HMF system

[badcarz]

I just installed a new HMF sport series and have a question for the others running it. I'm getting some minor popping on decel that doesn't seem to go away. The bike is an 06, stock needle, 110 main, k&N and no lid. I have tries the screw out between 2 3/4 and 4 turns with minimal difference. I put the lid back on to see if richening it up would make a difference and it stayed the same. It idles and revs fine. Do all of yours have no pop or is a little the norm. I am running the quiet core, I'm about 250 ft above sea level and its about 70 degrees today. Thanks for the imput

[tedwilley]

Well, I am at about the same elevation, and I run a 112 main, needle on the third clip, stock pilot, about 2-3/4 to 2-1/2 turns out.
Also no airbox lid with K&N and outerwear.
I get very occasional pop on decel, but every engine is slightly different.
The rule of thumb is if you can't get enough adjustment with the fuel screw, go to the next size pilot.
You can read more on jetsrus.com
They say that pop on decel when letting completely off the throttle, is from to small a pilot jet and fuel screw adjustment.
Of course, they sell jets, too.

[badcarz]

Is your 112 a Keihn or other? I really don't think it is lean, possibly fat and loading up when the throttle is opened a few times quickly. I have crappy neighbors and have yet to be able to put it under much of a load. Going riding this weekend and plan on doing some fine tuning. I have two that I just put the pipes on (kids) so I know what i'll be doing late Friday afternoon.:ermm:

[tedwilley]

I have the Dynojet jets.
If you still have the airbox lid on, take it off. That will lean you up. See if that helps, then you will know if you were too rich, and go down down a size or two.

[JBacon]

I have some popping on decel occasionally, all i have is a UNI filter...

[tedwilley]

Well, this isn't a scientific opinion, but I personally consider occasionally popping to not be an issue.
If you are regularly popping on decel, then you are running lean and might want to adjust the fuel screw or needle setting.

[m.h.s.c.#527]

popping can also be too rich i thought i m running a 125 main and popping

[tedwilley]

Yes, rich mixture does indeed cause backfiring. But in my experience it is a different type of pop. Usually one bigger pop right at the moment of letting off full throttle. Not the same as the pop., pop, crackle, pop of running lean.
Borrowed without permission from jetsrus:
"What symptoms indicate the engine is too lean?
a. Acceleration poor, surging.
b. Performance improves slightly as engine warms.
c. Better performance when choke/starter is used.
d. No color, overheated spark plug electrode (see reading plugs FAQ).
e. Removal of air cleaner makes condition worse.
f. Popping back thru carburetor.
g. Engine pings or knocks, excessive engine heat."
They have other great explanations and recommended procedures, too.

[badcarz]

I appeciate the input. It is a lean condition. Got to our riding spot friday night and took one of the bikes out for a run. Seemed ok but a little flat on the top end. No popping on decel underload from both partial and full throttle. Went back to camp, checked the plug which was still preatty white but I figured needed alittle more time (its never easy to look at the base of an insulator with a flashlight and no magnafiying glass), and took my daughter for a ride. On the way back in it was dark and I noticed her head pipe was bright orange at the head. Got back and pulled the plug and it was still still bright white all the way to the base. Put the lid back on and went for a short ride. Still orange but not quit as bright. I had no more jets to put in either bike so they were done for the weekend. Just goes to show some of the normal signs ar not always there. The only indicator besides the pipe and plug was it being alittle flat at the very top of a gear and flat out in fifth. Also good info for all 06 and newer owners. The non adjustable needle that comes with the bike needs to be replaced when adding a system like the HMF. I beleive that greatly contributed to my lean condition. I should have bought a jet kit with the adjustable needle but have had jetted other bikes successfully without one and took the same route. Oh well, still had a great weekend and am already looking forward to taking the bikes out next Sunday!

[klutchbuster250]

yea these pipes rn really really hot and when ur going slow in a trail i bet the pipe will turn red i bet mine has and my bike is really close to jeted right