Petrol hedgetrimmer problem

[muggo]

Hi John. I've finally had another look at the hedgetrimmer (it has been too cold in the garage for the past few months).
Yet again, I pulled the new carb off looking for air leaks. I removed the heat insulator too so I could actually see the piston. No air leaks anywhere that I could see & all mating surfaces are clean. The head bolts are tight.
Fired it up & it still bogs down & cuts out when in the vertical position. Slow running screw made no difference.
You previously mentioned removing the exhaust. What am I looking for? It starts OK so can't see the piston or rings being an issue.
Cheers. Paul

 

[Nige F]

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

Maybe it's just clogged with oil residue. I had a Raleigh moped once. Burned the muffler out on a fire - amazing difference how it pulled up a hill to work after that

 

[Burnerman]

For sure, this one is a real head scratcher....see if it runs with the exhaust off (it will be deafening) just in case there's a loose baffle.
When you pulled the carb apart, did you notice a thin spring beneath the needle valve hinge? I noticed it's not pictured in the repair kit.
John

 

[muggo]

Sorry for the late reply.
I'll try removing the silencer & see if it runs better. It used to run best when pointing upwards, but now it cuts out straight away when vertical. Maybe there is a loose baffle, as you suggest.
I'm fairly certain nothing is wrong on the inlet side or electrics so it makes sense to investigate what's unchecked. I'll be sure to let you know what I discover.
Cheers
Paul
BTW, I'm fairly sure there was a small spring below the needle valve hinge on both the old & the new carbs.

 

[muggo]

Maybe it's just clogged with oil residue. I had a Raleigh moped once. Burned the muffler out on a fire - amazing difference how it pulled up a hill to work after that

Thanks Nige. It went wrong quite suddenly so I doubt it's clogged. However, I'm not far from setting the whole thing on fire!

 

[Burnerman]

As these carbs are designed to run in any position, and the symptoms are the same both with the original and replacement carb, the only common denominator is the fuel supply.
What happens if you run the machine horizontal, and then slowly move it vertical - keeping the machine revving hard?
John

 

[muggo]

Maybe it's just clogged with oil residue. I had a Raleigh moped once. Burned the muffler out on a fire - amazing difference how it pulled up a hill to work after that

As these carbs are designed to run in any position, and the symptoms are the same both with the original and replacement carb, the only common denominator is the fuel supply.
What happens if you run the machine horizontal, and then slowly move it vertical - keeping the machine revving hard?
John

SUCCESS!
I finally got around to removing the (sealed) silencer & it appeared to be OK. I then spent 15 minutes bashing it against an anvil until I got lots of carbon deposits out. Reassembled & it runs perfectly at all angles.
Many thanks to all who got involved in this problem, especially John who gave lots of his time.
After a year of having a dodgy hedgecutter, I'm now back in business!

 

[Burnerman]

Great stuff! It sounds like there has been a lump of carbon blocking the exhaust outlet or similar.
Many thanks for the update, and happy cutting!
John