McCulloch 240 Carburetor

This topic has 6 replies, 3 voices, and was last updated 2 years, 4 months ago by davidbliss.

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October 28, 2023 at 10:19 am #41357
john-e-w
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I must be getting old – I have just replaced the fuel pipes on my leaf blower – the original feeder pipe had a filter attached to the end in the fuel tank and every time I tried to put it back on, the pipe split – so I fitted new ones. I have touched nothing else, but now the machine refuses to fire up let alone run. The question is – have I got the pipes on the right way round, I thought I would remember after a couple of hours, but apparently not!!

I thought the feeder pipe from the tank went to the top tube on the carburetor – can anybody confirm this please – see attached pic
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October 28, 2023 at 3:37 pm #41361

haytermower50
Participant

Hello,

When you prime the carburettor, does the fuel fill the purge bulb? or when you prime it does fuel seep out of the carburettor everytime you prime it? are there any kinks in the pipes that could prevent fuel flow to the carburettor at all, plus, are the diaphragms and gaskets ok in the carburettor. Its difficult to tell with the photo provided but the fuel pipe goes with the hose that has two notches (looks like two cones on the brass pipe, if that is the technical term for it) and the return hose goes to the pipe without notches, im not sure if that carburettor has the configuration I have described.

Hope this Helps,

October 28, 2023 at 4:39 pm #41362

john-e-w
Participant

When I prime it the fuel seems to go into the carb, it certainly doesn’t run everywhere. I don’t know about the diaphragm as I didn’t strip the carb down, just pushed the hoses onto the brass tubes. I didn’t notice any notches, but I will have a look tomorrow – as far as I can remember both tubes were smooth. I’m pretty sure there are no kinks in the pipes.

I did wonder if some of the decaying fuel pipe debris had found its way into the carb and was now interfering with the diaphragm.

Thanks for help so far
john

October 28, 2023 at 9:05 pm #41363

haytermower50
Participant

if the primer feels smooth to prime then I believe the pipes are assembled correctly and fuel is flowing into the carburettor, which is good, the filter screen may be blocked in the carburettor (pump side) which may be preventing fuel from entering the engine, or, the engine may be flooded, possibly too much fuel in the crankcase? maybe removing the spark plug and pulling the starter rope a few times to see if lots of fuel shoots out (liquid or gaseous effect). Are there gaskets either side of the carburettor when assembled, like on the manifold? theres a chance that lots of air may be entering the crankcase either by a cracked component (like the manifold) or that the gaskets arent assembled correctly (if the gaskets have small holes near the main hole that lines up with the carburettor openings?), it is quite hard to tell on this since it sounds very much like a fuel issue but may be something else, did it run before you replaced the pipes? does the engine spark and/or good compression?

hope this helps

October 28, 2023 at 9:44 pm #41364

davidbliss
Participant

Just a thought, carb to engine gasket, some have a hole in to allow crack case pressure to work the carb diaphragm, can be fitted up the wrong way.

October 29, 2023 at 10:25 am #41365

john-e-w
Participant

Thanks for all your help – it is now working.

So just for information:- the feed to the carb (in my case the small dia tube) goes to the lower brass pipe and the overflow which in my case was the larger dia pipe (return to the tank) goes to the top tube. Its not helped that both brass tubes are the same diameter although the neoprene pipes are different bores. Also when I took it apart, I noticed that there wasn’t a gasket between the carb and the engine, so I made one. I didn’t appreciate that there was a hole to feed the crankcase pressure into the carb, so I added that and Bingo all now works and i will be able to sweep up the leaves when they eventually drop.

thanks again for your words of wisdom
John e-w

October 31, 2023 at 7:49 am #41368

davidbliss
Participant

I don’t like small engines nowadays, what with plastic and catalytic exhausts, Ive had some really bizarre, like a briggs four stroke with a two stroke petrol mix and thought alright just to have oil in the petrol and poked a rod out the side, bore was ok though, just recently had a new Stihl to fix, good spark and wet plug should have gone, shot a cap of petrol down the carb and off it went and stopped, as had this sort of thing before so tipped the fuel out and refuelled with my mix, took a few caps of petrol to kick off but away with masses of smoke with a very hot exhaust, cats do not like a high oil mix and this chainsaw had been filled with white diesel, I should have binned this on the spot as a few weeks later it came back, absolutely no compression so took the top off to find no air filter, they had seen me tip petrol in to start it so somehow lost the air filter.
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