I had another look at the engine tonight to see whether I could find out why it cuts out without the choke being on.

I ran it for about 3-4mins with the choke full on but literally as soon as you pull the throttle or even turn the idle screw up it cuts out immediately.

I have now removed the carbs and opened the float chambers and removed the main and pilot jets and left them in carb cleaner, certainly one of the main jets was blocked with gunk and the pilot jets look a bit iffy, are you supposed to see a reasonable amount of light through the pilot jet or is it just a minute hole anyway?

Also is it ok to leave the jets in carb cleaner overnight and tommorrow can I just blow them through with compressed air?

Could someone also explain what happens when you pull the throttle cable, does it open the butterfly and main jet and what does the pilot jet do?? Am going to see if I can find a 'how it works' site on the web but any help or advice would be much appreciated.

Sorry if I sound a bit dumb when it comes to carbs but it's never something I have played with before!

thanks,
Rich.

I still bet it's the plugs...

If it was the plugs then why would it run fine on the choke?

IML(imited)O

It sounds like a carb setup or dirt problem. The cleaner should work without having to have the parts soaked overnight - unsure whether it would cause any damage though.

A good clean up and a check of the mixture is a good place to start - Choke adds fuel but not any more air (IIRC) and at Idle this would work fine when set up as it is. Adding Idle speed or shutting the choke is either adding air or taking fuel away. Hence the mixture would change and could be the problem.

If not, new needles and sels/orings would be a good place to continue and wouldn't be wasted if it isn't that as they last ages and would ensure everything is Top notch.

After that - you've exhausted my limited knowledge of carbs

(EDIT) Not sure on the idel bit actually I think it adds and takes away fuel not Air almost like a mini choke permenantly set.

[Edited on 11/2/05 by chunkielad]

i'm with Hellfire

I know very little about carbs, the engine pretty much worked straight off for me, and I did a rejetting mod to the engine, which again worked OK - so I didn;t have to tinker much at all.

That said....

Sounds to me like the carbs are only letting in fuel through the choke.
Does it rev at all when the throttle is activated?

My plug problems have (usually) been the plugs are wet and she won't start, or she'll go off one cylinder at high revs.

If the plug gaps are set properly then there isn't much reason for there to be a problem with them unless the mixture is wrong and putting crap all over the 'points'.

I would have thought a carb overhaul is a good idea anyway. Plus the choke being on causes the engine to run so the plugs must be working -ish.....

I'm actually thinking it may be fuel starvation, when I took the carbs off and opened the float chanbers there was no fuel in them which I'd expect.

It could well be that there's a problem with fuel delivery, in which case there is a small amount of fuel getting to carbs, enough to idle it with a rich mixture on full choke but when you pull the throttle cable there is no fuel being delivered and it therefore dies as it is effectivly getting air instead of fuel.

I am going to replace the fuel filter and check the flow rate and see whether it's delivering the correct amount of fuel.

Will let you know the outcome!!

I know what you mean about plugs Hellfire, been there, done that!! had to take a blowtorch to them to burn the fuel off!!

Thanks for all the advice guys, much appreciated.

Rich.

One last thing mate is the fuel pump itself - (dunno if there is a pump on this engine as standard or if it's gravity fed) but I saw something on a car prog on Motors TV where the fuel pump was too strong and the fuel was bypassing the carb altogether - have to added a pump to the setup? Maybe nothing to do with it but you never know!!!!

Thanks mate, using the standard blade fuel pump so should be ok but that said if it isn't pumping the fuel as it should then that would be an issue

If the pump's not working it will suck fuel through from the tank with the choke on and revs high by creating a vacuum. Usually if it's plugs it won't even start never mind run.

That's exactly whats happening! choke on full it's fine, without choke dies and when you try thottle it dies (as I guess the fuel is not being pumped as it should!)

disconnect pump, fill float bowls using a small
funnel on main fuel pipe, remove funnel and stick a bolt in pipe to stop leaks.
Start engine, it will run for a couple of minutes
on a float bowls worth of fuel.
If it does you know its pump related.

Al.

Still sounds like blocked jets to me, so if theyve not melted away overnight in the carb cleaner i`d give them all a blow out!
Then put it all back together with empty carbs, turn ignition on, let the pump prime the carbs. If it starts, choke or not, then the pumps ok. Failing that push it round the corner and call the AA

SHE LIVES AGAIN!!!!!

It turned out to be fuel delivery problem, basically th filter looked really clogged up and when I tested it I got nowhere near the right fuel flow.

Changed the filter and the pipe between filter and pump as this looked a bit iffy, also moved the pipe that was picking up from the jerry can so it sat in the middle of it.

Tested flow rate and all ok. Replaced jets and carbs after drying with compressed air and bingo!! she lived again, when I pull the throttle cable all ok and no choke needed.

Like Snoopy says the fuel pump sounded a bit iffy to start with, kind of like it was sticking and struggling, so I think I will get a spare pump or two just in case!

All I can say is thanks for everyones advice, always very helpful as ever.

thanks,
Rich.

Excellent mate - good to hear it!!!

Great