A50 Bottom end?

[shaun evans]

Hello all,

I'm getting a nasty deep grinding/scraping noise from what I reckon is the bottom end area of my '64 A50. The noise only appears when the engine is hot and is only apparent when the engine is at tickover when applying or coming off the throttle a little.

The bike runs fine at all other revs and through the gears. I've recently renewed both layshaft bearings and checked the gearbox and that seems fine. She doesn't smoke or use any oil at all.

Your thoughts would be greatly appreciated.

Thanks...............Shaun.

[DAVE BRADY]

Good morning Shaun,

Perhaps it is still there above tick over but the engine noise drowns it out.  Could it be coming from the primary case?  As you have had the clutch etc. off to do the layshaft bearings could the spring adjusters be catching the casing?  If it did not make this noise before then it is most likely connected to the work you have just done.  Did you check the layshaft end float after re-assembly?  Did the gear box turn easily by hand after tightening the plate that holds the cluster?  Can you hear the noise when you just turn the gearbox ie clutch lever pulled in?
A lot of questions but the answers may help to locate the problem.

Dave.

[shaun evans]

Hello Dave,

I'm pretty sure the noise is not from the primary. The noise was there before I replaced the layshaft bearings. I'm reasonably au fait with the primary and gearbox as I've had to sort out a very troublesome A65 box out last year (without the help from JulianS I couldn't have done it!)

The noise really is a low down scrape/grind. It's very noisy. I've had the bike running for 20 minutes today on the lift and can't replicate the noise! Only seems to happen after a good ride when she's really hot.

I think it may be coming from the timing side. Sorry to be so vague but hope this helps.

Cheers........Shaun.

[DAVE BRADY]

Hi Shaun,

I cannot think of anything that would make that sound and that you would not have noticed when you had the timing covers off to do the gearbox bearings.  If anything had loosened there would be witness marks on the cases.  Even if it has to be hot I would expect there to be marks of some sort when inspected.  Have you taken the sump plate off to see if there is any debris in there?   If anything is scraping in the crankcase it would show up in the sump.

Dave.

[shaun evans]

Hi Dave and thank you for your reply.

I'll take the sump off as soon as I can and have a look. The primary has got to come off again though as I've damaged the sprocket oil seal when putting it back together as it's leaking gearbox oil from there! I'll have a good poke around there as well.

Will keep you posted.

Cheers..................Shaun.

[shaun evans]

Hello Dave Brady and all,

Have taken the sump plate off to have a look and there's absolutely no metal in there, I filtered the oil & ran a magnet round, nothing inside the filter either.

Question is where do I look next? I was thinking primary and timing side covers off first and check in there again. As I said before, there was nothing noticeable when I replaced the layshaft bearings. Perhaps I should see if there's any endfloat on the crank or any play in the T/S bush>

Any pointers would be greatly appreciated!

Thanks................Shaun.

[shaun evans]

Ah, a photo sneaked in there! That wire was inside the filter. Assume as it was awkward to get out (let alone get in) it's the gauze securing wire....

[DAVE BRADY]

Good morning Shaun,

A process of elimination seems to be in order.
Have you run the engine with the primary cover removed?  If not then do this and see if the noise is still there or can be identified. Operate the clutch and watch the primary chain whilst blipping the throttle a bit.  Look but do NOT touch any thing that is moving. With the engine stopped you can check the end float. If all checks out ok in the primary switch to the timing side.  Obviously starting and running the engine is probably not easily possible but take off the outer cover to aid listening and remove the spark plugs.  Engage top gear and get a willing helper to turn the engine as quick as they can.  Pull in the clutch lever and just spin the gear box in each gear.  I know this is all clutching at straws but the more things eliminated the better.
Although the noise is associated with a hot engine it could be that with no engine noise it may be audible when just turning the engine.

Dave.

[shaun evans]

Evening Dave,

Thanks for your thoughts on this, I'll get onto it in the coming days and report back.

Cheers.....Shaun.