50cc Scooter - Loss of power)

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Hi there,

last week my drive belt got shredded so I had to replace it. However, since replacement I've lost some power. I know the buggers haven't got alot anyway but now it means I go even slower!

When revving, there doen't appear to be any difference after the throttle goes over approx 1/2 way. I have checked the valves and they're spaced correctly but after that I haven't a clue what else to look for.

Any ideas will be greatly appreciated.

Thanks
 
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Is the belt tensioned correctly?
does it have an idler wheel, and if so is this pressing effectively on the belt?

Wotan
 
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Thanks for the reply.

I couldn't see if there was any way to adjust the tension. I have double checked the belt and it is an exact replacement.

What's an idler wheel?

Thanks
 
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These scooters often adjust their gearing by the belt pulleys expanding and contracting as the engine speeds up.....that is, making the belt ride up the engine pulley.
Did you remove all of the old shredded belt?
John :)
 
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These scooters often adjust their gearing by the belt pulleys expanding and contracting as the engine speeds up.....that is, making the belt ride up the engine pulley.
Did you remove all of the old shredded belt?
John :)

Hi there,

all bits of the shredded belt were removed and the casing was thoroughly cleaned.

Even pulling off from a stand still isn't as nippy as it was if that's any more of a clue as to what's going on. Would a carb clean be worth a go?
 
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If the bike was running well before the new belt, it would be a wild coincidence for anything else to have gone wrong, really.....
However, do look at the air filter for contamination, especially if the bike tends to be a bit more smoky than before - this is particularly relevant if the bike was tipped on its side for the work to be done.
The rear brake hasn't been overtightened, has it?
John :)
 
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Thanks for the reply.

I couldn't see if there was any way to adjust the tension. I have double checked the belt and it is an exact replacement.

What's an idler wheel?

Thanks
An idler wheel is a smooth pulley that is spring loaded to bear on the back of the belt to remove slackness, from the belt, but I would suggest Burnermans reply to be correct.
 
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When I got the bike home when it went pear shaped I didn't have a clue what was wrong so firstly I took the cover off the valves thinking something had exploded in there but all looked fine.

After that I took the case off where the kit start is as I thought this is where a majority of the noise is coming from. So case off and there it was, rubber hell!

I got a hack saw and removed the fooked belt and then brushed out the debris. Using a combination a cloth and brush I restored the case to it's former glory.

After that the new belt arrived in the post and I popped it on, put the case back together and started it up. It started up first time of the kick and runs fine but the power is definately less.

The bit that belt goes round at the rear wheel end, could some bits have got into that gubbins of that? If so how can I undo the central nut?

Thanks
 
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I'm at a bit of a loss really but I'd pop the belt back off, and see if the wheel rotates freely enough with it disconnected.
I'm not sure about the rear nut - maybe it could be undone with the back wheel on the tarmac and brake on. We smart ass types have air guns to do the work for us..... :p
John :)
 
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I'm at a bit of a loss really but I'd pop the belt back off, and see if the wheel rotates freely enough with it disconnected.
I'm not sure about the rear nut - maybe it could be undone with the back wheel on the tarmac and brake on. We smart ass types have air guns to do the work for us..... :p
John :)

LOL - Thanks John. I'll take it apart again tomorrow and see if there is anything there.

On another note, whilst I was in get messy mode I thought I'd have a look at my starter motor as that hasn't worked since I got the bike. I took it apart and cleaned it good and proper and put it back together again. The thing now spins when the starter button is pressed but the gear thing it latches on to doesn't spin out and catch the cog. Just makes a noise like someone is ringing a bicycle bell. When I remove the gear bit I can manually turn it and the bit pops out without a prop.

Could the starter have been re-assembled so that the gear thing is being turned the wrong way and therefor not spinning out?
 
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Before diving into your starter motor, consider connecting another good 12v battery across yours and trying again.....small bikes like these have marginal electrical performance and any battery below par won't be much use!
John :)
 
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Hi there,

Starter now works. I gave the gear thing that the starter turns a really good clean and now that spins and pops out with ease.

As for the power in the bike, well it's still not right. I started the bike with the side case off and slow revved it to full throttle and it went all the way. So I checked all the cables/pipes and there are no kinks in anything.

But when riding the bike there still seems to be no poke in it after approx 50% throttle. I have to go up a small hill to get out of my village and when trying it this morning I am most definitely going slower when I reach the top than I used too!

I hope this additional info helps.
 
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Try the bike temporarily, and briefly, with the air cleaner off and see if the performance comes back - but be aware the fuel mixture will be weaker and the engine will run hotter.
There's no harm in a carb strip and clean but it can only be a coincidence if its needed now!
Presumably there's no misfiring or hesitation - if there is, replace the plug as a matter of course.
John :)
 
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Try the bike temporarily, and briefly, with the air cleaner off and see if the performance comes back - but be aware the fuel mixture will be weaker and the engine will run hotter.
There's no harm in a carb strip and clean but it can only be a coincidence if its needed now!
Presumably there's no misfiring or hesitation - if there is, replace the plug as a matter of course.
John :)

I'll give it a got in about an hour. Will going about 1 mile without the air cleaner be ok?

There is no misfiring or hesitation.
 
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If the air cleaner is an issue, performance should be immediately restored!
At the same time, stick a finger in the carb venturi (air cleaner off, engine off) and feel that the slide lifts completely out of the way when you open the throttle.
John :)
 
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