GMW M2 50cc bogs at half throttle By helix803 (Read 1,334 times)

[helix803]

I am working on my friend's scooter. I gave it a tuneup and it was having some electrical issues. The electrics are now sorted, but now the carb is pissing me off. The carb did have the EPA plug which I removed and can now adjust. No matter where I but the fuel mixture screw, the engine bogs at half throttle. It idles fine, but can't be ridden. I am about to give up. Please help.

[Alleyoop]

How is the Air Filter and Tubing going to the carb. Bogging means it is getting to much air or not enough fuel.
Did you take the carb off and take it apart to clean it?

Did you take the Diagpghram out and or checked to see if the Main Jet is clogged.
Alleyoop

[helix803]

I took the carb completely apart and cleaned it thoroughly. The jets are clear. The air filter is new.

If I apply the throttle slowly, it bogs less. If I apply it quickly if bogs severely.

[cyborg]

Several things to look at as Alley says,,,, vacuum line off or cracked ,,, diaphragm torn or pinholed and not lifting ,,, jet plugged,,, did you physically remove the jets and see light thru them ?( this is my call)

[Alleyoop]

Mar 7, 2015 17:03:43 GMT -6 helix803 said:

I took the carb completely apart and cleaned it thoroughly. The jets are clear. The air filter is new.

If I apply the throttle slowly, it bogs less. If I apply it quickly if bogs severely.

Yep to much air getting in when twisting the throttle quickly. So I would check the top of the Diaphgram make sure the rubber Diapghram is in the grove around the top of the carb and is sealing. Also make sure you put the spring back in.

[helix803]

OK, I'll check the diaphragm and look for vacuum leaks tomorrow. Yup, definitely can see light thru the jets.

Thanks for the help so far.

[rks]

You say the air filter is new. You didn't by chance happen to replace a factory type air filter with a high flow filter such as a K&N, or a Uni..?

[helix803]

• No pin holes in the diaphragm
• There is one vacuum line from the intake manifold to the fuel pump. It appears fine.
• The fat breather hose on the lower side of the cam cover goes to a filter/valve dohicky. It is OK, after the box it vents to atmosphere
• The upper breather hose goes to the canister and connects to the intake tube. That hose appears fine
• Factory airbox with a new filter, but the owner did not supply the airbox cover

[jerryscript]

How does the intake manifold look? Even a small crack on it can create an air leak that will cause problems.

[helix803]

FIXED!

Went back to square one. Took apart the carburetor and found a clogged jet (again). I reinstalled the carb and adjusted the mixture and idle until the engine did not die at half to full throttle.

Thanks Scooter Doc!

[jerryscript]

Right on, glad you got it running! Good time for some fuel treatment, if you are clogging jets, you may want to do a full flush!

[cyborg]

And I think an online fuel filter is in order if it even has one change it

[mpndb]

what is the problem with a high air flow air filter I bought one and now my keeway is bogging down is there a way to fix it

[jerryscript]

Nov 15, 2015 6:31:00 GMT -6 mpndb said:

what is the problem with a high air flow air filter I bought one and now my keeway is bogging down is there a way to fix it

It allows more air in, so you need more fuel coming in to make the right mixture. Try adjusting the air/fuel screw by turning it out 1/4 turn at a time. If you still have issues after 3 full turns out, you need to upjet.