Tap, Tap

[ramwing7]

Ater getting the carbs on the 1973 Bonneville to not leak, I took it out for a ride around the block for it's inaugural shakedown.
It flunked.   

The motor starts easily and runs nicely with good acceleration.   Instruments, lights, brakes, etc. work nicely.

 Problem is it sounds like someone is tapping on the primary case with a small hammer when you're riding along.  It only does it with the clutch engaged, but the noise seems independent of engine speed or bike speed. It's also a bit irregular in frequency.  Maybe it gets louder on acceleration.

I did put the bike on a jack and run it thru the gears while it was still in the shop.  No sounds coming from the primary case at that time.

Any suggestions on where to start finding this one?

[R]

Not knowing the 1973 personally, if that were mine 1st thing I'd check is primary chain and rear chain adjustment.
Both within spec. ?

2nd is chain joining link in the rear chain.
Clipped up correctly ? And not overly wide, like some can be.
Can't flap about and gouge on something sometimes ??

3rd is drain primary oil, and have a close inspection of what comes out.
No shavings or filings or chunks in the oil.

4th is check the toolbox (?), and that roll of tools is securely fastened and can't clunk about. !!
And that EVERY nut and bolt on this machine is tight and shipshape.

Independent of speed might mean its going to be something a little odd, so think outside the box ??
Alternator rotor was in good shape ?  Windings were securely fastened and can't flap about, or rub ?
Hopethishelpsabit ...

[R]

Perhaps we should also enquire if the clutch itself is securely fastened onto the end of the mainshaft.
And locked down solidly there. ?

If the clutch can float about - or outwards in particular - then all sorts of bad things may happen....

[Rex]

  It only does it with the clutch engaged,

Are you implying it doesn't do it with the clutch pulled then?
That could narrow it down a lot.

[ramwing7]

Correct.  It does NOT make the noise with the clutch pulled in.

[R]

So have you pulled the clutch cover off to have a look yet ?
We could speculate until the cows come home otherwise .... !

[Oggers]

If no noise when clutch is pulled in then perhaps the clutch plates themselves are  a wee bit loose and knocking against each other when the clutch is out. I have had this on a few old bikes, and it was simply a case of tightening up the clutch springs. 

[iansoady]

Can't see how you'd have any drive if they were that loose. Rattle when clutch lifted yes but that's not what he says.

[Oggers]

Ian - normally yes indeed, but I have witnesed similar a couple of times when clutch is also engaged. Plates seemed to be slack, sticking in/on the splines, or else not an even take up on pressure plate due to uneven spring tension. I seem to recall I fiddled about with the springs and maybe even possibly cleaned up the plates and splines, and it went away. Easy to eliminate at any rate.     

[ramwing7]

Good ideas all.

I haven't had the opportunity to dig in yet, but you've definitely given me a place to start.

All the clutch plates are new and I dressed all the grooves and slots before installing them.

I'm really curious about the spring adjustment.  Seems as if I remember it seeming a bit weird when I hooked up the dial gauge to adjust the run out.

It'll be a couple of weeks, but I promise to get back to you with my findings.

Cheers.   

[ramwing7]

The tap tap is resolved.  Turns out to be a motor mount bolt that was inserted with the nut side in.  Reversed it an put bolt thru from the inside and the tap is gone.

Thanks to all for your help.   

[R]

And that EVERY nut and bolt on this machine is tight and shipshape.

Aha !

I used to wander around the pits at races ( where this was permitted),
and point out to owners that various nuts were intent on jumping ship.
It was surprising - to me - how many I spotted....

[ramwing7]

Tight, shipshape and........................pointed in the wrong direction.     

[R]

Shipshape ...

[Rex]

Still a bit lost on this.
How can a motor mount bolt inserted from the wrong direction cause a tap tap when the clutch is pulled?