1998 yfm350 black smoke

[yfm420]

ive got a 1998 yfm350 it has a keihin pe 38mm carb with 178 main jet and 50 slow jet it has a fmf megamax on it i think it has a stage one megacycles hot cam i have not checked to see if it was bored over or not that's about all i know about it have not taken it apart or anything yet im fouling plugs every other day im using a ngk d8ea i get black smoke at idle and in the higher rpm range any tips on adjusting the air/fuel mix or should i rejet it im new on here to sorry for the newbie questions any help would be awesome thanks

 

[Gen1Pat]

First, see where your mixture screw is set. 2nd, is sounds like your pilot is way to big. Get yourself some genuine Keihin jets (pilot and mains) and do a rejet. Ofcourse, inspect your air filter and make sure it's clean. Sounds like you also need to back donwn on the main as well.

 

[yfm420]

mixture screw is at 1 turn out and ill get some jets in a few days and ill try it

 

[88WarriorBoy]

1 turn out would be way to rich. Try 2.5 turns out and what is your elavation

 

[Mathius]

1 turn out would be way to rich. Try 2.5 turns out and what is your elavation

We were just talk'n about this last week.. lol
Your elevation plays a big part in jetting your carb properly. If the bike seems to be running fine, I wouldn't really worry about the jets to much. Give it a bit more air, and it should clean it up..
If it's just puff'n black from an idle, that would be your pilot.
Threw out the complete RPM range, black smoke would require a complete rejet.
I wouldn't get to drastic. Grab a few mains, and pilots.. Just the next sizes down, and try that. :iagree:

 

[Mathius]

1 turn out would be way to rich. Try 2.5 turns out and what is your elavation

We were just talk'n about this last week.. lol
Your elevation plays a big part in jetting your carb properly. If the bike seems to be running fine, I wouldn't really worry about the jets to much. Give it a bit more air, and it should clean it up..
If it's just puff'n black from an idle, that would be your pilot.
Threw out the complete RPM range, black smoke would require a complete rejet.
I wouldn't get to drastic. Grab a few mains, and pilots.. Just the next sizes down, and try that. :iagree:

 

[Gen1Pat]

Yeah we a sticky, step by step, trouble shoot guide that pops up for all new member as AS SOON AS THEY JOIN. That way we don't have to keep reiderating ourselves.

 

[88WarriorBoy]

Yep lol that would be nice

 

[yfm420]

well i ended up getting a couple jets now its at 152 main and 45 pilot it was puffing black smoke threw the whole rpm range now its barley doing it at higher rpms now i think its close enough to call it good what do you guys think and my elevation here is roughly 1400 ft and cleaned and oiled the air filter forgot to tell you guys it has no air box just a uni hooked up to it

 

[Gen1Pat]

Sounds pretty good to me. That elev isn't too high. Is there still black smoke?

 

[yfm420]

very little but if i have it at idle and wot it it back fires some times with flames and trys to die is that normal? if i dont do that it runs great with very little black smoke at higher rpm range

 

[yfm420]

oh ya im around 2.5 turns out on my air/mix screw

 

[88WarriorBoy]

sounds like to small of a pilot jet and do the penspring mod

 

[yfm420]

be for i changed my jets it was smoking like my diesel truck at wot lol i didnt change my plug yet either ill be doing that tomorrow to see what color im getting now before it was pitch black and caked on there

 

[yfm420]

penspring mod?

 

[Gen1Pat]

He's not using the stock carb 88. The plug can be your entire problem, now. Get a new one in there asap.

 

[yfm420]

and i dont think my keihin 38 pe carb has a accelerator pump

 

[yfm420]

ill put a new plug in tomorrow after work i get off early so ill be riding it and seeing whats going on with it now

 

['00 WO-YA!]

Also, if it's too rich on the main it should pop and act stupid up high, if it's popping on devel then it's now a tad lean on the pilot. I'm pretty sure that you can screw the mix screw in on the 38 & richen it, try that

 

[yfm420]

ok so i got to ride it for about 30 mins plug is not so bad now but i think the pilot has to go a little smaller then 45 im getting a puff of black smoke in the 0-1/4 throttle range and it still dont idle smooth it kinda acts like its flooding its self at idle and my air/mix is set to about 3 1/2 out runs great when you drive it though no bogging no popping ect think its just the pilot now?