Mysterious metallic rattle

[rog60]

Since a rebuild my Indian GP200 seems to have developed a rattling sound appearing to come from the transmission area. Recent changes to engine as follows:
1.Indian chain was extremely slack so I fitted a spare 19 T front sprocket to take up the slack but the chain is very tight now(virtually no free play).
2. I thought it might be the gearbox bearings as the drive side oil seal failed recently and I drove with virtually no oil in gearbox for 40 miles so these were replaced.
3. I replaced the mag side and drive side bearings with SKF/FAG 'C' rated and oil seals with MBD Viton ones.
4. On advice from here I removed the bottom piston ring (3 cast thick ringed piston) and fitted NOS spanish piston gudgeon shims to Mazuchelli crank which has no shims on the big end (and sufficient clearance for the piston to take them).
5. Fitted new bronze bush to clutch bell.

The crank webs are not touching the casings.(i can get a thin feeler gauge between them)
Engine starts and pulls well and max indicated speed is just under 70mph and will maintain 50/55mph for long periods.

Engine is SIL GP200 S Stage 4, 19/47, 22mm Dellorto 123 main 48 pilot
Ignition 19 BTDC and checked with strobe. (had to move stator anti clockwise a little to get marks aligned)

Am I worrying needlessly or have I missed something.

Suggestions would be greatly appreciated or do you need a bit more info

[bristolmod]

three possible areas:-

1) removing the bottom ring may allow the piston to "tip" in the barrel and creat a knocking noise IMO

2) you've advanced the timing a tad by moving the stator anti-clockwise. Have you wandered into the realms of "pinking"?

3) you've taken up the slack in the chain by fitting a bigger front sprocket. I would have replaced the chain with a quality one of the original size. You state that there is very little play- is there a permanent pull on the bearings which has caused damage?

Chris

[rog60]

three possible areas:-

1) removing the bottom ring may allow the piston to "tip" in the barrel and creat a knocking noise IMO

2) you've advanced the timing a tad by moving the stator anti-clockwise. Have you wandered into the realms of "pinking"?

3) you've taken up the slack in the chain by fitting a bigger front sprocket. I would have replaced the chain with a quality one of the original size. You state that there is very little play- is there a permanent pull on the bearings which has caused damage?

Chris

Rattling didn't occur until some weeks later after removing piston ring so don't really think it's that.

I have now retarded the timing a little but no difference.

Play is about 1-2cm on chain, wondered if it might be chain 'singing'.

The rattle didn't occur til after running with no gear oil.

Engine now has 3400miles on with original piston/rings but I still have this thing fixed in my head about running 40 miles with little gear oil.