New Forester rim sprocket, won't align with MS290 chain

[a. palmer jr.]

Those sprockets fit the 346 and 353 Husky saws and the Husky makes that ms290 look like a drunk pig!

I bought a 346xp last week but haven't had a chance to try it out, been too busy working on other saws..

 

[AKDoug]

I learned the hard way. Just buy Stihl Rims, and you won't go wrong.
View attachment 421955

Holy crap.. I charge half that for Stihl rim sprockets.

 

[RedOctobyr]

OK, I checked this again.

I am comfortable that the clutch housing is seating fully towards the engine. The gap at the end of the crankshaft looks the same to me, for the Stihl, or the Forester, when pushed onto the crankshaft, with the grooves lined up with the oil-pump spring.

I took some measurements of the overall height of each unit, if you lay them on the ground, and measure down through the hole. That was 1.170" for the Forester, 1.245" for the Stihl. But that really doesn't tell you much, because they don't bottom out on the backs of their housings, that height doesn't determine their location relative to the bar. It is of interest, however, that the Forester would presumably have less engagement with the oil-pump's spring, since it doesn't extend as far back towards the engine.

The attached picture is the clearest illustration of the problem that I could manage quickly. I used a bar as a straightedge, and aligned each sprocket against the bar. This is effectively how they mount in the saw, as their sprocket faces would be up against the E-clip at the end of the crankshaft. So their location would be determined by this surface, not the other end, by the clutch and oil-pump spring.

Note, from the red line that I added, how the center of the chain groove in the Forester is shifted further out from the saw (or up, in this picture) than the wear-marks in the Stihl sprocket. This is, I believe, why the chain has to bend away from the saw, when it comes out of the bar, to line up with the Forester's sprocket groove.

The Forester clutch housing is marked with the same part number, W3/8LZ7C, that the box label shows. That label lists 029, etc. So I believe I received the correct parts. They simply don't fit properly. If I'm mis-reading this, please tell me, but it seems to me that the Forester unit was not designed/made correctly.

 

[ChoppyChoppy]

I forgot about that. You can only use a Stihl rim on a Stihl drum too, at least Im pretty sure

We stock Oregon brand and I run them on my Stihl saws with Stihl clutch drums. I'm not sure if that works for all Stihl saws though. Have them on a 026, 290, 460, 036 and 360.

 

[AKDoug]

I believe the large sized Oregon rims and Stihl rims interchange. The small size does not.

 

[fearofpavement]

In the pics in the previous post comparing the rims, those are two different parts. One is a small rim and the other a "mini" which is what the small Stihls take. Most aftermarket sprockets are made for the small rims and not the minis. Many of the aftermarket suppliers will send you a "small" and not a "mini" for the Stihl saws and they just don't fit. I have a pile of small sprockets here trying to get some to fit my small Stihls.

 

[nnero]

Ah OK I wasn't really sure. Things are clear as mud now lol

 

[chainsaw-57]

Good Morning,

I have used many of the Forester rim sprockets kits. They are too "thick". Either the chain is out of alignment or the clip will not go on.

I put them in my lathe and turn a small pocket on the inside of the drum, where it seats on the clutch. If you look at the STIHL sprockets, where they meet the clutch 3/4" hex, they have pockets. Be aware they are very hard and you need to cut across to joining pieces. This effectively moves the entire sprocket closer to the saw and also engages the worm gear tang better.

Hope this helps. Yes, I have informed them of this, years ago, to no avail. Still a good bang for the buck for me.

Take care, Larry. HOS

 

[RedOctobyr]

I just wanted to follow up on this. I finally got a Stihl 3/8" 7T rim sprocket setup. Installed it, and everything lines up nicely, the chain turns easily by hand.

This splined setup also provides plenty of lateral float for the rim sprocket. While the Forester, even if it had lined up properly, had a shorter splined hub, which could barely provide any lateral float anyhow.

The only thing I noticed about the Stihl sprocket is that if I push it in, towards the engine, while turning the hub/clutch housing, I hear a scraping noise, though I'm not sure what's rubbing. If you let the clutch housing shift away from the engine slightly, it's fine. The clutch housing is aligned properly with the saw's oiler spring.

 

[AKDoug]

Don't overthink it, it's fine. They all scrape a little like that.