gy6 50cc 4t electrical injection breaks down on idle.. By axyb (Read 1,358 times)

[axyb]

Hello,

I have a Chinese 50 scooter with 4-stroke electric injection

It breaks down 90% or 100% of the time when the engine is hot, usually after 2/3 hours of riding with it. The more I ride it, the more I know that the breakdown is approaching; I can hear it by the noise when I'm on the idle while waiting at the red light: there are drops in speed/sometimes the speed increases almost as if the scooter wanted to run away; you can hear the engine jumping too. It's a mix of all that.

When I break down, sometimes it restarts instantly with the choke and by playing with the throttle; sometimes I have to wait between 20 min and 1 hour and it ends up restarting by playing with the throttle and still with the choke. It's about 50/50.

What I did :

- spark plug

- rollers, belt, variator cleat

- valve clearance adjustment

- ignition coil test

- test injector that spurts correctly 

- pump test

- new air filter / I even removed a flange from the air box 

- cold idle screw adjustment 

What I think:

- it should not be an electronic failure because it is 90% of the time when the engine is hot; if it is an electronic problem it would be 90% of the time random as a failure. Cold, warm or hot. After that I could be wrong too.

Other details :

- Just after the breakdown, once restarted, it usually doesn't idle, I always have to put the gas pedal back on to avoid it cutting out. Then this problem disappears and it makes me strong increases in speed always at idle at the red light then after a few km it returns to a regular speed calmer but still not very "smooth" or correct.

- Also I can't start with the kick; my kick has never really been used and worked properly, we'll say that it works but when it wants; and not on this failure anyway. 

- apparently it's not the ecu / electronic injection box

- I was told the valve sealing but probably if that was the case I would also have failures in the acceleration phase apparently... after I was also told that it was not always the case for the acceleration phase... 


(If you can help me please use simple words cause I'm not english native)

[vapor]

Based on your symptoms, you may want to focus on an air leak. These engine’s problems are usually dramatic as they operate so efficiently. Check, or better yet, replace ALL the original rubber lines. Chinese rubber lines are poor in quality do not hold up to oxidation and heat of this high rpm engine and use. My diagnosis is based on you stating that your problem occurs after continued use and heat build up.

I just recently had another Chinese 250cc that had this exact issue. Even at times, when hot, varied engine racing. Air intake tube had very small cracks. Very small. This creates a lean mixture. Sadly, the owner was extremely frustrated with his “hit and miss” repairs before bringing for help. He tools around non stop now.

Design is good, typically workmanship and materials are your issues.

[slowhand]

When I took my state mandated 'motorcycle safety course' I elected to ride a scooter. Since that's what I was intending to ride it's what I wanted to take the test with. It also helps that it is MUCH easier to take the riding portion of the test with a small, easy to handle, light weight, automatic scooter than a heavy motorcycle with a manual trans. Anyway...

I had to take 2 sessions of the training class because the scooter died during my first day of class. Just quit during a training exercise. The couple running the class pulled me off the course and said: "not to worry, we have a back-up scooter." So they got me a second scooter and it wouldn't start at all. Turns out the fuel pumps on both machines died. These were both 50cc Suzuki scooters with fuel injection. If your scooter is fuel injected the electric fuel pump apparently is a common failure. See if you can find somewhere to have it tested. You'll need some sort of special adapter to connect to a fuel pressure gauge in order to test the pump.