strange cyclical whirring sound NOW SORTED!

[bristolmod]

no definitely mwa mwa mwa mwa

ning ning blang dang is more rear hub IMO................

[Craig H]

Pretty sure that was the noise I heard when on the way to Hastings my flywheel cowling broke up and hit the flywheel

[bristolmod]

I've just had a, serious, thought...............

If I recall, this engine still has the "cushed" rear sprocket (the one with the internal springs around its circumference). I'm wondering if one of these has broken up?

I shall find out next week and report back.

[bristolmod]

Had a look this morning- expecting the worst, but initially couldn't find anything amiss. The chain was properly adjusted; no missing rollers or apparent wear; front sprocket secure; rear sprocket had no visible play.

However..........there were 2 radial marks on the kickstart teeth on 1st gear, and a corresponding wear "ridge" on the plunger housing on the K/S shaft. It was apparent the K/S mechanism was just touching first gear although there was no "click-click" sound as per normal.

A quick replacement of the plunger and a bit of "dressing" to its housing and replacement of the chaincase gasket and alls well.

FWIW I had to tighten up the front sprocket about 6 months back, and at that stage I replaced the chaincase gasket with a thin paper type one as it was all I had at that time- this time, I've used the "chunkier" version which is about twice the thickness= chaincase is now moved out away from the clutch area a fraction and the K/S mechanism now clears everything.

Thats my theory anyway!!

Thanks to all that offered ideas

Chris

[Special X]

Sheeeit!!!! . . . . I've got that sound . . . and it's fitted with a thin gasket

[bristolmod]

I can't believe the tolerances are that tight on a 50 year old bit of engineering, but it seems to have done the trick.