So my dad gave me an MS260. It won’t run when throttle applied. Only starts on partial choke and runs as long as you don’t give it throttle. I bought a tune up kit, filter, plug, and caps. I’m going to clean the muffler spark arrestor as well. I turned the carb settings, LA and 1 top screw, all in and 1 turn out. Same issue still. Cap was leaking so I replaced it and the oiler cap. The top of the fuel tank, breather maybe, is leaking sometimes when tipped. Any suggestions as I do the listed above work? I just want to at least get her idling at this point. Also mine only has two carb adjustments.
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Had the same experience with a friend's used saw purchase, would only run at idle. The muffler was completely choked with carbon with only pinholes for flow. Took it off and burned it all out with a propane torch.
Find a fully adjustable carb, the saw will perform better with it.
A new tank vent can be just about any type as long as there is clearance for it. That style of saw doesn't have much room in there above the tank, so something narrow and short works best. On an 024 super I worked on the factory "vent" was just a short section of screw thread in a tube.
Find a fully adjustable carb, the saw will perform better with it.
A new tank vent can be just about any type as long as there is clearance for it. That style of saw doesn't have much room in there above the tank, so something narrow and short works best. On an 024 super I worked on the factory "vent" was just a short section of screw thread in a tube.
Make sure your muffler isn't plugged, if not I would drain all the fuel remove the fuel line and most likely replace it, at least check it for texture and leaks, take the carb off , either clean and install kit or best put on a new or cleaned reconditioned fully adjustable 1. Take a good look at the impulse hose inbetween the cylinder and behind the carb, if its cracked leaking at the ends it would be a problem. Also make sure your spark plug is gapped at .020 in.. Do the easiest things first and see if they correct the problem.
I think the after market carbs on eBay usually work well or someone on this site may sell u a good used 1.
Vibration dampners being weak or torn could indicate likely the impulse or manifold tube could be damaged also.
I think the after market carbs on eBay usually work well or someone on this site may sell u a good used 1.
Vibration dampners being weak or torn could indicate likely the impulse or manifold tube could be damaged also.
When I get a somewhat old saw which shows signs of a fuel issue...I put the carb back to factory specs. If that doesn't solve the problem, I just replace the fuel line and filter, impulse line, and put a full carb kit in it. All OEM. Along with a pressure/vac test and a spark plug...it sort of resets the clock on the saw.
Another thought. When I tip the saw the tank vent leaks. I assume it should not leak when turned any way. Correct? Also if that valve is bad could it not be priming and holding prime? Or is this system not dependent a vacuum being created?
Correct: it should not leak.
The vent is not causing your running problem. When vents fail such that they do not allow air to enter the tank, as the fuel is drawn down...that causes running issues. But, your vent fails in that it lets gas and vapor out of the tank...that does not cause a run issue.
Eventually, you will want to fix/replace the vent...but, just because you probably don't like gas dribbling out.
Roy
I bought a new vent this afternoon.
It seems that a lot of guys overlook the muffler and its function. The muffler is an engineered item to (1) reduce noise, (2) create the proper back pressure for the saw to operate properly. This is critical for a two cycle engine. Too much back pressure and the saw will not operate as intended, operate poorly, and in some cases, if clogged enough, not operate at all. It can even blow the crankcase seals and or the impulse tube.
Some guys use an ultrasonic cleaner for cleaning. I have one but quit using it for mufflers as I found that it will not dissolve the heavy carbon. I still use it on carburetors occasionally. I now use a good carburetor cleaner which I purchase by the gallon can. I soak mufflers for sometimes 2 to 3 days. When it comes out of the can, it's clean. Guaranteed. OT
Great info. Yeah we had an old dirt bike that ram like poop and the muffler was restricted. Ran like a top once cleaned.
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It looks like your piston is scored.
Check the compression. I bet that saw is blowing 100 psi, maybe a little more.
Check the compression. I bet that saw is blowing 100 psi, maybe a little more.
SteveSr
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Better yet... Pull the muffler cover and post photos of the piston through the exhaust port.
He did.
SteveSr
Addicted to ArboristSite
NOT a great photo... but the piston definitely looks scored. Also looks like some suspicious crud (carbon?) buildup in the exhaust port.
Well here’s the issue. Lol. Time for a rebuild. Suggestions greatly appreciated. Also debating new carb too while she’s apart. I didn’t even check the cylinder walls. I’m just going to replace the jug and piston and seals and such, and maybe upgrade carb too. MS260
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SteveSr
Addicted to ArboristSite
These are known to leak at the FW side crank seal. You may want to pressure test it before tear-down to find/confirm any leaks which may have caused the cylinder melt-down.
You might also ask your dad what kind of 2-stroke oil he was using. I have never seen buildup like that in the exhaust port... unless it was debris that went through a religious (i.e holy) air filter. BTW, what did the original air filter look like? Split the filter and post some photos with a light shining through it.
If you replace the carb go with a WT-194
