Big Bore Jetting question??

[JimAintYellow]

I have a 425 w/11:1, hot cam stage 2, ported by a well known shop, I have it jetted at 195 on the main, with 42 pilot, and the clip down 1 on the needle w/stock carb(no choke) tc racing revbox,uni filter, no lid, curtis sparks x4. It is running great, better than expected, just the porcilin on the plug is white as snow doing a wot through all gears test. I have checked for leaks between the carb and head,and none are present. I know it sounds odd to be running this large of a jet and having probs, thats why I am posting this question.

[oregonrider89]

I can't offer and help other than to agree with you that your main jet does seem very large. Your pilot jet may be a little small, I run a 50 in my 440. I don't know if that is your problem. LRD said that your engine runs on the pilot jet mare than you would think. Just a thought.

oregonrider89

[3x440ex]

i'm having the exact same problem with mine. i went all the way up to a 200main jet......it felt like it was too rich but when i checked the plug it was white. i called dunkin racing and the machanic there said that pump fuel will give a false reading. he sugested i go back down to a 175......he said just go by the way it feels more so than the color of the plug.

[oregonrider89]

The pump gas doesn't have enough lead in it to give am accurate plug reading. I've been told to go by how it feels too.

oregonrider89

[muff]

i'm runnin a 180 main on my 440, I'm gettin a 42 pilot soon but it runs good how it is right now, no lid and k&n w/ outerwear

[oregonrider89]

What size pilot are you running now? Why are you changing to a 42?

oregonrider98

[muff]

Originally posted by oregonrider89
What size pilot are you running now? Why are you changing to a 42?

oregonrider98

i've got a stock in there and it doesnt always idle the greatest

[Colby@C&DRacing]

Pump Gas can not be used to check a plug. Like was said before it has no lead. If you put race gas in your bike it will give alot better reading because it is leaded fuel. A good way to check your jetting is to make sure it is to rich and then work your way down till it runs correctly. I do feel that a 200 main is to rich I would use a 175 main 45 pilot and the needle on the four groove from the top. Just my two cents.

Colby at C&D Racing
308-696-7805