160 main jet

[bullet28027]

Well,
I got the ole girl running pretty good, so I decided to try to mess it up. I was running a stock 24mm carb with a 130 main jet, Uni filter, and free flow exhaust, I figured I would give the 32mm carb a try since it was laying right there, I put in a 137.5 main jet and she would bog at WOT. The only bigger jets I had was a 140 and a 142.5, so I went big, test rode and still bogging at WOT. So I made my way to the parts house and bought a 160 main jet, went home and put it in and WOW! Let me just say that I will be looking for oil coolers tonight. This baby flew with no bogging, I was on a four lane 55mph zone and I ended up in the fast lane keeping perfect flow with 5 pm traffic leaving Charlotte, downhill I almost saw 70mph/ 120kph on the chinometer at around 8500 rpms. I may need heaveier weights, also up a pretty steep hill from a dead stop at a redlight I stayed within a few lengths of the car in front of me to the crest at around 60 chinomiles p/h and still pulling. Then I turned around and did the same in the opposite direction, passing a few cagers along the way (hehe) so the wind wasn't a factor. I will know for sure tomorrow night when I'll have a gps. No matter what the gps says, I'm happy it's the best by far this bike has ever run.
Thanks to everyone who helped me get this baby right, I don't think you'll see Bullet waving anyone around anymore.

Thanks Scooter Rebels,
Bullet

[Rebel]

Bullet,

Let us know the official GPS speeds, it does sound like you hit a sweet set up, but running at 8500 RPMs might shorten the life of the motor, so be careful

[bullet28027]

yeah that was downhill for a short burst, I know better than to keep it over 8 for long. I took her out for a long run tonight and didnt see 8 on the tach but maybe once for less than a minute, I will keep you informed about the gps and tach readings.

[Doug in San Diego]

You didn't say what type of scooter or the mods you have

Geez a 160 main! If that's the secret I'll go order one today!

[Rebel]

He has an X-treme XM150

before the carb change it had; Mods: exhaust straight through design, coil, stage 1 cdi, Uni sock filter, new KF 24 mm carb, all new goodyear fuel and vacuum lines, new fuel filter, fuel cut off valve.

And was down on power with;

valves adjusted, needle in lowest position, 107.5 main jet, 35 idle jet, 12.8 gram factory rollers, new gates powerlink belt 843/30/20, factory clutch. fresh oil, and gear oil change, new ngk cr7hsa plug, bypassed the new mikuni fuel pump, as tank is higher than carb.

he started putting larger main jets in, then found out his compression was bad.

He got a new head and rings for it and that made it run like new. Now he has changed the carb out and the big jet.

[usfmarine]

I have a main jet of 170 in mine right now. My plug still reads lean but I think it's lying to me.

[Rebel]

that is one thing that does not lie, pluggs

[kliff]

Dec 12, 2009 15:00:00 GMT -5 usfmarine said:

I have a main jet of 170 in mine right now. My plug still reads lean but I think it's lying to me.

Probablly an air leak in the slide cover plate gasket, or manifolding. Unless a valve is still leaking. I don't install new heads with reseating the heads and lapping the valves.

[shiftless]

Ya'll gotta be leakin somewhere, 160, 170 mains is too big for a cv carb with stock bore and if you run a 170 on a slide... that's thick
My 61mm drag scoot has a velocity stack and an open header with a opened up head and a 28mm oko and a 130 main is fat on it to compensate for dry noz
Ya gotta be sukin air somewhere

Bullet.... 70 on the chinometer is closer to 55 real
Be careful with the r's over 8k..... you'll be tearin it down soon
valves float at 8-9k on a stocker

[oldchopperguy]

Good Grief!

As Barbara Walters might say: "I'm impwessed!"

I've got a 142.5 main jet (that's what came in it...) in a Mikuni 24 mm stock-type carb, and it's running great. I too have a Stage 1 CDI and Bando coil (those honestly made a noticeable difference!) and a UNI sock filter with NO intake runner. A free-flow exhaust will go on next spring, along with a Prodigy variator (WOT is over 8,200 rpm and 53-54mph, so the variator is needed!) and, after reading this, I think I'd better at least TRY a REALLY big jet... Certainly worth a try! I've changed them so often that I can probably do it blindfolded...

Thanks for the post! It's a real eye-opener!

Have a MERRY CHRISTMAS!!!

Leo in Texas

[kliff]

Dec 13, 2009 2:09:27 GMT -5 shiftless said:

Ya'll gotta be leakin somewhere, 160, 170 mains is too big for a cv carb with stock bore and if you run a 170 on a slide... that's thick
My 61mm drag scoot has a velocity stack and an open header with a opened up head and a 28mm oko and a 130 main is fat on it to compensate for dry noz
Ya gotta be sukin air somewhere

Bullet.... 70 on the chinometer is closer to 55 real
Be careful with the r's over 8k..... you'll be tearin it down soon
valves float at 8-9k on a stocker

Guess I better go ahead and assemmble some spring sets....whatcha think Skipp?,,
Sounds like someone is gonna be in need.

[Rebel]

Dec 12, 2009 18:03:17 GMT -5 kliff said:

Dec 12, 2009 15:00:00 GMT -5 usfmarine said:

I have a main jet of 170 in mine right now. My plug still reads lean but I think it's lying to me.

Probablly an air leak in the slide cover plate gasket, or manifolding. Unless a valve is still leaking. I don't install new heads with reseating the heads and lapping the valves.

Did you mean;

I don't install new heads without reseating the heads and lapping the valves. ??

[shiftless]

Dec 13, 2009 11:40:15 GMT -5 kliff said:

Guess I better go ahead and assemmble some spring sets....whatcha think Skipp?,,
Sounds like someone is gonna be in need.

[kliff]

Dec 13, 2009 2:14:28 GMT -5 oldchopperguy said:

Good Grief!

As Barbara Walters might say: "I'm impwessed!"

I've got a 142.5 main jet (that's what came in it...) in a Mikuni 24 mm stock-type carb, and it's running great. I too have a Stage 1 CDI and Bando coil (those honestly made a noticeable difference!) and a UNI sock filter with NO intake runner. A free-flow exhaust will go on next spring, along with a Prodigy variator (WOT is over 8,200 rpm and 53-54mph, so the variator is needed!) and, after reading this, I think I'd better at least TRY a REALLY big jet... Certainly worth a try! I've changed them so often that I can probably do it blindfolded...

Thanks for the post! It's a real eye-opener!

Have a MERRY CHRISTMAS!!!

Leo in Texas

LOL......and you are gonna NEED that Prodigy.....yesssirrreee, you're gonna NEEEEEEED it. Probably with some 13.5-14.5 DR P sliders..... and 1500rpm pills in the clutch!

[shiftless]

At sea level, a 115 main and a 38 pilot was the ticket for me
Stock Mikuni cv with uni filter and a freeflowing perf exhaust
This is on my daily
The Prodigy vari is a great investment (use a 842 belt) and my scoot has no problem sustaining 55-60 mph at 7000 - 7500rpm using 16.5g rolers 1500 contra & 1000 clutch springs I cant get it any higher... and don't want to
The spring combo allows it to not suffer off the line with the heavier weights
I used to run the same spring combo with 10g sliders in a NCY vari
It was fast off the line and topped at 55-60 at 9000+ rpm, but broke valve springs
Peak power is around 7500rpm on a QMJ exceeding that does nothing more for performance