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Old 07-10-2016, 05:57 PM
1997formula583 1997formula583 is offline
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Default carb tunning for bored over engine?

at low end I think it is rich and pretty close to good at top. I think the carbs are from a 670 mxz (40mm?). it had 60's for the polite I have already went down to a 50 and it is still rich I think should I go down another size or keep playing with the idle air screw.(does that even change anything with the polite?). what are the symptoms for rich and lean?. also if anyone has an idea for what jet should be used its a formula 583 but it has been bored over .030, if you have any ideas I really needs help with it right now
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Old 07-10-2016, 08:22 PM
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Summer or winter drags? The idle screw does nothing but idle, those carbs have a fuel screw if memory serves me correctly. Turning in leans it, out makes it richer (pilot circuit). You are entering into the test and tune world. Been there done that. As for what to start with, what temps and altitude? Here in MN we ran doo tripple sleds at Haydays. Lots of variables in play.

If it's too rich or too lean they act the same, loss of power and EGT'S are a mess. Good check is when on the throttle, give it some choke, or in your case hit the primer. Does it feel stronger? If so, it needs more fuel. If it falls on its face, jet down. Pilot circuit is only there for a short time, the race is on the main jet. Have you pulled the rave springs out yet? First thing we would do and get the lightest ones possible.

Be sure to do lots of plug checks.

We would set the idle apx 500~800 rpm below engagement. Since its a improver, you may be able to run a stutter button.
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Last edited by Mac-Daddy-Racing-212; 07-10-2016 at 08:26 PM.
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