Scooter stalls unexpectedly . . . any ideas?

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Scooter stalls unexpectedly . . . any ideas?

Postby Video Vertigo » Sat Sep 18, 2010 2:23 pm

Hi folks! I have a Vento Zip that has stalled on me twice recently, and now won't run. Here's the breakdown:

First time: I was driving about 30mph and the scoot lost all power and coasted to a stop as the motor "spooled down" (for lack of a better description). I pushed it home, replaced the spark plug, checked compression (seems fine), and tried to kick start it because my battery had died long ago. Couldn't get it to go. I checked spark with the new plug - some spark, but I can't say for sure that it was normal (without a reference point). Still couldn't start it, so I broke down and bought a new battery so it could really crank. Ordered the battery, got it, a couple weeks passed (hey, I'm a busy guy!) and I finally tried electric start with the new battery: started right up! Took it for a drive: seemed okay, ran just like before the stall.

Second time: About a week later, the same sort of stall occurred. I was only driving about 15mph or so, accelerating down the road when I lost power and coasted down again. There was one little puff where it seemed like maybe it would go again, but alas, 'twas not to be. Pushed it back home, tried a couple of different days to start it with the electric, but couldn't get it to fire up. Haven't checked the spark or compression again, but I have no reason to believe it will be any different than after the first stall.

Is there a fuel / choke / carb issue I can check for? What about spark - is it usually "all or nothing" or could there be an intermittent problem with the CDI or something?

Any help would be appreciated. Thanks a lot, everyone.
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re: Scooter stalls unexpectedly . . . any ideas?

Postby Tab » Sat Sep 18, 2010 9:20 pm

Could be the vacuum fuel petcock loosing its vacuum or simply not functioning properly.
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re: Scooter stalls unexpectedly . . . any ideas?

Postby Video Vertigo » Sun Sep 19, 2010 4:07 pm

What's the best way to check for proper functionality of the petcock? Is it repairable or is the best thing to replace it (if it's bad)?
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re: Scooter stalls unexpectedly . . . any ideas?

Postby mountainmoped » Mon Sep 20, 2010 8:23 am

Disconnect fuel line at carb. Disconnect line from vacuum petcock to intake manifold and suck on it. I use a hypodermic syringe but you can use your mouth (be careful--if the diaphram is broken you could get a mouth full of gas). If the vaLVE IS WORKING GAS WILL FLOW FROM THE GAS LINE. The Zip is the same scoot as the Keeway Hurricane. They have a piss-poor check valve in oil injection system that often sticks filling the carb float bowl with oil. You might check to see if the sparkplug is oily. There is a drain screw valve on the bottom of the carb that will allow you to drain oil without removing the carb.
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re: Scooter stalls unexpectedly . . . any ideas?

Postby Video Vertigo » Mon Sep 20, 2010 7:14 pm

Thanks for the info! I'll take a look at it and let you know what I find (probably Wednesday).
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re: Scooter stalls unexpectedly . . . any ideas?

Postby Video Vertigo » Fri Sep 24, 2010 4:16 pm

Hi again, folks. I tested the fuel vacuum petcock with a syringe as described, and the fuel came pouring out just as nice as can be. Moving on . . .

I pulled the spark plug to check for excessive oil. Doesn't look bad at all:
Image

A bit of new info, though. I had noticed that the motor spun faster for the first second or so when trying to use the electric start. I initially chalked it up to a battery losing a bit of juice, but now that the battery is actually beginning to lose juice, I can clearly hear that the motor fires right away when I try starting it after a long idle period, then nothing, just the starter turning over the motor. It's as though the scoot is flooding immediately when I try to start it. I'm not giving it any throttle whatsoever so as not to disturb the automatic choke. Any ideas for me?
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re: Scooter stalls unexpectedly . . . any ideas?

Postby oilyhans » Sat Sep 25, 2010 4:04 pm

your auto choke is operated by battery power and has nothing to do
with the throttle action other than making the carb rich so the scooter will start.
not starting when cold could be the AC is disconnected or just bad
test it has continuity and the resistance is about ~25 ohms.
check the AC is warm and that the plunger is working.

you can check it by removing it
place it on a piece of paper secure the AC so that it doesn't move and mark where the plunger comes to
plug it in and about 5 min it should be longer than the mark on the paper.

when your scooter just dies all of a sudden generally its electrical
when it sputters ,chokes and dies that is fuel

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re: Scooter stalls unexpectedly . . . any ideas?

Postby Video Vertigo » Sat Sep 25, 2010 6:53 pm

My bad . . . I had read somewhere that the auto choke disengages as soon as the throttle leaves "idle" position. I'll check out the auto choke and see if it tests ok. Is it possible for it to fail in the engaged position so the choke is always on?

Thanks!

PS: I tested for spark again, looks ok.
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re: Scooter stalls unexpectedly . . . any ideas?

Postby oilyhans » Sat Sep 25, 2010 6:57 pm

it could ,but test it
also make sure you have voltage at the connector
the AC plugs into..

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re: Scooter stalls unexpectedly . . . any ideas?

Postby Video Vertigo » Sun Sep 26, 2010 9:07 pm

Ok, now I think we're getting somewhere! I pulled off the auto choke and checked the resistance at 35.8 Ohms. I thought that was perhaps a bit high, but at least in the ballpark.

But when I checked for voltage across the connecting terminal where the choke plugs in, I got nothing. I checked with ignition off and on, same result both times. Just to be sure, I plugged in the choke and waited ten minutes to see if it would move. Nope.

So I guess I'll dig a little deeper into the wiring, but at least now I feel like I've found something wrong! Until now, everything I've tried seems to be fine, so this feels like progress I guess.

How do I tell if my choke is currently in the "on" or "off" position? I'd be curious to know, because to me the scoot behaves as though it's choked.

I'll let you folks know what I find.
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re: Scooter stalls unexpectedly . . . any ideas?

Postby Video Vertigo » Thu Sep 30, 2010 5:18 pm

Update:

I'm currently suspecting a bad rectifier. I traced the auto choke wires to the rectifier and verified that there is no voltage here either (though there is good continuity in both wires from AC to rect). I purchased a new rectifier and it seems to have two terminals reversed from my current one. An Internet search finds that there are at least two visually identical, indistinguishable rectifiers. Goody.

Does anyone have any experience with these? Here's the rectifier from my scoot (the pins I've labeled 1 & 3 seem to be reversed on my new one):
Image

Here are the rectifier connector and auto choke connector:
Image

Any input would be appreciated. Thanks everyone!
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