what is the effect of too much clearance on idler gear?
and too much clearance on primary gear?

by too much just say 10thou

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77 Leyland Clubman
1293cc, LCB extractors, pulsar dizzy (recurved), cooper s disc brakes, 40DCOE Weber

Too much Idler gear clearance (0.010 or so) will make it noisy, particularly at idle.

On the Primary Gear, do you mean end clearance or bush-to-shaft clearance?

Too much end clearance again will make it noisy and it may weep a bit of oil in to the flywheel and on to the clutch.

Too much bush-to-shaft clearance can give clutch shudder and oil on the clutch and possibly oil leaking past the seal.

Too much primary gear bush to shaft clearance (front bush worn) will make it noisy too.
Easiest way to fix this is fit a floating front bush. No machining needed (once you get the old bush out). Available from Karcraft or Minisport SA.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

i mean end clearance the gap between primary gear and c clip and washer

what would you say too tight clearance on both will cause eg under 3 thou?

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77 Leyland Clubman
1293cc, LCB extractors, pulsar dizzy (recurved), cooper s disc brakes, 40DCOE Weber

Under .003 on the idler is a real worry. A friend once built a motor which had only .0015" or so clearance cold. When the motor heats up the clearance reduces, he had trouble getting gears.
We had to pull it apart and change a thrust washer.

Under .003 on the primary gear and you won't get a decent oil film on the bronze thrust washer or into the bushes. Could seize up.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.