Chinese Scooter Club

GibbyTheMole · Wed Jul 09, 2008 1:40 pm Dry Black Spark Plug Fouling

Hey gang.

My 2008 49cc 139QMB scooter has 1200 km (745 miles) on the clock & has developed an issue with fouling plugs. This makes it a pain to start, but after starting, it seems to run ok. The NGK plug was fouled so I cleaned it & popped it back in & after a couple of days riding it around, it was fouled again. I swapped it for the original plug & the same thing happened.

It idles the way it should, and on the road it seems to run ok with no hesitation.

I have a new Champion plug still in the box, but I want to get the issue resolved before put the new plug in.

I've added Seafoam to the gas & thought I'd see if that clears it up. Anything else I should do?

Sorry if it seems like a basic question, but I'm still new to this mechanical stuff.

Cheers,
Gib :-)

Fox · Wed Jul 09, 2008 1:46 pm

That's carbon from not completely burning the fuel. Sounds like you need a bit more air. If you have removed the air box restrictor, then maybe a hole in the air box cover will help.?

GibbyTheMole · Wed Jul 09, 2008 2:19 pm

Hi, Fox.

Haven't removed the airbox restrictor. Not sure exactly where it is, for starters.

What about moving the clip on the carb needle up a notch? It's in the middle notch now.

Cheers,
Gib :-)

halley · Wed Jul 09, 2008 3:35 pm

GibbyTheMole wrote: Haven't removed the airbox restrictor. Not sure exactly where it is, for starters.

Uh oh, I think Fox has an image which demonstrates this restrictor, but it's a scary photo. Fox, put your armor back on if you're going to hold parts up to the webcam! :)

Gibby, have you found the downloadable service manual for your GY6 50cc engine? It's useful to learn the basic anatomy of the scooter, and has some troubleshooting charts in there too. http://www.scootdawg.com/downloads/GY6_50CC_MANUALscooter.pdf

As Fox said, too much gas and not enough air will leave soot on your spark (and the whole interior of the cylinder). If I recall, the opposite situation is a chalky residue when you're running too lean. I'm going to be switching sparks myself, as soon as the mail arrives. I'll take a photo or two.

timtheenchanteruk · Wed Jul 09, 2008 3:36 pm

moving the needle probably wont help, apart from possibly reducing your power,
a 50cc is likly to be at full throttle most of the time, so it is the jet that does the mixing, not the needle, the needle does from tickover to approx 3/4 throttle.
when was the last time you cleaned the air filter? a clogged filter would reduce airflow to foul.

can we presume its a 4-stroke?

JumpSteady555 · Wed Jul 09, 2008 3:47 pm

Oil mabe running into your filter and clogging it. Clean your filter, it its real oily disconnect that little hose from air box (the one where the other end goes to top of engine) and route it to the ground.

GibbyTheMole · Wed Jul 09, 2008 3:53 pm

Hey guys.

First, thanks for the link to the manual. The manual that came with my scooter is almost useless.

Yeah, I was thinking I should maybe clean the air filter. It's never been cleaned, so that's a possible culprit.

Thing is, after looking at the manual PDF link, it says not to attempt to clean the air filter, but only to replace it. This is the air filter in front of the air box. But some other photos have shown an air filter on the front of the carb. So.... I'm not sure which one I should clean, or what.

Obviously you guys know your way around much more than I, so that's why I'm asking for your help.

Cheers,
Gib :-)

halley · Wed Jul 09, 2008 4:08 pm

GibbyTheMole wrote: Thing is, after looking at the manual PDF link, it says not to attempt to clean the air filter, but only to replace it. This is the air filter in front of the air box. But some other photos have shown an air filter on the front of the carb. So.... I'm not sure which one I should clean, or what.

By "air box", you probably mean the thing shown on page 40 (PDF numbering), section 3. Scheduled Maintenance: Air Filter. They say not to attempt washing it, but after asking here and looking at mine, I don't see any reason not to. It's just a block of foam, or two layers of foam glued to each other. I think the advice was along the lines of "use soapy water, mash it dry, put it in damp, and go for a drive." Just don't shred it and you'll be fine.

There are pictures all over the place of these fancy aftermarket cone-shaped attachments to go on the carburetor intakes. My scoot has a large rigid tube leading to it, instead. Tell us what you've got there.

timtheenchanteruk · Wed Jul 09, 2008 4:25 pm

I have always used a bit of petrol for cleaning my air filters and never had a problem, then a drop of my 2 stoke oil to re-oil it.

done this on my yamaha scoot, and my 2 125 bikes.

GibbyTheMole · Wed Jul 09, 2008 5:17 pm

Hey all.

Here's a photo of my carb from the top, and a pic of what I'm referring to as the "air box":

Yep, the air box is the thing shown on page 40 (PDF numbering), section 3. Scheduled Maintenance: Air Filter.

Is the large flat piece behind the air filter cap the one I'm supposed to clean & if so, how? Gasoline then oil? Or the warm soapy water, mash dry, replace damp method?

Is there another filter on the carb somewhere inside an air intake to clean instead?

Fox · Wed Jul 09, 2008 5:20 pm

Clean the air filter in dish soap and water. Squeeze it in a towel and put it back in. You don't need to oil the filter foam. Oil is for if you ride on dusty dirt roads a lot or live in 3rd world countries that have only dirt roads.

Air box restriction:

Lowering the needle might do the trick as well.

PS: Clean that air filter every month!

Fox · Wed Jul 09, 2008 5:24 pm

halley wrote:
Uh oh, I think Fox has an image which demonstrates this restrictor, but it's a scary photo. Fox, put your armor back on if you're going to hold parts up to the webcam! :)

There nothing scary about it. If you lived in Los Angeles, you would know that having no shirt on is normal behavior when it's 115% Fahrenheit outside. :roll:

halley · Wed Jul 09, 2008 5:26 pm

Fox wrote: PS: Clean that air filter every month!

That's one real downside to the cheap Chinese construction. This is a part that must be opened and closed often, yet they used self-tapping screws and soft plastic. I foresee a bungee cord in my future.

Fox · Wed Jul 09, 2008 5:32 pm

halley wrote: Fox wrote: PS: Clean that air filter every month!

That's one real downside to the cheap Chinese construction. This is a part that must be opened and closed often, yet they used self-tapping screws and soft plastic. I foresee a bungee cord in my future.

Yeah, I have a couple of over-size screws in my air box due to strippage. :happens:

GibbyTheMole · Wed Jul 09, 2008 5:36 pm

Cool! Thanks for the advice. I'll get right on it & let you know if that fixes the plug fouling issue.

Thanks,
Gib :-)