weather change, time to rejet carb?

[chaz35]

It has warmed up around here.  I got ready to go riding, and my scooter won't start.  At 1st I thought it was the pesky auto petcock, but after awhile I realized engine was flooded.  In cooler weather, it was usually too lean when hard to start.  Temp has gone from 50's to 70's, so carb/ engine must be pretty sensitive to air temp.

I also turned out the idle mixture screw and it helped some.  Before, the idle mixture screw didn't seem to make much diff, liked it best to be almost turned all the way in, so I ran it maybe 1/2 turn out.  With warmer weather, it liked 2 to 3 turns out.

As I recall, have 95 main jet, and 35 idle jet installed.  I guess will try 92 main jet to see it that makes diff.  Was cool again today and scooter ran awesome.  Cheers

[BettinANDlosing]

If turning the mixture screw out helped, that indicates it's lean, out means richer. Was this the first time you rode it in a while? Could have a plugged idle jet.

[Triesandluth]

What size carb are you running? I don't recall catching that in your other posts... 
I know I'm definitely in need of rejetting.  Going from riding in thirty degree maximum to now average of high sixties.  Not to mention the pipe upgrade...

[chaz35]

I have OEM carb Keihin PB16 I think.  I think idle mixture screw is air screw, so turning out gives it more air.  Had the same problem with my People 50 2T, hard to start, when weather was cooler was very easy to start.  True, haven't ridden it everyday, but maybe only sat 7 to 10 days.  If idle jet was clogged, is clear now, idles nice once I got it started and idle mixture screw turned out some.  Thanks for replies, cheers.

[BettinANDlosing]

Is the screw on the intake manifold side of the slide? I'm 99% sure it's a fuel mix screw.

[chaz35]

I think on manifold side, is closer to engine than idle speed screw.  You are probably right, I was pretty close to taking off the carb for a cleaning, when it started with WOT, ran rough, then cleared out.  Would not idle, so I started adjusting the idle mixture screw and when I turned it out it settled down to a nice idle.  So IDK?

[chaz35]

I looked at plug, installed new plug before last ride, burned approx 1 gal gas, so long run, looked rich.  So, installed 92 main jet, took out 95.  Will report back.  Idle mixture screw still learning.  Thanks for replies.  Cheers

[Triesandluth]

You're also running a aftermarket pipe,  right?  As usual,  just trying to leach info from you so that I may dodge some unnecessary carb removal then installation,  then removal and on and on. 

[chaz35]

I got scooter used and already had Tecnigas pipe on it, I assume Next R, but not sure.  My People 50 2T has OEM exhaust and runs well compared to Super 9 with Tecnigas pipe, seems like Super 9 has a little more top end, and is a lot louder.  The People is probably better 0 to 20 mph.  I got a Tecnigas Next R pipe for it too, but haven't installed it yet.  Have 85 main jet in People with OEM exhaust and seems about right.  I think the Tecnigas pipes require a larger main jet, has been my experience.

The 92 main jet was good, ran about the same, maybe a little more top end, a little slower mid range.  Haven't looked at plug yet.

[Triesandluth]

92ish  (gave it a few rough strokes from a torch tip cleaner) is what I'm running now with also an unknown Technigas. By my recent new plug check it seems possibly a bit lean (stock carb). I'm going to repack the pipe in the next two days and see if there's any difference before I get too carried away.
Seemed to run rather well as it was.  I just don't want to prematurely ruin the top end.  That would give me an excuse to put in the airsal though...

[chaz35]

I bet the packing will help it run better, maybe change the jetting a little, maybe not?  The kart engine pipe was designed to be optimum with the proper packing installed (I am assuming that's the case with Tecnigas too).  Anyways, that's my experience with the kart engine, when the packing needs replacing and you restore it, seems to run a little better again.

I don't remember having to rejet for new packing vs old, but we were always changing main jets for temp, altitude, humidity at different tracks trying to get a little more power.  Fastest was lean, but I always thought you gave up a little mid range if really lean, plus very expensive if engine fails.

Seems like I run my scooter WOT 90% of the time, so I want to be a little rich for sure.  Cheers

[BettinANDlosing]

Nice that's a fuel mix screw for sure. Also tuned pipe will make the bike more weather sensitive.

[chaz35]

Have Uni air pod on it now 38 idle jet and 105 main jet.

With idle mixture screw turned out approx 3 turns definitely boggs some starting out from stop.  Once going and hits pipe 105 main jet seems about right, really takes off and has good top end.  Then I tried idle mixture screw turned out 1/2 turn and ran better starting out from stop and easier to start too.  Ran it again yesterday with idle mixture screw turned out approx 3 turns, and performance was definitely off compared to having it turned out 1/2 turns.

IDK, but idle mixture screw sure acts like air bleed to me.  Appears to run richer if turn in, leaner it turn out, still learning though.  I ordered 40, 42, and 45 idle jets to try.  Hoping to get it to start easier.  45 idle jet probably waste of $'s, but may be just the ticket this fall.  Cheers