adjusting clutch on McCulloch Mac835AV chainsaw

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  #1  
Old 05-08-10, 09:51 AM
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adjusting clutch on McCulloch Mac835AV chainsaw

hi.

I can't adjust clutch on my chainsaw, either the chain moves permanently (even when pulling chord, or when it runs idle), or it won't run at all (even when you press the accelerator to the maximum).

I tried adjusting it's nut in smallest steps I could, but it just won't work normally - when it runs idle, chain shouldn't move, when you press accelerator, it should start moving.

I've even found this manual online and seen that the necessary torque to tighten that nut is 180 IN/LBS, so I measured the length of my wrench and used scale to pull it with force necessary.
In fact, I could only get to only half of the force necessary, because the spring under the clutch was already pressed and deformed to maximum and the nut is too tight again, because the chain moves all the time.
So it didn't help.

This is how the clutch looks in reality and I've replaced old spring because it became deformed after trying all possible torques on the nut, so the new spring is the one with thicker wire, but with it, same as with original one, the adjustment just can't be done...

Could you tell me what I'm doing wrong and how to do it right, please?
This nut is making me nuts, literally.

Thanks in advance, if you need some extra info, just tell me please.
 
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  #2  
Old 05-08-10, 12:54 PM
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Flip the drive weights over (the one in the middle with the heavy spring around it) and post that picture. You either have something missing or the drive is bound up against something.
 
  #3  
Old 05-08-10, 01:00 PM
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  #4  
Old 05-08-10, 02:43 PM
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Yup, take that thing, by itself and see if it's keyed to the end of the crank - where you screw the nut onto. In other words put it on the end of the crank and see if you can turn the engine over by turning that drive by hand.
 
  #5  
Old 05-08-10, 03:00 PM
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There's a needle bearing in there & if it's siezed, the chain will run all the time... If it's siezed,, check the condition of the crankshaft as I think the bearing runs on the crank as an inner race.... Roger
 
  #6  
Old 05-08-10, 03:05 PM
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Yup, the needle bearing is in the drum, but he's not getting a drive in higher rpms = may be missing the key to the drive.
 
  #7  
Old 05-08-10, 03:25 PM
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Marbobj,,, Are the weights of the clutch not threaded onto the crank??? I'm not real sure about this model,, but any saw I've had apart,, the clutch drum went on the crank,, than the center part (the weights) were screwed on to the thread on the end of the crank,, (Turn clockwise to remove)... I may be wrong tho, as I said I'm not sure about this saw,, & I don't recall any adjustments to the clutch as he mentioned... Tks,, Roger
 
  #8  
Old 05-08-10, 03:32 PM
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Marbob,, I looked @ his manual closer & I think you'r right,, It appears as if the nut after the dust shield holds everything together... I think your right,, either the key is missing or if it was a part of the clutch,, it's sheared off & requires the center part of the clutch replaced... Roger
 
  #9  
Old 05-08-10, 03:35 PM
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I don't think this is a normal setup, like you're talking about. I believe this is a keyed to the crank drive and everything is held together with the spring and end nut.

If that is the case, I don't know why they did it like that. Most saws have the reverse threads on the drive and no end nut. That keeps the drive in perfect alignment to the crank. Then the drum aligns itself when it engages.

We'll get him figured out, but we have to get a couple more pictures.
 
  #10  
Old 05-09-10, 08:27 AM
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Thank you guys, I appreciate your effort very much.
I see you've got interested in this and I'm really glad you have.

Here, I think it's the best if you see the problem for yourself, I've recorded a 8 minute video showing all the parts in question, trying with both new and old spring and I just can't adjust this thing correctly.

I don't see anything wrong on the assembly or it's parts, no key marks, needle bearing looks good and working, nothing else there. Drum looks good to me to, I've tried separating jaws with screwdriver and I could do that (hard to do it but it can be done).

So here's the video, if you need some more info or some other details on any of parts, just say.

drop.io vt53r7j
 
  #11  
Old 05-09-10, 10:14 AM
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That setup isn't keyed to the crank, but you haven't got enough pressure on the drive from the nut. The shoulder of the crank may be damaged and worn a little.

When the nut is tight, the center of the drive should be locked to the crank. The clutch engages when the flyweights kick out and engage the drum.

Just for diagnosis, leave off the outter disk (dust shield) and put the nut on without it. See if torquing the nut down locks the center of the drive to the crank so you can turn the engine over by turning the drive (the thing with the heavy coil spring around the weights).
 
  #12  
Old 05-09-10, 11:53 AM
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Alright!
Seems like I did it.
Thanks again for all your advices!

This is what I did.

First I removed everything except the drum (clutch) and the central drive. I tightened the nut on those two and that proved me that it works fine, the drive was tight on the crank and moved the piston when rotated, while the clutch was free.

Then I removed old spring and it's limiter ring (washer) to insert new, wider and weaker spring which now presses on the engine casing on one side (entire crank goes through it) and the clutch drum on the other side.

Then, when you set clutch and drive and dust ring in place, it works correctly. (I still don't know why the original assembly won't work, but it just won't).

Now that this is done, it looks like there might be some power issue, it seems less powerful now, so I guess I'll have to learn how to check for compression, 'cause there might be a leak somewhere (I had to tear entire engine apart to get new sparkplug thread, so maybe now some of my gaskets isn't doing it's job, or there's a leak under sparkplug...).

Anyways, thanks for your help again and marbobj thanks for your advices on the other thing, B&S lawn mower, after I deal with these other things on my list, I'll listen to your advices on that one.

C ya.
 
  #13  
Old 05-09-10, 12:09 PM
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Is this saw one that you just bought or have you had it and it was working before.

The problem is not being able to lock the clutch drive to the crank. The spring that you have on it - I'm not figuring out what that thing is even for. I'm speculating on this a little, but I would suspect, if this is a saw you haven't had since new or at least in a complete and working state, the following has happened....

The inside shoulder of the crank that seats the rear of the clutch had gotten worn and someone put the spring on it to hold the drum over against the clutch. The manual you have posted isn't showing that spring.

When you tighten the end nut the dust shield seats against the outter most shoulder on the crank and doesn't allow pressure on the clutch drive to lock it to the crank. The distance between the two shoulders that borders the clutch is too great.

That setup isn't one of an adjustable clutch - the clutch engages and disengages based on rpms and is solely within the clutch drive. The rpms of the engine exert a centrifugal force on the flyweights of the clutch - they engage the drum, the rpms drop and the spring around the weights pull them back in release the drive to the drum.

The fix is pretty simple which is putting a small shim washer between the clutch drive and the rear shoulder. There are other things that could be done, but that would be the simplest. Since the spring isn't shown on a parts list, I would be inclined to take it out altogether and see how everything fits.
 
  #14  
Old 05-09-10, 12:15 PM
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We'll just leave it that you got it fixed. That's the important thing. I still don't know about that spring, though. Maybe that's a version of a saw that isn't in the manual.

I was just writing the previous post while you were writing yours, so disregard it since you're up and running.

You write better English than I do. I thought Croatia was more of a Slavic language?

Take care.
 
  #15  
Old 05-09-10, 02:21 PM
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1. the chainsaw is like, 10+ years old. all the parts are original, no one has messed with this clutch assembly before, I'm the first and only owner.

2. You're right, I've just noticed there is no spring in the manual. I first thought it's listed under number 77 in figure 2, but after checking more closely, it turns out to be a needle bearing!

However, before I had to dismantle whole thing, it had worked perfectly as it was.... so I'm really boggled by this weird setup.

3. Sure, Croatian is a Slavic language, but I don't see what it has to do with me writting English. are, in your knowledge, slavic people having more problems learning english?
anyways, I'm not that happy with it, I was much better just a few years ago, while we were having courses in university (technical english for students in mechanical engineering)but then I got lazy and stopped using it, so now I'm having problems even with simpler words and/or sentences, it takes longer for me to recall how to say this or that, not mentioning more and more undermining vocabulary&grammar errors showing up.

Interesting, but every time I return to this topic to check for new answers, I find myself re-reading some of the old posts and finding all those silly little beginner errors (which were highly unlikely to occur, in that volume, before).

But hey, practice makes perfect, ehBeer 4U2
 
  #16  
Old 05-09-10, 03:01 PM
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Sure, Croatian is a Slavic language, but I don't see what it has to do with me writing English. are, in your knowledge, slavic people having more problems learning english
No I didn't mean that at all. I think it's an unfair expectation for everyone on the planet to be able to read and write English. I thought maybe you had a background that steered you in that direction.

We get a lot of posts from Canada, Australia, and Great Britain. It's interesting to get input from those areas.

Small world

Take care
 
  #17  
Old 05-09-10, 03:17 PM
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Oh, I see.
No, no 'background'.

Small world, I agree, but at least temporarily, the volcanic ash cloud is making it bigger again.
 
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