Troublesome Ms261

[lewisyounger16]

Came to me "no spark"

Turns out it was a straight fuel. Saved the cylinder, new meteor piston and caber rings great.

 

Pressure and vac tested @ 10psi for 10 minutes diagnosing a leaking deconp valve, new valve, fixed tests passed.

 

Compression tested at 120 psi.

 

New rubbers and diaphragms in carb, new fuel lines top and bottom. New plug.

 

Ran it into wood and it was fine for about 15 minutes then started to not pick up on the revs from idle without bogging down and stalling, (that's when fuel lines were replaced after this)

 

Saw will pop on choke and run on half choke until flicked off, then will idle and eventually die, but will not rev unless the trigger is pulsed. Not sure what else to try it's doing my head in, what I thought was a bargain saw is being a total pig.

[Stubby]

7 minutes ago, lewisyounger16 said:

 

Came to me "no spark"

Turns out it was a straight fuel. Saved the cylinder, new meteor piston and caber rings great.

 

Pressure and vac tested @ 10psi for 10 minutes diagnosing a leaking deconp valve, new valve, fixed tests passed.

 

Compression tested at 120 psi.

 

New rubbers and diaphragms in carb, new fuel lines top and bottom. New plug.

 

Ran it into wood and it was fine for about 15 minutes then started to not pick up on the revs from idle without bogging down and stalling, (that's when fuel lines were replaced after this)

 

Saw will pop on choke and run on half choke until flicked off, then will idle and eventually die, but will not rev unless the trigger is pulsed. Not sure what else to try it's doing my head in, what I thought was a bargain saw is being a total pig.

 

Split impulse line ?

[lewisyounger16]

Split impulse line ?

Think it's built in to the carb manifold, I couldn't see any faults with the manifold, but when idling I sprayed some carb cleaner behind the carb as best I could and it would stall. Which makes me think that the manifold is compromised. However I would have though the pressure and vac test would have picked that up.

[Stubby]

3 minutes ago, lewisyounger16 said:

5 minutes ago, Stubby said:

Split impulse line ?

Think it's built in to the carb manifold, I couldn't see any faults with the manifold, but when idling I sprayed some carb cleaner behind the carb as best I could and it would stall. Which makes me think that the manifold is compromised. However I would have though the pressure and vac test would have picked that up.

We need Spud . He will be along shortly I expect . Having said that 120 psi is kinda on bottom limit I would have said .

Edited December 11, 2018 by Stubby

[lewisyounger16]

We need Spud . He will be along shortly I expect .

Good god I hope so.

Worth noting that the crank side is okay, I fitted a new bearing and a new oiler. It ran for a good 25 minutes in the wood fine and dandy cut lovely, then acted as if it was running out of fuel and then this problem started.

[Stubby]

Just now, lewisyounger16 said:

Good god I hope so.

Worth noting that the crank side is okay, I fitted a new bearing and a new oiler. It ran for a good 25 minutes in the wood fine and dandy cut lovely, then acted as if it was running out of fuel and then this problem started.

That sounds like an air leak . crank seals ? 120psi is on bottom limit don't you think ?

[lewisyounger16]

That sounds like an air leak . crank seals ? 120psi is on bottom limit don't you think ?

It was at around 50 with the knackered piston and rings, I am assuming (maybe wrongly) that the new piston rings need to bed in before the compression rises accordingly. It does sound like an air leak, I think I will pressure test it again just to make sure.

One thing I didn't do was whilst testing turn the crank I don't know it that's a correct method or not.

[Stubby]

Just now, lewisyounger16 said:

It was at around 50 with the knackered piston and rings, I am assuming (maybe wrongly) that the new piston rings need to bed in before the compression rises accordingly. It does sound like an air leak, I think I will pressure test it again just to make sure.

One thing I didn't do was whilst testing turn the crank I don't know it that's a correct method or not.

Did you hone the bore ? The ring do need to bed in .

[lewisyounger16]

Did you hone the bore ? The ring do need to bed in .

I did my best, used brick cleaner to remove the aluminium transfer then lightly sanded with fine wet and dry and finished with a bit of scotchbrite. Honed as best as I could, it didn't look awful.

[Stubby]

8 minutes ago, lewisyounger16 said:

9 minutes ago, Stubby said:

Did you hone the bore ? The ring do need to bed in .

I did my best, used brick cleaner to remove the aluminium transfer then lightly sanded with fine wet and dry and finished with a bit of scotchbrite. Honed as best as I could, it didn't look awful.

You can get spring loaded ( three legged ) hones that you can put in a drill . This ensures , pretty much , that it stays round .