Help! Urgent. Why has my scoot started running too rich?

[ArmandTanzarian]

After 3500 trouble free miles, my Lambretta has started running really rich.

I've checked the obvious. i.e. cleaned the filter out and checked that the choke isn't getting stuck and while it's a bit better, it still wont tickover, bogs at low revs and is smoking more than usual.

Can someone confirm which way you turn the mixture screw on a 30mm dellorto to weaken the tickover mixture

It has an LTH reed block fitted. Could that do anything to the running if the petals were a bit worn. I'm baffled and I'm supposed to be going to Mersea in an hour and a half!

[ArmandTanzarian]

Found it!

One half of the float full of petrol.

Have I been Ethanoled?

[victor]

Found it!

One half of the float full of petrol.

Have I been Ethanoled?

If your float is of plastic and since ethanol is less aggressive than petrol on most plastics then probably not.

[bazman]

After 3500 trouble free miles, my Lambretta has started running really rich.

I've checked the obvious. i.e. cleaned the filter out and checked that the choke isn't getting stuck and while it's a bit better, it still wont tickover, bogs at low revs and is smoking more than usual.

Can someone confirm which way you turn the mixture screw on a 30mm dellorto to weaken the tickover mixture

It has an LTH reed block fitted. Could that do anything to the running if the petals were a bit worn. I'm baffled and I'm supposed to be going to Mersea in an hour and a half!

Could be your atomiser and or needle have became worn.

[WINTERMODEL150]

Expect its the warm weather ,3 of us had to adjust carb settings last weekend ,take it out at night when its cooler and see if it runs any different.

Dean

[clubbook]

Had exactly the same problem last week. Humidty seems to play mine up!!!!

[ArmandTanzarian]

FFS!

I thought I had it sussed. A mucky air filter, a sticky choke and a float full of fuel seemed pretty conclusive but I've fixed all three and its as bad as ever.

The problem seems to be at small throttle openings. Give it some beans and it seems to clear.

I've stripped the carb right down and cleaned it but I'm running out of ideas. I don't think its the weather because it first started playing up when it was cold and damp. Also its run rain and shine for three years without trouble.

I could compensate by re-jetting but I'm loathe to do that because that might just be masking a problem that will bite me in the arse later.

I'll try a new plug but I'm clutching at straws now.

Just in case the internet has steered me wrong, can someone confirm how the mixture screw works on a PHBH 30


HELP!

[leigh]

pretty sure its in to weaken

[Special X]

Yes . . . . clockwise to weaken . . . what jets are in it?

[ArmandTanzarian]

the setup is a Mugello 240 with a phbh28 and an LTH reed block and an Indian big bore

I've just weakened the pilot from a 60 to a 53. No difference at all. I've checked the reeds and they're fine. I've even put in a new plug. It's definitely too rich, even without a filter or panels. It runs ok once I get going but just won't tick over. Turning the mixture screw doesn't seem to make any difference. The only exception to this is if I turn off the petrol. As the level in the float chamber goes down it starts to tick over OK.

I'm baffled. Its been fine for the last 3000 miles or so!