Reply To: Howard the Hunter.

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Carburettor adjustments are the first step in the process and nine out of ten times you will find that they cure the problem.

Don’t start fiddling with governor settings or anything else until you’ve adjusted the fuel/air mixtures, you will only make the matter worse.

Start by setting the main jet- run the engine at working speed and screw the main jet in slowly until it runs rough; note the position of the screw head. Then unscrew it back out again slowly- it will run smoothly then rough again the more you screw it out- again, note the position of the screw head when it starts to run rough again.Screw the main jet in halfway between these two positions and you will find that it will run smoothly at it’s working speed.

Next, turn your attention to the idle mixture screw. Run the engine at a slow idle and perform the same process with the idle mixture screw. Once it’s running smoothly at idle you can then reduce the revs using the external screw on the throttle lever.

You haven’t finished yet!

When you increase revs from idle, does the engine hesitate before it picks up? If it does you will need to richen up the idle mixture slightly. The reason is that when idling the butterfly is nearly closed with only a small gap between it and the venturi wall. If you look closely inside the venturi you will see some small holes drilled just where the butterfly meets the wall- this is where the fuel/air mixture from the idle jet comes out and it not only allows the engine to run evenly at idle but also helps with the acceleration from idle to working speed. If it hesitates you either have one of the holes blocked or the mixture is too weak to bridge the gap between idle and working speeds.

It sounds complicated but it takes less time to do it than to read this piece!
Good luck!