Misaligned bar on MS390

[WolfpactVI]

Hello all, long time lurker here, and I have a problem with my MS390.

The spur drive was getting pretty worn and grooved (I think I got the saw in 2005), so I decided it was time to upgrade to a sprocket drive. Bought the Oregon kit off ebay, about 4 months later finally got around to putting it on. Put on a new Rollomatic ES 20" bar and a brand new chain too. Reassembled it and went to use it and the saw cut horribly. Wouldnt cut straight, was bogging down like crazy in the log. So I took it all apart and discovered that the tail end of the bar is significantly misaligned with the sprocket, causing the chain to bind and curve sideways over the short distance between the rim and bar. The tail is pointed in towards the body of the saw and but the sprocket cant move in that far.

Here are some pics so you can see how misaligned everything is (none of the pics would upload here, so here's the link to a google drive folder they are in):

https://drive.google.com/folderview...JZcmtIRFhCNGhTMF9lYTVzYzV2RTVyakE&usp=sharing

There are two things I think could be the problem, but neither really explain it in my mind. I'm hoping someone can come up with another option to look into.

First, where the bar rests against the saw body, is getting worn slightly on the tail side vs the nose side. I've attached a pic. However, it is worn in so little (maybe 1/32" if that) compared to how much the bar groove doesnt match the rim grooves (at least 3/32") that the geometry just doesnt seem to indicate that that is the problem.

Second, maybe I have the wrong drum installed. The part number stamped on the drum is 34162, whereas Oregon's website lists 34162X as the part for my saw (though they call that the rim sprocket system, and I cant find anywhere the part number for just the drum). However, it seems to fit perfectly between the clutch and the washer and retaining clip so I'm not very convinced it is the wrong part.

Two things I do know: the bar is perfectly straight, and the rim is the correct rim, at least in terms of being a 3/8-7 rim.

My questions for all of you are, has anyone had this problem, and did you solve it by 1) shimming the tail of the bar, 2) putting a different drum on, or 3) something else. If I have to go back to a spur drum I will, but I'd really like to stay with the rim system.

Thanks in advance for any help!

 

[HarleyT]

The x at the end of the sprocket number just means "bearing not included".
Show a better pic of the 2 bar studs, and
"Are you running it without a sprocket cover?", or is that just to get a look at how it mates with the saw?

 

[HarleyT]

Take the 5th pic over again but flip the bar first.

 

[WolfpactVI]

That would be scary. No, I just have the sprocket cover off to better show how the bar lines up to the rim. And I did put a new bearing in too.

 

[WolfpactVI]

Two pics added. Both studs, and bar flipped. Still not aligned to rim by same amount. There isn't a shim plate that's supposed to be between the bar and saw body is there? I know my 026 has one, but I never remember this one having that.

 

[HarleyT]

how about a pic of just the sprocket/rim,washer,clip. The rim needs to be able to slid up against the drum, and all of the way out to the washer/clip. Is the sprocket
notch nestled on the oil pump worm driver correctly?

 

[WolfpactVI]

Yes the drum is correctly seated and the oil pump drive clip in the notch. There is also about 1/16" or 3/32" play in the rim (it can move side to side). The problem is when the rim is tight against the drum (and the drum tight against the clutch and shoulder on the driveshaft) it's still not far enough in to line up with the bar tail.

 

[WolfpactVI]

Any other suggestions?

 

[ChoppyChoppy]

Oregon part number is correct, 34162. (I just happen to have the Oregon sprocket book about 4ft from the shop computer). The "X" isn't part of the the part number, it just means that when you order a 34162 it doesn't come with the bearing and you have to order it seperate. The bearing is 37325.

Same clutch and bearing fits the 029, 034, 034 Super, 036 and your 039 in case you care to know.... maybe if you have any of those saws you can borrow the clutch to see if there is the same problem.

 

[WolfpactVI]

I think my dad has an MS290. I'll see what that looks like. Thanks for the suggestion.

 

[hawkins111]

What is the part number of the bar you are using?

 

[HarleyT]

The drum on your saw looks too high/far out from the saw's center, but since there is plenty of room for the washer and clip, I
am guessing that something is wrong with that drum, so I would scrounge around for the old one, or put on the one from your
dad's saw, and see how the bar lines up then.

 

[Gypo Logger]

What is a MS 390? Is that a saw?

 

[WolfpactVI]

Bar part number 3003 000 8822. 3/8 .050 72DL. I checked, it's the same thickness as the old bar, and the old bar is also misaligned. I measured the rim too. It's 9/32" thick. There's no part number on it, just says Oregon and 3/8-7. Maybe I have the wrong rim and I need a slimmer one? Does Oregon even make a slimmer one?

 

[Rockjock]

Bar part number 3003 000 8822. 3/8 .050 72DL. I checked, it's the same thickness as the old bar, and the old bar is also misaligned. I measured the rim too. It's 9/32" thick. There's no part number on it, just says Oregon and 3/8-7. Maybe I have the wrong rim and I need a slimmer one? Does Oregon even make a slimmer one?

Have you access to an OEM one? Bar nuts in all the way?

 

[HarleyT]

Look at pic#1, that drum is too high.

 

[AKDoug]

Looking at those pictures, the bar is mounting correctly on your saw. When you tighten it down it will snug up against those steps on the bar studs. Therefore, the issue is the drum for whatever reason. You cannot shim the bar without some serious machine work because the bar HAS to seal against the saw so the oiler will work. If you strongly desire to have a rim sprocket, I would get the Stihl 1125 007 1002 kit.

 

[WolfpactVI]

HarleyT, I agree, the drum is sitting too high.

Rockjock, I dont have access to an OEM drum at the moment (seem to have misplaced the old spur one). Yes, the bar nuts are snug and the bar studs in the correct amount.

AKDoug, my thoughts exactly on shimming the bar. Thanks for the part number. I'm about ready to just order the OEM one for no other reason than curiosity to see how it compares to the Oregon one.

Finally, according to the service manual, since I have the 1127/00 clutch, I need the clutch cover (which goes between the clutch and oiler gear). I left the cover out anyway, just for kicks, and it makes things better, and might even work...but just barely. Since it didnt clearly and obviously makes the bar and rim align with room to spare, I'm thinking that's not the solution.

Thanks all for the suggestions. I'll order the OEM one and see what happens. So much for saving money going aftermarket.

 

[HarleyT]

Borrow the sprocket
off of your dad's ms290 to compare the drums, etc. The ms290 and 390 are pretty much identical except for the piston size.

 

[hawkins111]

Did you ever get to the bottom of your sprocket problem??