Drew4522
ArboristSite Member
So I recently acquired a nice condition ms390 20" from a desparate friend for next to nothing in trade.. It sat for quite some time, so it was long overdue for service. I certainly know my way around engines, so I went into it thinking it would be easy.
After a piston and ring kit, carb rebuild, air filter, fuel filter, intake boot, plug, fuel line and impulse line, it has developed a low end bog and a quirky idle I cannot figure out. From a cold start it starts normal, as in choke till it pops, then half throttle for a few seconds, then to run position.. as any saw should; but most of the time will not idle without messing with the L and L/A screws. Every..single..time. Once I get it idling, it will run fine and cut, but will bog when throttle is squeezed for a quarter second until reaching high rpm. It seems to cut ok, not was I was expecting for a 64cc saw tho..kind of falls on itself. Yes I've dialed in the H screw (not with tach, by ear...). Muffler is opened up a bit, arrestor removed, nice white/blue spark on plug..shoes on clutch are good, and drum spins free..no, brake is not engaged.
My question is more for anyone who has ever had similar symptoms and what the end result was. I dont want to dump money into unnecessary parts if theres something I'm missing. Thanks!
After a piston and ring kit, carb rebuild, air filter, fuel filter, intake boot, plug, fuel line and impulse line, it has developed a low end bog and a quirky idle I cannot figure out. From a cold start it starts normal, as in choke till it pops, then half throttle for a few seconds, then to run position.. as any saw should; but most of the time will not idle without messing with the L and L/A screws. Every..single..time. Once I get it idling, it will run fine and cut, but will bog when throttle is squeezed for a quarter second until reaching high rpm. It seems to cut ok, not was I was expecting for a 64cc saw tho..kind of falls on itself. Yes I've dialed in the H screw (not with tach, by ear...). Muffler is opened up a bit, arrestor removed, nice white/blue spark on plug..shoes on clutch are good, and drum spins free..no, brake is not engaged.
My question is more for anyone who has ever had similar symptoms and what the end result was. I dont want to dump money into unnecessary parts if theres something I'm missing. Thanks!