Cleaned carburetor, tested fuel tap, still stalling. By frolicndetour (Read 1,075 times)

[frolicndetour]

Hey guys,

Working on my 2003 Derbi GP1 Predator, liquid cooled (2 stroke, 50cc, piaggio engine). I bought it second hand, and it only has ~600km on it.

At first, it was stalling about a quarter mile down the road at my first stop sign from the house. I played with the air/fuel mixture screw and idle, and it seemed to get worse. Currently, it will idle for around 15-30 seconds, and bog out. It will not restart immediately, but if I try it after some time has passed I will get again a start of 15-30 seconds, lights flicker on dash, bogs out and won't immediately restart.

I just tested the fuel tap by applying vacuum to the vacuum line and I got a good, consistent flow of gas. The flow stopped when vacuum was released. I have decided the fuel tap is in good shape.

I pulled the carburetor and sprayed all the orifices with carb cleaner and when I was satisfied I replaced it. I still can only get the bike to start for 15-30 seconds, bogs out, lights flicker and it won't immediately restart.

I am at a loss and don't know what to check next. I've decided to drain my gas tank and replace it with fresh gas because I fear there is varnish or water in the tank. Any other suggestions are greatly appreciated!

[Alleyoop]

With 4 stroke motors First thing to do if when coming to stops after the motor is warmed up it wants to die unless you play with the throttle is Adjust the Valves. Do this before messing with the carb. At this point it was running good with the settings on the carb so the valves are suspect and or you have a AIR LEAK. Vacuum line came off, or some other hose came off or hoses are old and cracked and or leaking etc..

You can suspect the carbs Fuel Mixture setting IF the stalling started to happen after a 25+ temperature change.
If thye temp was 70+ and it was running good and now the temps dropped dramactically down into the 50s and 40s and crap started to happen, then you need to feed the motor more fuel so turn the fuel mixture screw Counter Clockwise at least 1 full turn. If the opposite happens Low temps and it was running good and the temps went up into the +70 range then you need to LEAN the motor out turn the fuel mixture screw Clockwise about 1 full turn.
Alleyoop

[frolicndetour]

Received. I forgot to mention it is a 2 stroke (I tried to remember to mention all relevant attributes).

The vacuum line I used to test the fuel tap seemed to be performing okay when I applied vacuum to it. It was resecured tightly. Any other vacuum lines I should be concerned about, or other issues to look at?

[Alleyoop]

My bad(HAHA), you did mention it is a 2 stroke. So since I know temps have dropped in your area adjust eht AIR MIXTURE on your 2 stroke carb.
Alleyoop

That screw is on the right side of the carb near the AIR TUBING SIDE Turning it Clockwise RICHENS it up by cutting some air off which in COLD WEATHER motors need more fuel. Counter Clockwise allows more air and LEANS it out.
Alleyoop

[frolicndetour]

Alleyoop- I'm a novice at all this. Do you think that me messing with the settings on that air/fuel mix screw could be the culprit? I would be SOOO relieved if that was all it was.

I've read your response to pissedmopedman (link) that I need to turn it to tight, then turn it back 2.5 turns counterclockwise to find the openness it should be at. I did that, and it is still stalling. Which direction would you suggest I should turn it if it is cutting out like it is?

[Alleyoop]

Oct 24, 2014 11:28:31 GMT -6 frolicndetour said:

Alleyoop- I'm a novice at all this. Do you think that me messing with the settings on that air/fuel mix screw could be the culprit? I would be SOOO relieved if that was all it was.

I've read your response to pissedmopedman (link) that I need to turn it to tight, then turn it back 2.5 turns counterclockwise to find the openness it should be at. I did that, and it is still stalling. Which direction would you suggest I should turn it if it is cutting out like it is?

No that 2.5 turns is for 4 STROKE carbs where they have a FUEL MIXTURE SCREW your Carb has a AIR MIXTURE screw big difference.

So on YOUR CARB everything is the OPPOSITE of that on a 4 STROKE CARB. Also your CARB is very finicky so follow this procedure on Your Carb From where the Screw is set at START it UP:
Alleyoop

scooterdoc.proboards.com/thread/7678/2ts-carb-tuning

[frolicndetour]

thank you thank you. I think you suggested I read that article in the past and I didn't understand the difference in the screws between 4t and 2t. I'm learning slowly but surely.

I have lost the setting entirely because I have made drastic turns. Where would a good starting point be? If my air mixture screw is opposite of the fuel mixture screw, then it should be only TIGHTENED by 2.5 turns as a starting point (i.e., much looser than fuel mixture screw)?

[Alleyoop]

If you turned it out counter clockwise 2.5 turns turn it Clockwise 1/8 at a time and after each 1/8 try to start it but only a couple of hits on the starter. The motors should start with only 1 or 1 SHORT hits on the starter if you have to crank and crank the motor over for it to start something is not adjusted right or something is not right like maybe dirty air filter or air leak from a hose or something.

Then once you get it started let it warm up THEN DO THE PROCEDURE from that SETTING to find the HIGHEST IDLE adjusting the air mixture screw.
Alleyoop

[frolicndetour]

I lightly seated it, then backed it out 1.5 (per my Haynes manual) and its running now for about two minutes!!!!

[cyborg]

If I read the original post correctly you said the lights flicker then it dies,,, I would check the main fuse and all ignition related electrical connections also ,,, from the battery onward to the Ingnition switch ,,, it may be intermittent and is flooding out the plug on the spin down,, it may have the spark drop off but the piston is still pumping fuel mix ,, just a thought

[Bashan]

Spin down....spark drop off.....this guy has built too many Ducatis.

[frolicndetour]

I dunno buy a battery tender? I don't know how to examine those things yet.
It runs at night, but in the cold morning it wouldn't start.

[Alleyoop]

I think to many Harley's with bad wiring

[Bashan]

A battery tender never hurts but it should start in the morning. I'm horrible with two strokes but does that bike have a choke you have to manually pull out or an auto-choke?

[Alleyoop]

Take a couple of pictures of the carb area Left side and hoses so we can see what the setup is on the motor and what kind of carb is on there.
Alleyoop