Moped acceleration problem

[GREENI3]

Well my piece of scrap (moped that is) has decided to add something else to the never ending list of things to go wrong...acceleration.

Yesterday it just completely dropped in power.
Usually does 30/35 mph on the flat, now it's more like 10/15 mph.
Any incline results in about 5 mph or less!
Made for a very eventful 20 mile ride home. Had about a 15 car tail back behind me at one point. Oh the shame.

On the stand with no load it revs as normal, but as soon as I take it off the stand it will barely move. Top speed is really low, but still revs.

Any ideas?

[joshdudeha]

Is it a two smoke?
Is it bogging a lot?

Could be a few things actually, but sounds like something to do with fuel. Dirty/blocked carb, bad spark plug, dirty air filter etc.
check all of these.

[69chris]

drive belt slipping ??

[Nope.]

[Fairies attack]

Have you run it out/low on go go juice?

The CB is struggling with what you have described right now. It used to do 70mph cruising, now it does 48mph. And after that feels like it is running out of fuel and going to die.

Remove the float bowl of the carb and give it a clean, or take the carb off, remove the float bowl and blow through the jets to clean them out.

Mine made the fun trip from Brigg tonight at 25mph after deciding 50mph was too fast then picked up in a 30 with a fart and shot off upto 50mph.

[GREENI3]

I've checked for a spark, there is one, so it can't be that.

The wheel spins like crazy with full throttle on the stand, but then on the flat road just outside my house it will only manage 5-10 mph.

Power band use to kick in almost instantly and now it's non-existent.

Does anyone know for definite what it might be?

Thanks to the rest of you guys for the replies.

[Nope.]

[joshdudeha]

[GREENI3]

Well I was advised by my dad to take the exhaust off first to see if that was the cause, so took it off went down the road and back (noisy as hell) and it absolutely flew! (for a 50)

So it seems the exhaust is in need of a de coke.

Would a bike/car garage be able to de coke the exhaust for me and if so, how much do you reckon it would cost?

[Redoko]

[timsmith]

if you took the exhaust off yourself then you can de-coke it too! there should be a screw/bolt/nut visible at the back of the silencer that when removed will allow you to pull out the baffle. You can then scrub off any carbon with a wire brush and see that exhaust gas can get out. you may need to strip off packing material and re-pack afterwards. Its an absolutely filthy job so best not done in kitchen or clothes you may want to wear again
Also don't listen to anyone who suggests caustic soda to clean it. its a fast route to A&E with serious burns.
Good luck!

[GREENI3]

Everything is back to normal, if not better!

Used caustic soda for the de-coke.

Added 200g of caustic with 2 liters of water, put it in the exhaust and left it for about 20 hours.

Tipped it all out. Was a dark brown colour with black flakes.

After that I put some hot water down the exhaust to clean out any remaining crap and poured that out.

Put the exhaust back on and went for a 7 mile ride to dry it out and the acceleration was perfect.

Hopefully it'll be at least another 6 months before it needs doing again.

Highly recommend caustic soda for de-cokeing exhausts.

[bass2k8]