Petrol hedgetrimmer problem

[Burnerman]

The carburettor is still struggling to supply the engine with enough fuel, I'm afraid - the clue being that it won't rev at all until its got warmed up a bit.
Does the carb have two adjustment screws on the side, marked H and L by any chance, or is there only one?
I would be inclined to go for a new Walbro carb, but they are difficult to get in the UK just now - I've just sourced one from China - it was here within two weeks and only cost a tenner but it sorted a problem I couldn't find!
John

I'll just edit this one...does fuel dribble out of the air cleaner area when the machine is left alone?
J.

 

[muggo]

The carburettor is still struggling to supply the engine with enough fuel, I'm afraid - the clue being that it won't rev at all until its got warmed up a bit.
Does the carb have two adjustment screws on the side, marked H and L by any chance, or is there only one?
I would be inclined to go for a new Walbro carb, but they are difficult to get in the UK just now - I've just sourced one from China - it was here within two weeks and only cost a tenner but it sorted a problem I couldn't find!
John

I'll just edit this one...does fuel dribble out of the air cleaner area when the machine is left alone?
J.

Thanks John. I just get the mist when running without the air cleaner. No leaks as such. I've just stripped again (3rd time), engine cleaner in all holes, blew out with compressed air, ultrasonic clean, another blow though & it's just the same. No H & L screws I'm afraid. Only tickover adjustment. I'll have a look on eBay to see if I can find one for a tenner.

 

[muggo]

The carburettor is still struggling to supply the engine with enough fuel, I'm afraid - the clue being that it won't rev at all until its got warmed up a bit.
Does the carb have two adjustment screws on the side, marked H and L by any chance, or is there only one?
I would be inclined to go for a new Walbro carb, but they are difficult to get in the UK just now - I've just sourced one from China - it was here within two weeks and only cost a tenner but it sorted a problem I couldn't find!
John

I'll just edit this one...does fuel dribble out of the air cleaner area when the machine is left alone?
J.

Found a site that sells carbs from China for about a tenner. I've thrown away the details of exactly which carb it is so it has to come off, again!
Cheers

 

[muggo]

I've just been watching a very informative YouTube video on what causes bogging down ie weak mixture. I'm going to loosen the filler cap first & if that doesn't fix it, I'll double check all gaskets on the engine side of the carb to see if it's sucking air in. I'll keep you posted, John.

 

[Burnerman]

https://www.ebay.co.uk/itm/Replacem...761344?hash=item26324e7b00:g:vyoAAOSwApleMBdM
This is the carb I bought to replace a MZA carb on an Eckman tiller.
Try as I might I couldn't fix it - it would flood all of the time, even when the engine was switched off. This one sadly went missing in the post so I got one from China - thankfully all was well afterwards.
John

 

[lostinthelight]

May be worth a look in the muffler to see if there’s a part clogged spark arrestor screen

 

[muggo]

I've checked & rechecked anywhere that can suck air in behind the carb. No joy. I've now ordered a new carb from China for the princely sum of £8. Fingers crossed! Thanks again for the advice, John.

 

[Burnerman]

Lets hope it gets it this time.....!
I had yet another machine with fractured fuel pipes, just below the grommet, last week. This fault is increasingly common and I'm wondering if it's the ethanol percentage in the fuel that's causing it.
John

 

[muggo]

Lets hope it gets it this time.....!
I had yet another machine with fractured fuel pipes, just below the grommet, last week. This fault is increasingly common and I'm wondering if it's the ethanol percentage in the fuel that's causing it.
John

Ethanol causes more problems than it's supposed to solve. Perhaps my problem is an air leak into the black rubber fuel pipe but I don't have any spare. I've tried putting my finger around the grommet while it is running but it doesn't cure the fault. Hopefully a new carb will. 1 month before it arrives so I'll update you on my progress later.

 

[muggo]

Lets hope it gets it this time.....!
I had yet another machine with fractured fuel pipes, just below the grommet, last week. This fault is increasingly common and I'm wondering if it's the ethanol percentage in the fuel that's causing it.
John

Hi John. Well, I fitted the new carb & it still bogs down & runs faster or slower depending on which way it's facing. Could it be a fracture in the heatproof manifold that's sucking in air to cause bogging down? I'm running out of things to replace! Cheers, Paul

 

[Burnerman]

Ye gods its trying your patience, this one.....crazy symptoms! If it's exactly the same then unfortunately we aren't on the right track.
Personally I've never had the manifold fail (its called an emulsion block for some reason) but I guess it's possible.
When you tilt the machine, see if you can check that the fuel filter doesn't float clear of the fuel......this is potty!
John

 

[muggo]

Ye gods its trying your patience, this one.....crazy symptoms! If it's exactly the same then unfortunately we aren't on the right track.
Personally I've never had the manifold fail (its called an emulsion block for some reason) but I guess it's possible.
When you tilt the machine, see if you can check that the fuel filter doesn't float clear of the fuel......this is potty!
John

Thanks John. We know it has to be fuel related so there aren't too many things it can be on a simple 2 stroke engine. Plenty of fuel in the tank & no air bubbles in the fuel line. BTW, the new carb doesn't have the tiny air hole that leads to the crankcase like the original carb had but the symptoms are just the same without it. It has a screw on the top that adjusts something but not sure what. It's in line with the fuel input but adjusting it either way doesn't help. The only thing I haven't changed is fuel pipes. The filter appears to be fine & tank isn't dirty. I could perhaps try running with no fuel filter. I'm so frustrated with the damn thing!
Paul

 

[Burnerman]

If its the carb I’m thinking about, the small brass screw is to adjust the slow running mixture....a picture could help!
I notice on one of your earlier posts you mentioned a louder than normal induction noise? This sounds unorthodox but look at the joint between the cylinder barrel and crankcase for possible gaps or gasket failure.....look at it with the engine running if possible. Also check for any missing screws in that area.
I have to conclude that so far we are on the wrong track with this one, much to my dismay!
John

 

[muggo]

If its the carb I’m thinking about, the small brass screw is to adjust the slow running mixture....a picture could help!
I notice on one of your earlier posts you mentioned a louder than normal induction noise? This sounds unorthodox but look at the joint between the cylinder barrel and crankcase for possible gaps or gasket failure.....look at it with the engine running if possible. Also check for any missing screws in that area.
I have to conclude that so far we are on the wrong track with this one, much to my dismay!
John

Thanks again, John. Yes, I think it's the slow running mixture screw, but it's full throttle I'm having the problem with. I did fit this replacement engine as I loaned it to someone who ran without oil & seized it. I'll strip & inspect as you suggest, looking for air leaks.
I'l keep you posted.
Cheers
Paul

 

[Burnerman]

Look forward to it Paul, one quick way of a general diagnosis is to pop the exhaust off and look at the piston and rings from there.
John