'They' wouldn't start, I am NOT happy!

[mrcaptainbob]

So, the ongoing MS310 saga: The old hard working MS310 got heart transplant and was upgraded to a 390 engine. Dinkin' around with it I got it running pretty good. Idle was great, quick engine response to the trigger, top rpm's were set at 12,800. It was MISERABLE cutting !! Went back to the barn and played some more. Started from zero and reset the idle screw, low  speed screw and the high speed screw. Had a 10" cherry piece near the barn and did four test cuts and it worked GREAT! Get out to the field and it runs semi-okay when held vertical, but spit/sputtered and died when felling. Couldn't even make it's way through a four inch sapling. Spent almost an hour dinkin' with it in the field to no avail. I'm upset. SO...I go to the OLD Ward's saw just to get the day's project at least started. Twenty pulls later...and IT would not start either! It was a strain, but I actually 'placed' them in the tuck bed. Much restraint to keep from tossing them both!
Glad it rained all day t'day, as I'm still kind wound up with them. If weather permits tomorrow, I'll delve into it some to see what the heck's going on. The Ward's has ALWAYS givin' great performance. The 'new' Stihl has yet to act right.

[Al_Smith]

Some times you just have to walk away until cooler heads prevail .

[mrcaptainbob]

Well! They both started fine today! The Wards ran super great and I did a yard project with it. The Stihl, however, dies when in the cut. Seems at slight throttle it would sort of be okay...if I was gentle with it and did not let the weight of the saw press the chain too much. Well, THAT'S no way to cut pine! It just won't keep running!  So, lemme ask this: Since I went to the 390 block, should I have upgraded the carb, too? This carb is from the 310 block. Is there a larger jet or such?

[JohnW]

Could this be a fuel line problem?

[angelo c]

Well! They both started fine today! The Wards ran super great and I did a yard project with it. The Stihl, however, dies when in the cut. Seems at slight throttle it would sort of be okay...if I was gentle with it and did not let the weight of the saw press the chain too much. Well, THAT'S no way to cut pine! It just won't keep running!  So, lemme ask this: Since I went to the 390 block, should I have upgraded the carb, too? This carb is from the 310 block. Is there a larger jet or such?

Will it 4 stroke out of the cut ? Take look at the clutch springs just for chits and giggles but I'm thinking "fuel delivery system" if there is anyone nearby that has a carb to swap on for a test run it would be great to eliminate it from the "list" fuel line, filter, and fuel vent are also tops on that list. I've had quite a few that run great at idle or run great for a while then die....rebuild the carb to 50/50 odds of success . Usually a carb swap out gets it done. Maybe I'm no good with carbs ? I'm about 50/50 with the cheap Chicom Virus replacement carbs too

[Michael]

I think you used a Chinese kit for the 039 conversion. Sometimes good sometimes not.

[mrcaptainbob]

I'm sure it is a Chinese conversion unit, Michael. I plan on doing a vacuum test today. I do have a question about the muffler mod I did. If I over did opening the muffler, could that cause it to die in the cut? I can get the idle, (what I think..) is perfect. And set the high speed at 12,800. Seems like that should pretty much be it. The idle speed is the mid-point of stumbling both directions. The idle is turned so as to juuust baarely make the chain move. This is done with chain and filter in place. And after it's been running for a few minutes. Put it in some wood and it bogs and stumbles. Carefully jerking the trigger does nothing to help bring it back up. It dies. I can get it to start again, but ....same story over and over. Muffler over-opened? Leaky pulse line? Did the red, high temp rtv on both block surfaces and let cure for a few minutes, at least fifteen, before assembling.
New carb time? New muffler?