can anybody help? backfiring

[exracer416]

i tried posting this in the jetting post but no luck, heres my deal
i have a 400ex stage 1 hot cam 416 11:1 piston 450r carb full yosh pipe uni filter no air box lid. it has a 52 pilot jet 175 main and the needle has the clip all the way down to the richest setting. what its doing is when i hold the throttle about half way the header gets red, and when i let off it backfires. am i too lean on the main?? and it will idle for a little bit then backfire through the carb and shut off. anybody have advise???

thanks

[bigbad400]

way too lean do not run it like that, you definatly need to go bigger on the main 52 pilot seems way to big too but is a 416 so i dont know but mine has a 170 so.....

nonethe less thow if your headpipe gets red your piston is about to melt do not run it like that if you want to keep it.

[exracer416]

it has a 450r carb a 38 pilot wouldnt even start it

[BEAVER.989]

A leak somewhere would cause these issues. Is everything plugged up right? Intake boot secure?

[exracer416]

yeah everythign is tight it runs fine i have a 180 in it 5th clip down and a 52 pilot jet how can this thing still be getting hot???? i rode it around to see if some air circulation would help but still got red. im starting to wonder if its an oil circulation problem. its a different bottom end than what i had, i seized the piston to the crank in the last one so i threw my spare in but im reusing the head and cam im wondering if that has anything to do with it

[BassHunter0123]

im no expert but you are the first person i have seen that had the needle clip all the way down. try moving it up a notch and adjusting your air screw

[exracer416]

the needle is at its richest setting on the 5th clip down so its getting as much fuel as possible

[nakomis0]

I also think its a leak or a carb problem. If your jetting is on the big side of where it should be. Do you have or can get another carb to swap out.

When I first bought a brand new FCR carb it was running really lean I put huge jets in it and nothing helped. Luckly I had a friend with an extra carb we swapped it out and it worked. I returned the FCR for a new one and it worked. So bad carbs do happen.

[exracer416]

put the air box lid on seems to run better now header doesnt get red. was hoping i coulda run without it. have a race on sunday, guess we'll see what happens....sprayed around the carb with some carb cleaner and it didnt rev up or anything so we'll see
thaks for the help guys

[neff400ex]

My old 250ex had a hmf full and all i did was put a hopup kit in it made it not as loud but stoped backfireing

Originally posted by neff400ex
My old 250ex had a hmf full and all i did was put a hopup kit in it made it not as loud but stoped backfireing

what is a hopup kit?

[neff400ex]

jet kit

[storms400ex]

jet kit = hop-up kit LOL :p

then call it what it is instead of some stupid name...