[Philip Posts: 2444 Status: Offline 12" above the Earth's surface WWW]

Im currently wading thro carb woes on a classic car where the New needle , and jet refused to start the car. Eventually wacking my hand over the air inlet whilst cranking- the engine burst into life, only dying again as I removed my sucked off hand!
Much head scratching and Ive found the new needle was supplied 2.4 mms too long. THIS resulted in the fuel being closed OFF totally even when on choke!. removal of excess 2.4mms started car, but supplier has sent me new (correct?) needle rather than my guesstimated 2.4mms shortened version.
Carb used to flood- found brass float (87 yrs old) had petrol inside!
Eventually drilled a hole in brass, allowing slow but total removal of petrol. Hot fan blowing over for a few hours, until ZERO fumes left and have soldered the hole up with low melting point 137C lead free solder paste £4-50p to seal off.
I will double check there is no longer a leak, but this could have been in there for years.
Carb was also still flooding and found there was debris inside carb which presumably stops float closing off.
In short- engines are pesky things. 

One of my lockdown projects was a "restoration " of my dumptruck. One thing to be done was make the fuel gauge work again, discovered that the float had a hole in it. Raided wifes stash of little plastic bottles used for airline travel (she wont need one for a while!) and found one that slid snuggly into the damaged float. I now have a functioning fuel gauge for the first time in 15 years

[Al Posts: 1008 Status: Offline WWW]

Well looks like the starting issue is fixed.  I went out for a 40 mile bike ride this afternoon, when I got home applied choke, and some throttle, hover burst in to life 


I may take it out for a test flight, but weather looking yuk for the next week when I'm not working, but at the same time I wont be able to make & fit the skirt as have to do that outside. 

[Nick Flint Posts: 5067 Status: Offline]

Im currently wading thro carb woes on a classic car where the New needle , and jet refused to start the car. Eventually wacking my hand over the air inlet whilst cranking- the engine burst into life, only dying again as I removed my sucked off hand!
Much head scratching and Ive found the new needle was supplied 2.4 mms too long. THIS resulted in the fuel being closed OFF totally even when on choke!. removal of excess 2.4mms started car, but supplier has sent me new (correct?) needle rather than my guesstimated 2.4mms shortened version.
Carb used to flood- found brass float (87 yrs old) had petrol inside!
Eventually drilled a hole in brass, allowing slow but total removal of petrol. Hot fan blowing over for a few hours, until ZERO fumes left and have soldered the hole up with low melting point 137C lead free solder paste £4-50p to seal off.
I will double check there is no longer a leak, but this could have been in there for years.
Carb was also still flooding and found there was debris inside carb which presumably stops float closing off.
In short- engines are pesky things. 

[Al Posts: 1008 Status: Offline WWW]

I undone the drain bung on the float bowl and plenty of fuel ran out, so that eliminated no fuel in the carb.  So I removed the carb from the engine, but left the choke cable attached, so I could check that it was operating as it should.  It worked perfectly.  Next I removed the choke butterfly, so I could take out the black plastic block behind which I assume is some sort of jet.  All looked OK, none of the holes were blocked, rubber gasket behind was intact and seated correctly.  So I put it back on and refitted the choke butterfly.  So nothing obvious there.


While carb was off I thought I just as well check in the float bowl, as easy to remove.  Hey presto I think I found the problem.  There is a rubber ring that seals the carb jet housing to the float bowl.  It is supposed to sit inside the jet housing and the float bowl fits inside it.  It wasn't seated correctly and had been pinched on the side of the housing.  I fitted the O ring out of the old carb and put everything back together.  Applied choke and within 6 to 10 rotations of the engine it started.  I left it half an hour, tried it again and a couple engine rotations it burst into life again.


The carb couldn't have been put together in the factory properly, as I haven't taken the float bowl off before.


I've added a couple of pictures of the problem.  I have shown it on the old carb, hence why it looks dirty

[John Robertson Posts: 5272 Status: Offline WWW]

It has to be the choke or the bypass in the carb.  Are you sure the choke butterfly is closing OK?  The flap usually has a hole in it on simple carbs to act as a bypass (you need air travelling through the carb venturi to pull fuel through the jets) - more complex carbs have a bypass channel often with a jet in it to supply extra fuel when the choke is closed.  Either way, take the air cleaner off and stick your hand over the inlet when cranking - if it still won't start then the carb choke circuit is blocked/dodgy or there isn't any fuel in the carb bowl (easily checked by unscrewing the bowl drain).

[Al Posts: 1008 Status: Offline WWW]

That makes sense.  Tomorrow I'll hook it up and take it somewhere out of the way and run it for a while then see if it starts when hot.  I don't want to upset the neighbours by letting it run too long.  Tomorrow our remit goes from stay at home to stay local :-)

[Warby Posts: 1045 Status: Offline]

Al, if it was faulty fuel pump it wouldn't continue to run.
If it runs fine after it starts by pouring fuel down the intake it must be something related to the choke.
Does it re-start ok when hot?

[Al Posts: 1008 Status: Offline WWW]

The engine is a Briggs Professional 26hp

[Al Posts: 1008 Status: Offline WWW]

I'm thinking possibly a float level issue, but see what you all think.


Briggs 26hp vertical shaft motor.  I replaced the carb last year with a new one as the old one was beyond repair due to rust and c**p inside carb.


New fuel filter, new fuel lines, new fuel, I replaced the diaphragm pump, but made no difference, so put the original one back on.  Hover is parked on a slope, engine end at lower end of slope. 


Prime the fuel bulb and try starting the engine, wont fire, turns over pretty quickly.  with or without choke doesn't want to fire.  Remove air filter and pour a small amount of fuel in the air intake, pop filter back on turn over and it starts and runs OK


Any ideas as to why it's such a pain to start?  Is it because it's on a slope and the float level isn't correct?  possibly fuel pump and new one faulty as well?  carb no good even though it was a new one, but a chinese copy.


Whats your opinions on this?