Super 8 150 idles, won't run on-throttle

[Kevin]

Super 8 150 with about 6500 miles on her.
Daily driver for my 50 mile round-trip commute - has been flawless every day until this morning.
Ran out of gas on Friday (three days ago) coasted to the pump, filled with 91 octane (I always use super), started up and rode home the last 2 miles fine.
Parked on Friday afternoon uncovered outside (I usually park under an awning) and it rained last night pretty heavy.
This morning it started fine just like every other morning, but it wouldn't do anything over an idle after warming up for about 3-4 minutes (my daily routine).

Blip the throttle and she sputters out immediately.
Eeeeeeeeease on the throttle a tiny bit and she would increase rpm a little, but if I gave any more twist - poof and she quits.

after a couple of back-to-back stalls and restarts, she stopped starting (motor turns, but no startup)

If I let her sit for a minute or two, it seems like the bowl maybe fills with enough gas that I can fire her up and she'll idle for about 10 seconds before dying...


That's where she sits now - starts and idles for about 5 seconds before dying.

any ideas?

Thanks!
--Kevin

[ce]

Check the carb diaphragm for tears or cracks, check all hoses for air leaks or poor connection

[old mod]

Was it hot when you filled up? Could be a vapour lock, try starting with the fuel cap loose, or it may be dirty fuel, blocked fuel filter? just guessing, hope you solve it. Please let us Know the outcome.

[Kevin]

Thanks guys.
It was hot when I filled up, but I have since pulled the cap off and run it open with same result.
Idles 5 seconds then dies.
Working on it right now and have the fuel filter (?) off. It says 'flow' and is right under the tank. Seems to flow fine since it poured gas all over when I pulled the line off...

[Kevin]

update:

so, I have it idling regularly now - no idea exactly why...

what I did:

disconnected most of the fuel delivery system and blew through the hoses. got it to the point where i had a hose going directly from the bottom of the tank to the fuel delivery inlet on the carb. My wife said dinner was ready so I told her I wanted to put all the hoses back where they belong before I forgot (I didn't label them... #1 sin of troubleshooting, I know...) In any case, after reconnecting them all, she idled on her own for a little bit.

again, if you give her barely any throttle, she perks up and gains rpms a little bit.
too much, and she chokes out.

at this point I'm thinking the idle or "slow" jet is clean, and the main is clogged.

I believe that the slow jet is enough to bump the rpms up a little when I lean out the mixture by giving her a tiny bit of throttle, but as soon as there's too much air for the slow jet and the main jet doesn't kick in, she dies.

I hate taking apart carbs - I never get them back together right... of course my last carb rebuild was probably 25 years ago when I was like 12 years old...


I'm open to any other possibilities anyone can think of before I crack open the carb. I am however thinking that I may bump the jet size by 2 since I'm in there. I've heard this is the way to go in addition to more open air and exhaust for more power...

signed,
Too Dumb To Leave Well Enough Alone

[Kevin]

Update:

Looks like it may be the "bystarter" or electric choke.

I checked the resistance at the bystarter plug according to the manual and got 14.5 ohms instead of the 10 it called for.
My buddy, who is a factory KTM mechanic, stopped by and pulled it off after he listened to the idle and subsequent death at part-throttle. His first reaction was to pull the bystarter, measure the distance of the needle tip from the base (11mm) and then turned the ignition on. he said the needle should push out after about a minute or so, but it never did. we left the ignition on for several minutes and it didn't move at all. He said it sounded like the bike was trying to run with full choke.

Going to the Kymco dealer in the morning to get a replacement and I'll update the thread here after I get it installed.

--Kevin

[Kevin]

Yup, it was the 'bystarter' or electric choke on the carb...

Picked one up at a local shop for 19 bucks, plugged it in, fired her up and rode off into the sunset.



--Kevin

[mrpackerguy]

 

[teknik1200]

sounds like a little adventure.  i'm glad you got her running again.

[nuRider]

This sounds exactly like the problem I'm having with my Quannon 150. Starts up and idles fine, SLOWLY give it gas and its ok, but if I twist the throttle with a little more confidence it bogs down. I'm glad to hear that they're only $20.

[Kevin]

So this problem just cropped up on me again, and I thought there was no way the new bystarter could be bad already...

To make a long story short, after fiddling with the bystarter, regulator, chasing 'shorts' that didn't exist and every other electrical thing I could imagine (thanks to zombie and others for the help!) - I realized I was testing the bystarter wrong. I had only turned the key to ON and not started the scoot. This meant the bystarter was only getting about 0.1V and would never be able to extend properly. The right way to test it is to start the motor so the leads get 12V (the bystarter has to be installed on the carb to keep the motor running, it doesn't actually have to be connected to the electrical system though).

Anyway, I said my long story would be short. I'm a liar.   

I pulled the top of the carb off to see if the diaphragm was damaged (I swear I had already done this, but I don't think I pulled the slider all the way out, just looked at the diaphragm to see no holes) and pulled the slider out to get a real good look at the underside of the diaphragm. Yep, not a thing wrong with it at all.

Put the whole shootin' match back together and fire her up just to make sure I didn't make it worse. And wouldn't ya know it - she revved right up happy as a clam.

The only thing I can figure is I "unstuck" the slider that I didn't know was stuck.

Since then I have run a little Gumout carb and injector cleaner through a few tanks of gas and she seems just fine.

Is there anything I should lube the slider with?

Thanks!
--Kevin