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Slow Jet vs. Main Jet

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Can someone tell me the difference between the two jets, also one other question I've seen people saying to change the main jet to #42 for easier starting and reduce backfire??? My book specs a # 178 for the Main and a #40 for the slow jet is this correct or is everyone just as confused in calling the slow jet the main??? Any help would be appericated I'm going to check valve cleaence in the morning but this thing is just to hard to start and it's backfiring under decel I will also check the air screw I assume its under the carb from the cofiguration of there special tool. We have to leave for a race on thursday I need to get this thing working properly.

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the 178 is the main.... the 42 or 40 is the "pilot jet" which controls idle to 1/4 throttle i think?

THe main jet controls 3/4 to Full throttle.

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pilot jet is from idle to 1/4 throttle

needle is from 1/4 to 3/4

main is from 3/4 to wide open.

fuel screw needs to be 2 turns out from closed.

you need to change the pilot jet from 40 to 42 to get rid of the bog and easier starting.if its stock dont touch anything else.

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loosen the clamps on the carb and turn it sideways.on the leftside of the carb,underneath the float bowl is the fuel screw.it is hard to see cause it sits up in.turn it all the way in,then back out 2 turns.

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The #42 pilot jet will stop most all the pop on decel for normal altitude riding. It will also lower the operating temps when riding very slow (such as thru the pits at a race)as the bikes are running lean with a #40 jet.A "t" handle air screw from 1 of the aftermarket companies is a great addition. These bike are a little sensitive to air settings as the temps change during the day if you want to keep it right on the money.

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Check your sparkplug, if it is black then a 42 pilot won't help you any. You would need a smaller pilot.

Just because the plug is dark doesnt mean the pilot jet is causing the richness.... ENLESS u would just happen to start ur bike up and idle it every single time u ride... meaning...there are more than just the pilot screw that can make ur plug dark (rich)

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zmann, are u saying u don't let the bike warm up before you bike? :cry: :cry: I agree with the fact that the pilot may not be the jet at fault, however going to a richer pilot won't help you any either.

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Thanks all for the post I did go to the #42 and now it starts first kick...

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