Jetting help with new HMF full system

[leasureryan]

Hey, how many jett sizes do you guys think I should jump after adding this HMF full system? It was jetted larger than stock, (Current size in sig.), with the FMF, but now that I have the full system, just need a round about jetting spec for this upgrade. Has aftermarket EHS airbox lid, and HMF full system...and that is it. Everything else is bone stock. Well, motor wise anyways.

Current jet size is 152 main and a 40 pilot. I am getting and awfull back fire, super loud, so I know it is lean as hell, but how high main should I go????? And should I have to change the pilot???

Sorry guys, I can jet a 2 stroke like no other, but I am just now getting into 4 strokes. Help a brother out here.

Thanks in advance!!!

[honda300EXtreme]

id start with a 155 main, a 42 pilot about 2.5 turns out, and then fine tune from there

nice quad by the way

[leasureryan]

That's it? Go up for a 152.5....to a 155???? That doesn't seem to be nearly enough man. This thing has a wicked back fire! I say it is way lean.

But hey, you guys know better than I. Like I said I am used to 2 strokes. It wasn't anything for me to jump from a 230 main...to a 360 main just barely adding any mods to it. This 4 stroke **** has me all goofed up. I just don't understand. It is throwing my perception of air/fuel mixtures WAY off!...lol

Any other opinions?

I grabed a 155, 158, and a 160 main from work before I left. Any other opinions what I should try first???

[NickG5755]

if its backfiring in the exhaust isnt that rich not lean?

and if it backfires in the airbox its lean

thats what i always thought..then again im with you in the 2 stroke boatout paddlin around in 4 stroke waters haha

[miller821]

With just the HMF S/O i'm running a 155 main, and 42 pilot, and it's running me good... I'd say a 158 or 160 should do. Try those and just check your plug.

[leasureryan]

lol to the 2 stroke comment


Dude...with this pipe on here......I can get to the top of 3 or 4th gear, let off the throttle, and I get about 3-4 extremely loud shotgun sounding back fires. These ain't the little gurrgles or detonation sounding backfires.....these are wicked. And there is no way this thing can be running rich. I think I am going to toss a 160K main in it. See how it reacts. If it acts funny at WOT or anywhere between (major), I will just bump it back down to 158 and so on and so on


thanks for the replies guys!

Ryan

[NickG5755]

from my knowledge those shotgun sounds coming from your pipe is unburnt fuel..aka a rich condition...\

haha i think im gunna put that in my sig

"im in a 2 stroke boat paddling in 4 stroke waters"

hows that sound?

[leasureryan]

well....rich or lean.....I just threw that 160K main in it and nothing really change much. There is no bogging or stumbles in it at all, so I know this thing was begging for more fuel. I think that the back firing actually got a little better. I think the rest can be tuned out by the air screw and needle.....maybe.


Man.....where is everyone???????? Must be a holiday weekend or something...lol I need some more input here.

[Wheelie]

Try this: 40 pilot, A/F screw out 2.5 turns, lower the clip on the needle once notch and install a 158 main.

[leasureryan]

uuuuhhh.....already running a 40 pilot, and a 160 main. Thanks though!

To get rid of backfire, do you turn the fuel screw in or out???

[Wheelie]

Out.

[honda300EXtreme]

popping on deceleration means your lean on your pilot circuit, this can be fixed by either

turning your mixture screw OUT, or bumping up your pilot, in you cae i would recomend a 42 pilot jet, it will also cuse any cold start problems.

[leasureryan]

Thats the answer I've been looking for! Thanks man!