Hi as per the title my light blue series 1 carb car has succesfully started after fixing some electrical connections, new points plugs and fuel in the tank.

This is exciting but splutters a fair bit doesnt want to rev and backfires blowing fuel out of the front carby and AED then stops.

Fuel starvation/lean mixture?

Checked leads in the right firing order.

Anybody got ideas where to start? I thought check timing. Then look at the fuel situation. My bet would be fuel.

The car has had a long layoff probably hasnt been started for ten years. Prior to that was restored and carbs were "done" I believe.

Mick

 

I will assume it has the HD8 SU carbies???.

Is there oil in the damper tubes??, lack of oil will cause the piston to rise toooo quickly and give a lean burn and a backfire.

IF it is the HD8 be careful adjusting the mixture, as that model has a diaphragm on the bottom of the main jet, and they go crusty with age and fuel, and when moved (as in adjusting the mixture) they crack/split, and leak fuel and cause fires.

The HS8 carbies have no such arrangement.

Even if the carbies were "done" as you say, 10 years is a long time, and a strip and clean would be my first starting place, simple to do, and eliminates them from the equation.

HD series carbies need to come off to do the diaphragms. HS series can be cleaned insitu. Done them many times over the years. Both suffer with sticky pistons in the bell chambers, and that will give a backfire every time also.

There will be more additions to the list, but getting those 2 carbies sorted is really step #1.

 

Thanks grant. I was thinking about the pistons dampers, the do have a bit of oil them but will top up. Have some of the right oil in storage I used on the su on my six cyl leyland p76.

Re the jag carbs they are SU HOW DO i TELL IF HS OR HD?

Theres an interesting little overflow coming out the top of the float bowl on the front carb the petrol was pouring out of it at the start. Maybe some lack of use indicated there as well. The AED was quite wet externally maybe needs a gasket kit through it. AED parts are expensive on the sg barratt website!

Good to get her going and up to 2000 rpm and the oil pressure was 60 lb at that point.

Nice old s1 on ebay love to buy it for spares but nowhere to put it....

 

HD series have the float in the bowl.

HS series have the float attached to the bowl lid.

HD have a single banjo bolt holding the bowl lid in place.

HS series have 3 screws holding the bowl lid in place.

Many, many other differences, but that is the quicky way to ID the 2 series.

Your description of the "overflow" as interesting has me thinking HD series carbs, which is correct for S1. They are a a pain and many have updated to the HS series long ago. Also that AED is really just a "3rd carby", and used for starting purposes, at least that is how I am reading your description. It was attached to the front carby and shared the same fuel level, so if the front carby fuel level is too high, that "3rd carby" will flood badly.

Try SU Midel in Sydney for bits. I have used them forever, and no complaints, 02 97595598, and I think they go by Fabre, or Sabre or similar, forgot already.

 

Grant filled the damper for the piston with oil. sae 20 as supplied by penrite and still same symptoms, backfire , slow to respond to accelerator gets to 2000rpm for a few seconds then just dies off. May have to put a kit through the carbies but Ill check the static timing first, will also whip off the fuel line and see whats coming out...

 

Agreed.

Timing check is a good idea.

Put that fuel line into container and see what flow you get.

Next I would be removing the bell chambers and clean the soot/gunk out them, and the piston circumference as well. it simply could be the pistons sticking in the chambers, and that is a common enough complaint. No parts required for that task, just some "carby cleaner" in a p/pack can, and some clean rags.

 

Grant - do those SU's have the 'tickler' pin so you can lift up the piston + check it falls 'clunk' ?
The needle + jet being non-concentric can cause problems.
Takes me back 50 years - I had a friend with an RR Phantom III with (I seem to remember) four 2" SU's.

 

One other thought, and please forgive me if I missed the comment; have the fuel tanks been flushed and filled with new petrol?

Did you check the fuel pressure? It does seem you have sufficient fuel since the carbs are overflowing due to stuck valves or float level that needs adjusting.

 

If they haven't got the lifter oin, take the filter cover off and lift the pistons with your finger, check the movement over the full range and let them drop a small distance. They should both be free moving.