Timing and carb settings

[a101960]

I have had an on going timing/carburettor setting issue for quite some time. Anyway this morning I removed the carburettor and replaced the anti bias spacer with a conventional flat spacer. I noticed that the flat spacer induction hole was smaller than the drip tray hole, and that the gaskets had the same fault, so I spent some time opening them out. I perhaps should mention that the timing side cylinder was running slightly leaner than the drive side cylinder before removing the carburettor. Anyway the careful aligning of the the gasket and spacer induction openings has definitely proved to be worthwhile. Both cylinders are now burning identically and the engine revs out smoothly and eagerly. I had previously had a magneto problem.The magneto housing was was causing the shaft to run eccentrically and the cam ring was unequally spaced. Having had this fixed there was still a problem. Things did improve but still the engine was not giving its full potential. Well it would appear that there was an induction problem due to ill fitting gaskets and the anti bias spacer. I would suggest if you are experiencing a difference between the cylinders it would be wise to first check out the mag to ensure that the shaft is indeed running true, and secondly to ensure that the induction gaskets are not masking the flow. I was initially deceived into thinking that I was suffering from induction bias, and fitting an anti-bias spacer did slightly improve matters, however this was not a real cure, and the spacer was merely masking the symptoms. I cannot believe how the engine has been transformed, and I will freely admit it has taken a long time and led to going up many blind alleys before I resolved what seemed to be an insoluble problem. I cannot tell you how many times I have re-timed the engine, re-tuned the carburettor, double checked the valve clearances, and swapped plugs. I thought I would pass this information on in case it is useful to any one else.

John 

[tombeau]

Interesting stuff John,
I've also noticed a discrepancy between gasket, drip tray. I keep meaning to do something about it.

I'm also experimenting with an anti bias gasket at the moment but am now wondering, as LJ suggested, if my problem could be down to an ill fitting exhaust pipe. My pipes are now a far better fit in the head thanks to the "Snowbeard System" backed up with a dod of silicone gasket sealer.
Cheers,
Iain

[A10Boy]

John
Thanks for the info, well worth remembering.

[LJ.]

Good Stuff John! also great to have met you at Calne last Saturday, fantastic RGS you have and I'd not worry a jot about your gear change as you had been worrying about. It felt perfectly okay to me, not unlike my own.