MS390 With 25" 3/8" .050" Setup?

[SteveSr]

Hello,

Did some Hurricane Florence disaster recovery work and one of the guys brought a MS390 with the above b&c setup. I did most of the sawing with it on a 42" DBH pecan tree that failed the high wind test. the saw had a spur sprocket on it and showed some wear but not terrible.

The original chain (stihl RS) was not in good shape so after a few cuts the first day I sharpened the cutters that evening. While doing this I noticed that a goodly percentage of depth gauges were too low but decided to see how it would cut anyway. The chain cut but was very "grabby" and "catchy". Like to beat me to death trying to control it. I finally asked if he had any new out of the box chains and he did so I switched. Cut much smoother.

Finally got to the base of the tree and probably ran into some "hardware". Put on a second new chain and continued until I think I hit an embedded rock or maybe some more hardware. Went back later in the day and tried to remount the better of the 2 new chains so that I could field sharpen it only to find that they wouldn't fit in the bar groove any more. It appears that the end of some of the drive links had been peened.

So what likely caused the drive link peening? Worn sprocket or was it catching on the embedded hardware?

When I got home I found that this saw is only spec'd for 20" 3/8" setup. This may explain the weak bar oiling as well.

I am assuming that he will want to keep the 25" setup. Can you make any recommendations to "improve" this setup? My only thoughts are rim drive conversion and semi-chisel chain. Any thoughts about running half or full skip to lighten the load on the powerhead and oiler?

Thanks,
Steve

 

[Franny K]

Intresting story. A rim drive sprocket will most likely be able to pull on the chain from more drive links than a spur one, especially a spur with any amount of wear. There is peening from use and then there is getting banged up from coming off. If the chain fit in the bar prior and does not later then it would seem the bar has closed up some, or burrs. I just looked in the catalog (Stihl) I see 5 kinds of skip chain for 3/8 all available in 0.050 and three in 0.063. If that bar is 0.063 getting the chain you have in mind might be frustrating.

 

[SteveSr]

Interesting story. A rim drive sprocket will most likely be able to pull on the chain from more drive links than a spur one, especially a spur with any amount of wear. There is peening from use and then there is getting banged up from coming off. If the chain fit in the bar prior and does not later then it would seem the bar has closed up some, or burrs

I don't think the bar closed up but the chain may have come off once or twice. I think it was stretching from heat due to the oiling issue with this long bar. I have had chains come off before and had never noticed any drive link damage. Didn't think about this being a possible cause.

I just looked in the catalog (Stihl) I see 5 kinds of skip chain for 3/8 all available in 0.050 and three in 0.063. If that bar is 0.063 getting the chain you have in mind might be frustrating.

The bar is .o5o" so that won't be an issue.

 

[Huskitoter]

It's common for a few or several links to get buggered when the chain throws. Just file the burr off with a flat file or dremel.

 

[captain dangers]

I believe you can fit an adjustable oiler off an 034 or something like that to accommodate larger bars. I'm guessing its already had the muffler mod as I'm not to sure if a stock/standard 390 would entertain a 25" bar due to the heavily restricted muffler ? but I'm sure someone with direct experience will correct me if I'm wrong ? CD

 

[Ketchup]

It's common for a few or several links to get buggered when the chain throws. Just file the burr off with a flat file or dremel.

That sounds like your problem.

A 390 can cut soft wood to 25", but pecan? Half skip would be better. A muffler mod and timing advance would also help.

A more powerful pro saw would be better still. Something the owner will likely be looking at if that saw continues to be used this hard. You want 70cc behind that bar for hard work.

 

[SteveSr]

I believe you can fit an adjustable oiler off an 034 or something like that to accommodate larger bars.

I would like to find one that could just be bolted on. I thought that the 034 was a slightly smaller 036 Pro saw. I wouldn't think that the olier would be compatible with this consumer clamshell.

 

[SteveSr]

That sounds like your problem.

I think that you're right! It wasn't all of the drive links just some. But then I have never experienced drive link peening from a spur sprocket before.

A more powerful pro saw would be better still. Something the owner will likely be looking at if that saw continues to be used this hard. You want 70cc behind that bar for hard work.

I would agree but this was for mission work cleaning up after Hurricane Florence. It took 3 people and a small tractor 3 full days to disassemble this tree and clear out the tons of green brier and privet that it fell into just to gain access to the tree. With this sort of work you never know what you will find. I can see why this tree was still untouched 6 months out. I suspect that we probably provided about $10K of tree removal service for an 85 year-old woman.

 

[motorhead99999]

I believe you can fit an adjustable oiler off an 034 or something like that to accommodate larger bars. I'm guessing its already had the muffler mod as I'm not to sure if a stock/standard 390 would entertain a 25" bar due to the heavily restricted muffler ? but I'm sure someone with direct experience will correct me if I'm wrong ? CD

Muffler mod will definitely help. For example I had a stock ms290 and ms390. I muffler modded the ms290 and it would put cut the 390. I muffler modded the 390 and it will pull a 25” bar in maple and oak all day long

 

[PogoInTheWoods]

When I got home I found that this saw is only spec'd for 20" 3/8" setup. This may explain the weak bar oiling as well.

Those are specs for a MS290. A MS390 is a 64cc saw that will pull and oil a 30" bar and chain, though that's a bit of a stretch in the specs imho. A 25" setup is perfectly acceptable for an 039/MS390 and a properly functioning (and adjusted) oiler will handle it. And a muffler mod is super easy on an 1127 saw and makes a big difference in performance.

Check all the usual places for oiling problems beginning with the bar and ending with the tank filter. Often times the oil pump spring/driver rod on the worm gear isn't correctly located in the clutch drum notch after the clutch drum is changed or pulled and reinstalled. Pull the clutch drum and check it just to cover that possibility as well.

 

[anlrolfe]

My old 039 has no problem pulling 25" of sharp saw chain through hard or soft wood. It has adjustable oiler and a light muffler mod. It's a vintage with H/L carb so it can be retuned accordingly once opened up.
Friends, don't let friends run saws without spark arresters.

 

[jltrent]

I had a MS390 that was to close to 170 compression. It had a 25" bar and full skip chain and would do a pretty good job with it. If a MS361 can handle a 25" bar a MS390 in good shape will handle one just about as good.

 

[dmb2613]

Other than being on the heavy side a ms390 will pull a 25 in bar no problem at all, sharp chain is the key. Open up the muffler some and let it rip , be carful advancing the timing , no more than 4 or 5 degrees it came with a high output oiler from the factory
I sell them with a pop up piston and firewood cutters love them, will cut with a stock ms440 if the tree is not over 28 inches or so