Thread: 2.25 petrol runs fine till it gets warm

If it is running well while some choke is used, but won't run when hot because it is too rich with the choke out and too lean with it in, it will be either a blocked jet or passage in the carburetter, or a leak into the intake manifold, or the vacuum advance line/diaphragm. This can be the gasket under the carbie or the manifold gasket and possibly a sticking or damaged inlet valve.

John

Hi John,

yeah it runs well when cold... Vacuum advance is operational but boy it advances a long way when it is working. What makes me think that it is the manifold gasket is the ferocity of the backfire when it happens.. In my mind the air fuel mix is going down the wrong "path" and then goes bang. Gee the backfire is loud.....!

Thanks for your input.

Phil

Hi John

There are long time LR mechanics who don't like the Webber carby used on SIII 2.283 cc engines nor the Zenith for that matter because the fuel bowl is too small and they suffer from vapour lock when they get hot.

More than that I can't explain.

Diana

Is the coil the right one Phil?

Not starting when hot is also a symptom of a weak spark. I think the proper coil does not have a ballast resistor,

Cheers Charlie

90% of webber downdraft carburettors need an extremely good heat reflector and/or isolator under them or extractors fitted so they dont overheat.

and then you have the angle problems

zenith and stromberg can have the heat problems as well but no where near as badly as the webber tends to.

I would be a little dissapointed Charlie if it wasn't the "R" model.. because when I purchased it I had a non "R" in the shed already.... I am pretty sure it's right though.?!?

The little bugger starts and runs beautifully .... until it gets warm (not even hot) then BANG!! BANG!!.. Backfire heaven..

Thanks for your input Charlie.. all the best


Phil

Thanks incisor... It's a Stromberg and not a real good one either... It's going to be in parts this long weekend for a good going over..

Phil

Strombergs are great IMO... well mine is haha, good power and relyability. Just watch out on steep hills as they starve themselves, I learn't that out the hard way when out 4WDing

So it's not getting really hot, just warm? how far up does the temperature gauge go? If it's not getting real hot, real quick then a lean jet could be partly ruled out...

Gaskets are pretty cheap and it's probably worth replacing the manifold-head gasket as well as the carby-manifold gasket. Dribble a little bit of water over the manifolds as the engine is running to pinpoint if they are leaking, the water will be sucked in above the intake if it's leaking and bubbles will appear above the exhaust if they are leaking. Also double check you timing with a timing light if possible.

Best of luck