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Licensed Joined: 05 May 2005 Posts: 130 Location: St. Paul

my bike's running great, so this is more out of curiosity than having a real problem. i just don't remember other engines i've known acting like this...

i'm running a stock 2003 LML 150 engine with no oil injector in a 70'a Vespa, fyi.
i've got the idle mixure set pretty good i think because it idles fine and it starts and runs like a top. my plug's gapped right and is always a lovely chocolate milkshake color...

but here's my issue, it always starts right up, but for the first minute or two as it's warming up, if you try and goose the throttle at all it bogs and almost dies. if you don't touch it it just putts along until it's a bit warmer and then it's fine.

like i said, it's no problem, i just don't touch it for that first couple minutes, but i don't remember the rally engines i've had or my ex-girlfriends p200 that i rode a lot being like that. they might have needed a minute to warm up and run smooth, but i don't remember it being so fussy about the throttle...

...and it's also a bit fussy with the choke. it almost always needs choke to start if it's cold, but if it's "warm" or if it's a hot day, it'll need the choke, but if you don't pop the choke back in after 2 or 3 "putts" it'll kill. it's like a game, if you get the choke in fast enough it just putts right along.

anyway, really i'm just bored at work and my scooter runs great... i just wanted to know if there's small thing i might do to fix this stuff, or if it's just my scooter's individual specialness and i should just let it be a bit fussy since it runs so good otherwise?
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Licensed Joined: 19 Jan 2005 Posts: 771

That engine should need the choke if it is started cold. Even on a warm day. After it is fully warmed up you should'nt need the choke unless the engine has cooled down for an hour or so.

If you can start your cold scooter without the choke then your idle mixture is probably set too rich.

Licensed Joined: 05 May 2005 Posts: 130 Location: St. Paul

it always needs choke, just sometimes not much, like 2 seconds of choke. too rich maybe?

what about the touchy throttle during warm-up thing?

and clockwise is leaner, counter clockwise is richer, right?

Licensed Joined: 19 Jan 2005 Posts: 771

O.K. It sounds like the idle mixture is to LEAN. How do you set your idle mixture?

I get it to idle as fast and smooth as possible with the mixture screw and then adjust rpm screw down and then go back to mixture screw agian until I have the fastest setting with the mixture screw and the correct idle speed. The engine HAS to be at running temp. HOT!

Then do the blip test. Let your engine idle for a few seconds and then blip the throttle. It should pick up fast and clean with no flat spot. If it stalls or lags, richen the mixture a little and try again. You might have to richen it a little. If you have to richen it alot there is some other problem.

You should be able to get a clean burning smooth idle that blips good. If you can't then something is wrong. I prefer to find the leanest setting that allows good bliping and smooth idle. It helps keep the plug from loading up at idle but does NOT effect mid to high rpm mixture.

Your choke should also then work as discribed.

Don't freakout and adjust your idle mixture a billion times. Remember the idle mixture screw effects idle and just off idle ONLY! It does not do anything else. You should be about 1 to 2 1/2 turns out from closed. If your way more or less you might need a different idle jet.

Once you get it set -leave it alone!

Licensed Joined: 05 May 2005 Posts: 130 Location: St. Paul

i pretty much set it the way you described, but i think i'll give it one more go with your exact procedure, it's a little more systematic than what i was doing...

am i right about the clockwise=lean counterclockwise=rich ?

i'm a little dislexic and i always get that mixed up...

thanks again, derrick...

Licensed Joined: 19 Jan 2005 Posts: 771

Yes, that is correct.

Noob Joined: 21 May 2005 Posts: 14

My 150cc Aprilia Scarabeo does the identical thing.
The manual clearly states, warm up engine before
riding or excelleration will lag or die. I start the scooter,
let it idle for 2 minutes, and it never occurs.

The Aprilia is a 2003, there is still a sticker on the
handle bar that states "warm up engine".

Bob

Licensed Joined: 19 Jan 2005 Posts: 771

The Aprilia is a totally different scooter.

The majority of what I said about Morgan's scooter would not apply to a modern 4 stroke scooter.

Licensed Joined: 05 May 2005 Posts: 130 Location: St. Paul

so i richened it last nite by a bit more than a quarter turn. it's right in the 2-and-a-half-ish-turns-out area, and it seems to be better although i want to just watch it and let it be for a couple days.

it started with choke this morning but i think i had the idle speed a bit too slow and so it sputtered out a couple times. i fixed the idle speed and the throttle was "blip-a-ble" even when it was warming up, so that was way better. had a nice ride to work, and it does seem a bit stronger right off idle.

one thing i noticed when i was working on it, though, was that it idles steadier when it's a bit too lean. it's idling fine enough right now, but it's not as even as it was a quarter to a half turn leaner. but aren't 2 strokes supposed to have slightly uneven idles anyway? is this the balance you strike between too rich and too lean or does any of this sound abnormal at all?

thanks again for all your time and advice derrick...

Licensed Joined: 19 Jan 2005 Posts: 771

I don't know. I guess as long as you understand what you are doing you should set it up the way you prefer. If you prefer a smoother idle vs great blipping O.K. Or if the choke thing drives you crazy, set the mixture a little richer.

You have to find a happy medium.

Nothing is perfect. (Except Japanese stuff) Vintage Italian design is far from perfect but they do give you things to play with. Thats were most people get into trouble.

Licensed Joined: 19 Jan 2005 Posts: 771

Are you talking about a scooter or someone you know?

me <-- ? I have a stella fireball.

Dave

Licensed Joined: 19 Jan 2005 Posts: 771

Not necessarily.

Don't use your choke longer then required.

Make sure you turn your fuel valve off after riding.

Thanks. I will give it a try.... better rich than lean.

Dave