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How can I make an FCR 41mm MX work?

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Ok, today I called keihin and they told me the carb on my bike is an FCR 41 MX! 🤣

I bought it used with this carb and I dont know what I shall do to fine tune it.... my mileage is low as hell, about 100 km at 8 litres of fuel. I love it though, I just want to fine tune the airflow to make up for the excess fuel i guess. I'm thinking about a DNA airfilter and tuning it up at a dyno for smooth performance...

Also my bolt-on exhaust needs to have a little upgrade... I'm thinking of buying the yosh trs without the silencer, as I have a Ti silencer from mivv. Will the yosh fit there? :banghead:

Any help appreciated, buying used bikes that have been improved is a hell to find out whats there and there, but this bike was to good to pass... :banghead:🤣

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Depending on what main is in it I might drop the needle a notch to start. Possibly Burned has already tried this carb?

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Cant tell. I'm not familiar with jettings so I reserve to look at the carb with some amazement and mystery.... I must find someone who knows and a dyno. Anyone had this carb / know someone who has it, etc?

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A 400cc engine will be way over carburated with a 41mm carb. A stock 400cc engine would require no more than a 37mm or at the most a 39mm carb. :banghead:

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Can I make the carb put less fuel than it does now, or shall I just raise the amount of air in the engine...? Better mileage would be great

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You just need to dive into it and find out what jetting is in there now: Pilot jet size, Pilot air jet (or pilot air screw position if it has the conversion), Fuel screw position, Needle and clip position, Main jet, Main air jet. And leak jet size in the accelerator pump circuit.

Being that it is bigger than normal, you may have to use bigger fuel jets to compensate for less velocity thru the carb. Of course you can change it. It is very tuneable.

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:banghead: I'll wait till i get a full exhaust to have some outlet and then straight for the dyno-jetguy. I'm too intimidated to work with such a carb on my own!

Thanx for the info guys :banghead:

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