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FCR Carb Jetting Woes

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Well I have been fighting with this carb off a RMZ450 for 2 weeks now.

Sea Level

55pilot

165main

1 setting richer than centered on needle

Uni Air filter

FMF slip on

Uncorcked

With the above I tried almost every different fuel screw settings from .25 turns out to 3 turns out

The same sympton still kept coming up (a stumble fart if you will)

Then swapped out the 55 pilot for a 48 pilot, followed the instructions given on here on setting idle the same problem still arises

I rode it to work today and it does ok at cruising speeds but updon deceleration it stumbles or even dies?[/indent]

Edited by selztoad

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Fuel screw is for idle only. Set it for a perfect idle and leave it alone.

You need to adjsut eh AP, tha is the part of the carb that deals with a bog. Do the oring mod or wire the linkage or get a Merge Racing APS spring. Check/set the AP timing ensure you have a good squir tand that it just barely misses the slide.

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Fuel screw is for idle only. Set it for a perfect idle and leave it alone.

You need to adjsut eh AP, tha is the part of the carb that deals with a bog. Do the oring mod or wire the linkage or get a Merge Racing APS spring. Check/set the AP timing ensure you have a good squir tand that it just barely misses the slide.

I checked the AP squirt and it seems right, what is the cause for stumble after letting off the throttle if its not the Pilot Jet? It will idle fine for a minute or two and then cough/fart

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Pilot jet and fuel screw are for idle ONLY. It is the AP that causes a bog when you accelerate.

If the bike stalls when idling, then you have the pilot wrong and or the fuel screw wrong. I assume the rest of the engine is healthy and the idle speed is not too low.

You last post does not make a lot of sense. you are stating two distinctly different things.

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Is your hand off the throttle, when the smoothly running motor is idling, then stumbles?

If that's the case, it does not sound like a jetting issue; more like a fuel starvation or ignition issue.

Can you 'force' it to keep running by pushing up the idle, or blipping the throttle?

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