derbyking, I have the exact same problem: I am using a Yosh full system, 155/160 mains, 25 pilots, clip pos=3, dyno jet needles/springs, Prodesign foam filter, and no air box lid with Outerwears lid cover. I even have the glowing pipe problem(best seen at night). The trouble still occurs if I remove the filter altogether(leaner) or if I cover a majority of the intake up(richer).

I haven't tried 4 turns out on the mixture screws yet & haven't tried 27.5 pilots either.
All the literature/advice says the same thing: we are lean on the low end- try 4 turns out each & if still occurs then try 27.5 pilots & readjust mixture screws.

Yesterday I went to try 4 turns out each & before I did I got it backfiring pretty good by chopping the throttle at low rpms & all of the sudden a huge backfire blew the carb boots off & smoke came pouring out the intake side of carb. My boots don't seem to be ripped & I couldn't find any air leaks either. I need to check my exhaust/header connection as well. Raising the idle decreases the problem & it was also recommended for the boots blowing off problem. This is obviously a low end problem but it would be nice if it could be fixed without raising the idle to the point of being annoying!

I'll let you know if I solve the problem with 4 turns or bigger pilots even though it sounds like it didn't work for you. Somewhere in the equation we are probably a little too rich on top(not noticeable) & that is somehow causing this too lean on the bottom condition. Probably related to the Dynojet needles. I must say, if its lean at the low end, like everyone says, then I'm not sure why it still happens when I try covering up the air box intake(richer).

Stay in touch!

 

You basicly answered your own question. You say the problem decreases if you raise the idle. Adjusting your mixture screw out, increases (gas) idle as well. If after 4 turns out the problem is not cured get larger pilot jets. JMO

 

derbyking, I just thought of something, maybe we should try high octane gas to see if it alleviates the problem. I know its not a fix but if it works it will be easier on the engine until we can fix the problem!
I remember talking to CT Racing about their recommended jetting & Allen said if you don't like rejetting alot when changing elevations/temp zones, then try using high octane gas when running lean & regular when running normal/rich.

 

wshrdskin, thanks, I will take any/all advice. I know that putting in bigger pilots increases gas flow at idle but turning up the idle increases both since it opens the throttle valve, right!?. Any thoughts?

 

alright, my local bike shop didn't have 27.5 pilots so I bought 30's instead. Now that's rich, I don't think I've heard of anyone using ones that big, if those bad boys don't cure the low end lean problem I'm not sure anything will....

 

The High Octane gas isn't going to help you any. I am having the same problems with mine. It didn't happen with 150/155 DJ jets, but my pipes glowed red in the dark, so I figured I was to lean. I bumped it up to 155/160 and it started doing it. It pops and crackles coming off wide open throttle in 4th and 5th gear. I thought it might be a float problem,, but they seem okay. Is it ok for the pipes to glow red like that? They were only glowing at about the first six inches out of the motor. The plug didn't show that it was too lean. I have a 180/185 mikuni jets I might try with the stock needles. The yz426 has the same popping problem, but it never seems like it is running out of gas like my raptor carbs are doing.

 

Guys, adjust your mixture screws for highest rpm and this will go away. If not, up the pilots.

 

Well, approx 4 turns out each has resolved the problem but I am told that it is too far out for the fuel screws so I am waiting for my 27.5 piolt jets & when I get them installed & readjust the mixture screws I'll post where I set the screws.

 

Airraptor, I agree, however, most people have told me if your 4 or more turns out its time to go with bigger pilots & then readjust the screws, I guess the theory is to keep the screws around 3 turns out for the widest adjustment range?
Anyway, tell me more about using a dyno, do you mean the dyno can tell you the best fuel screw settings? Does it use O2 sensors to do so or are you somehow looking at the highest horsepower at idle?
I assume it can tell you whether you are lean/rich at any/all rpm?