024 & 026 Clutch Drum Confusion

[nedsim]

Looking to replace the well-used spur sprocket drum on my 024AV with a rim sprocket drum. Oregon says their 100791X kit is "For use after serial number X25809074. " I got a not very clear explanation from Oregon on how to interpret the "X" in the serial number. I asked, "Does the "X" in the above serial numbers mean ignore the first digit in the serial number?" They replied, "the X means that any additional numbers that come before the 2 in the serial number break they will fit." Not sure how to interpret that.

The 024 IPL does not reference different S/N's when calling out the drums.

My 026, which already has a rim sprocket, is S/N 219843420 (ca 1987, made in VA Beach); the 024AV is S/N 114007643 (ca 1985, W Germany).

So, is there an early/late production difference that requires different drums? Is there a tell-tale sign I can look for independent of the S/N?

 

[ballisticdoughnut]

Not all that familiar with the 024 but I do know the 026 uses a different drum than the 026 pro which has a adjustable oil pump. 026 drums are no longer available from Stihl, I suspect this is the same drum the 024 uses. 024 and 026 are nearly identical in design, assuming the 024 has a non adjustable oil pump OEM drums are no longer available. I’d imagine there’s a aftermarket one one available however. I’ll see if I can find more information.

 

[ballisticdoughnut]

Good used rim drums can be found on eBay just make sure it doesn’t have the notch for driving the worm gear on adjustable oil pump saws.

 

[nedsim]

Thanks. Just ordered a NOS Oregon 100791X on ebay. I still can't figure out what Oregon is saying about s/n's, but $15 for the drum kit is a bargain compared to the time it'd likely take to suss this out.

 

[SteveSr]

026 drums are no longer available from Stihl, I suspect this is the same drum the 024 uses. 024 and 026 are nearly identical in design, assuming the 024 has a non adjustable oil pump OEM drums are no longer available.

Where did you get the idea that the OEM drums are NLA? I see a listing for the "no notch" 024/026 drums in the 2022 Bryan catalog. If these are available I am sure that the newer notched variants are also available as they also fit on the 260.

However, you cannot just buy the rim drum. you have to buy the rim conversion kit which contains the rim and the drum. The part number stamped on the drum goes nowhere.

 

[ballisticdoughnut]

I got the idea because I my shop has been a Stihl dealer since 1963. And yes I did look them up. If you read my first comment I state OEM drums are NLA from STIHL. Aftermarket is a different story. Non adjustable oiler vs adjustable oiler drums are different on the 026. Later adjustable oil pump clutch drums are different and not backwards compatible.

 

[82F100SWB]

The first number of the serial is country of manufacture, it is not part of the production sequencing. What Oregon is saying is ignore the first number.
Besides having the notch for the pump or not, there were different width drums as well, with early saws having narrower friction area. I have the service bulletin here somewhere.

 

[1hp]

some info in this.

 

[nedsim]

The first number of the serial is country of manufacture, it is not part of the production sequencing. What Oregon is saying is ignore the first number.
Besides having the notch for the pump or not, there were different width drums as well, with early saws having narrower friction area. I have the service bulletin here somewhere.

Thanks, I tried to get Oregon to confirm that the "X" means "ignore the number in this position" but their answer was gibberish. If the drum in the Oregon kit I ordered is too wide, but otherwise the same, a few minutes in the lathe should fix that. Or worst case it's a $15 gauge to discriminate between old & new clutches.

 

[nedsim]

some info in this.

Good stuff. I didn't see anything as late as the change Oregon implies. This and ballisticd's post make me wonder if the last of the 024/026's used a clutch that was destined for the 260. The Oregon cutoff s/n is much higher than either of my saws and occured around 1991 (according to the Stihl s/n decoder).

 

[ballisticdoughnut]

Good stuff. I didn't see anything as late as the change Oregon implies. This and ballisticd's post make me wonder if the last of the 024/026's used a clutch that was destined for the 260. The Oregon cutoff s/n is much higher than either of my saws and occured around 1991 (according to the Stihl s/n decoder).

Someone correct me if I’m wrong but I believe all 024’s had a non adjustable oil pump. 026 uses the same drum (spur or rim sprocket) the change came with the 026 pro with adjustable oil pump. Those drums were deeper and have a notch that engages with the wire arm that drives the worm gear. Clutches are more or less the same on 024, 026 pro, MS260, and MS261 it’s the oil pump setup that matters here.

 

[ballisticdoughnut]

Found a OEM rim sprocket kit that will work on your saw. 1121 007 1001
https://www.ebay.com/itm/3258650290...b40rr_rqny&var=&widget_ver=artemis&media=COPY

 

[SteveSr]

Looking to replace the well-used spur sprocket drum on my 024AV with a rim sprocket drum. Oregon says their 100791X kit is "For use after serial number X25809074. " I got a not very clear explanation from Oregon on how to interpret the "X" in the serial number. I asked, "Does the "X" in the above serial numbers mean ignore the first digit in the serial number?" They replied, "the X means that any additional numbers that come before the 2 in the serial number break they will fit." Not sure how to interpret that.

The 024 IPL does not reference different S/N's when calling out the drums.

My 026, which already has a rim sprocket, is S/N 219843420 (ca 1987, made in VA Beach); the 024AV is S/N 114007643 (ca 1985, W Germany).

So, is there an early/late production difference that requires different drums? Is there a tell-tale sign I can look for independent of the S/N?

The only difference that I am aware of is the change to a taller drum to accommodate the oiler worm drive "notch" This option occurred c.a. 1996 with the introduction of the 026 PRO. The older non-notched drums should still available from Stihl as follows:

Integrated Drum Spur Sprocket:
1121-640-2000 - 0.325 7T
1121-640-2001 - 0.325 8T

Rim Sprocket Conversion Kit:
1121-007-1001 - 0.325" 7T
1121-007-1002 - 0.325" 8T
1121-007-1004 - 3/8" LP 7T
1121-007-1005 - 3/8" LP 8T - NLA
1121-007-1035 - 3/8" 7T

 

[HarleyT]

The x means that it does not come with a bearing.

 

[nedsim]

Thanks for all the advice and info. The Oregon kit I purchased should show up tomorrow or Monday. I'll follow up then.

In the meantime I'm a bit distracted. Just as I was starting to make turkey gravy yesterday our septic alarm went off -- lift pump had failed. It didn't interfere with dinner, but I spent the evening trying to switch in a used spare pump with the sump flooded. We were close to success when the lift ring on the pump failed and the pump sank to the bottom of the sump. I was lucky to get someone to pump it out this AM, but now I have to get my hands on another pump and install that. At least now that the septic tank is empty I have a few days to a week before it fills.

 

[ballisticdoughnut]

Thanks for all the advice and info. The Oregon kit I purchased should show up tomorrow or Monday. I'll follow up then.

In the meantime I'm a bit distracted. Just as I was starting to make turkey gravy yesterday our septic alarm went off -- lift pump had failed. It didn't interfere with dinner, but I spent the evening trying to switch in a used spare pump with the sump flooded. We were close to success when the lift ring on the pump failed and the pump sank to the bottom of the sump. I was lucky to get someone to pump it out this AM, but now I have to get my hands on another pump and install that. At least now that the septic tank is empty I have a few days to a week before it fills.

Always something isn’t it.

 

[nedsim]

As predicted, the Oregon 100791X kit has a wide drum with a notch. My original is .530 inch deep from the inner face of the bearing race to the drum inner face. The Oregon 100791X is .650 inch deep and has the notch. The notch is .120 deep, exactly the difference in width between the two drums. The steel is quite hard, but cut nicely with carbide in a rigid setup. Fortunately for me, the OD of the spline is finish machined and was easy to grip in a collet. If a collet is not available, it'd be easy to turn up a stepped arbor with a female thread in the end for a cap screw & washer to mount the drum. Takes much longer to describe than do.

Interestingly, according to Oregon, 100791X fits:

• 024 (after serial number X25809074)
• 026 (after serial number X25809074)
• MS 260,
• MS 260 Pro,
• MS 270,
• MS 270 C,
• MS 270 C-B,
• MS 270 CQS

but a search on 026 PRO says no drum is available.

Thanks again for all the help. I'll give it a test tomorrow. (After installing my septic pump.)

 

[nedsim]

Always something isn’t it.

Well, it's something.... Under control now.

 

[SteveSr]

Interestingly, according to Oregon, 100791X fits:

• 024 (after serial number X25809074)
• 026 (after serial number X25809074)
• MS 260,
• MS 260 Pro,
• MS 270,
• MS 270 C,
• MS 270 C-B,
• MS 270 CQS

but a search on 026 PRO says no drum is available.

As you found out aftermarket (even Oregon) cross reference application information can be incomplete or just plain wrong.