2.25 petrol runs fine till it gets warm

[Philip Regan]

G'day Guys and Girls,

Got my freeby 1972 109" home and got it started after about 3 hours doing the "checklist"

Replaced the points, condensor, leads, plugs, coil (GT40R) and adjusted the timing.

Put a "kit" through the fuel pump and replaced the fuel pickup hose with 5/16th rubber.

Flushed out the old oil and threw in litres of fresh oil.........

so good so far eh! One would hope...

Now what happens is it will start and run quite well until it gets warmed up and then.... bang (backfire) flames out of the tailpipe and carby and dies.

This is a bit of a concern... once it konks out if I give the carby a "squirt" there is plenty of fuel vapour so it isn't a fuel problem... but it won't start for quids again till it cools down.

OK over to the brains trust..... HELP.... is it an inlet gasket? a sticking valve....

Thank you in anticipation.... Phil

[JDNSW]

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

[Philip Regan]

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

[Lotz-A-Landies]

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

[chazza]

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

[incisor]

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.

[Philip Regan]

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

[Philip Regan]

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

[Newbs-IIA]

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 :p

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 :)

[dandlandyman]

Wrong coil. GT40R is for use with a resistor - it should say so on the base. That coil is for dual circuit ignition systems. You need a GT40 coil.

An auto-electrician friend explained the dual circuit ignition to me once - while the engine is running the coil runs at about 8 volts through the ballast resistor, but during starting the resistor is bypassed to give a stronger spark of 12 volts. You will cook a resisted coil if run at 12 volts constantly. It's a very common mistake though, most people think R stands for Race, or higher performance. Hope this helps.

Dan.
69 2A 88" pet4, 68 2B FC pet6.

[Philip Regan]

Hi Dan,

Well we have a parts supplier here in town about to get a coil inserted........ ;)

Hmm, I have a non "R" coil here. I'll give it a go.

Thanks

Phil

[Philip Regan]

Well well well.... I finally had to give in and get a mechanic involved.. It is a mate of mine.. does that count.. hehe

The heat up / cut out problem is with the points. After much fiddling and setting the old girl runs like a beauty. Idles like a Rolls and just when I was getting excited..

BANG.. B B BANG..

Anyway long story short it was the points.. as they heated up their internal? resistance made it impossible for the coil to work and the bang bang was when it finally did with all that unburnt air fuel mix in the chambers.. The other thing that was very dodgy was the amount of "play" in the distributor shaft. The timing mark was all over the shop moving up to 10 degrees from TDC in both directions.

I am now searching for a replacement dizzy.. probably out of Britian because it is only $90.00 landed versus $150.00 locally.. I hope to keep everyone posted on the results shortly..

Phil

[agrojnr]

Mate have a look at ebay uk there was a bloke on there selling a dizzy on there for next to nothing

I have inlaws there in the uk so if the post is sky high let me know and I will ask a favour of them

Also look at paddocks, craddocks or lr series to see if a new one is worth it

Adam

[RobHay]

I bought 4 new distributors from Paddocks for 15 pound each ( around about the $40 mark) .....or was it Craddocks one of them anyway.....great dizzy, then I bought the electronic unit that fits into them from Gary CLR4wd...I have his phone # if you interested

[Philip Regan]

Hi RobHay,

Searched e-Bay and found Gary's website and low and behold he is only 20 minutes away from my place so I whipped around and grabbed some stuff off him. Nice bloke and very helpful.. reckons he can get anything I need and his pricing seems fair.

Changed out the old dizzy and the bloody thing runs like a dream (well almost) and the backfiring has stopped. The idling is a bit rough still but I can get that a bit better with a carby overhaul.

Thanks to all who have offered suggestions and help.. It is very much appreciated.

Now for the rego....

Phil