SB50P going slow at WOT HELP!
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SB50P going slow at WOT HELP!
Here's the problem. I just replaced a recently new petcock (Honda OEM) because it kept sucking gas into the vacuum line. I installed the new one today and it started right up and took it for a ride around the block, no big issues were seen during this ride, but after I came back on put it on its centerstand, I saw that the vacuum line was letting in fuel once again! The tube is filled with bubbly gas at both ends (the one attached to the manifold and the one attached to the petcock) What could be the problem?! This is another brand new petcock doing the same thing. I also installed an inline fuel filter. I made sure it was the one that was gravity fed (Briggs and Straton, the red one). After this mishap, there came another. I tried starting it up again and it took forever to start, even with gas. It eventually started up, BUT even when I gave it full throttle, the wheel was moving so slow! It was not rapidly speeding like it would be if you gave it full gas, it seemed like it was going 5mph. I've had so many issues with this scooter and had it for a month so far. This is my first scooter and it's a real disappointment. I will sell it soon, but rather get everything running before. If anyone can help, it will be greatly appreciated. (P.S. Thanks Bear for helping me in my previous problems!)
Re: SB50P going slow at WOT HELP!
Update: I checked the belt and it seems fine. The starter pinion on the other hand seems really loose, is it suppose to be like this? I can just take it in/out with my hand, but I don't think this is the problem. As I said before, it starts up with the electric start and some throttle, but the wheel spins slow while doing this.
- Wheelman-111
- Moderator

- Posts: 10683
- Joined: Wed Oct 22, 2008 5:09 pm
- Location: Deepinnaharta, Texas
Re: SB50P going slow at WOT HELP!
Greetings:
The Bendix assembly just slips in and out, held by the belt cover when that is installed.
I had a petcock that was bad brand-new out of an Approved Honda-san box. Even if not exposed to fuel fumes for 25 years, if the rubber was molded in 1985, it's still old. Have the dealer you bought it from replace it, or go to an inline fuel valve too.
Don't use a paper filter. Cone O'Stone only for thirsty 2-strokes.
The Bendix assembly just slips in and out, held by the belt cover when that is installed.
I had a petcock that was bad brand-new out of an Approved Honda-san box. Even if not exposed to fuel fumes for 25 years, if the rubber was molded in 1985, it's still old. Have the dealer you bought it from replace it, or go to an inline fuel valve too.
Don't use a paper filter. Cone O'Stone only for thirsty 2-strokes.
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
Re: SB50P going slow at WOT HELP!
That's the weird thing. My parts dealer just ordered this for me from Honda. The previous petcock did the same thing, but never caused this issue of running slow. I just want to diagnose this problem asap.
- Wheelman-111
- Moderator

- Posts: 10683
- Joined: Wed Oct 22, 2008 5:09 pm
- Location: Deepinnaharta, Texas
Re: SB50P going slow at WOT HELP!
Greetings:
If there's gas in the vac line, it's being sucked in at the manifold, horribly over-richening your mixture. If you can run a straight line from the tank, cap off the vacuum port at the manifold. I found all the parts I needed one year at the Home Depot's plumbing odds 'n ends section. I can post pics Manana.
If there's gas in the vac line, it's being sucked in at the manifold, horribly over-richening your mixture. If you can run a straight line from the tank, cap off the vacuum port at the manifold. I found all the parts I needed one year at the Home Depot's plumbing odds 'n ends section. I can post pics Manana.
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
Re: SB50P going slow at WOT HELP!
Could that even be the cause of my running slow while giving it full gas issue? It never happened with the other faulty petcock either. So, I'm not sure it's the petcock causing it. With the other issue of the petcock, are you telling me not to have one anymore and just run one straight line from the gas tank to the carb? And plug up the vaccuum port at the manifold?
- Wheelman-111
- Moderator

- Posts: 10683
- Joined: Wed Oct 22, 2008 5:09 pm
- Location: Deepinnaharta, Texas
Re: SB50P going slow at WOT HELP!
Greetings:
Yes, until you can procure a petcock that works. You should always have a way to shut off fuel flow besides the float valve in the carb, but at least you could test the theory with a straight fuel supply.
If you try this, capping the manifold port is mandatory. Otherwise you'll be sucking air and horribly leaning your mixture. That can destroy a top end pretty quickly.
Yes, until you can procure a petcock that works. You should always have a way to shut off fuel flow besides the float valve in the carb, but at least you could test the theory with a straight fuel supply.
If you try this, capping the manifold port is mandatory. Otherwise you'll be sucking air and horribly leaning your mixture. That can destroy a top end pretty quickly.
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
Re: SB50P going slow at WOT HELP!
Thanks for that advice! Now, I need someone to address the issue of my Elite going slow. 
Re: SB50P going slow at WOT HELP!
Still need some advice please. =(
Re: SB50P going slow at WOT HELP!
Have you checked for an air leak?
1986 Spree w/ '87 SE50 motor
1985 Aero 50 w/ Dio motor: On Hold
1985 Aero 50 w/ Dio motor: On Hold

