cold weather anomalies.

[double-o-soul]

recently, with the onset of chilly weather, i've noticed some changes in my stella's performance and wanted to run it by the community to ease my mind whether or not these are normal changes.

*I've gone from 2 turns on the mix screw to 2 and a half, and adjusted the idle accordingly. idles fine.*

I've noticed that I've lost some power in the first gear after around 10 mph. the initial torque is still what it was in the summer. Along with this slight loss of power, the engine sounds much louder.
All the other gears seem to function as per usual, with maybe a tad more noise. any idea's on whats going on?

I've also gone and given the carb a good cleaning so there's that.

[BuddyRaton]

Why adjust the mixture screw? Just stick the winter plug back in the top of the air box.

[double-o-soul]

ah, the winter plugs been there the whole time, even in the dead of summer lol
reason is, even though it's not a tuned engine, I've done everything but and figured getting a tad richer in the winter wouldnt be a bad idea. besides 2 and a half turns is the sweet spot anyway right?

[az_slynch]

Colder air is more dense. The colder the temps are, to greater the density of the air passing through carb is. More air requires more fuel to combust properly.

Is the bike down in power through the whole gear, or just at the top of the gear?

Also, what's the spec of your current setup? Filter, jetting, cylinder, exhaust, etc.

[double-o-soul]

funny thing, today she was running exactly as before!
I think it's because the weather has finally settled into a groove instead of going from 55 in the morning to 85 during the day, giving the tuning a chance to settle down as well.

in any case, I'm running:
bald john jetting (except for a 103 main, a 105 is in the mail)
deblued air filter with holes drilled above the jets
removed seat air filter
226 hot reed
sito+ exhaust

the engines stock otherwise...
2 and a half turns out on the mix screw

[az_slynch]

funny thing, today she was running exactly as before!
I think it's because the weather has finally settled into a groove instead of going from 55 in the morning to 85 during the day, giving the tuning a chance to settle down as well.

in any case, I'm running:
bald john jetting (except for a 103 main, a 105 is in the mail)
deblued air filter with holes drilled above the jets
removed seat air filter
226 hot reed
sito+ exhaust

the engines stock otherwise...
2 and a half turns out on the mix screw

Looks decent. Good call on the main, especially with a non-stock pipe. Look into the SIP Road sometime. It hides under the bike nicely and makes better mid range power that the Sito, and still allows you to out-rev a Sito. Howardr has one on his Stella (along with a little extra voodoo) and she'll eat most mildly tuned P200s for lunch under acceleration, even while decked out in accessories.

[double-o-soul]

Little update with a question...
got the 103 main in with 3 turns out on the mix set with a slightly high idle (seems to start up easier in the mornings). i've been noticing the engine racing away at the top of all the gears where i would previously have a healthy response...
ie.
in 2nd around 30 mph (indicated)
in 3rd around 45 mph (indicated)
so on and so forth...

is this underperformance normal? should i just accept it?
do i need to go even richer? the racing means lean right?

**also if i gently nudge up to those speeds it doesnt seem to happen, onyl when i'm gunning the throttle...

[alexandercase]

do the 4t's have this 'winter plug'..

[az_slynch]

Little update with a question...
got the 103 main in with 3 turns out on the mix set with a slightly high idle (seems to start up easier in the mornings). i've been noticing the engine racing away at the top of all the gears where i would previously have a healthy response...
ie.
in 2nd around 30 mph (indicated)
in 3rd around 45 mph (indicated)
so on and so forth...

is this underperformance normal? should i just accept it?
do i need to go even richer? the racing means lean right?

**also if i gently nudge up to those speeds it doesnt seem to happen, onyl when i'm gunning the throttle...

I thought you were putting a 105 in?

Racing at the top of the gears sounds like you're going lean. Have you done a plug chop at the top of 3rd? Drop a fresh plug in for best read.

BE3 mixer? I didn't see it in your spec, figured I'd ask.

Bald John seemed to like 3.5 turns out on the mix screw, IIRC. For some reason, I seem to recall Howardr's Stella having a 110 main in it after Bald John initially tuned it, and Tucson's at 2500ft. ASL. He had the P200 filter on it, though. I know you should be richer the closer to sea level you are. Thinking that a 110 in Tucson is analogous to a 112 at sea level, but I might be off.

[az_slynch]

do the 4t's have this 'winter plug'..

Alexander, the 4T Stella has an 18mm side draft carb that hangs in the breeze above the crankcase, mounts to the engine via a curved intake manifold and feeds fuel-air into the cylinder head. The 2T Stella's have a 20mm carb that bolts directly to the crankcase and feeds fuel-air directly into the crankcase. The winter plug screws into the air box, which encases the Carb on the 2T models. It allows access to the fuel mixture screw and allows additional airflow into the air box when removed for warmer, lower density air in the summer, and can be installed to reduce air intake into the air box during periods of cooler, higher density air, ie. Winter.

The upshot of this is that you don't have a winter plug. Just pull the choke and leave it engaged a bit longer on cold days.

[double-o-soul]

ack sorry for the typo.
yea its the 105 which is why its kind of perplexing. be3 as well so now its officially bald jon jetting. dunno how much it matters but its also a fireball so it has p200 gearing, unlike the other stellas. i dropped the idle back down a bit and kept the 3 turns... seems to be running a tad better now though i havent been gunning the throttle as before... just funny cus in the summer i can ride her like its stolen.

thats weird about the elevation... i always heard the higher you are the richer you gotta go. im in philly which is essentially sea level.

[double-o-soul]

oh and my filter might as well be a p200 filter... its the stock one with the blue mesh taken off and holes drilled above both jet stacks... ive been told its basicly equivalent

[az_slynch]

ack sorry for the typo.
yea its the 105 which is why its kind of perplexing. be3 as well so now its officially bald jon jetting. dunno how much it matters but its also a fireball so it has p200 gearing, unlike the other stellas. i dropped the idle back down a bit and kept the 3 turns... seems to be running a tad better now though i havent been gunning the throttle as before... just funny cus in the summer i can ride her like its stolen.

thats weird about the elevation... i always heard the higher you are the richer you gotta go. im in philly which is essentially sea level.

Huh, the idle screw only sets how far the throttle slide can return when the throttle is closed, it shouldn't affect top end. Maybe the screw's in far enough that it's dragging on the throttle slide? I've seen that in a few Spaco carbs; because of that, I've taken to cracking the throttle when adjusting the idle screw.

I need to do a tooth count to be certain, but I believe that the Stella has the same gearing as a the later Vespa "EFL" gears. I'm basing that on the gearing calculations I ran when building Howardr's stroker Stella. If this is correct, that means that the only difference between the standard Stella gearbox and the Fireball gearbox is in the clutch (7-spring, 115mm diameter, 23 tooth drive gear, stock is a 6-spring, 108mm diameter, 21 tooth drive gear) and in the cush drive gear (65 tooth on the Fireball versus 68 teeth on the stocker). The clutch cover is slightly different too, with the oil wiping channel clearanced to allow for the bigger clutch.

Simple rules on air density:

1. The higher you go, the less air there is, thus lower air density. A bike jetted at sea level will run rich at higher altitudes.
2. The warmer the temperatures are, the lower the air density is. A bike jetted in the winter will run rich in the summer.

[az_slynch]

oh and my filter might as well be a p200 filter... its the stock one with the blue mesh taken off and holes drilled above both jet stacks... ive been told its basicly equivalent

It is similar, but I can say with certainty that their are minor differences in the filter material that seem to affect performance. I swapped out the late US P200 filter on my bike for a Euro PX200 filter when I was having trouble dialing it in between two jets. The filter allowed a bit more air in and made it easier to set the bike up.

I put my old US filter on Howardr's bike when it was still mostly stock and it worked a bit better than his de-blued and drilled filter. When it was rebuilt as a stroker, I had a bit of trouble with mid-throttle richness that was mostly resolved with a Rally 180 (Dell'Orto #3) throttle slide, but finally cleared by swapping on another Euro air filter.

I can't say for sure what the difference is, as both versions of the 200 filter are drilled above the jets and share the same dimensions. My guess is that the weave of the Euro filter is less restrictive. Regardless, I've used them on three different bikes now with good result and recommend it for anyone looking for max flow from a stock-style filter.

[fisher1]

thats weird about the elevation... i always heard the higher you are the richer you gotta go. im in philly which is essentially sea level.

Double-0, thats bad info you got. The thinner the air at higher altitude, the leaner the jetting you will need.

Also, I'm in your area, and my performance improved when I also richened the midrange by removing the 55/160 (2.9) SI Pilot/idle jet and replace with richer 52/140 (2.7). Larger SI#s are leaner.

ALso, what plug are you running? And are you doing city or suburb riding?

[double-o-soul]

oh yea shoulda mentioned that!
the 7 i had in there from the summer was fouling so i put in the 6.
I'm a city block to block rider with lots of lights and stops, but I will fairly regularly hit longer strides of 3rd and 4th gear for a few minutes.

I dunno why i just didn't remember I did that LOL. PROBABLY has a little to do with the change in expected performance :-/
I'm an idiot.

[az_slynch]

the 7 i had in there from the summer was fouling so i put in the 6.

Follow up plug question: who's the manufacturer of plug are you running?

I know that Bald John favors NGKs; I prefer to run those too. I know that some folks run the short reach plugs for Polini heads and will recommend the HS plugs. Stock Stella's and Vespas use the longer reach ES plugs. Make sure you have the right length plug as well; a stocker will run on a short plug, but your engine's power will be down.

Six is fine, I run one year-round in my P200 and it does well even in the hot summer months. I recommend sevens for kitted motors or higher-compression setups.

[double-o-soul]

yep it's an NGK 6 ES, i use the most standard stuff possible. scooter shop recommended stuff.