Post by willie97 on Aug 14, 2010 11:57:26 GMT -5
Hello everyone. I am a newcomer to scooters. I am working on my cousin's new Jonway (YY50QT-21) and I am hoping someone could give me some input.
First here is some history of what has transpired since the scooters were un-created. (Please bear with me, this will be lengthy but I think more info the better when asking for help troubleshooting)
My cousin and her husband bought two identical scooters brand new. They said initially one of them ran perfectly but the other one would not start. My uncle found if he disconnected the tube that goes to the air cleaner to the back of the carb and held his hand over the carb the machine would sometimes start. Figuring it might be the electric choke (or enrichment valve depending on what you call it) my uncle pulled the carb off of the "good" running scooter and swapped it with the non running scooter. After doing this, the "good" running scooter still ran good and the non running scooter still would not run without choking it with your hand.
They swapped the carbs back and continued to ride the good running machine until a few weeks back when it stalled and would not start again. These machine have less then 20 miles each on them.
I currently have the machine that was running in my shop. The engine will turn over with the electric starter and the kick starter but doesn't give any sign that is trying to start. Even if I out starting fluid in the spark plug hole, not even a pop.
That being said, here is what I have tested / found:
OK, that is it in a nutshell. My thought is I have a bad intake valve seal or guide or maybe a broken spring (I don't see a break but that would allow the valve to stay open.) I would be grateful for anyones feedback on this in case I am missing some trick with these little engines. I find it hard to believe I would need to tear down a engine on a brand new scooter to do valve work but I know it is possible. I haven't looked at the other scooter yet but it also concerns me that since 2 machines have the same issue now I may be missing something simple.
Thank you so much for your time.
Bill
First here is some history of what has transpired since the scooters were un-created. (Please bear with me, this will be lengthy but I think more info the better when asking for help troubleshooting)
My cousin and her husband bought two identical scooters brand new. They said initially one of them ran perfectly but the other one would not start. My uncle found if he disconnected the tube that goes to the air cleaner to the back of the carb and held his hand over the carb the machine would sometimes start. Figuring it might be the electric choke (or enrichment valve depending on what you call it) my uncle pulled the carb off of the "good" running scooter and swapped it with the non running scooter. After doing this, the "good" running scooter still ran good and the non running scooter still would not run without choking it with your hand.
They swapped the carbs back and continued to ride the good running machine until a few weeks back when it stalled and would not start again. These machine have less then 20 miles each on them.
I currently have the machine that was running in my shop. The engine will turn over with the electric starter and the kick starter but doesn't give any sign that is trying to start. Even if I out starting fluid in the spark plug hole, not even a pop.
That being said, here is what I have tested / found:
- Checked the spark with spark tester and by grounding on the block. Machine has good strong consistent blue spark.
- Checked over all hoses and fittings. Didn't find and cracks or pinched lines.
- Checked over all electrical connections I could find and made sure connections were tight.
- Tried choking by holding my hand over back of carb, machine didn't even sputter but gas ran out all over my hand.
- Checked and adjusted valves (.005 on intake and exhaust)
- Disassembled and cleaned carb
- Checked compression, my understanding is these machines should have about 100lbs or so for compression. This machine has only 60lbs
- Did leakdown test. While at TDC with valve cover off could hear air escaping from area around intake valve. Put valve cover back on and could clearly hear air hissing through the carb. Also, I didn't notice this initially but when I try to start the machine now after cranking the electric starter for a few seconds a "gush" of fuel will shoot out of the overflow on the carb. My guess is when the engine cranks it is pushing air back into the carb and not letting the fuel in the engine so it accumulates in the carb until it purges.
- I also pulled the rockers and redid the leakdown test. Same deal. (was making sure rocker wasn't holding valve open)
OK, that is it in a nutshell. My thought is I have a bad intake valve seal or guide or maybe a broken spring (I don't see a break but that would allow the valve to stay open.) I would be grateful for anyones feedback on this in case I am missing some trick with these little engines. I find it hard to believe I would need to tear down a engine on a brand new scooter to do valve work but I know it is possible. I haven't looked at the other scooter yet but it also concerns me that since 2 machines have the same issue now I may be missing something simple.
Thank you so much for your time.
Bill