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470 jetting with a 39mm FCR-MX

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After a lot of searching, I only came up with recommended jetting for the BB+stroked motor with a 41mm FCR.

If there's somebody out there already running this combo with a 39mm FCR, post up your jetting setting.

If I remember correctly, Eddie did a dyno run with this setup on Jonathan's bike. Maybe he can chime in.

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Would this be a good base for sea level?

158 main jet

200 main air jet

emn needle

clip 3

45 pilot jet

2 turns fuel screw

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I checked my pilot jet circuit today and found out that, when idle speed is set properly, the bike seems to be running/idling the best with the fuel screw at 0.75 turns out.

Is it possible that it might need a smaller jet than you recommended?

42?

Again, I'm at sea level.

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If you are running an alloy fuel screw, needing a smaller pilot is not uncommon. Personally, I'd run a brass one (like the Merge Racing or Kouba) or stainless steel (Keintech) and not have this issue.

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It's a stainless screw.

I did try to set the idle as low as possible.

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Could that explain a slight 1/2-3/4 throttle hesitation as well?

Should I try to replace both the jet and the needle? Or replace the jet and play with the clip position?

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Could that explain a slight 1/2-3/4 throttle hesitation as well?

Should I try to replace both the jet and the needle? Or replace the jet and play with the clip position?

I would think so...... If you order from sudco they have a minimum order $....So to fill it I`d get the jet as well. You can find great info on their website about the needles in the catalog download pdf....:p:lol:

Erling

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The more I ride it the more it makes sense that the needle jet might be worn out.

My jetting should be pretty good. I just replaced the o-ring so squirt should be good too. Despite that, the motor still chokes sometimes when blipping the throttle from idle, hesitates a tiny bit around 1/2-3/4 throttle and has a hanging idle every now and then. A little blip of the throttle always fixes the hanging idle - almost as if the needle was getting stuck. The cables are lubed and set up right, and the throttle is returning smoothly.

Do these symptoms make sense for a worn out needle jet?

Also, I was trying to locate it in the Sudco FCR-MX diagram so I could order it but with no luck.

Is it #26 - Main Nozzle?

http://www.sudco.com/Diagrams323728/expfcrmx.gif

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Thanks Eddie. Does it sound like this might be the source of my jetting issues based on the symptoms?

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I guess I can start with replacing the needle jet and work from there. Thanks again :p

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