038 chain movement

woodworkingboy

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This new old 038 that came into my hands recently, even when tensioned properly, the chain want to spin slowly at a very slow idle. Turning the rpms down to the point where the chain stops will kill the engine. I know that worn out clutch springs can be the cause of that, but the saw appears to have not had much use. I thought it might be a running issue, but I have cleaned the carb and checked it out, and the saw runs sweet. I greased up the clutch bearing too. Maybe running the saw when cutting will straighten things out, it hasn't seen much use lately. I have noticed that more torque oriented engines can have this tendency. Does anyone have an idea about how to solve this? I guess i should check it out with my tach to see what the idling rpms are, but I don't know what the recommended idling speed is. I know that opening up a muffler too much can cause this, but it was doing it before I messed with the muffler.

Thanks for the ideas.
 
Gunk buildup in the centrifugal clutch won't allow the clutch shoes to retract fully at an idle, meaning the chain will spin. I had this problem with my first Husky 346 because I over greased the clutch bearing. Over time the grease hardened and turned into a hard crud that plugged up the works. I suggest you pull the clutch shoes off and scrape out the crud.
 
It's always been a controversial subject about greasing clutch bearing as well as bar tips .My contention is that any thing holding grease should have a seal of some sort .Now of course many might not agree with that idea .

Here's what happens .The grease attracts bits of wood fiber ,grit and crud which either plugs things up or turns into grinding compound .
 
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  • #5
Thanks for the ideas about the clutch. I did pull it off to grease the bearing, but only took a superficial look at it. I might do better to examine it more closely. I've noticed that the bearing grease disappears very quick on saws, and it spins mainly dry. A reason I have thought that the Husky idea about greasing through the hole in the end of the driveshaft was a good one. Quick and easy for regular maintenance, unlike Stihl. I would guess that the vast majority of saws get run without the bearing being greased. It never occurred that greasing might not be good. I've only ever seen one bearing blow out, but that was when a saw was terribly racked by a tree.
 
A reason I have thought that the Husky idea about greasing through the hole in the end of the driveshaft was a good one. Quick and easy for regular maintenance, unlike Stihl. I would guess that the vast majority of saws get run without the bearing being greased. It never occurred that greasing might not be good. I've only ever seen one bearing blow out, but that was when a saw was terribly racked by a tree.

This is the only way it can work with greese. It pushes the crudout from inside. But it is often plugged up or not working correct as they don't do it often enough.
Better with bar oil. Pump at max and let it drip. Oil is cheep compared to repairs...
 
Jay I suggest to check the wall of the clutch drum as well.. Like the drum brake of an auto, if it is dished out and worn, might add to the issue. Not generally a real expensive part to replace. Probably costs more in Japan though
 
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I'm going to give it one good running to see where it gets me, then take it apart again if required. Wish there was more work about to check it out.
 
It would only take a minute to see if there's buildup on the clutches. Remove the bar and chain then pop off the E clip holding the sprocket in place. Slide the clutch drum off and look at it. Reach in with a tiny screwdriver or other small tool and knock some of the crud loose, blow it out and slap it back together. THEN take it out for a test run. ;)
 
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I broke it down to the clutch and it all looked pretty clean, there isn't anything hindering the spring movement. I scraped off what little crud there was, and the chain still ticked around after assembly again. The idling revs are low. It must be the springs are worn, as Ed suggested. They come up at ebay. Glad I took it apart and better checked, the oil pump was pretty loose. Thanks for the thoughts.
 
Now those are pretty stiff springs in that thing .Does the drum rattle up and down very much ? If so it could possible the inner part of the drum hole is worn or the bearing is loose as a goose causing it to rock and roll and snag a shoe every so often .

Also there's a thin little washer that goes between the clutch and the drum .If that thing is not there most likely it could catch and turn every so often .If you have an IPL it's part number 1119 162 8925
 
Does the chain spin after it gets warmed up good?? If it does you probaly have a clutch problem

It is not unusal for some of those older saws to have the chain creeping around slowly till they come up to operating temperture. Some of my older Sthil's do the same thing but they settle down after they get warmed up. Doesn't take long. My guess is the cylinder is still cold so to speak and isn't burning off all the gas mix or a minute air leak in the seals. Everything expands after the engine gets warm and seals up and the chain creep goes away.

I gave up on trying to adjust the carbs so this problem would go away. The saws didn't run quite as good with the idle turned down or the low speed turned out. I can deal with a little chain creep or spin till the engine gets warmed up.

I don't know about a 38 but I think some of the older Homelites of that same era were set at idle to have the chain creep a little even after they got hot. Strange as it may sound but this was before chainbrakes and safety concerns.
 
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I happened to have a new drum sprocket and installed it, so everything is snug around the clutch bearing, no extra play. Al, you must be referring to the washer under the clutch? It's all intact, I believe. I appreciate the part #.
Larry, the chain does spin less after warming up. With what seems a proper idle, it spins a little faster than what might seem normal with those old saws. It sure seems like it has a lot of torque, what is pushing the chain around. Not a big problem, it might sort itself out with some use. Thanks.
 
The 038's had a long exhaust meaning around 99-101 degree exhaust port timing .This would tend to lead towards more torque .

You have something around 46 thou piston /deck clearance or often refered to as squish .Removing the base gasket and using sealent in leau would probabely drop that clearance to around 28 thou which would jack the compression and lengthen the exhaust by 2-3 degrees .

What that should do is increase the torque somewhat but should slow it down a tad bit .It might cut faster with more torque ,less r's ,may not . If it doesn't just stick the gasket back in and leave it alone or do something else if you want .

The 038's are fairly easy to modify if you want and respond real well to alterations .
 
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Is an 028 built along the lines of an 038? All I did was replace the base gasket with sealant on the one I have, and it left the squish at around 20 something thou. It's a strong cutting saw for the displacement, very reliable too. I like to use it in the winter with it's handle heater. I was thinking that switching to an 8 pin sprocket might be good for the 038. Give up a little torque for some added chain speed. Maybe then eliminating the base gasket, even shaving a bit off the base to get an even tighter squish, given the eight pin, it could make for something pretty interesting.
 
The 028,038 ,042 and 048 are all the same basic design . Depending on the model that squish can vary some by a couple of thou .

Reguarding the 038 's ,the Av used an offset combustion chamber and a hemi domed piston .The mag used a center chamber and a flat top piston .

Seems to me in taking stock port degree numbers on both those models if the av might have had about 2 more degrees of exhaust .Someday I'll take the time to make note of these things for future reference .Then try to not loose my notes .:roll:
 
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