GY6 dies after a few minutes of WOT |

mathias999us
New Puppy Dawg

Posts: 2

GY6 dies after a few minutes of WOT Apr 2, 2011 19:11:20 GMT -5

Post by mathias999us on Apr 2, 2011 19:11:20 GMT -5

Hey Folks, first post here. Hoping small engine gurus can help me out. I got a brand new one of these a month ago (well, it had 80 miles on it):

www.scooterdepot.us/150cc-Gas-Scooter-Motorcycle-Style-p-688.html

It's a 2009, so it had been sitting at the dealer's for about 18 months. I got $300 off because it was winter (in Minnesota) and because it hadn't had the PDI done. Well, the snow finally is melting, and I got to take it out for the first ride today. I'm having a problem though. Bike starts and runs great. However, after I get a few miles away from my house, it just dies at about 45 mph. Maybe 5-10 minutes after I've been riding. If I let it sit for a few minutes, it will start again, and then die a minute or two later while riding. If I ride a few hundred yards, pull over and idle, ride a few hundred yards, pull over and idle, etc. I can make it all the way home (thanks goodness). Sounds like a vacuum leak maybe? Here's what I've done so far:

Inspected vacuum lines - don't see any obvious problems
Inspected fuel filter - there isn't one! Doh, I'll need to take care of that quickly
Removed and cleaned carb - looked nice and clean already, but I sprayed it all with cleaner and compressed air. Nothing obviously wrong with carb (to me anyway).
Also, cranked the engine with the fuel line to the carb put in a jar. Plenty of fuel dispneses (enough I think anyway?) WOT while cranking doesn't produce any fuel doing this, but is that a valid test?

Any ideas what I should try next? If it helps, I believe this is a setup with a fuel pump instead of a petcock.

Thanks so much for your time!

Mathias

ce
Great Big Guru Dawg

Posts: 579

GY6 dies after a few minutes of WOT Apr 2, 2011 23:22:24 GMT -5

Post by ce on Apr 2, 2011 23:22:24 GMT -5

Change the Tees in the vac lines to 3/16 size from the auto parts store. You may have 1/8 size now, which will inhibit proper vacuum to the pump resulting in fuel starvation at WOT. also check the float valve in the fuel bowl for proper adjustment.

Bluefront
Great Big Guru Dawg

Modded Xingyue ITA150

Posts: 3,055

GY6 dies after a few minutes of WOT Apr 3, 2011 5:13:42 GMT -5

Post by Bluefront on Apr 3, 2011 5:13:42 GMT -5

A few things to check.....valve adjustment. Many of these scoots ship with tight valves. After a few miles they get even tighter, and may not be closing all the way after the engine gets hot.

Gas tank/cap venting.....if the vent system is not working, the engine starves for gas after a few miles of riding. Check this by riding with a loose gas cap.

Either of those problems will cause the same symptoms.....and allowing to cool down for a few minutes will temporarily fix the problem (till you ride again for a few miles).

1/8" vacuum lines are plenty big unless the line is too soft, allowing it to collapse. At WOT, there isn't much vacuum available on these small engines.....

rockynv
Great Big Guru Dawg

Posts: 2,349

GY6 dies after a few minutes of WOT Apr 3, 2011 8:25:41 GMT -5

Post by rockynv on Apr 3, 2011 8:25:41 GMT -5

On a bike that has been sitting at a dealership for 18 months I would start by putting an ounce or two of Berrymans B12 Motor Tuneup in the gas tank to clean up the carb, fuel pump and free up the rings/valves. When mine starts to act up like that it is usually either time for a valve adjustment or a good fuel system cleaning. On yours after sitting for that long and a month of ownership it is probably time for both.

scottish1
Great Big Dawg

Posts: 97

GY6 dies after a few minutes of WOT Apr 3, 2011 10:50:20 GMT -5

Post by scottish1 on Apr 3, 2011 10:50:20 GMT -5

try a new cdi. make sure you get the right one that is ac or dc. just plug that test puppy in and see if it does the trick.

scootdawg.proboards.com/index.cgi?board=talk&action=display&thread=37442
and uhuh.. valves are a must to be right

mathias999us
New Puppy Dawg

Posts: 2

GY6 dies after a few minutes of WOT Apr 3, 2011 11:48:43 GMT -5

Post by mathias999us on Apr 3, 2011 11:48:43 GMT -5

Hey Guys,

Thanks for all the replies. I found the problem this morning! I decided to go for the valves first because I have all the tools to do that. As I started taking the bike apart to get to the engine, I inspected the fuel pump. Took it apart, and there was no obvious problem there. Then I decided to inspect the vent line from the tank, as I've read about folks having the hose nipple on the tank completely painted over. The nipple was fine, but I noticed that I couldn't blow into the hose that connected to the tank vent. It leads from the tank down to a carbon canister. Along the way, it was passing through a small round plastic unit. I cut the zip tie it was mounted with, and pulled it out. It turned out to be a check valve, THAT WAS INSTALLED BACKWARDS! Meaning air could only LEAVE the tank, but not enter! It seems like a cheap check valve too, because I could blow a very small amount of air through it in the reverse direction. That explains everything. I'm glad I didn't have to mess with the valves yet, because the way the engine is mounted in this, you'd practically have to take the whole bike apart to get to the head - the frame totally blocks access. I'll save that for a rainy day. Here are a few pics:

You can just see the edge of the check valve under the lower right part of the fuel pump, held on by the white zip tie. The check valve is symmetrical, so it would have been a very easy mistake to make during assembly. Just got back from a nice long ride and the bike is running top notch. Will hit 65mph on flat ground. Also, it actually has TWO fuel filters installed. One is down by the carb, and the other is visible in these pics. The fuel filter near the tank was also installed backwards, and I have corrected that. The thing I thought was missing a fuel filter is the white plastic canister in the upper left of these pics. After examining this more closely, I believe it is some type of anti-siphon device, as it empties back in the gas tank through a third hose when the engine isn't running.

Anyway, problem solved. Thanks so much for your time and suggestions!

Mathias

EDIT: Hmmm, apparently this board doesn't like my links to picasa.

Last Edit: Apr 3, 2011 11:50:29 GMT -5 by mathias999us

sprocket
Guest

GY6 dies after a few minutes of WOT Apr 3, 2011 12:00:10 GMT -5

Post by sprocket on Apr 3, 2011 12:00:10 GMT -5

The WOT test is not valid. The fuel flow is more or less constant to the carb. The throttle controls the carb not the fuel flow...the float bowl fills at a rate GREATER than the engine can use it at WOT, so there is always fuel.

The fuel filter may be in the tank mounter petcock. If the tank is mounted below the the carb then you have a fuel up system. If the tank is above the carb you have a gravity feed system...

GY6 dies after a few minutes of WOT