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FMF with Powerbomb...recommended jetting?

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Just picked up a 2002 450 with a full FMF Powercore 4 with Powerbomb header....I checked FMF's website, and it says standard jetting should work....I have 146 Main & 45 Slow jets...right now. Everything I have read so far on here talks about at least a 165 for Main....can't remember the size for the Slow jet now. I was looking for some guidance please, mainly because the bike is hard to start and I was thinking perhaps the Slow jet needed to go bigger? "Valve lash" is within spec, so I ruled that out. New Iridium Spark Plug....any advice would be greatly appreciated.

Thanks.

Edited by suz1100

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Just picked up a 2002 450 with a full FMF Powercore 4 with Powerbomb header....I checked FMF's website, and it says standard jetting should work....I have 146 Main & 45 Slow jets...right now. Everything I have read so far on here talks about at least a 165 for Main....can't remember the size for the Slow jet now. I was looking for some guidance please, mainly because the bike is hard to start and I was thinking perhaps the Slow jet needed to go bigger? "Valve lash" is within spec, so I ruled that out. New Iridium Spark Plug....any advice would be greatly appreciated.

Thanks.

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Thanks for the link. This is what I found as well. They recommend all Stock jetting...I also see they have a Jet kit available to use with their exhaust system...why would u need it if they recommend Stock jetting? :/ Thx.

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Thanks for the input. I will check that off my list of potential reason for the "hard start".

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Thanks for the input. I will check that off my list of potential reason for the "hard start".

 

I have an 04 that was hard to start.  Previous owner took it to a couple Honda shops that couldn't fix it.  Turned out the timing was off by one tooth.  Really small difference when looking at the chain/gear but now starts first kick every time.

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Good to know,

Thank you! I will check that out next. Just got done taking the carb completely apart and cleaning it real good. Had a heck of a time getting it to start after putting it all back together. Tried the "compression stroke" kick teqnique, and so far, I have had a little better luck getting it started. Mine want a little gas when I kick...I guess they are all different. Thanks for taking the time to respond.

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Good to know,

Thank you! I will check that out next. Just got done taking the carb completely apart and cleaning it real good. Had a heck of a time getting it to start after putting it all back together. Tried the "compression stroke" kick teqnique, and so far, I have had a little better luck getting it started. Mine want a little gas when I kick...I guess they are all different. Thanks for taking the time to respond.

How does it idle? I had a hard time getting mine to start a while back. Turns out I had the idle screw ajusted out so far after a good cleaning and the slide was completly closed so the intake could not get air/fuel delivered to it

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In addition to ensuring your cam timing is absolutely correct also check that your ignition timing is correct. I bought a 2004 and it was horrendous to start. Turns out the woodruff key had been pushed out of it's slot by the last mechanic who installed the flywheel and the ignition timing was off. Found the woodruff key laying in the ignition cover. Thank God it didn't get caught up in anything. Also check that fuel screw is about 1 and a half turns out from full clockwise. The throttle slide plate MUST be installed with the notched side down and the thin rubber sealing ring must not be deformed and installed so the angled edge is toward the slide. Good Luck and keep us informed of your progress. I did not have to change my jetting after installing complete FMF Power Bomb System, HotCams Stage 2 and Wiseco 13.5:1 piston. Starts first kick with 3 full twists of throttle and jetting is spot on.

 

Elevation 6000 ft

55 Leak Jet

42 PJ

Needle 3rd clip from top

168 MJ

FS 1 1/2 turns out

Edited by Yodiracer

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Thanks for the informative posts. I will definitely investigate all these options. I am taking a couple of days break from it and will get back into it later in the week. I will update this thread with hopefully a positive result which in turn will hopefully help someone else.

Thanks.

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If its hard to kick check your auto decompression mechanism adjustment.

And as mentioned.

Your cam timing.

Vaccum release plate seal and set your fuel screw with the low slide method.

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my 04 was hard to start and the vacum plate seal was backward. i couldn't find anything to show the direction that the seal goes. i flipped it around under fustration and fixed the problem

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