Pete

[Stubby]

2 hours ago, Pete H said:

Thank you all for your help, sorry for late reply, working.  I’ll do what suggested but, in all honesty I’ve already been down that route.  There is plenty of fuel to carb and air filter is the washable type which I’ve done.  I’m feeling guilty that I may appear to be ignoring you, I’m not at all.  
Stephen asked about usage, it came to me second hand, so until me I have no idea but it was mildly difficult to start, 10-12 pulls but once warm fine.

My latest attempt needed me to drip fuel onto the air filter and once going after a minute or two it seemed to scream ( weak mixture???) followed by “bogging down” eventually stopping and refusing to restart.  As much as I threatened it with the skip, it would not start until more fuel drips.

 

 

You got an air leak somewhere me thinks .

[peatff]

16 hours ago, Pete H said:

My latest attempt needed me to drip fuel onto the air filter and once going after a minute or two it seemed to scream ( weak mixture???) followed by “bogging down” eventually stopping and refusing to restart.

 

That's just a saw running out of fuel. Check out a few carb rebuild videos and make sure your diaphragm is the right way round and the metering arm is set plus everything is clean. It doesn't sound like there's a lot wrong if it will fire and run.

[Pete H]

Thank you Stubby, Peatff,

appreciate the reply, I’ve always repaired mowers strimmers saws, for myself and friends etc.

I’ve started to watch carb vids to learn more.  This has confused the life out of me, that’s my I’ve turned to you professionals.

I’m a mechanic by trade, and remember certain cars had certain stupid faults that you would never believe if it hadn’t happened.

I was hoping something like this would be the case…🤞🏻🤞🏻🤞🏻🤞🏻🤞🏻

Anyway, I’ll follow all the advice I’ve been given, thank you all.

Pete

 

 

[Muddy42]

I agree it sounds like an inconsistent air leak somewhere.  If you have exhausted the other checks it needs a pressure test.  If you are relatively handy you can strip a saw down and test it with a bicycle pump and a bucket of water.

 

BUT as I said above replacing seals is not the easiest repair.  So if you need to get help they might as well do the testing as well.

 

Or sell on ebay as 'spares or repair' some of the prices being achieved are crazy.

[spudulike]

I am assuming that the impulse line is correctly pushed on to the brass connector just under the cylinder between the air box and cylinder?

I am asking as I have had a lot in with this issue and it would cause an air leak.

Another favorite issue is the diaphragms (both pump and metering) and spacer gaskets being the wrong way round.

It may be a split inlet manifold - as others have said, a pressure and vacuum test would make sense. It sounds like it may be a large air leak so if you plug the exhaust port, inlet manifold and plug hole, you could just blow down the impulse line and see if leaks.....if you don't have the correct kit.

 

[Pete H]

Thanks again all.

[Pete H]

Hello Muddy,

Do you mean dunk it in a bucket of water while pumping it up, excuse the daft assumption.

 

[Muddy42]

10 minutes ago, Pete H said:

Hello Muddy,

Do you mean dunk it in a bucket of water while pumping it up, excuse the daft assumption.

 

 

 

Don't go near the water until the saw is stripped down and you have all the exists to the cylinder closed off.  The water just helps you tell where a pressure leak is from the bubbles - its the best method out there.  I remove as much as possible, cases, exhaust, starter mechanism etc.)  Then as above you need to plug all bar one hole into the cylinder. I generally plug the exhaust port, spark plug hole and inlet manifold (behind the carb) and apply pressurized air to the impulse line.  You can DIY a bike pump to do this.

 

Once pressure is applied you might hear the leak but if not dunk the whole saw and test mechanism in a bucket of water to reveal where the bubbles are coming from.  Then dry the saw out, it won't cause it any harm.

 

 

[Pete H]

Your a star Muddy, I’ve got compressor in workshop with regulator.  If I turn pressure right down that should work hopefully or I’ll rig up a wheelbarrow tyre and use that.

cheers.

The odd thing about this saw was that when we acquired it, the two nuts holding the carb in place were missing.  The only thing holding the carb in place were the air filter screws.  I cut down two nyloc nuts, but, when scratching my head and thinking of old engines needing choke I thought as mentioned by you all, air leak.

When I checked my nuts, excuse the pun, they were a little above the face of the air filter box, perhaps not sealing the filter face to the carb body????
What do you professionals think?
Pete

[ChrisNewport]

If thats the case and more air is getting into the carb when using full choke from cold because the air filter isnt sealing to the carb, as the choke is inside the air filter its pretty much pointless using the choke to cold start it and will cause cold starting problems.