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Old 04-29-2013, 11:13 PM   #1 (permalink)
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Default Have a midrange studder and light popping

Ok let me first say I done my engine build just this last winter in the 30 degree range for temps. My mods are 434 kit. old hot cams, head porting, full exhaust and FCR 40. My carb has a 170 main jet 42 pilot and the NCVQ needle with clip in the 4th groove from the top. Ran great all winter. Today was the first warm day I rode it "about 80 derees" and it seemed to somewhat studder and pop out the exhaust at cruise on the road. Anything below and above the mid range was fine. Pulled the plug and it looked a little rich. Center was very dark brown and the metal on the outside was black. At first it seemed like a lean condition but the plug tells me other wise. I dropped the needle down one clip position so the clip is now in the 3rd groove from the top. Seems to run alot better and has little to no studder and popping. Now I just went out and ran it with a new plug and now the plug looks white. Does it take a while for the plug to turn colors? I rode for about 10 min. and came back to check it. Plug went from looking rich to lean with just dropping one clip position. New plug though. Do I need to run it for a while longer?
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MODS KFX 400
Namura 434 bbk
CP 12.5 forged piston
Hotrods +4 stroker crank
Wiseco forged valves
Kibble white double springs
ported head
web 539+3/539+3 cams
LRD exhaust
custom head pipe from kfx guy
Dynatek programmable ignition
FCR 43 carb with quickshot 3
custom air intake with UNI filter
HID headlights
1 inch wheel spacers F&R
YFZ 450 front brake calipers

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Last edited by mvvette97; 04-29-2013 at 11:14 PM. Reason: spelling
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Old 04-29-2013, 11:42 PM   #2 (permalink)
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Sounds like you cured your problem with the needle change.IMO I wouldn't depend on a plug reading.. Can't see crap in those tiny plugs anyway, and you have to do a reading for each circuit, killing the motor. Pain in the butt.. Like you found out, it will let you know if the jetting is off...
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Old 04-29-2013, 11:51 PM   #3 (permalink)
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I would try going up on the pilot
Dont know if it will help
I have a 48 in the carb I got from you
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Old 04-30-2013, 01:08 AM   #4 (permalink)
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Quote:
Originally Posted by ctnstabber View Post
I would try going up on the pilot
Dont know if it will help
I have a 48 in the carb I got from you
wouldn't that make it more rich yet? I have a 45 pilot in my jet kit but I used the 42 just because it was stock in the carb.
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MODS KFX 400
Namura 434 bbk
CP 12.5 forged piston
Hotrods +4 stroker crank
Wiseco forged valves
Kibble white double springs
ported head
web 539+3/539+3 cams
LRD exhaust
custom head pipe from kfx guy
Dynatek programmable ignition
FCR 43 carb with quickshot 3
custom air intake with UNI filter
HID headlights
1 inch wheel spacers F&R
YFZ 450 front brake calipers

https://www.facebook.com/marc.vanderflught
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Old 04-30-2013, 02:23 AM   #5 (permalink)
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Quote:
wouldn't that make it more rich yet?
Yes, a bit

Now that its warmed up you might try to drop the main one size as well. Might be a bit crisper on top.
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Old 04-30-2013, 10:22 AM   #6 (permalink)
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If you dropped the the clip it will lean it out
This is why I suggested going to a 45 pilot
because you say the plug shows it to be lean

I know I had my carb off and on so many times
I could do it in my sleep
It took some time to get it dialed in correct
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440 bbk
+4 crank
webs cams
port &polish head
FCR39
Yoshi full exhaust
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Old 05-01-2013, 11:18 PM   #7 (permalink)
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Quote:
Originally Posted by ctnstabber View Post
If you dropped the the clip it will lean it out
This is why I suggested going to a 45 pilot
because you say the plug shows it to be lean

I know I had my carb off and on so many times
I could do it in my sleep
It took some time to get it dialed in correct
I think I may try the 45 pilot. I went on a several hr ride today running mostly in the low to mid range and just pulled the plug and it still looks white. That being said it does run wonderful considering the mods I have. No spitter sputter or hesitation or anything. I see most people do run a 45 pilot. My fcr 40 came with a 42 stock and it seemed to idle great. So I'm guessing after putting a 45 in I will have to turn the mixture screw in a bit?
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MODS KFX 400
Namura 434 bbk
CP 12.5 forged piston
Hotrods +4 stroker crank
Wiseco forged valves
Kibble white double springs
ported head
web 539+3/539+3 cams
LRD exhaust
custom head pipe from kfx guy
Dynatek programmable ignition
FCR 43 carb with quickshot 3
custom air intake with UNI filter
HID headlights
1 inch wheel spacers F&R
YFZ 450 front brake calipers

https://www.facebook.com/marc.vanderflught
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