More Performance Problems By learae (Read 1,501 times)

[learae]

It's spring and riding season again, so I took out the Shanghai Shenke 150 cc you all helped me fix this fall and I am having some problems.

Reference this thread where we solved the problems before, it was running good after these troubleshooting steps... scooterdoc.proboards.com/index.cgi?action=display&board=150cc&thread=7216&page=1

At the end of last season and now this season, I am seeing very low performance again. At WOT I only get to about 4000-5000 RPM and it sounds fairly "hollow". It only gets to around 25 MPH after a very long run.

(My Roketa at WOT is around 7000 RPM and has some 'Grunt' to it, they definitely don't sound the same!)

I already rechecked the valves and they are fine, and the mixture adjustment seems good. The engine starts right up and idles fine, and it doesn't die when idling or when the throttle changes suddenly. The spark plug is good and was just replaced before putting it away for the winter.

Where should I start?

Thank you!

[tvnacman]

Did you drain the bowl in the carb before you left it the last time?

John

[learae]

I didn't, but I did put Stabil in it and start it up occasionally throughout the winter for a while. And this started happening before winter, but it's worse now.

[tvnacman]

I would think it is carb related . Sometimes its just better to get a fresh start with fresh gas carb , intake manifold, spark plug and valve adjustment .

John

[Alleyoop]

could also be your Variator weights or belt. But follow and do what you did last time on the previous post. It could also be the diaphgram not raising the needle out due to rips in the rubber.
Any number of things you just have to check it one.
Alleyoop

[learae]

I took the CVT cover off yesterday and it was pretty messy and sticky with something. It is possible the variator is jammed up or stuck. I neglected to check when I had it open.

I was trying to fix the kickstarter, but I think it's missing pieces, so I am probably just going to take it off. It doesn't engage with the engine shaft when kicking down, or sometimes it partially engages just to let go and bust up your ankle ;-; OUCH

I think I'll open it up again and make sure the variator works as I rev up the engine. If it seems to be working ok, I'll take the carb out again and give it a good cleaning.

[Alleyoop]

Cool, also take the top off the carb and check the diaphragm for rips or pin holes. If that is leaking it will keep your rpms low and loose a lot of top end because it will not raise your needle out enough. But usually what happens is since you have the throttle wide open and allowing the max air to come but not enough gas it will bog on you.
Alleyoop

[learae]

Alrighty got the CVT cover off and the variator seems to be working correctly. The belt is still in good shape, but I think I am going to replace the belt on both scooters pretty soon anyways.

I took the diaphragm out and it looks ok, no problems that I can see. I was also surprised that the engine could start without it and idle pretty smoothly. With the engine running and the diaphram and main needle out, should I see fuel come out of the main jet? I saw nothing.

What causes the main needle to move up when you give it throttle?

Thanks :-)

[Alleyoop]

Very cool, the needle moves up when enough air pressure gets into the Cylinder that holds the needle and pushs up the RUBBER DIAPHRAGM which in turn moves the WHOLE cylinder up and out of the Main jet and defuser. So yes during idle no fuel will come out of the Needle guide that the needle goes down into.
Alleyoop

[learae]

Okay so I took the carb out and cleaned everything, the passages are clear and everything seems in order.

I'm still having the power problem. I tried to adjust the mixture and I found that no matter how far out I took the low speed mixture screw there was no change in the engine. I know 100% that the passages are clear, so what would cause that?

I'm puzzled because everything seems in order, and yet I can't get up to speed.

Thoughts?

[Alleyoop]

Try this:
Start the scoot let it warm up at least 5 minutes.
Then turn the Fuel Ratio Screw CLOCKWISE until it stops Let me know what happened.
Alleyoop

[learae]

It runs with the needle all the way clockwise, but not well. It did eventually die when I started to open it again. I opened it about 3/4 turn before it started to run smoothly again.

[Alleyoop]

At 3/4 turns what are the rpms, if you turn it counter clockwise 1/4 turns at a time and wait about 10 seconds or so to allow the motor to catch up does it idle higher?

Did you change the jets in that carb or do any changes?
Alleyoop

[learae]

At 3/4 turns it is about about 1300 RPM. I've gone out another 3/4 turns now and it is still steady at 1300 RPM, no change.

[Alleyoop]

Almost turning it out another full turn with no change I think you have some clogging going on.
If the rpms did not move and if it was to much fuel the rpms would have started to drop or start to act up trying to keep running.
I think you have a clog in either the TINY holes by the butterfly or it could be the Rubber-O Ring in the Fuel Ratio Screw is partially blocking the passge.
Alleyoop