Need MS250 + MS310 help

[Woodslasher]

The MS250's problem and story goes like this: My brother gave me a lightly used MS250 he got off of an ex logger that I believe 10 years old or less. He ran it at the guy's place and cut wood with it, etc and it ran like a champ. Fast forward 1 month and I get it. It hasn't been run since he initially ran it and the fuel was left in the tank. A few days ago I received it and went to run it, after robbing an oil cap off of another saw since it's was missing, but it wouldn't run at full throttle. It would bog down at about half throttle and die if you tried to push it higher As it was 30 degrees with a strong wind chill we figured it needed to warm up like Dad's husky 445 which does the same thing. After it idled for 4-5 minutes and still wouldn't run we gave up on it for the day. The next day, we could get it to run at full throttle and cut wood but it wouldn't idle. After that we decided to take it in to a shop and get their opinion while getting an oil cap and air filter cover for it. The guy at the shop said the carburetor was bad so I got a oem zama off of ebay and figured that would fix it. Tonight as I was pulling the carb off to swap the new one in and I noticed the fuel line was cracked. Is that the problem or is the carburetor the problem? I figure I'll buy a new fuel line and try that and the old carb anyways but I want to get y'all's opinion on it.
Now for the MS310: Same logger, different story. My brother got it with the issue of it dying anywhere from 15-30 seconds depending on how you ran the throttle. It fires up, cuts wood while it runs, and then just throttles down to nothing. The same shop said carb for this guy as well and a new carb is sitting on my desk. Before I go back into the cold and rain and move it from storage to shop to check the fuel line and mess with the carb, is it the carb on this guy like the shop said, the fuel line, or something else?

 

[Saw Fixr]

A cracked fuel line will definitely do that on your 250.
Try a new fuel Line on the 310 as well. Can’t hurt. You’d know pretty quick either way....
Since you’ll have the carb off anyway, it wouldn’t hurt to go thru it, and give it a good cleaning. Especially if either saw was run with ethanol fuel, or even stored for a while without being run.

 

[rd35]

I agree with Saw Fixr. If it were me, I'd hold off on both carb replacements. I'd start by dumping the old gas (although 1-month old gas is really not old at all), cleaning the fuel tank by sloshing a bit of new gas around and dumping again, install a new fuel line and filter, disassemble and clean the carburetor, re-assemble, pour in new fuel, fire it up and tune it correctly. This procedure works for me 95% of the time on a saw that runs erratic. Just last night I has an old 028 on my bench that was running all over the place. Lean one minute, flooded the next. I did as I described above....and now it runs beautiful. Strong acceleration and idles smooth as silk....(well, I guess no 2-stoke engine idles smooth as silk...but you know what I mean)

 

[Woodslasher]

Stupid question but do you mean the in tank fuel filter should be replaced?

 

[lambs]

I think that's what he means. If you change the fuel line, you'll be removing the existing fuel filter, so you might as well replace it and eliminate it as an issue.

 

[SteveSr]

With 10 years of age and dubious fuel storage or quality I would definitely put an OEM kit in the carbs. Kits are only $5-10. How much is your time worth?

Flaky main nozzle check valves in the carb can also cause failure to rev (stuck closed) or failure to idle (stuck open). This should be considered non-repairable unless you have a lot of time or a rare high value carb.

 

[Woodslasher]

Well, I stopped by the saw shop and picked up my air filter cover and got a new bar for my brother's Sachs-Dolmar along with fuel lines and fuel filters for both saws. A half hour later the MS250 was wearing its new cover over a new carb and fuel line and cutting firewood like a champ. However, the new fuel line for the MS310 didn't match what was in it so the fuel line will head back to the shop. The MS310 only runs with the choke on and even then it revs and dies despite having the new carb in it so that needs to be diagnosed. The old carb was a Walbro so my brother thinks he'll try messing with that and try to get it working. Another fuel line issue? The old line doesn't appear to be cracked but stranger things have happened.

 

[rd35]

I wouldn't do much cutting with that 310 until you get it ironed out. I have replaced the piston and cylinder on more than one of this series saw due to lean running causing a scored piston and cylinder. Seems to be a problem with this series more that the others for some strange reason. Yet...my Dad has an 029 that he has run for many years and simply loves it! Great saw. I'm betting a new fuel line will have you up and running pronto!

 

[Woodslasher]

A brief update on the saws. Me and my brother cut 15 trees down with either the MS250, his 281, or both this afternoon. During lunch I found a fuel line for a stihl in my dad's box of saw stuff (despite his not having a stihl saw in about 10 years) that fit the MS310 so I installed it in the shop after the light ran out for felling. The saw will be tried out tomorrow so we'll see if it fixes it. Ps. My brother said the old fuel line wasn't cracked but after pulling it off it turns out the line was cracked halfway through right above the tank gasket.

 

[SteveSr]

My brother said the old fuel line wasn't cracked but after pulling it off it turns out the line was cracked halfway through right above the tank gasket.

Common place for cracks as the rubber is exposed to atmospheric ozone and stress at the bend. That may solve a lot of your problems!

 

[Woodslasher]

We'll find out tomorrow! I'm hopeful though. I have no chainsaw maker favorites but I don't want Stihl getting a bum rap and my Huskqvarna brother getting to gloat.