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43mm FCR carb Vs XR615cc .... will there be issues?

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The 2003 Wr450f came with a 39mm carb.........

 

...and yes, you will be pulling 15 times more vacuum pressure just above idle, so you will need to fine tune it.

Clean and lube the hot start and choke plunger, clean the apump system, put in a new diaphragm, and pilot jet

 

http://www.dirtrider.com/features/protips/141_0707_keihin_fcr_carb_rebuild/

you will need to get an adjustable remote fuel screw so you can determine pilot jet size, test the apump for good 1 sec squirt that does not hit the slide, and probably replace the pilot with a new 45

Edited by TheKoolAidMadeMeSick

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The 2003 Wr450f came with a 39mm carb.........

 

...and yes, you will be pulling 15 times more vacuum pressure just above idle, so you will need to fine tune it.

Clean and lube the hot start and choke plunger, clean the apump system, put in a new diaphragm, and pilot jet

 

http://www.dirtrider.com/features/protips/141_0707_keihin_fcr_carb_rebuild/

you will need to get an adjustable remote fuel screw so you can determine pilot jet size, test the apump for good 1 sec squirt that does not hit the slide, and probably replace the pilot with a new 45

Awesome mate,thankyou!!Performance wise....Is it all worth it?And the carb ive got is 43mm...Was off the WR,Im in new zealand so they may be different and or aftermarket size

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All WR's came with a 39mm world wide

The 43 is an aftermarket carb, but why I don't know....they put them on 750 in line fours and supermoto guys love them for ported and camm'ed motors.

They also came stock on the quad motors before FI.

If it has the 'blank' spot on the left side of the carb for something that is 'not there' (ACV valve) then you have a recent carb, which is what you want.

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