BIG Jetting problems

[thebutelr]

Ok here's the deal, I just installed a 172 main jet in my 350x because the 152 wasn't big enough to even color the plug and now when I start it it will only run with the choke all the way on and it has to be full throttle or it'll bog out and die out. Also when I had it running last night the header was glowing red and I couldn't get it running anything past 1/2 throttle when I was actually out riding it. What does this sound like to you guys? Oh yeah and when I took the plug out after revving it up in the barn and tryin to keep it from dyin it didn't have a ton of carbon build up on it and a patch of the porcelain was white and the tip of the plug was a light greyish color. Thanks. Later.

[BigGreenMachine]

What have you done mod wise? Is it the stock carb? Too many variables that you haven't told us.

[Wickedfinger]

Why did you jump so many sizes?. I don't recall what the stock main is but I would start with stock and up-Jet one size at a time. Red header "usually" means you are still too lean - but the 1/2 to mid stumble sounds like you are way too rich ..... as BGM said - what mods have you done to the motor?. Pipe, airbox mods all affect.

[slothminx]

Could the new jet he put in have crud in it? that would make it not want to go over half throttle and run lean:

[Tri-ZNate]

wow stock is only a 140 main. Why did you throw a 172 in?

[conig]

when I had mine jetted wrong and too rich my header turned orange. I thought I was too lean so I jetted up some more and it got worse.

I think it may do it rich or lean, even though I always heard lean was hot.

[Wickedfinger]

Leaner is always hotter - however, I have seen where substancial carbon build up on a header pipe, caused by an engine running too rich, will lead to hot spots, and cause the pipe to glow - but - usually only in the first few inches. Lean cherry pipes will glow for further down the pipe.

[Unclediezel]

Just for giggles----
If you put the old jet back in---will it run????
Retarded valve -or ignition timing can also cause glowing exhaust- The leaner jets can mask an existing problem elsewhere----go back to basics before condemning anything---Also---Look carefully at the jet--it may have been stamped incorrectly, or it may have been damaged during handling-shipping -installation--Etc

[trimoto55]

all 4 stroke headers glow in the dark i race motocross and at arenacrosses at night they all glow in the dark thats nothing to worry about...hope that helps ya

[thebutelr]

Thanks for your replies guys. Now on to the jetting. The mods I have for this bike are: supertrapp exhaust running 12 discs, k&n with no lid, 10.5:1 wiseco, and a lower grind web cam. The reason I jumped up so high on the main jet is because the 152 I had in there wasn't big enough to put any color at all on my plug when I would do a plug chop (and yes I was doing it correctly). I'm thinkin now that it wasn't my jet I put in there that made it act weird, because earlier today I went ahead and put the 152 I had in there and still the exact same symptoms. The bike runs really hot and can only be started with the choke on all the way and won't stay running unless its 3/4-WOT. With these things said, what do you all think it could be? Just throw out ideas at me because I'm totally stumped. Thanks. Later.

[BigGreenMachine]

Sounds like when you put it back together you set the timing wrong. Might want to clean the carb and check all passageways and if that fails then check the timing.

[Tri-ZNate]

any idea what your elevation is? I know some guys run 200 main jets because they are so far up.

[Unclediezel]

Definitely check timing-------You have all the symptoms of retarded timing---Did it backfire at all?

[thebutelr]

Sounds like when you put it back together you set the timing wrong. Might want to clean the carb and check all passageways and if that fails then check the timing.

My timing was off after I rebuilt the motor so I had to go back and take the head apart again and that time I checked and checked to make sure that the timing was dead on, so thats not my problem. This bike ran great before I messed around with the needle clip, then it just all went to sh!t. Since then I've put it back in the stock position but no luck. Any more ideas before I go and tear the carb back apart?

[thebutelr]

Definitely check timing-------You have all the symptoms of retarded timing---Did it backfire at all?

No it doesn't backfire anymore, it did really bad when it was out of time a little bit right after I put the motor back together the first time.