chainsaw clutch drum needle roller lubrication?

[David Heaf]

My Sachs Dolmar 123 clutch is slipping occasionally while sawing old oak about as wide as the 24 inch bar. The assembly is shown in the diagram attached. History: the needle roller siezed last year after 31 years use. It had a metal cage/keeper. I put in a new one from Makita. It had a plastic cage/keeper. I generously lubricated it with sprocket nose grease. It failed this year apparently due to overheating. I noticed that the chain was more prone to stall under full power, i.e. motor still running. On dismantling, I noticed that the bearing was completely dry, but there were traces of decomposed grease on the clutch shoes and drum.

 

There is apparently no component that stops grease being flung from the needle roller bearing into the clutch drum.

 

My question is: should the needle bearing be lubricated and if so, with what and by how much?

[openspaceman]

 

My question is: should the needle bearing be lubricated and if so, with what and by how much?

 

It was always one shot of grease per week on old Husqvarna saws

[Al Smith]

As a general rule most do not lubricate the bearing for the simple reason that it attracts tiny wood fibers which will clog the bearing .There are some who will argue to lube it also .

[GardenKit]

IMO bearings love a bit of grease. The ones I see failed are always bone dry.

[Reddog]

If the clutch is slipping easier than 30 years ago, the drum or shoes may be glazed. This will build more heat which in turn takes out the grease and the plastic bearing cage.

 

So my thoughts are you ether need some new clutch parts or if clutch is in good working order, are pushing the saw to much in the cut causing it to slip and build heat.

[woody paul]

The clutch roller bearing only comes in to play when saw is idoling so it dos't need much lube. Only ever had 1 clog up when milling with fine dust.

[spudulike]

Right, the plastic replacement bearing has probably failed due to the build up of heat with the clutch slipping. The friction between the clutch slipping on the sprocket will cause this area to build up a lot of heat and the plastic bearing has failed due tho this.

 

Greasing the bearing probably won't help the issue but I DO grease these bearings, they are manufactured to be lubricated and some Huskys even have a drilled out crankshaft end to allow greasing through.

 

The first issue is to find out why the clutch is slipping, after theis time, it is likely the clutch shoes are worn down and need replacing - it is also worth checking the sprocket as this can also have a channel worn around its inside where the clutch contacts it.

 

If you resolve the slipping issue, you will probably find the plastic needle is fine as some of the later Stihls use them with no issues.

 

You may find that using a skip or semi skip chain would reduce loading or a narrow kerf one would help but this is rather masking the route cause!

 

Hope this helps - interesting post!

[Cut4fun]

I only lightly grease the bearing when replacing or having to work in that area and bearing is out.

[David Heaf]

Wow, thanks everyone for your help!

 

I'd not considered the drum being glazed. Presumably it's OK to roughen it with emery paper? The clutch is metal-on-metal, i.e. the shoes are just metal.

 

I checked for drum wear. It does have a slight ridge on the crankcase side. Measuring the inside of the drum beyond the ridge, i.e. where it contacts the shoes, it is 70.5 mm diameter. The shoe unit is 68.6 mm diameter. I have no measurements from when new. So the clearance all round is 0.85 mm when stationary. Would this indicate significant wear?

 

The manual says: 'When replacing the clutch drum renew the high melting point grease in the needle bearing...' Can anyone recommend a suitable grease?

 

The spur sprocket now has more than the 8 thou (0.2 mm) wear recommended in the manual, so I'm looking for a replacement first of all in the UK. As the saw is obsolete, an exact replacement is unlikely, so I am trying to find a clutch drum, rim sprocket and spacing washer assembly.

 

A more recent Dolmar parts diagram shows this assembly as items 36, 37 and 38 (image appended below). There is a photo and Dolmar part numbers at Dolmar or substitute chainsaw clutch parts sought. Can anyone point me to where I can get this?

 

On another thread, someone suggested to Arbtalk member wayne 4098 that an Oregon Powermate 16372x rim sprocket drum fits. I've spent several hours trying to locate such a part in the UK, so far without success. Some leads would be much appreciated.

 

. . . and if anyone is thinking of scrapping a Sachs Dolmar 123 I'd be interested in talking to you.

[Cut4fun]

I use high temp front end bearing grease for cars disc brake wheel bearings, chassis, suspension, universal joints and constant velocity (CV) joints.