Help. Scooter starts but doesn't rev.

[SE50_4_ME]

Hi All. I'm at a loss with my Honda Dio SK50 SR. AF18E. (Completely stock.) It starts easily, and idles, but when you give it throttle, it tries to rev but doesn't and then wants to stall.
I put a new spark plug in, no change.
I pulled the head off and replaced a suspect looking gasket, no change.
Also bore looked good.
Should I look at carby or a new spark plug lead/electronics??

Anyone had this problem before?
Any advice would be appreciated.
Thank you.

[tazland001]

I would clean the carb out with some compressed air and carb cleaner. Also make sure the pilot jet is clean. Then clean the air filter. Do that and tell us if that fixed the problem. If not we will find the problem. I would also check the muffler for carbon build up.

Taz

[kuromi]

I've got a Chinese mini bike that has those exact symptoms if you try revving it with the choke (air restrictor type) on.

Likely points to clogged air filter like Taz said.

[SE50_4_ME]

I would clean the carb out with some compressed air and carb cleaner. Also make sure the pilot jet is clean. Then clean the air filter. Do that and tell us if that fixed the problem. If not we will find the problem. I would also check the muffler for carbon build up.

Taz

Hi Taz, thanks for your advise and enthusiasm. I took your advice and got a new air filter thou. I haven't done the job yet, but I did try to run the bike with no air box. And same problem, wouldn't rev.... But will strip and clean carby this weekend and see how that goes.

[Wheelman-111]

Greetings:

Consider carefully if it's even a little WORSE without the airbox & filter, which tend to richen the mixture a little. Even worse in colder temps? If so, there's not enough fuel getting mixed in with the air. Too lean. This is a common symptom of a gummy carb/Pilot circuit.

If it runs a little BETTER with the air box off, then somehow the jetting is too rich, but I doubt that. Another possibility, depending on mileage, is a clogged exhaust.

[SE50_4_ME]

Well, after removing carby, removing jets and cleaning it all, reinstalling it. I thought surely this has to fix it now....
But NO!
So I remembered someone said something about exhaust.
I had a spare pipe lying around, so I thought it couldn't hurt to try... It's only 2 bolts and 2 nuts. So I replaced the exhaust and boom.
IT RUNS PERFECT!!! I couldn't believe it. An exhaust pipe cause that much of an issue.
Well thanks all for your advice. That pipe is now in the bin.
And if nothing else, it's got a new head gasket, new air filter and the carby is nice and clean.

[EastCoastCB]

You can clean out that pipe, man.

[motormike]

You can clean out that pipe, man.

^^he's right...all it takes is a bonfire or a BBQ grill to roast that pipe until all the oil residue is burnt away.
Then a few coats of high-temp paint to make that pipe money in your hand instead of scrap metal going to the dump.

[MrJumps]

Or use a torch and compresor

[patthesoundguy]

You can clean out that pipe, man.

^^he's right...all it takes is a bonfire or a BBQ grill to roast that pipe until all the oil residue is burnt away.
Then a few coats of high-temp paint to make that pipe money in your hand instead of scrap metal going to the dump.

Baking a clogged pipe in a super hot bonfire is a lot of fun. If its that clogged up the bike won't run you will see lots of cool flames come out of the pipe when its glowing red
Make sure to let the pipe cool completely on its own before doing anything with it, do not spray with water!!!!

[kuromi]

My neighbors wouldn't take kindly to a bonfire/ BBQ clean
So I pressure wash with water to get the worst out then fill it with white spirit/ turps for a few weeks.

Then clear that out and pour in dilute caustic soda/ sodium hydroxide (careful!) leave for 24hours and give it a water blast to wash through.

If it's a stock pipe it's a PITA because the baffles make it hard to get all the liquids out.

BBQ method is better tho' - and quicker