? Is headsteady eating a hole in the petrol tank ? Try slackening rear chain , if a tad on tight side it might pre load the isolastics..have alook in the vicinity of the primary chain case and prop stand...

oldmikew said:

Is it worse in gear or stationary... Why one wonders does pulling the clutch in resolve matters? Could it be that clutch centre nut is loose ? Is headsteady eating a hole in the petrol tank ? Try slackening rear chain , if a tad on tight side it might pre load the isolastics..have alook in the vicinity of the primary chain case and prop stand...

Click to expand...

The drive chain can't preload the isolastics

when mine has been on the tight side and with a pillion then it makes this felt through the footrests on over run ,presumably to do this it is affecting the normal operation of the isolastics.

o0norton0o said:

The early type headsteady was a huge piece of crap.

Click to expand...

Yes, they appear to have brought up the entire stock of bed springs from a spring bed company!

Thank you all for the replies on this thread. Some good input. Managed to check the battery tray and oil tank mountings. Have the early central tank. Both check out fine with no cracks or loose parts anywhere. Clearance to cradle is ok as well. Horn is also clearing the cradle. Swingarm is clamped with no play.

Vibes are coming from engine moving or standing still. On the move they go away if I pull the clutch and let the rpm drop.

I have a Taylor head steady at home but can't fit it due to a poorly machined clamp. Replacement from vendor is underway. Once received I can eliminate that as a potential source. If that doesn't work I'll play with iso clearances. They are currently set by the book with the front slightly tighter. Rubbers predate me and I don't know the definitive age.

It will take a few days until I can continue. Will report back here when I make progress. Thank you again for your help so far.

Good luck with that .... I pushed and pulled at mine for a few years .... at this point it smooth as my Ducati and smoother than Griso .... never realized there were so many different options that might cause unwanted vibes , you will get it eventually , hopefully in a more timely manner than me ....

Scrutinize the clutch/basket/mainshaft.

A dry or rusty or the wrong type of drive chain even badly hooked sprockets can cause such a vibration.

Try pushing the bike and if you can feel hear the chain there's a good chance that's your problem.

Dave

oldmikew said:

when mine has been on the tight side and with a pillion then it makes this felt through the footrests on over run ,presumably to do this it is affecting the normal operation of the isolastics.

Click to expand...

When I have played with settings on my shocks and gotten them too soft, I can feel a buzz in my foot pegs when running over humps in the road. While my response to this has been to stiffen the shocks a bit, I have always assumed it was caused by the drive chain.

Inspecting the sprockets for excessive wear is mentioned above and a good idea. I can imagine it is possible that when using the clutch the vibration could change due to the chain rotating without tension on it.

Edit: Oops missed the OP comment that it happens sitting still as well! Oh well, maybe ideas here will help someone else.

rvich said:

When I have played with settings on my shocks and gotten them too soft, I can feel a buzz in my foot pegs when running over humps in the road. While my response to this has been to stiffen the shocks a bit, I have always assumed it was caused by the drive chain.

Inspecting the sprockets for excessive wear is mentioned above and a good idea. I can imagine it is possible that when using the clutch the vibration could change due to the chain rotating without tension on it.

Edit: Oops missed the OP comment that it happens sitting still as well! Oh well, maybe ideas here will help someone else.

Click to expand...

yes I used to jack the Girlings up a notch if caught out . But the more I think about the OP ought to satisfy himself all is well behind the primary chain case cover...

Managed to work on the bike this evening. I removed the exhaust and bent the pipes somewhat. S-Type this is. In some parts it was too close and possibly touching during certain rpm. Also increased iso clearance at the front by 0.1mm. Can report now turbine smoothness from 4000rpm onwards!

Must be iso clearance after all or some binding with the exhaust. Will increase play further if required after mounting the new head steady and bring it hopefully down to 3000rpm. Thanks again to everybody who took the time to comment.

Are the iso rubbers original? If so I'd recommend replacing them for peace of mind at least. (Only because I just did mine over the winter.)
It was the second time for the fronts and first time on the rears. The big rubbers were compressed some and the small ones looked new after 46 yrs and 40K miles. I expected to find them turned to dust. I was glad I looked though. No rust anywhere.
Was a good workout and I don't work out much. I did not remove much of anything. Even the air cleaner was untouched. Primary intact. I had an easy job of removing the iso bolt/studs because I had them out a few times searching for iso shim nirvana years ago and had used anti-seize. Some are not so lucky and have had to saw through the rear bolt. The only difficulty I had was getting the new rubber covers in place. It was a true test of patience. I had to walk away a few times but suddenly they magically assume the correct shape.

Anyway, to get to the point, if they are the originals, you might consider having a look in spite of any pitfalls. Glad you found the problem. You knew what you were looking for and that is always is a plus.

Glad you are sorted , but would still have a peek behind the primary chain cover just to make sure clutch centre nut or something is not loose.The tell is that pulling in the clutch made a difference