Thread: Chainsawmill running really hot :-(

Originally Posted by weaver

Well I have found the problem.
I new it had gotten hot but not that hot.
When I took the clutch cover off the plate and nut just fell out.
Not stuffed I hope but I wouldn't know? How much does a new clutch cost?

That looks to me like the clutch nut was not torqued down properly. It has to be tightened really hard and preferably using a torque wrench. As soon as it started the nut and cover came loose and laying over on its side the clutch popped one of its shoes.

When I had the sprocket changed they had trouble getting the clutch off to change the sprocket. They said that it had been "locktite"ed on. They couldn't work out why this may be so.

Maybe we have just worked out why?

I don't think Henderson Mowers of Ballarat would have made such a basic mistake of not tightening up the clutch nut enough. Espeacially when they took the care of not wanting to brake my saw when changing the sprocket but stranger things have happened.

Now what to do. I think I have a torque wrench in fact if I do I have two. One end fits into a socket, big long bar, handle with a gauge on it in foot/pounds and metre/kgs.

So I put the clutch back in (any tricks do this as I have already had a half hearted attempt). Then tighten up the clutch nut to what "tightness". Won't I need some sort of locking tool to stop the engine turning as I tighten up the clutch nut?

Originally Posted by weaver

When I had the sprocket changed they had trouble getting the clutch off to change the sprocket. They said that it had been "locktite"ed on. They couldn't work out why this may be so.

Maybe we have just worked out why?

It's pretty common to use blue loctite on the 075/076 clutches when milling as they are notorious for coming off when they cut on their side as they do in milling . Mine has come of maybe 5-6 times (it's no fun groveling for half an hour in the sawdust looking for the nut) but it has never done what yours did because I don't use the stock clutch cover. I made a custom cover that has enough room for the whole clutch to fall out. Look here; https://www.woodworkforums.com/f132/b...tml#post533871

I don't think Henderson Mowers of Ballarat would have made such a basic mistake of not tightening up the clutch nut enough. Espeacially when they took the care of not wanting to brake my saw when changing the sprocket but stranger things have happened.

Maybe they did not torque it on properly. To do that, something (the Stihl piston stop or I just very carefully use a piece of nylon rope) has to be placed down the spark plug hole to stop the crankshaft from turning and then the nut has to be torqued up - if it was was done by a young apprentice they would not know to do this. Personally I would take it back although if I was the mower dude I'd be raising my eye brows at the amount of damage and asking why you didn't stop earlier in the process, after all, the crapiata should be cutting like butter

Now what to do. I think I have a torque wrench in fact if I do I have two. One end fits into a socket, big long bar, handle with a gauge on it in foot/pounds and metre/kgs.

So I put the clutch back in (any tricks do this as I have already had a half hearted attempt). Then tighten up the clutch nut to what "tightness". Won't I need some sort of locking tool to stop the engine turning as I tighten up the clutch nut.

OK - firstly not just any old torque wrench will do. the nut is a left hand thread and the torque wrench has to be reversible (ie can set the torque in the anticlockwise direction) and not many can do this. And do you know how the correct torque?

To get the clutch on I use 2 screwdrivers and a multigrip or clamp, push one of the shoes on and clamp as far down as it will go. Then us the 2 screwdrivers to lever on the other shoes. It seems impossible at first but keep persisting - it will go on.

Before you put on the clutch, have a look at the drum bearing, see as the drum experienced so much heat that bearing could be stuffed, if it looks OK clean it and apply a little moly grease before you put it back.

Before we go any further thanks so mcuh for your help Bob. I'm sorry if I'm sounding a bit of a noob but while I have been sawing and felling for about 3 years it has all been on new saws and this milling caper is completely new to me.

Originally Posted by BobL

Personally I would take it back although if I was the mower dude I'd be raising my eye brows at the amount of damage and asking why you didn't stop earlier in the process, after all, the crapiata should be cutting like butter

Yes I know but I wasn't trying to push it through very hard and I was concentrating on every other aspect of the mill since this was its first cut and I assumed that since professionals had been doing stuff to my saw it would be ok at least at first. If this had happened after I had started cutting I reckon I would have known something had gone wrong but the nut must have come off almost straight away. As it was I stopped after cutting only about 600mm.

Originally Posted by BobL

OK - firstly not just any old torque wrench will do. the nut is a left hand thread and the torque wrench has to be reversible (ie can set the torque in the anticlockwise direction) and not many can do this. And do you know how the correct torque?

Yep the guage goes in both directions. No, I have no idea how much torque I should apply.

Originally Posted by BobL

Before you put on the clutch, have a look at the drum bearing, see as the drum experienced so much heat that bearing could be stuffed, if it looks OK clean it and apply a little moly grease before you put it back.

So here I think I need some more detail on the nylon rope trick. How thick a rope and how do I insert it correctly. Alternatively how much does a piston stop cost?

I'm guessing that to get to the main bearing I've got to take the fitting off that the clutch shoes fit around yes?

Originally Posted by weaver

Before we go any further thanks so mcuh for your help Bob. I'm sorry if I'm sounding a bit of a noob but while I have been sawing and felling for about 3 years it has all been on new saws and this milling caper is completely new to me.

Yes I know but I wasn't trying to push it through very hard and I was concentrating on every other aspect of the mill since this was its first cut and I assumed that since professionals had been doing stuff to my saw it would be ok at least at first. If this had happened after I had started cutting I reckon I would have known something had gone wrong but the nut must have come off almost straight away. As it was I stopped after cutting only about 600mm.

Don't worry I make plenty of mistakes - I just don't always post them on the web!
A couple of weeks ago I miscalculated the depth of my cut and managed to just clip a crossbar on my steel log rails and it knocked a good bit of life off the cutters.

Yep the guage goes in both directions. No, I have no idea how much torque I should apply.

75 Nm

So here I think I need some more detail on the nylon rope trick. How thick a rope and how do I insert it correctly. Alternatively how much does a piston stop cost?

The correct way to torque the clutch is using a special Stihl tool but that costs a fortune. A piston stop is not ideal since it puts a lot of pressure on a small part of the piston and neither is the nylon rope method, but if you are careful it should be OK - I and plenty of others have done this successfully many times.

Get your self about 1/2 m of clean 6 - 8 mm diam nylon rope that has no loose fibres and make sure it has no grit or dust on it (wash it). Melt the end of the rope so there are no loose fibres there either and let it cool down. Insert the rope into the spark plug hole and twist it so it forms as much of coil inside the cylinder so that it stops the piston coming all the way to the top and stops the crankshaft going around. Be careful when removing it that no nylon fibres remain inside the cylinder.

I'm guessing that to get to the main bearing I've got to take the fitting off that the clutch shoes fit around yes?

The bearing is in between the clutch drum and the crankshaft.

No, I have no idea how much torque I should apply.

75 Nm and absolutely no more than this or you may damage the piston.

I'm having trouble getting to the main bearing. I think that I have to undo the threaded fitting that the clutch boots fit around. Then I'll be able to get to the sprocket and bearing. Is this correct?

If correct how do I get it off? It is very tight and while I can probably cobble something together to get it off I don't have any sort of tool that would fit it properly.

i stuff the cylinder full of soft rope to stop it turning over ther there is a nut molded on teh clutch to put a plug spanner on

Originally Posted by weisyboy

i stuff the cylinder full of soft rope to stop it turning over ther there is a nut molded on teh clutch to put a plug spanner on

Unfortunately there's no moulded nut on the 075/076. A special tool is needed to screw the shoes on and off.

Martrix has a How to for this at
https://www.woodworkforums.com/f13/st...tml#post490553

I also made my own adapter like Tim's.

Originally Posted by weaver

New chain is definitely 3/8 which is why I got the new sprocket.

Bar and chain were purchased off Sawchain. I used both for the first time today and I assume he has given me the right gauge for the bar.

Why would bar not being parallel to rails be a problem? Surely you can cut weather boards with a chainsaw mill?

But problem. The other bars that I have for saw were to take .404 chain. Am I correct in surmising that chains with matching gauges but different pitches can be used on the same bar? If so I can hopefully just make up another chain out of the roll of 3/8 chain if it matches the guage of the bar, yes? How do I check?

Anyway bed now tomorrow I'll try the saw off the mill if all goes well.

Have seen the pics from the later thread and If this is the case I would be asking the gut who installed the rim sprocket and removed the previous 404 star sprocket. In response to the question of gauge There are TWO limiting factors regarding this 1 is the overall diameter of the sprocket driving the chain and the other is Whether you are running a sprocket tip bar or if it is a hard tip or duromatic type bar. Generally speaking if the guage is correct and you are using a duromatic bar you should get away with running a 3/8 chain on a 404 bar as the radius is easily accepted bythe smaller 3/8 chain. However if you are using a sprocket tip bar designed to run 404 DO NOT run 3/8 for obvious reasons and this applies for sprockets as well.

The other is a little more tricky to diagnose, and correct me if I am wrong bob, the 075 is a low revving powerhead and should be running an 8 tooth sprocket with 3/8 chain this ensures that the drive tangs of the chain meet the bar far enough up the bar that they do not clash on the entrance to the bar. I.E. they meet the bar approx 15 to 20 mm from the rear end of the bar well up the ramp which provides an entrance for the chain into the groove. If you were running a 7 tooth on the same bar the chain may bite into the entrance of the groove if you understand what I mean, and will show this in many different ways, one of which will be the peening of the leading edge of the straps on your chain and another will be damage to the leading edge at the bottom of the drive links.

Bar not being parrallel causes other problems one being that the bottom of the tang of the drive links rubs in the groove on the high side of the bar and the other side rubs high on the tang. This will generally cause a saw to not cut straight but also widens the groove and weekens the chain and causes excessive heat and increases the load on the powerhead, thus reducing the cutting efficiency of the saw. however this should not be the problem for overheating the clutch.

On huskies I have seen the clutch smoked because of their stupid design of chain break running as a strap around the ridiculous outboard clutch where gum and sawdust have gotten trapped between the strap and the clutch, especially when ripping, This is one of the many reasons I will buy a stihl over a husky. Many will say that the big huskies supply more oil to the bar and chain than a stihl but the fact is that they are more inneficient at lubricating and need the extra oil. Stihl have won awards because they can do what others do with far less environmental pollution and consumption of products through innovations such as their oilo matic chains. Dont get me wrong husky make some good saws too but I do not see that they even compare, especially not in saws more than 10 years old.

Honestly I would be questioning the guy who changed the sprocket over for you, because I have seen and used a lot of different saws and never had the problem you have with the nut being loose to the point it falls out. I may be wrong but I believe that the thread on it is opposing to the direction of engine rotation so that it in a way becomes self tightening. If he doesn't change the clutch for free he should at least do it at cost.

Originally Posted by weisyboy

i stuff the cylinder full of soft rope to stop it turning over ther there is a nut molded on teh clutch to put a plug spanner on

Most people use the starter rope, however there are tools which you can buy to screw into the spark plug hole. I THROUGHLY DO NOT reccomend that you buy one of these they cause more trouble than they prevent. some people I know simply leave the plug in and use a rattle gun without any blocking of the piston. this generally works but it also guarantees that you are not going to bust the top out of your piston.

Originally Posted by Travis Edwards

The other is a little more tricky to diagnose, and correct me if I am wrong bob, the 075 is a low revving powerhead and should be running an 8 tooth sprocket with 3/8 chain

The 075 is the same as the 076, 111 cc, carby governed to 10,000 rpm so it's no slouch especially given its age.
Maximum power is developed at 7000 - max torque is 5000 rpm. I haven't had my tacho on the 076 in a big cut but it likes to sit around 7 - 8 krpm in smaller log (compare that to the 880 which sits at 9.5 - 10.5 krpm)

Its not like the earlier 090 or similar vintage which max out 7 or 7.5 krpm

Originally Posted by weaver

When I had the sprocket changed they had trouble getting the clutch off to change the sprocket. They said that it had been "locktite"ed on. They couldn't work out why this may be so.

Maybe we have just worked out why?

More like they tried to take it off the wrong way possibly stripping the thread. don't laugh I have dealt with more incompetent "specialists". I buy my stihl gear from stihl dealers usually but that is as far as our relationship goes, As far as service and maintenance goes it is performed "as I go" "by myself". I have dealt with too many "COWBOYS" in the industry who are supposed to be specialists That know less about my saws than my 2 year old son.

Originally Posted by Travis Edwards

More like they tried to take it off the wrong way possibly stripping the thread. don't laugh I have dealt with more incompetent "specialists". I buy my stihl gear from stihl dealers usually but that is as far as our relationship goes, As far as service and maintenance goes it is performed "as I go" "by myself". I have dealt with too many "COWBOYS" in the industry who are supposed to be specialists That know less about my saws than my 2 year old son.

The thread holding the 075 clutch on is pretty robust, and given the stihl dealer would almost certainly use a piston stop to take the clutch off, before they stripped the thread they would put a hole in the top of the piston. I agree there are some cowboys dealers out there but for every cowboy dealer I'll bet there are 20 times more cowboy operators. It has taken me a few years but I have eventually found a couple of very good stihl dealers in my area. One of them will hunt down and find second hand parts for me and give's good free advice over the phone. I have seen them deal gently with newby's and give the cowboy operators the comebacks they deserve.

Originally Posted by BobL

The thread holding the 075 clutch on is pretty robust, and given the stihl dealer would almost certainly use a piston stop to take the clutch off, before they stripped the thread they would put a hole in the top of the piston. I agree there are some cowboys dealers out there but for every cowboy dealer I'll bet there are 20 times more cowboy operators. It has taken me a few years but I have eventually found a couple of very good stihl dealers in my area. One of them will hunt down and find second hand parts for me and give's good free advice over the phone. I have seen them deal gently with newby's and give the cowboy operators the comebacks they deserve.

Still doesn't make up for the dickheads out there who are supposed to be professional representatives of an internationally renowned company, that barely have enough intellect to tie their own bootlaces let alone service your chain saw. Chainsaws are like women and lawnmowers you don't lend em to anyone especially your best mate and you proceed with caution when getting them serviced...lol