Long story... long, I picked up this ms290 that was being thrown away by a lawn care company a couple years ago. It was run hard and totally thrashed but I had it running in about 20 minutes with a new fuel line so i figured what the heck, put a cheap 20" B/C on it and use it for cutting down rotten trees, stumps, fence line trees with nails in them. I have a small hobby farm and some nicer 50cc saws that see a lot of use on smaller stuff, but usually once or twice a year i have something thats big and ugly and its nice to have a big dirty saw for those jobs, and if i drop a tree on it no biggie.
Got the cheap china B/C and some missing parts, but it felt weak so I grabbed a china 390 jug thinking it was wore out.
Rebuilt it with the china jug and some OEM parts, still didn't run right, found out it needed a 390 main jet so i ordered that, waited, lost it, ordered it again, found the one i lost.... blah blah blah.
2 years later, its finally reliable enough that its worth dragging out into the field, I used it last week to cut down 4 crappy weed trees and sure enough a squirrely box elder took a roll and warped the bar. Lucky it was only 12 bucks. I managed to get it bent back pretty good but you can tell that its cutting a hair-off.
Now that i'm running it a bit, its not as terrible as i've thought. Heavy, and i don't like how it balances with the chitty 20" b/c, but its got a lot of torque and it actually does a nice enough job that it might be worth dragging it out to buck firewood. That said I'm ready to put a little time and money into making it nice (er).
All told i've got less than $100 into the saw and the most expensive thing was $55 for the two oem fuel/oil caps! So i don't mind throwing a few bucks at it to get it to do the job of a poor man's 380. My buddy has a really nice 038 with 20" b/c, specs say the 390 is 4.6 hp and the 380 is 4.9 but his saw seems like it goes through wood about twice as fast.
1) first thing it sounds like is i need to do the muffler mod. Reading what some folks are saying, it definitely feels 'choked down'... it doesn't really rev out and the WOT 'no load' speed doesn't pick up as it goes lean. I'm hoping the high rpm torque improves considerably, right now it feels like it drops off really quick in the cut but then maintains torque at a lower RPM than what i would like. I noticed when i've modded other mufflers, it seems to pick up the rpm of the torque peak a little bit, and this dog needs it badly.
2) Is a 20" bar too much for this saw? I see a lot of 290's fitted with the 20, so i don't think i'm being greedy.
3) Is there a chain that would be a better choice? Narrower or more efficient? I was thinking just going with the basic Stihl Rollomatic and rs3 maybe? Given my usage i'm open to suggestions. I know almost nothing about chain and bar selection. I think the china chain i bought was a semi-chisel, its a little bit grabby but i only use this saw for bigger stuff so it doesn't really bother me, but as a weekend-warrior i'm always a big fan of safety.
4) is there anything else that i could/should do tuning wise? advance timing? any other carb changes i should have made. I think my tune is pretty well spot on at this point but haven't checked the plug after about 4 tanks of gas through this setup. The low speed screw doesn't do much between 3/4-1.5 turns, it dies below that and above that, otherwise i have the idle a bit on the high side or it kills when it comes down quick from WOT, which i don't like because its kinda dangerous IMO.
Thats about it, any other tips or tricks to get this $100 trash picked plastic saw to do the job of an $800+ saw would be greatly appreciated.