Several Questions By wedoo2 (Read 659 times)

[wedoo2]

My nephew bought a scooter and it does not start.  The kid he bought it off of said that it needed a new piston, and gave one to my nephew.  I want to start it first.  The bike is a Chinese make, from a company called Benzhou and I have not been able to get any kind of service manual, or even something that can identify the bike; such as size of the motor.  From what I am reading it seems like the Chinese scooters are very similar so I wanted to post some pictures to see if anyone can help me get it started.  I have spark but no gas.  Here are a couple of pictures:



I am not able to get gas, at least into the fuel filter, even with the throttle pulled.  This is the petcock that I have and it seems to be fairly standard:



There are two lines, one to the carb, the other to the intake manifold tubing.  When I turn over the motor it seems to have compression, but I have no idea if the vacuum is strong enough to push the gas into the carbs.  My question would be why would I not be getting gas?

Can anyone identify the motor?  It is a four-stroke, but I have no idea of its size.  The piston that was included in the sale is 50mm in diameter but that us only half the displacement measurement.  Here is the motor:



On the left side of the carb is a female electrical fitting that did not have anything plugged in.  Can someone identify what that is and what is it for, and I guess, more importantly, do I need something plugged in it?  It is the big black thing in the middle.



There are not a lot of people around here that work on these things so I may be on my own here.  I have restored motorcycles for years and can do the work with a bit of guidance.  If anyone can ID the motor, help me diagnose the gas problem, it will get me started.

[tdi]

Hi try to check if there is any stamping on the side of the engine.
It can help to identify the engine

[Alleyoop]

The motor is most likely your basic 139QMB motor which are very common on the 50cc scoots. You will find the motor stamped on the motor case by the sidestand. To check for fuel take the fuel hose off the carb and put it in a container and crank the motor over fuel should stream out into the container. If NOT then check if the fuel filter is clogged and or if the VACUUM line going to the petcock is not cracked. You can also suck on the vacuum hose going to the petcock to check if the petcock is working. If not fuel comes out of the petcock the tank outlet may be clogged and or the petcock is bad.

That black thing you mention is the ENRICHER(Choke) which is supposed to have two wires and a plug that plugs into the scooter harness. You definitely need a new one.

One other thing you want to DO FIRST is Adjust the valves to .003 inchs both of them. Also I noticed the carb has a plugged Fuel Ratio Mixture so you will also want to drill out the plug or get an aftermarket carb that has the mixture screw not plugged.
Alleyoop

Carb with parts labled :




Motor Number:

[wedoo2]

I really appreciate the responses.  The motor is indeed a 390QMB, so I guess that makes it a 50cc.  That makes sense because we have a local law that allows  people to ride them without a license.  I was able suck on the vacuum tube and fill up the fuel filter so it looks like the petcock is okay.  I am going to replace all of the tubing and the fuel filter.

Are there some instructions for adjusting the valves on this motor here on the forum, or somewhere else? 

I will look for a new carburetor I think.  Is there a certain part I should be looking for? 

Also, I have looked high and low for a set of wires to plug into the choke and cannot find that??  Will it have a connector attached? 

[Alleyoop]

Here is how to adjust the valves: It is all the same for any size motor it is just the gap that is different, for 50ccs .003 inchs works good for 150s .004 works good for 250s .004 for the intake and .006 for the exhaust.

Also on the ENRICHER the ENRICHER WIRES have been cut off so you need a NEW ENRICHER. If your going to get a new Carb they come with a new Enricher.
Alleyoop



New Carb:
www.chinesemotopartswholesale.com/18mm-carburetor-welectric-choke-for-gy6-50cc-moped-scooter-p-1721.html

[wedoo2]

You are super. I will just go ahead and order the carb and some other stuff. I found a PDF, but was not positive of the GY6 moniker. Got it now. What will I plug in the new enricher to?

[Alleyoop]

You will see a PLUG by the frame close to the carb with probably a green wire and maybe yellow or red wire The plug will have voltage ONLY AFTER THE MOTOR STARTS.
Alleyoop

[wedoo2]

OK, since my last post I ordered the new carburetor suggested by Alleyoop and have installed that. The part was an exact match as far as I can see, except for the complete choke. I still cannot get the bike to turn over. I am getting spark,although it does look a bit weak, but there is spark. It has gas and I know that for two reasons; one it is leaking out of the overflow, and I have sprayed gas into the intake. I have a good battery.

Ideas of what to track down from here? I have air, gas, fire.

[jct842]

Compression. The part about the extra piston makes me question compression.

[Alleyoop]

Do this Crank it over IF IT DOES NOT FIRE and attempt to start at least ONCE take the plug out and see if it is WET OR DRY.
Now since it DID NOT FIRE at least once:
1. IF the plug is WET that means the plug is not firing.
2. If the plug is Dry then no fuel is being sucked into the motor.

Also can you take a picture of the Carb area like you did in the early post here of the Throttle cable side.
Alleyoop

[wedoo2]

Here is a pic of the right side of the carb.  I kicked over the bike 10-12 times and the plug was dry.  Mmmm

[Alleyoop]

Ok I see that the Idle speed screw does not have the throttle a little open so Turn the Idle speed screw about 1/2 turn clockwise to open the throttle a little and see if then attempts to start.
Does it FIRE and attempt to start or just cranks and cranks.

Have you checked that fuel is getting to the carb? Also have you checked to see if you have SPARK by grounding the plug on the VALVE COVER.
Alleyoop