As there is effectively no mixture control on the MG2 carb I have found that the only way to get a slow enough tick over to avoid gear crunch is to play around with ignition timing by both adjusting points gap and magneto. The valve clearance also effects slow running so again have a play with the clearances. I also find that unless you run any MG crawler for about 5 minutes from starting to get it all hot then slow running and crunching are worse. Changing the clutch springs may help but shoes may make it worse.Getting it all hot and good oil in the air filter would be first on the list.
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