Re: Hot Starting Problem
Posted:
Tue May 21, 2019 7:05 amby CHRIS in MARGATE
Can sometimes be something as simple as a loose exhaust manifold where the brass nuts have vibrated loose.
Re: Hot Starting Problem
Posted:
Tue May 21, 2019 7:41 amby LammySX
rossclark wrote:you need to do a leak down test, basically find a means to pressurise the cylinder and crankcase and see how long it holds pressure for.
A simple way to do it is with the piston at BDC place a section of bicycle inner tube with one end over your carb manifold and the other over the end of your exhaust U bend. Pump it up to about 5 psi and see if it holds - if not start spraying soapy water round the various joints - inlet manifold, cylinder head, base gasket, round the mag housing etc.
The engine has been completely rebuilt in the last six months and it is running fine when it gets going. I think this would be a last resort.
Re: Hot Starting Problem
Posted:
Tue May 21, 2019 7:54 amby LammySX
MickYork wrote:The choke adds more fuel, altering the ratio of fuel to air.......so you have either either too much air (air leak) or too little fuel (bigger pilot jet).
With the over rev' you mentioned previously this would point to an air leak.
An air leak can cause serious problems, with the potential of holing your piston.
Over revs was a one-off, hasn't happened since last week, I'll assume it was a sticky cable
Re: Hot Starting Problem
Posted:
Tue May 21, 2019 8:56 pmby LammySX
I've been out this evening, ran it for about 30 minutes and then stopped, fuel off first then ignition. Sat around for 5 minutes, fuel on kickstart with no revs / throttle, did that twice and it starts Ok.
I went reserve which surprised me as I put 5lt in at the weekend and I haven't been anywhere, checked for leaks but couldn't see anything.
The breather hole on the left of the carb near the mixture screw was weeping a bit.
Seems Ok for now, I'll need to monitor it.
Re: Hot Starting Problem
Posted:
Tue May 21, 2019 9:18 pmby Storkfoot
LammySX wrote:MickYork wrote:The choke adds more fuel, altering the ratio of fuel to air.......so you have either either too much air (air leak) or too little fuel (bigger pilot jet).
With the over rev' you mentioned previously this would point to an air leak.
An air leak can cause serious problems, with the potential of holing your piston.
Over revs was a one-off, hasn't happened since last week, I'll assume it was a sticky cable
Air leaks are the weak point of all two strokes. Don’t ignore a high revving engine as this is a classic sign of an air leak.
I am strongly suggesting you buy Sticky’s manual and Lambretta Workshop Manual and get your head around all this. Owning a Lambretta is not all glitter and gold.