Identifying a rattle

[a101960]

I tend to agree with Muskrats suggestion that it could be a loose valve guide. In fact I think that a loose guide is the most likely cause, and the reason that I say this is because you say that the noise is eminating from the top on the left hand side. Often you will see evidence of oil burning, but it is not always apparent until you remove the head. The rattle sounds like a badly adjusted tappet, and and as Muskrat has said, normally the rattle is absent on a cold engine, but becomes increasingly audible as it warms up. If you lift the head, the guide will appear to be tight because it only becomes loose when the head is warm, although it might just be loose enough to drop out once you have removed the valve spring. This problem is quite common on ally heads, less so on iron heads but it is not unknown for iron heads to suffer in this way too. Also check the left hand plug. Does it look as if oil has been burnt?

John

[duTch]

As I was waking up(yawn), I did the thinking I should've done before I wrote, that being, if the shims/thackeries are in wrong side would be fairly obvious as the adjusters likely won't sit on the stem well(if at all)..duh  ?
 Back to the corner, duTch

[K1100]

Hi A101960 and Muskrat ... I will certainly check the valve guides. This rattle is there right away from cold.  The fact that it disappears on the overrun and comes back at a steady engine speed still bugs me as being an important clue. I am trying to think what sort of top-end wear or damage would sound worse under load?

[a10 gf]

lol amazing amount of possibilities. I'd start an elimination method by checking piston slap \ rings \ big+small ends, as suggested in a post above. I've had worn small ends, making quite some noise.

[Rookie_V#60]

Yes, I also tending for my case to the small end,....the often reviled Haynes says: ... worn small end bushes produces a noise somewhat similar to piston slap. ..

but they also say: ... a clicking noise from the vicinity of the rocker boxes is the usual symptom of advanced wear of spindels or rockers ...

 ???? Rudolf  

[BSA_54A10]

If the guides are slipping up & down in the head you should be able to measure variations in the tappet clearences

[bsa-bill]

If the guides are slipping up & down in the head you should be able to measure variations in the tappet clearences

How does that work then Trevor

[Topdad]

In 1966  I owned a beautiful A7SS ( rfy708) which definatley had a loose exhaust valve guide problem , there was no rattle at all from it ,the only way it showed itself was serious misfiring with spitting and farting when trying to get to full bore when I stripped her down the offending guide fell out when I turned the head upside down and the alloy head was cold! When run around town which I'd been doing for some time on lower throttle openings no problems and would tick over as well as any A7 and without any noise at all,infact people used to comment how low the mechanical noise was from her. I know this confuses things and don't wish to contradict other more knowlegable thoughts but I felt it was worth mentioning, best wishes BobH.

[Butch (cb)]

Maybe just keep riding and see if it gets worse?

[chaterlea25]

NO !!!!
Fix it before it gets worse !!!!

John

[K1100]

I think I have found the cause of the rattle .... these two short videos show it.

http://www.youtube.com/watch?v=oNaMQ2NpZsE

http://www.youtube.com/watch?v=DTpS9cYqL1g

The clearance between piston and cylinder on the left cylinder is 20 thou and on the right cylinder 15 thou. So that seems to me to explain the rattle on the left. And I imagine that the answer is rebore and new pistons. According to the paperwork belonging to the bike it is 11,000 miles (and 10 years) since the last rebore/pistons, which doesn't seem a very high mileage.

[muskrat]

 G'day K1100. watched the video and yes there is a lot of movement there but there should be some. Does seem a lot for 11,000 miles. Piston clearance is measured at the bottom of the piston skirt at front or back. Depending on the type of pistons 1 1/2 thou for split skirt up to 5 thou for forged.
 Yes I would be doing at least a bore and piston job on her, and have a good look at everything else while your at it. Feel for crank end float, con rod play (up & down), little end play, t/s bush, cam & follower wear etc, etc. Have a look at pistons for signs of wear on the sides (gudgeon pin hole side) indicating little end out of line.
That should keep you busy for a while.
Cheers

[K1100]

This is the piston from the rattling side: there is a nick in the top front edge, visible in the photo, and heavy scoring that looks as if something has got between piston and cylinder. Both cylinder bores are perfect, and there is no ridge at top or bottom of either side ... absolutely smooth. The other piston also looks to be fine: no scoring and no burning.

[muskrat]

 Yep she's had a seizure. I'd get the bores checked for size and parallel, you might get away with just new pistons & rings, and a light hone of the bores. Strange there's no marks on the bore. May have nipped after a re-bore and just honed and slapped back together.
Cheers

[trevinoz]

That's one of the worst cases of seizure that I have seen!
Probably not enough clearance last rebore.

Trev.