Saw dies under load

[mking7]

A few weeks ago I replace a piston and cyl on an ms260. It ran good and I took it out this weekend to cut and it performed well the first day. Took it out the second day and it would start and idle and you could rev it out of the wood but when you put it under load it would die. I have the carb set at the 'standard' setting noted in the manual, basically one turn out.

Do I have bigger problems than I thought I had when I bought this saw? Any ideas of what to check?

Thanks guys!

 

[troutfisher]

How old is the fuel filter? maybe dirty and starving the saw for fuel?

 

[jomac11]

I am not sure what the part is called, but it goes from the carb to the cylinder. My 028 was doing the exact same thing, and that hose had a crack in it. replaced it and all was well.

 

[mking7]

I am not sure what the part is called, but it goes from the carb to the cylinder. My 028 was doing the exact same thing, and that hose had a crack in it. replaced it and all was well.

Ya, that is a possibility. I had a tuff time getting that on when I replaced the cylinder so I may have boogered it up getting it on.

 

[jomac11]

Yeah, it sure is a pain. I'm not looking forward to getting it back on when i replace the tank on the 028...

 

[Dan Forsh]

I am not sure what the part is called, but it goes from the carb to the cylinder. My 028 was doing the exact same thing, and that hose had a crack in it. replaced it and all was well.

It's the impulse hose and you'll find it easier to put back on with needle nose pliers.

Dan

 

[sugarbush]

Yeah, it sure is a pain. I'm not looking forward to getting it back on when i replace the tank on the 028...

put it on the cyl first, after slipping cyl over piston, tie a string around hose and pull through, but i usually just poke it through.

 

[tek9tim]

It's the impulse hose and you'll find it easier to put back on with needle nose pliers.

Dan

put it on the cyl first, after slipping cyl over piston, tie a string around hose and pull through, but i usually just poke it through.

Talking about 2 different things. Just so happens there are 2 rubber "hoses" that go between the carb and cylinder. Just leaves one to wonder if the original comment was about the impulse line or the intake.

I've also had an insufficent gap on my spark plug cause the exact same thing.

 

[Dan Forsh]

Talking about 2 different things. Just so happens there are 2 rubber "hoses" that go between the carb and cylinder. Just leaves one to wonder if the original comment was about the impulse line or the intake.

I've also had an insufficent gap on my spark plug cause the exact same thing.

Ah! Yes, I see what you mean. Sorry, I might be confusing the issue. The intake boot, I never consider that as a hose, but yes it is, and yes that can be a B itch to put back on. And yes, this could be the problem.

I need to read more carefully next time. The impulse hose actually connects to the crankcase not the cylinder.

 

[sugarbush]

Ah! Yes, I see what you mean. Sorry, I might be confusing the issue. The intake boot, I never consider that as a hose, but yes it is, and yes that can be a B itch to put back on. And yes, this could be the problem.

I need to read more carefully next time. The impulse hose actually connects to the crankcase not the cylinder.

I think you read it correctly as the implication was the hose from the cyl. to the carb and there is only one. the other hose as you noted connects to the case and isn't to difficult to attach. tip the handle alittle and reach in with neddle nose pliers.

 

[jrclen]

My Homelite did the same thing today. I replaced the sprocket and bar a couple weeks ago. Ran good before that. As long as I was inside the cases I blew things out with an airhose, cleaned the air filter, and put it back together. It runs great until I put it in a log. Then it bogs down. It doesn't kill but has no power. I'll look for something amiss and also check the plug gap in the morning.

 

[mking7]

Well, hate to dig this old thread back up but I'm a little frustrated. I swapped out the intake manifold and it ran great for a while then started to do the same thing. I would say it ran 5-10 minutes then started do in the same thing. It acts like it's starved for fuel but I am no expert. I set it at the standard mixture (1 turn out on this saw). It was fresh gas. I can't deal with it anymore today but I may check the plug gap and if it's right maybe try a new plug but I don't think that's it. The saw was run on straight gas and I replaced the piston/cylinder fwiw. Just not sure why it runs good for 5 minutes or so. The plug doesn't look like a fouled plug would in a 4 stroke to me but not sure what I should be seing on the 2 stroke. I do know that when I pulled it down to replace the manifold I cleaned the plug with a wire brush so maybe it is fouling a bit or getting carboned up as it runs longer?

Also, I put a few teaspoons of 2 cyle oil in the crank case when I put it back together the first time but no so much that I would think it would be fouling the plug but I've probably only burned a tank or so through in total since it does this everytime I try to run it. I would think that would be burned out but maybe that's hurting me?

The saw was almost new looking when I bought it so I don't think it's the fuel filter but I will pull it and clean it or replace it if you think that might be it. Just odd that it's after it runs for a while each time. Any ideas guys? Thanks again...

 

[dustytools]

Have you checked out your fuel tank vent. Maybe its stopped up? Just guessing here.

 

[Lakeside53]

Definitely check the tank vent.. fill the tank half full (so you don't spill gas)and then loosen the cap if it start to play up, if the problem disappears, it's your vent...

If you haven't replaced the fuel filter in the past year or so, replace it (or the insert) anyhow.


If this doesn't fix the porblem, then you need a full pressure and vac test.

 

[RiverRat2]

yeah your getting some excellent input here

cant ask for much more than that,,,,,

also the metering diaphram could be borderline stiff,,,,, just enough to idle just wont produce enough fuel on the big end.... fuel filter, spark plug, all the easy stuff first,,, KISS

 

[mking7]

Thanks a lot guys. I hope to figure this out. I bought this saw as a learning experience in rebuilding one and it's definitely turning into that. I hope I can figure this out. I'll post after I try the things suggested here. Thanks again!

 

[mking7]

Definitely check the tank vent.. fill the tank half full (so you don't spill gas)and then loosen the cap if it start to play up, if the problem disappears, it's your vent..

DING DING DING DING....We have a winner!!!

Went out tonight and it started up fine. Ran for a while and started acting squirrelly so I loosened the tank cap. Bam, back to normal. I am assuming the tank gets pressurized when the vent is clogged and won't feed enough fuel?

This would make sense since it would run for a bit when I put gas in it but then after running and building the pressure differential it would bog down and die if pushed.

I will have to get out there and get that vent cleaned out and go back to the woods in a couple weeks to make sure but I think I found the problem thanks to all you guys' help. Thanks again.

 

[mking7]

DING DING DING DING....We have a winner!!!

Went out tonight and it started up fine. Ran for a while and started acting squirrelly so I loosened the tank cap. Bam, back to normal. I am assuming the tank gets pressurized when the vent is clogged and won't feed enough fuel?

This would make sense since it would run for a bit when I put gas in it but then after running and building the pressure differential it would bog down and die if pushed.

I will have to get out there and get that vent cleaned out and go back to the woods in a couple weeks to make sure but I think I found the problem thanks to all you guys' help. Thanks again.

Actually I thought about this for a minute. I haven't had Physics in 20 years but doesn't stuff flow from an area of high pressure to an area of low pressure normally? Feel free to explain if anyone has the energy. Thanks.

 

[SmokinDodge]

DING DING DING DING....We have a winner!!!

Went out tonight and it started up fine. Ran for a while and started acting squirrelly so I loosened the tank cap. Bam, back to normal. I am assuming the tank gets pressurized when the vent is clogged and won't feed enough fuel?

This would make sense since it would run for a bit when I put gas in it but then after running and building the pressure differential it would bog down and die if pushed.

I will have to get out there and get that vent cleaned out and go back to the woods in a couple weeks to make sure but I think I found the problem thanks to all you guys' help. Thanks again.

Not pressure. Vaccum, and if the tank vent is clogged it will only suck so much fuel before dying.

Good to hear you got it lined out.

 

[mking7]

Not pressure. Vaccum, and if the tank vent is clogged it will only suck so much fuel before dying.

Good to hear you got it lined out.

ahhhh...vacuum....oh ya......dumb me..Told you it had been a while...