YY250T-2 won't rev

[slipf18]

Wife has a Jonway YY250T-2 with the 244cc upright motor. Only has 250 miles on it. Wouldn't start this spring. I assumed it was bad gas because it had not been run in a while. I drained the gas tank and replaced the filter.

Now it starts and will idle but will not rev up. It will increase RPM up until the rear wheel begins to spin and then will bog down and stall out. I removed the cover and air filter (what a pain). If I cover the air inlet about three quarters of the way it runs well and will rev up and the back wheel spins etc.

I got it good and warm and adjusted the valves and also increased the idle speed a tad. However it still won't rev unless you restrict the air flow. I can't find any vacuum leaks or crack in the air intake system. Tried spraying carb cleaner around and motor doesn't even notice unless I get close to the air filter area and it sucks it through there.

Obviously too much air is getting in. So I'm guessing auto choke is stuck or carb needs adjusted. I don't know about the latter though, this problem didn't happen over time. Ran fine last fall
(last time it was run).

Any ideas?

[scoot-away]

Hello slip, normally when you restrict the air flow, and that has a positive effect, it would point to the engine not getting enough fuel. Your hand effectively becomes a choke. My first guess is dirt in your carb. The petrol in the states (assuming you from the US) is from what i read laced with ethanol. Perhaps the long standing of the bike caused some residue. I would strip the carb and clean it out especially the jets. Use carb cleaner and a good power blow through.

[slipf18]

Yes, I was hoping I wouldn't have to take the carb apart since you have to take the whole bike down to bare bones to get at it.

Oh well.

[tomcas]

I agree with scootaway that it's time to strip and clean the carb. Remove everything and blow out the passages and jets with a rubber tipped blow gun. The choke doesn't seem to be bad given the symptoms.

[JR]

Woe!! Hold the bus!! You said you adjusted the valves warm? Like this?



If not and you did it with the engine not running and with feeler gauges it has to be done with the engine cold! JRR

[scoot-away]

Slip you don't have to strip the bike away to remove carb, you can do it through the top, granted small hands are better.

JRR this is the 244cc honda engine no feeler gauges needed??

[slipf18]

It is the Honda 244 clone with external adjusters. I did it warm.

I may try to go through the top but I don't have small hands!

[yoster]

Don't run to the carb just yet!! Of course covering the hole once the filter is off will make it run better; have you seen how small those two holes are with the cover ON? It's going to run like crap with the filter off unless you cover almost all of the hole.

What you're describing with the filter off and hand on is perfect operation. You now need to get the SAME airflow with the filter on. Here's my advice:

Ran into a similar problem myself. The problem was 2-fold:

1) The air filter box cover wasn't sealing correctly. I got some right-stuff gasket maker and sealed the box better so that no air would leak in other than the two small holes on the box cover.

2) There was a small crack in the tube coming off the carb. Once that was also sealed, problem solved. Until then, the scooter wouldn't rev above about 3500 rpm.

[JR]

May 24, 2010 8:11:49 GMT -5 slipf18 said:

It is the Honda 244 clone with external adjusters. I did it warm.

I may try to go through the top but I don't have small hands!

You still didn't answer the question? Did you do it like in the video, warm and running? If so then fine but this engine can be done the conventional way too cold and by removing the valve cover and using feeler gauges which is what some people do. If done this way it's got to be cold.

JRR this is the 244cc honda engine no feeler gauges needed

Knew that all along, used to own one and what do you think the video I posted was? JRR