250 cc scooter stalls at stops! please HELP!!

[hailrhino]

hello! please help me someone...i have a 2007 250 cc scooter..its like a roketta touring style..i really dont know the make..one guy that searched the vin says its a "benzhou ". anyway, i took it to a shop and they charged me 50 bucks to raise the idle and tell me i needed a new carburetor (it wasnt fixed). well. i had a friend of mine take the carb apart and clean it and it still does it! the carb looks fine..what the heck is going on...? it runs great except the stalling at a stop...it tends to bog down just before the stop and then die..

thanks!

[skuttadawg]

Valves need adjusting mine did they same thing but after they were adjusted it was new again

[hailrhino]

thanks soo much for the reply skuttadawg...thats what i thought...is it a big job to get to the valves?

[trailheadmike]

Gobs of posts on this for you -- if its a Honda 244 clone, here is a good thread that even references other threads: scootdawg.proboards.com/index.cgi?action=display&board=200cc&thread=22492&page=1#270022

If its the linhai 257 clone, look at the very first post in the 250cc section of the forum.

[hailrhino]

i also just noticed it doesnt have an oil filter screen...what will happen without it??

[imnts2]

I am not sure you know what an oil filter screen is. Did you remove the cover?

[hailrhino]

you know..the little screen that goes in the spring..

[rockynv]

Without it any bits of gasket material, casting slag, etc that flake off will go through the oil pump and lead to an early failure and cause premature engine wear. They could even plug the oil feeds to the crankshaft or head and cause sudden catastrophic engine failure.

[imnts2]

Yes I know what the oil filter screen was. I was sort of surprised with your choice of words. "I noticed" it missing while you are trying to solve a stalling issue. How did you notice. But none of that matters. Rocky is right. You need it.
Getting back to stalling. I would first check valve clearances. Important and probably a little overdue.

If they are OK, then check the deceleration diaphragm in the carb and the vacuum line to it. When you let off the throttle, there is a smallish vacuum diaphragm that feeds a little air/fuel to the carb for a few seconds to keep the engine from stalling.


Does it idle OK except on stops?

The cheapest fix may be a new carburetor.

cheers
Good luck
keep us posted
lefty2

[ce]

There's nothing wrong with the carb, you need a valve adjustment.

There's two valve covers, upper, intake, and lower, exhaust, 2 bolts on the upper, 3 bolts on the lower.
Remove the battery cover and observe the upper valve cover. Cut a hole in the plastic above each bolt and insert an 8mm socket on a swivel at the end of an extension. Use a magnetic bolt retriever to capture each bolt as it is loosened.

Tap the starter to advance the engine to the compression stroke, where both valves are closed. The intake rocker arm will have a little play in it at this point, so adjust the valve lash to .004"

Now remove both lower side panels and free the bottom panel and drop it down to allow access to the exhaust valve cover. You'll have to wedge a block between the bottom panel and the frame to keep it out of the way, it's flexible and won't be harmed.

Open the cover and note the eccentric position of the bolts for reassembly, the rocker arm may not move, or only have slight play, indicating that it has closed, which is usually where tha misadjustment occurs. Adjust it with the feeler guage to .006", and it should be noticable looser than the intake valve by touch, as it heats up more and that's why it closes up over time.

This procedure takes less than an hour, and is very difficult because you're upside down and working with the left hand in an area difficult to see, but it does evade removing all the plastic to expose the engine.

You may develop an easier or more precise technique, but this has worked for me for 14,000 miles on a pair of 257cc engines. It's not for the novice, but if you like engines, and I think you do, you'll do fine. Worst case is if you're off kilter and the valves start clattering and tapping, you'll know it's open to far. If it won't start when cold and dies while idling, it's too tight, usually both symptoms are caused by the exhaust valve. The intake rarely changes, but still must be checked.

Simplicity, it's part of the design. Have your friend that cleaned the carb help you, it'll be a mystery for you to solve. Then go by that shop and tell them they're a bunch of phony dicks that rip people off because they don't know enough about engines to even work on a simple Chinese scooter. Do some burnouts in their parking lot, flip 'em off, and come back later and egg the building.

[imnts2]

It will be intersting to here how this works out.
Keep us posted.
Cheers

lefty2

[mrpolymers]

I have the same scoot primarily. A JCL 257cc with the Yamaha/Linhai engine. I had a similar problem with the scoot stalling out at stops. Now, I did a valve adjustment prior to this just after I purchased it used. So, I knew this was another problem. Turns out, it was a vacuum issue. Do this test.. Place the scoot on the center stand. Start and let it idle. They should idle around 1,800-2,000rpms tops. Now, try squeezing the various hoses around the carb to see if you hear an increase is speed. If you do, then see where the tube originates. Also, the engine is only as good as the air it can breath. I took my OEM foam air cleaner out and replace with a more traditional car filter. My scoot has not stalled in 10,000 miles now..

[imnts2]

He could also try the propane test. And ordinary propane torch . Start and let it idle on center stand with rear wheel off the ground, open the valve, don't light it and wave it slowley arond the engine. If you find a leak the engine will speed up. Sinde it idles good, I supect the decell valve.