Engine dies out at lights and now wont start at all

[redeye]

Hello everyone. This is my first time posting here and have a real stumper to both me and my mechanic friend. I have a 2012 VIP 49cc moded to an 80cc (50mm piston). It was running great and started to die out at stop lights. I tried changing fuel filter and lines, changed the vacuum lines too just in case. It ran great for a couple of days then started diying out again. On my way back home it died and wouldn't restart. I noticed that fuel was coming out of the top vent hose near the top of the carb. In exploring the carb I realized that it must have been getting way too much fuel. I decided to change the carb out for a new one. I have now tried changing the coil and the stator thinking that maybe its not getting enough spark to fully ignite the fuel. I've checked the compression and its fine. No oil leaks and oil level is fine. I broke down the top end and didn't find any issues either. I know it has fuel, compression and spark, thanks to the jolt I took earlier. Just not sure what could cause it to suddenly stop firing???

I would greatly appreciate any ideas you might be able to throw my way.

Thanks in advance,

Red Eye Scooter Guy

[shakerdriver]

Have you checked your valves? You may be getting compression because they're not opening properly.

[highsocietyscooter,cpi70cc]

I have had a bad ignition do this

[90GTVert]

Check all connections in the ign system and your engine and frame grounds.

[redeye]

Shaker: I did check the valves and the exhaust valve was a little tight so I oupened it up a bit. Intake is at .002 and exhaust is now at .004.

Highsociety: Are you talking about the actual ignition or an ignition coil?

90GT: I have checked or replaced all of the electrical components at one point or another. I swaped out the CDI and R/R with known good ones. I have replaced the stator and ignition coil as well. I am however unable to locate a engine to frame ground. I did try hooking one up but had no change. The battery has 2 wires from the ground terminal. One straight to the valve cover and the other goes into the woiring harness. The weird thing is that it ran without that ground for almost 8000Km.

I did have to change out the engine mount to the frame. There is a small section of frame that attaches to the engine mounts and then attaches to the frame that had a bad bushing. I simply changed that entire piece. I didn't notice any ground wires that I might have not hooked back up. I am completely at a lose. By all means it should be firing.

Thanks for the ideas guys. Keep them coming and we'll get this thing running again.

[Deleted]

youre valves are way off. ive been doing this for a long time now and .002 on the intake is toooooo tight.

I put both on .003 with excellent results.

[highsocietyscooter,cpi70cc]

The ignition itself and yes .003 is a good valve adjustment but i usually do it by feel

[redeye]

Ok, changed vavlves to .003 and still nothing. I took the air intake off the carb and now it acts like it wants to fire but still wont.

[Deleted]

Mar 22, 2013 15:52:24 GMT -5 redeye said:

Ok, changed vavlves to .003 and still nothing. I took the air intake off the carb and now it acts like it wants to fire but still wont.

Okay first things first.

Verify mechanical timing.

Verify compression.

Verify spark (nice fat blue spark or weak yellow?)

Verify the jets are tight (i have had jets come loose and flood me out)

Verify the petcock is working properly

Ground wires: battery neg to valve cover, valve cover to frame. Ring terminals, wire and crimp too at auto zone.


I dont see anywhere you actually say you can see a nice fat blue spark jumping the spark plug gap.

hmm contaminated fuel? Water is heavier than gas so the water will settle at the bottom of the tank. Had a brand new out of the crate taotao that the guy put gas in on a warm day after being VERY cold, the inside of the tank 'sweated' like a beer bottle and it wouldn't crank. I would TRY to fire but wouldn't. Drained some gas out of the carb bowl and it was milky looking...classic water-in-gas look.

[highsocietyscooter,cpi70cc]

nice

[redeye]

1FASTQMB: checked timing twice. It was right on the money. Compression went up to around 130lbs within I'd say about 6 to 7 cranks. The spark however has been more of an orange glow now that I think about it. Not the standard blue. I did try a new carb out of the box along with taking apart and cleaning the old one.Verified petcock was working by both sucking on the vacuum and by taking fuel line off carb and cranking. I even put another on just to be sure. Itried the ground from frame to valve cover too. I drained the fuel from the bowl and tank and tried fresh 93 octane fuel as well. This is why I turned to the boards. I believe Iv'e tried just about everything. But thanks for the ideas. Keep them coming if you've got more. I figure it has to be something simple. I figure it has to be too much fuel, not enough air or weak spark but not sure how to rectify those issues other than how I've already tried.

[Deleted]

'The spark however has been more of an orange glow now that I think about it. Not the standard blue.'

you want a hard fat blue spark SNAP! (hot) and not a thin yellow orange weak one (cold) so verify that

also...

What jetting are you using? might be flooding out.

[scootertech]

Along with everything else check the gap between the flywheel and the ignition pickup, a business card makes a decent feeler guage. Too much gap will give you a weak or nonexistent spark.