LCGB Forums

Need a lot of advice, got the SH2/24 Dellorto carb assembled & on, Turn on the petrol & petrol is pouring out of the bellmouth, stripped it down & checked the jets if not blocked,& the float seems to float, could it be the float needle? Would any wearing of this start this flooding?

Wear in the float needle or float needle seat would cause petrol to pour out uncontrollably.

Try putting your float in a cup of petrol to make sure it floats. Next, try a new float needle if you can see any wear in the tip of the existing needle.

Hi, tried another needle, couldn't see any wear on the tip, the float floats ok aswell, could it be from the petrol tap? It's a reverse fast flow

Thinking it could have been the fuel tap, which there's nothing wrong there, as I tried an Amal, & no flooding at all!

You need to concentrate on the carb. The carb has a role in regulating fuel flow. It does this in several ways, but before it regulates the flow of fuel into the engine, it has to regulate the flow of fuel into its own float bowl. It does this using the float and needle to automatically start and stop the fuel flowing from the tank.

It is unlikely to be related to a fuel tap further up the line.

I think it's the needle valve, can you get new valves for a sh2?

One way to tell is to take the bowl off, hold the float up and turn the petrol on. If it leaks past the needle you'll know.

Thanks mate, I'll try that, though if it is the valve, on the SH2, it dos'nt look interchangeable?

9 out of 10 times,the needle is responsible for this symptom.
What carb top do you use?
SH2/22 and SH2/24 have interchangeable valves (slides).
The 24 slide has a cutout so that a screw can adjust the tickover.
Have you blanked this screw or do you use the original setup?
The 22 carbs don't have this screw.

Hi, I have blanked this screw on the SH24, As i can`t find any slides with the cut out, So i bought from Dellorto uk, new parts, usual carb top,spring, rod, Had to also change the banjo, This morning before work, i did the test with taking the bowl off & holding the needle & linking up the fuel line, & turn the fuel on, & the needle did stop the fuel,Can it still be the needle?

This doesn't sound good.
Is petrol coming out from the right brass hole?
If yes,check if there is any small hairline or if the brass is badly worn.
This is the worst case scenario,I don't know if it can be repaired.

I had a similar problem when I fitted the original Dellorto 22 to my rebuilt GP.

The float had wear around the point that the float needle sits on it, this in turn raised the fuel level in the float bowl, this in turn allowed the float to just touch the body of the carb when the the fuel level was at its limit. Any vibration was disturbing the float needle seat and allowing a small amount of fuel to run into the float bowl which then flooded with monotonous regularity making it a pig to start (and also it made a mess of my floor).

I lowered the fuel level by 0.050" by putting a bit of soft solder on the base of the float needle effectively lengthening it, then repeatedly rubbing a bit off and reassembling the float bowl until the fuel just weeped out into the choke, I then measured the needle length and re-did the solder and rubbed it down again till the length was 0.010" longer than my previous measurement.

The scoot doesn't flood now and starts well now with no problems.

Hope this makes sense......

The petrol is coming out of the atomiser/main jet/ middle of the bell mouth, i`ve ordered a new needle, i`m also thinking of trying a new Jetex float, if that would make any use? also what about fresh fuel? as the fuel been in the tank best part of the year! Thanks for the comments so far,by the way

Robert, you've had some sound replies. Think of it another way; the float and needle are similar to an old fashioned ball cock in your toilet cistern or header tank. If it's not lifting enough (punctured float) or not shutting off due to the needle not sealing in the needle valve you will get symptoms just as you are experiencing. It could well be that the old fuel has gummed up the valve seat area and despite the needle and float being ok it will not seal. Try flushing this area through with carb cleaner to flush out the gum.

Paul

Dimitrios_231 wrote:This doesn't sound good.
Is petrol coming out from the right brass hole?
If yes,check if there is any small hairline or if the brass is badly worn.
This is the worst case scenario,I don't know if it can be repaired.

I checked & cleaned everything & turned on the fuel on, and it is coming out the right hand side brass hole!

I had 3 SH1 carbs leaking from there,two 18mm and one 20mm,
I never managed to fix them
Two of them were cracked,one had worn brass.
If the brass is just worn, there must be a way to replace it but I never tried

I`m going to try a new needle,thats in the post, and take it from there, I did try also a Spaco sh2, and again it`s flooding at the same brass hole aswell,

tried a new needle today & it`s still pissing! last call now, ordered a jetex needle( extra long?) float pin & float

If you assemble the float and needle but don't put the bowl on then turn the carb upsidedown does the float seem to be 'springy' or does it feel solid? if it feel springy I would say the needle is seating well, if that is the case does the float seam look parallel to the mounting face of the float bowl?

stick a new 25mm dellorto carb on and be done with G.