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Walbro carb problem


openspaceman
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I told myself not to play with the einhell spear and jackson saws again after I gave the one I got given away to a member of the family but...

 

at the repair cafe I was asked to fix one that wouldn't run other than tickover. I had to bring it home as petrol powered equipment is verboten  in the hall.

 

Anyway I got nowhere with it, stripped the carb and found nothing amiss but borrowed back the one I had given away, swapped carbs and it ran fine but smoky.

 

I stripped the bad carb again and reassembled it on the good saw. With both jet screws out 1.25 turns it runs on choke at idle but dies as soon as the choke is released.

 

The thing is everything looks new with even the paint on the bar looking as new. I have only ever given up on a carb once before, again a walbro from a stihl HL75. There's no way this is worth a replacement carb, the owner has already told me to dispose of it if I cannot fix it but it is a challenge.

 

Has anyone any thoughts or guidance on how I might bend the metering lever up as it appears to be a case of fuel just not getting into the jets??

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The fact it will idle and not go full tilt would lead me to think the high speed circuit is gunked up so taking the H screw out and blasting some cleaner down it may help - check the fluid is coming out of the check valve and in to the main throat/choke of the carb. If you have an ultrasonic cleaner, try giving it a good boil with all the accoutrements (H&L screws included) removed.

Have you tried undoing the H screw out a few turns....it may work and after a while clean out the shyte blocking it. Aspen can sometimes purge resins in cases like this. 

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You say everything looks like new, I wonder if it ever ran properly ? Maybe there's aluminium where there should be a hole or the check valve or jet thats defective from new.

 

There is a risk associated with this.... but you couId disassemble the good and bad carbs side by side to compare their inner workings 😃😃

 

Hope you fix it, worth nothing financially but it'll bring you a smidge of satisfaction.

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2 hours ago, spudulike said:

The fact it will idle and not go full tilt would lead me to think the high speed circuit is gunked up so taking the H screw out and blasting some cleaner down it may help - check the fluid is coming out of the check valve and in to the main throat/choke of the carb. If you have an ultrasonic cleaner, try giving it a good boil with all the accoutrements (H&L screws included) removed.

Have you tried undoing the H screw out a few turns....it may work and after a while clean out the shyte blocking it. Aspen can sometimes purge resins in cases like this. 

I have done the carb cleaner through both the Hi and Lo screw holes as well as back washing the mesh filter from the metering valve hole. I'll try winding the hi screw out a few turns. If that fails now it is reassembled I will squirt down the Hi hole and see if it comes out of the main jet.

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4 hours ago, Alan Smith said:

Yes, in this situation before I have had a degree of success bending up the metering needle lever. You might find you need a couple of goes at it but it can work.

Yes it could be a bit hit and miss, I'll look at the other options first.

 

I have a distant memory of watching a Husqvarna salesperson/mechanic using a hand pump with a gauge to test the pop off pressure of the metering valve. Then with the mixture screw opened one at a time and the diaphragm pushed to open the metering valve watching the speed the dial went down showing the air exiting via the jet smoothly. That was probably on a Tillotson carb and I never saw it done again.

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12 hours ago, adw said:

I would suspect the main jet check valve, H screw out, pipe over H jet opening, thumb over the fuel feed to the main jet, now blow suck, you should feel the check valve open and close, no close and it’s not working.

Before I get enough enthusiasm to look at this again; what is the purpose of the check valve.

 

As it is supposed to open one way from the reservoir to the main jet I take it  that when I squirt carb cleaner through the Hi jet adjusting screw hole the spray should not come back past this check valve into the reservoir (it does) but only come out of the main jet into the throttle body?? Are they replaceable?

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Have you tried to richen the low and high needles? Some of the cheap chainsaws run garbage as they are too lean. If the check valve is gone they can't usually be replaced, well not easily and it mainly affects the high speed side or when throttling up, tick over is usually ok.

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