150cc scooter not running right

micco · 05-14-2022, 05:46 PM

Hi All,
my 150cc tomos nitro has been sitting for the last couple years from the pandemic - now looking to get it back on the road.

What's currently happening is any throttle and the engine bogs down, like its starving for fuel.
What i've done so far:
* removed the old gas from tank and carb
* cleaned main and pilot jet, all holes on main are visible nicely
* confirmed spark
* put in some newer gas
* checked valves, intake is at 0.003 and exhaust is at 0.004

I'm coming to the end of my knowledge, the carb needle doesn't seem adjustable, rather this is no clip but rather a washer - suspect i would need to stack them to raise, which i don't have.

It was running ok prior to being parked, other then I replaced the stator.

Any additional input/suggestions from the community would be appreciated.
thanks!

sc00ter · 05-23-2022, 11:19 AM

If I recall that Tomos Nitro should be a re-branded Hyosung. I know the 50cc scooters were. Now:

Why did you replace the stator?
Are you sure the new stator is good?
Also sure its the correct stator for the motor?
Now no more stator questions!
If it was running before being parked up I would think fuel related.
Sometimes the float gets warped causing fun fueling issues.
If it ran prior then I'd doubt the needle needs any adjusting.
To adjust the needle some better hardware stores sell machine washers that work.
If it is Hyosung based maybe hit up a Hyosung forum?
I'm drawing a blank at this point without seeing it.
Oh! Does it have that weird CV carb, with the rubber diaphragm on the top, that regulates air pressure? If so they can sometimes come unseated on the edge, dry rot or get a pinhole.

Keep us posted on your findings.

kz1000st · 05-24-2022, 10:35 PM

The Nitro was built in the SYM factory in China. I would have checked cracked vacuum lines or a cracked intake manifold before replacing parts. A lack of top end usually indicates an air leak, exhaust restriction or carb crud. Sitting for two years didn't help.

sc00ter · 05-27-2022, 11:10 AM

I could never get parts for my SYM CityCom 300i but I've heard that the situation is much better now. I still wanna slap that Mike guy from Alliance if I ever see him though. Anyways, yes to what kz1000 said. My old Honda Helix was known to crack the intake manifold. I did the tennis ball mod until I could get all the parts to do the new and improved carb bracket to solve that issue.

And sitting around with our nasty gasoline doesn't help either. We had a string trimmer in the lab last week that kept stalling. We checked everything and could never get it to idle correctly. I finally replaced the carb with a new one and it ran great. Not even 3 years old trimmer but it was sitting for almost a whole year. I'm making it my goal to trouble shoot the old carb!

05-23-2022, 11:19 AM	#2
sc00ter Join Date: May 2017 Location: Norfolk, VA Posts: 607	If I recall that Tomos Nitro should be a re-branded Hyosung. I know the 50cc scooters were. Now: Why did you replace the stator? Are you sure the new stator is good? Also sure its the correct stator for the motor? Now no more stator questions! If it was running before being parked up I would think fuel related. Sometimes the float gets warped causing fun fueling issues. If it ran prior then I'd doubt the needle needs any adjusting. To adjust the needle some better hardware stores sell machine washers that work. If it is Hyosung based maybe hit up a Hyosung forum? I'm drawing a blank at this point without seeing it. Oh! Does it have that weird CV carb, with the rubber diaphragm on the top, that regulates air pressure? If so they can sometimes come unseated on the edge, dry rot or get a pinhole. Keep us posted on your findings.
	0

05-27-2022, 11:10 AM	#4
sc00ter Join Date: May 2017 Location: Norfolk, VA Posts: 607	I could never get parts for my SYM CityCom 300i but I've heard that the situation is much better now. I still wanna slap that Mike guy from Alliance if I ever see him though. Anyways, yes to what kz1000 said. My old Honda Helix was known to crack the intake manifold. I did the tennis ball mod until I could get all the parts to do the new and improved carb bracket to solve that issue. And sitting around with our nasty gasoline doesn't help either. We had a string trimmer in the lab last week that kept stalling. We checked everything and could never get it to idle correctly. I finally replaced the carb with a new one and it ran great. Not even 3 years old trimmer but it was sitting for almost a whole year. I'm making it my goal to trouble shoot the old carb!
	0