Xciting 250 runs but stalls out almost immediately. Needing some help.

[SVX_Blue]

So I'm at a loss with my 07/08 xciting 250.
 
Since I've bought it last month I've only been able to wrench in it. The person I bought it from said that it wasn't charging the battery and it's been sitting.

When I brought it home I did the standard tune up stuff : new oil, plug, air filter, cleaned the carb and jets.  When trying to to run it, the scooter runs for a while - ,maybe 3 or 4 minutes then it dies. Sooner if I try to give it throttle.  After it dies it is a hard start and when it does it runs really rough and will only run for a minute.
Any who those are the symptoms...

 Then I started testing the charging system. Reg/rectifier tested good, but the stator didn't.

So I bought a new stator, installed it, started to refill the fluids, and noticed the water pump mechanical seal was leaking so I replaced that as well.

I get it back together and it is running the exact same.
I double checked that the new stator was good, checked the reg/rectifier again, cleaned the carb again, checked the fuel pump and filter for good flow.

Can any of you suggest something else to check?  Like I said I'm at a loss as to what to do with the scooter.

[CROSSBOLT]

I think that model has a crankcase operated fuel pump. Meaning just like some lawnmower engines have a diaphragm pump that works on varying crankcase pressure to move the diaphragm. I apologize if I am beating this to death since you have done an excellent job so far in trying to resurrect this really nice machine and probably figured this out already. There should be three hoses to this pump, one to the crankcase, one to the carb and one from the low mounted fuel tank. This pump and its hoses need careful inspection. Make SURE you straighten me out if this is all wrong!

[SVX_Blue]

Thanks I'll be sure to check all the vacuum lines.

[CROSSBOLT]

No, not vacuum lines! First, find the pump. Then if it has this type of pump there will be no vacuum lines but two fuel lines, one from the tank and one to the carburetor. And then a single line to the crankcase or valve cover. Three tubes.
Make sure to conduct all your start and running testa with the gas cap loose or open.

[SVX_Blue]

I did check the line. It is in good shape no cracks or other damage to it.

I do have an update though. I've narrowed it down to a carburetor issue. Unplugging the bystarter (electric choke) stops the behavior. Which means I'm dealing with a 'rich' condition.

According to the service manual I found could mean any of these things:

Rich mixture

• Damaged vacuum piston diaphragm (I assume they mean the Throttle valve here)
• Automatic valve opens excessive
• Clogged diaphragm hole
• Faulty float valve
• Float level too high

When I cleaned the carb I did notice the Throttle valve piston diaphragm seemed to be stiffer than what it should be. My guess is that is going to be my problem - There is probably a crack in the diaphragm that I missed.

[dan v.]

Unplugging the bystarter solves the issue?  Odd, the bystarters work by extending the plunger after operating for a few minutes, closing off the enrichment circuit on the carb.  Unplugging it would keep the enrichment circuit open, a rich operating condition.

Does it smell rich when idling?  They can really stink when running rich.

I bought a used B&W that didn't run well.  Found out previous owner had "cleaned" the carb.  It was missing the O ring in the idle screw, and the needle jet - which sits above the emulsion tube between the brass tube and carb body.  Both are easy to misplace, and will keep the scoot from running well.

The idle screw is usually set 2-1/2 turns out.

The diaphram is difficult to install - if you can get it in the "middle", not pushed all the way down or extended up it will install easier.

I guess a little clarification on the symptoms will help.  Runs for three or four minutes, then dies.   Dies at idle when doing nothing, or moving the throttle after the three minutes?  Or trying to drive off after three minutes, which puts a load on the engine?

[SVX_Blue]

Unplugging the bystarter solves the issue?  Odd, the bystarters work by extending the plunger after operating for a few minutes, closing off the enrichment circuit on the carb.  Unplugging it would keep the enrichment circuit open, a rich operating condition.

Does it smell rich when idling?  They can really stink when running rich.

I bought a used B&W that didn't run well.  Found out previous owner had "cleaned" the carb.  It was missing the O ring in the idle screw, and the needle jet - which sits above the emulsion tube between the brass tube and carb body.  Both are easy to misplace, and will keep the scoot from running well.

The idle screw is usually set 2-1/2 turns out.

The diaphram is difficult to install - if you can get it in the "middle", not pushed all the way down or extended up it will install easier.

I guess a little clarification on the symptoms will help.  Runs for three or four minutes, then dies.   Dies at idle when doing nothing, or moving the throttle after the three minutes?  Or trying to drive off after three minutes, which puts a load on the engine?

Doesn't solve the problem but unplugging it corrects the behavior - letting me narrow down the problem to the carb.

• It dies at idle when I just let it idle after a few minutes. Any throttle it will bog down and stall. No load on the engine - it has been on the center stand since I brought it home since I had to change the stator. But it ran this way before I changed the stator.
   
• It only stank the first few times I fired it up because it had been sitting so long it was burning stuff off.
• I did re-adjust the idle screw to 2-1/2 turns because it was set at 3-1/4 turns out. But that didn't change how the scoot was acting.
• I'll check the the needle jet again just to be sure. 

I'm still leaning toward the Throttle valve piston diaphragm being the culprit

[SVX_Blue]

needle jet

Checked that last night. It was clean with no damage.

[dan v.]

I guess I'm not understanding you.  When you say "Doesn't solve the problem but unplugging it corrects the behavior"  what do you mean?

So when you unplug the bystarter, it will idle for more than four minutes and not die?

When you say "unplugging" the bystarter do you mean disconnecting the electrical connector, or do you mean physically removing the bystarter unit from the carb body?

[SVX_Blue]

I guess I'm not understanding you.  When you say "Doesn't solve the problem but unplugging it corrects the behavior"  what do you mean?

So when you unplug the bystarter, it will idle for more than four minutes and not die?

When you say "unplugging" the bystarter do you mean disconnecting the electrical connector, or do you mean physically removing the bystarter unit from the carb body?

Yes it seems to run fine when I disconnect the bystarter. But running without the choke isn't normal. So yes it does fix it but it's not exactly right

[dan v.]

The bystarter works by heating a wax that expands and extends the plunger into the hole on the carb that closes off the enrichment circuit. That process takes about three minutes.  Like shutting off the "choke".

If you disable the bystarter by unplugging the wires to it, the plunger cannot extend.  The "choke" will always be on.

Think about it.  When working as designed the plunger extends after a few minutes as the engine warms up and the mixture is leaned out at idle.  The rpm's drop back to normal idle speed.

If it dies when the plunger extends, then I would look at a plugged jet or passage, and check that the idle speed adjustment screw is set properly.

[SVX_Blue]

The bystarter works by heating a wax that expands and extends the plunger into the hole on the carb that closes off the enrichment circuit. That process takes about three minutes.  Like shutting off the "choke".

If you disable the bystarter by unplugging the wires to it, the plunger cannot extend.  The "choke" will always be on.

Think about it.  When working as designed the plunger extends after a few minutes as the engine warms up and the mixture is leaned out at idle.  The rpm's drop back to normal idle speed.

If it dies when the plunger extends, then I would look at a plugged jet or passage, and check that the idle speed adjustment screw is set properly.

I don't know man it seems like we are saying the same thing just two different ways:

• It shoudn't run like it does with the bystarter unplugged
• There is still a problem with the carb

Which is why I said it doesn't solve the problem but unplugging it corrects the behavior. There is still a problem but doesn't die when giving throttle any more.

[KymcoRockr]

From everything you are saying, it does sound like a carburetor problem. With a bike that old that's been sitting that long, replacing the carburetor is often the best course of action. Many people find this out after spending a lot more money and time trying to fix the parts of the carburetor they believe aren't working and replacing a number of perfectly good parts.  It's probably a fairly standard carburetor, and if you buy a brand name one, and not the cheapest thing someone claims will fit on ebay or amazon, you have a pretty good chance of resolving this issue.  You can get the OEM carb out of Taiwan on Ebay for about $250. If it's a 30mm carb, Keihin is usually a very good choice, that's what I would look for first. If you want to go a bit cheaper, there are companies like Naraku and NCY that purchase better quality Chinese parts. Find one that looks about the same and you should be fine.