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@michaelharrisco avatar
UTC

Enthusiast
2005 Vespa PX150
Joined: UTC
Posts: 75
Location: Raleigh, NC
 
Enthusiast
@michaelharrisco avatar
2005 Vespa PX150
Joined: UTC
Posts: 75
Location: Raleigh, NC
UTC quote
Hello,

I'm having a very intermittent / random / every now and then issue on my PX150.

At full throttle in 4th gear ~45mph it stutters out a little bit almost as it is low on gas feeling. It doesn't happen every time I ride it and I can't seem to find any root cause. I'm speculating it may be one of these, but I'd love to know if anyone else has any ideas:

1) I don't let it idle long enough when I first crank it and just take off right when I crank it.
2) some type of gas line needs cleaning out / carb? but I'm confused why it only happens at full throttle.

does anyone know how to fix this? it happens infrequent enough that it doesn't bother me too much, but I sure don't feel comfortable in traffic when it happens so that makes me want to fix it.
UTC

Banned
Joined: UTC
Posts: 466
Location: Washington MFing DC
 
Banned
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Posts: 466
Location: Washington MFing DC
UTC quote
Re: Random stutter on full throttle
Given that it is random, and I mean truly random in that you have been in 4th at 45mph and it hasn't happened at all, and other times you are also in 4th at 45mph and it HAS happened, I would look to one of two things:

Plug wire - check that it's screwed into the cap and the CDI snugly. Of course it could have a break on it inside and what you're experiencing is that break separating under certain conditions, meaning you don't fire for a moment, then you do. If it's a small break, or it isn't connecting all the time at the cap or CDI you likely wouldn't notice it in 1-3 gears.

Fuel flow - under full throttle you are sucking the most gas. Could be there's a bit of crap in your tank that is momentarily blocking the flow and then you hit a bump and it dislodges.

If it were more regular then there could be other things to look to, but those two are the easiest.

Get your tank down low, shine a light in there and have someone shake the scooter back and forth. If you see shit swirling in the gas that's your culprit.
@chad avatar
UTC

Olivia Newton-John
p200, vbb, gt200, px150, vnb
Joined: UTC
Posts: 4494
Location: chippewa falls, wisconsin
 
Olivia Newton-John
@chad avatar
p200, vbb, gt200, px150, vnb
Joined: UTC
Posts: 4494
Location: chippewa falls, wisconsin
UTC quote
i had a similar problem once, and it was a stupid solution.

i wasn't opening the fuel tap all the way as far as it would go. at higher speeds, the engine wasn't getting enough fuel and it kept bogging down/dying.
OP
@michaelharrisco avatar
UTC

Enthusiast
2005 Vespa PX150
Joined: UTC
Posts: 75
Location: Raleigh, NC
 
Enthusiast
@michaelharrisco avatar
2005 Vespa PX150
Joined: UTC
Posts: 75
Location: Raleigh, NC
UTC quote
great suggestions and I'll do them this weekend. I'm leaning to the CDI since I had an issue with it causing trouble with cranking a few months ago and I wonder if the crimp connections are loosening up again.

I'm going to be in there changing the gear oil tomorrow so I'll take a look.
@starreem avatar
UTC

Ossessionato
07 GTS250(RIP), 07 LX150, Several Lambrettas
Joined: UTC
Posts: 2834
Location: Raleigh, NC
 
Ossessionato
@starreem avatar
07 GTS250(RIP), 07 LX150, Several Lambrettas
Joined: UTC
Posts: 2834
Location: Raleigh, NC
UTC quote
I'll bring a spare CDI 8)
OP
@michaelharrisco avatar
UTC

Enthusiast
2005 Vespa PX150
Joined: UTC
Posts: 75
Location: Raleigh, NC
 
Enthusiast
@michaelharrisco avatar
2005 Vespa PX150
Joined: UTC
Posts: 75
Location: Raleigh, NC
UTC quote
it always cracks me up when a person down the street responds on such a large scale forum

I'm thinking its those crimp connectors that we tightened up last time have become lose again and we just need to tighten them up again.

I have to leave around noon so I hope that gives us enough time.
@ronin avatar
UTC

Addicted
Vespa Rally 180 BMW R1150R Suzuki Burgman 400
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Posts: 871
Location: Royal Oak, Michigan, USA
 
Addicted
@ronin avatar
Vespa Rally 180 BMW R1150R Suzuki Burgman 400
Joined: UTC
Posts: 871
Location: Royal Oak, Michigan, USA
UTC quote
The next time that it does it, reach down and pull your choke to see if that helps. My Bajaj is doing the same thing, but pulling the choke (mine is on the right handlebar) smooths it right out, so I'm back to the carb/fuel flow investigation. I've pulled and cleaned the tank and the petcock filter, verified the fuel flow and cleaned the carb. It's a perplexing little shit, that Bajaj.
OP
@michaelharrisco avatar
UTC

Enthusiast
2005 Vespa PX150
Joined: UTC
Posts: 75
Location: Raleigh, NC
 
Enthusiast
@michaelharrisco avatar
2005 Vespa PX150
Joined: UTC
Posts: 75
Location: Raleigh, NC
UTC quote
Um, interesting thought about pulling the choke out when it happens. I'll give it a try if it occurs again after with check the CDI connection tomorrow.

Royal Oak is a cool city, I lived in Plymouth for 2 years and used to go to Royal Oak from time to time. I love Red Coat Tavern there...they have the best burgers in the country in my opinion.
⬆️    About 27 days elapsed    ⬇️
OP
@michaelharrisco avatar
UTC

Enthusiast
2005 Vespa PX150
Joined: UTC
Posts: 75
Location: Raleigh, NC
 
Enthusiast
@michaelharrisco avatar
2005 Vespa PX150
Joined: UTC
Posts: 75
Location: Raleigh, NC
UTC quote
Guys,

It still seems to be stuttering out every now and then (even after we tightened the CDI connections). It does seem to happen more often when the tank is low. Any suggestions on running tank empty and then cleaning it out to make sure there is no contamination in there blocking lines?

I totally forgot about the idea of pulling choke out. I'll try to remember to do that next time.

Until then...
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