Torquing a clutch

[KMB]

I have 2 reasons why I want to take the outboard clutch off my Olympyk 970 (got it a few weeks ago) - to check the condition of the rim sprocket and to confirm what gauge of chain I'm running. According to factory specs, the bar and chain combo was for 3/8" x .058" chain. So before ordering spare chains, I want to make sure of the chain specs. The chain that came with the saw is made by Total and has 'J1' stamped on the drive links. I did a Goggle search and it seems that it is 3/8" x .050" (indirectly determined). I also did a Goggle search on the bar model number, which turns out to be a Jonsered bar in 3/8" x .050". But I want to be absolutely sure, so I want to check the rim sprocket. I did a search here on AS regarding piston stops and clutch removal. There's a nut on my clutch so I won't be needing a special tool, I have made note of which direction to go when taking off the clutch, and I'll be using rope for a piston stop. Will a large rachet and socket work, or is torqued on tight enough to use a breaker bar for the clutch removal? I don't have immediate access to an air gun. I have also found out that it is not recommended to just 'tighten' the clutch when reinstalling - it should be torqued on. I can't find in my owner's manual what torque setting the clutch needs. I there a general minimum torque setting I should use? Or should I find the exact setting? If motor size is revelant, the saw is 71cc.

Kevin

 

[HiOctane]

You can remove it by using a ratchet.Beware if you use an air gun ,the shoes can fly away IF you dont hold the sprocket and always pushing it while unscrewing the clutch.I dont argue the value of using a torque wrench to tighten the clutch,but ive never used it and never had problems.

 

[rbtree]

While it is a good idea to replace the sprocket if it's worn and grease the bearing, there is no need to remove it to tell if it is worn. A visual inspection will suffice. Nor is there any need to take it off to tell what it is. For that saw, it's most likely a large spline 7 tooth. As I think you've already found out, I believe Efco, Husky, Jonsy, and Dolmar all take the same bars, pretty much. (Though my old 920S Jonsy bars were a bit different than Husky) Sprockets are not gauge sensitive. Call Bailey's, they stock a huge assortment of chain types, and have the best prices, and will easily be able to tell you what you have. .050 is much more common than .058......

If you do remove the sprocket, you need to either stuff some starter rope down the plug hole, or screw in a piston stop (specialty item available at a saw shop), then remove the clutch, which is reverse threaded. There is no need to torque the clutch back on, as the engine centrifugal force will keep it tight.

 

[KMB]

While it is a good idea to replace the sprocket if it's worn and grease the bearing, there is no need to remove it to tell if it is worn. A visual inspection will suffice. Nor is there any need to take it off to tell what it is. For that saw, it's most likely a large spline 7 tooth. As I think you've already found out, I believe Efco, Husky, Jonsy, and Dolmar all take the same bars, pretty much. (Though my old 920S Jonsy bars were a bit different than Husky) Sprockets are not gauge sensitive. Call Bailey's, they stock a huge assortment of chain types, and have the best prices, and will easily be able to tell you what you have. .050 is much more common than .058......

If you do remove the sprocket, you need to either stuff some starter rope down the plug hole, or screw in a piston stop (specialty item available at a saw shop), then remove the clutch, which is reverse threaded. There is no need to torque the clutch back on, as the engine centrifugal force will keep it tight.

7 tooth sprocket it is, and a good visual check proved the sprocket to be in fine shape. I have my bro-in-laws 029 over here and it has a 3/8" x .050" chain and since it has the same amount of drive links, I thought I'd try it on my 970 - and it fits - proving that I was right about the right chain size. So I'll leave the clutch alone until I have to mess with it.

Kevin

 

[DMessin]

My 044 is a 70cc saw and the clutch is torqued to 37 ft*lbs. Your saw may be similar if thread pitch and shaft diameter are close. Hope this helps.

-Dave

 

[Lakeside53]

There is no need to torque the clutch back on, as the engine centrifugal force will keep it tight.

Absolutely not true... and dangerous... while the direction of rotion of an accelerating engine does tend to tighten the clutch, if the clutch isn't tight enough (i.e., torqued down) and the engine slows down abruptly (or faster than the mass of the rotating clutch), the clutch will if off in a heartbeat... Happened to me a month ago... and I know (should have) better..


The published torque setting is to make sure the clutch won't come off during deaccelaration or shock and to ensure that the threads don't get damaged by too much torque. The threads are pretty strong, so if you don't have a torque wrench that can work on left hand threads (many do not) err on the side of too much rather then too little.. The bigger the clutch (mass), the more the likelihood of a problem. My 066 has a 51.5 ft/lb torque setting for the clutch... Would it come off at 30? no idea, but I'm not risking it.

 

[KMB]

Absolutely not true... and dangerous... while the direction of rotion of an accelerating engine does tend to tighten the clutch, if the clutch isn't tight enough (i.e., torqued down) and the engine slows down abruptly (or faster than the mass of the rotating clutch), the clutch will if off in a heartbeat... Happened to me a month ago... and I know (should have) better..


The published torque setting is to make sure the clutch won't come off during deaccelaration or shock and to ensure that the threads don't get damaged by too much torque. The threads are pretty strong, so if you don't have a torque wrench that can work on left hand threads (many do not) err on the side of too much rather then too little.. The bigger the clutch (mass), the more the likelihood of a problem. My 066 has a 51.5 ft/lb torque setting for the clutch... Would it come off at 30? no idea, but I'm not risking it.

Was kinda wondering when you'd find my thread and offer your advise. Thanks for the info. I'll be borrowing or getting my own torque wrench when I do a clutch removal. I like peace of mind.

Kevin

 

[cord arrow]

i don't torque 'em, but i do hit the chain brake at WOT a few times.

 

[Lakeside53]

Was kinda wondering when you'd find my thread and offer your advise. Thanks for the info. I'll be borrowing or getting my own torque wrench when I do a clutch removal. I like peace of mind.

Kevin

If you borrow one, make sure it works in the left hand direction... Put it in the vice and try it before working on the clutch

 

[KMB]

If you borrow one, make sure it works in the left hand direction... Put it in the vice and try it before working on the clutch

Thanks again. That would really suck if I had the clutch off and couldn't use the torque wrench - especially since I'm in the country and about 30 mins. from a store that might have a torque wrench. One of my pet peeves is working on something, and finding out in the middle of the project that I don't have the proper tool to finish the job . I must learn to plan ahead better .

Kevin

 

[rbtree]

Thanks for correcting me, Andy. good to know clutches could come off. I don't recall, but I may have once had one come loose....

I usually just give mine a good nudge with whatever tool is needed for the clutch being worked on....whenever it's time to take them off, they are always on preety snug.

Whoohoo, my $14k poplar job is finally a go....in 2 weeks, the buggers better not be in leaf by then