Power loss when in 3rd and 4th gear

[Gsparky]

Hi, I took my li 125/175 scooter out today but had a real struggle with it, started easy after been sat for 6 months, on my ride great until in 3rd and 4th for a while, then lost power, pulled over, after a few kicks started again, same thing again fine in 1st and 2nd then 3rd or 4th lost power, was quite dangerous as have no where to stop safely, again a few kicks started again headed for home in 2nd.
I took the carb off cleaned jets everything looked ok, drained fuel tank, put new fuel in and set off again but unfortunately the same again.
Any ideas ?
Regards Gary.

[Storkfoot]

Check that you can blow air through the breather hole in your petrol cap.

Potentially, you may have lightly seized too. Has the engine been run in? Any signs of an air leak around cylinder head or exhaust manifold?

Is it points or electronic?

[Gsparky]

Thanks I will try the breather hole on the petrol cap, it’s electronic ignition; it’s been sitting for 6 months but last time I was out on it 6 months ago, at full speed or near enough in 4th; it would stutter/ lose power but if I dropped the revs it would be ok
I was thinking why but now it’s doing the same in 3rd, I have just now tried it without air filter and replaced spark plug but no different, knackered now! Slight seizure may be the answer and explain why it starts easy enough

[Gsparky]

Breather hole on cap is clear

[MickYork]

What's the spec' on caeb (jets etc).

Might be worth measuring the flow rate from tank as it sounds fuel related...…..or stator/electrical

[Gsparky]

When I drained old fuel from tank, seemed to be a good flow of fuel, I have started to think about ignition, but it starts so easy!

[Fast n Furious]

Sounds like you may have lost some cylinder compression.
Do a compression check and see what Psi you get.

[Gsparky]

Ok thanks I will try that.

[MickYork]

Reading the posts again, when you say "power loss" do you mean the engine just dies/stops...... or there's not umph and you slow down (with the engine still running) ?

[Scooterdude]

Try a different cdi, it could be that breaking down when it gets hot.

[Gsparky]

It is just dying on me, as soon as I get up to a reasonable speed, I have to pull over, kick a few times and it will start again, I keep going trying to blast through it but, not really getting very far at all, would the cdi fail over such a short distance?

[MickYork]

it sounds like either fuel starvation or electrics, if electrics i'd plump for the stator first.

[Gsparky]

Ok thanks, I took the carb apart checked and a quick clean, so I don’t think it’s fuel starvation, I had the stator replaced years ago so maybe that’s a possibility, thanks

[Storkfoot]

If the engine is stopping running when it gets warm, it is likely that there is a problem with the pick up on the stator. If the problem happens at high revs, which is sounds like it is not, it could well be you CDI at fault.

You can check the pickup by using a multimeter between the red and white at CDI. You should have a value of .03v approximately.

[Gsparky]

Ok great thanks for the advice, is that value when the scooter is not running, or running?

[Gsparky]

Sorry I said that without thinking, 0.03v when it’s running!

[MickYork]

No. You should be measuring resistance (ohms) when not running. Wires disconnected at CDI and measure there.

Might be worth buying a Sticky's manual. Most people offering advice will have one.

[Gsparky]

Ok I saw the value as 0.03v, I have got a sticky manual. I will get on it towards the end of the week, and post my results!
Thanks again for the advice

[Storkfoot]

It does make more sense to set the multimeter to ohms and do all the resistance checks mentioned in Sticky’s manual but, especially in your case, the red and white. The reading between those two should be 95 - 120.

It also helps to have a spare stator anyway. So, you may wish to get one and replace it. But, if that resolves your issue, you’ll still not know precisely what the problem with the stator was.

[Gsparky]

Ok thanks, I let you know how I get on