best way to pull a clutch ???

What's the best way to pull a clutch hub ? for example, to change a wornout inboard drive sprocket, or clutch.

The Service Manual for one manufacturer says pull the muffler and insert a "piston stopping wedge" in the exhaust port. Then unscrew the clutch as usual (left hand thread.)

Frankly, I was wondering whether that was the best method -- it would seem to put the piston near BDC, which would amplify the torque through the lower bearings, as twist is applied to the crank and is transferred up to the exhaust arrow on the piston top. Jamming the lip of the piston at the exhaust port would also tend to twist the piston around the wrist pin, with the piston at BDC and minimum cylinder walls to prevent damage to piston skirts. (To me, it seems a better method to do would be to slip a hardwod block into the exhaust port, and align it with the wrist pin so there is no twisting applied to the piston skirts, and then crank piston so that the rod is about 90 degrees +/- to the crankshaft offset. That way the torque woudl go straight from the wrist pin (no piston twist), to the rod, to the crank at 90, to clutch nut. ... ??)

The nut holding the flywheel is smaller and has a lower torque rating (25 NM v 35NM, and it also looks like its right hand thread-? ), so I probably shouldn't use that ... or maybe I should try that ... ??

Or I could try to slip an adjustable steel band around the flywheel body (loosening the ignitoin gap if necessary), and rotate the tightening lug on the band until it lodges against something on the frame-- ??

Other methods - ??

Thoughts welcomed ...

rope

Put rope thru the sparkplug hole, enough to stop rotation. It has a slight cushion and will more evenly apply pressure to the top of the piston.

Molecule, l use a clutch tool on my stihl...screws in the spark plug hole..it would be easy to make with an old plug...just tig weld a stud onto the bottom of the spark plug...stud being half the length of the stroke

I second stihltechs' advice, rope it.

Some say don't use an air wrench, but I do, and have "never" had a problem. LJS

my 2 cents are if you are going to use a wrench or something in that line use the rope , I donot like piston stops , the rope puts the force alot better over a bigger area .

but I use the air wrench , never had a problem as well and to me is easier on the crank than some guy with a 1/2 inch torque bar putting alot of force on the crank trying to get the clutch off

Look in the Stihl tools catalog. There are at least 4 different piston stops listed - some screw in (both Plastic and Metal versions) and others are shaped like a "spoon" (plastic). If your saw is an older type with the spark plug in the top (say 011) of the bore, the screw in types work fine. If the spark plus is angled (like 026), use the spoon type. If you use the screw-in plastic type in the angled plugs, it will last only a few times.

I don't buy the "cushion argument" - the clutch will undo at a certain torgue, and cushioned or not, the force on the crank/rod is the same. If you're beating on the bar with a hammer, that may be a different story, but I try not to to that!

I find a constant pressure with a breaker bar is MUCH better (gentler) than using an airtool, but sometimes you have to... can't say I've ever damaged a rod or bearing either way, but....

....and, no, don't use the flywheel nut as the opposing force... sometimes it works, but oftens it simply unscrews. In any case, you will need to retorque it afterwards, and how are you going to hold it in place without messing with the clutch side torque setting?

If you clamp the flywheel as you suggest, never use an airtool on the clutch side - great way to shear of the flywheel key (on those cheaper flywheels with the key cast into the wheel). Don't ask how I know this...

i just had an idea, how about remove the flywheel, screw a second nut onto the crankshaft so it's snug against the original, then hold either the inside or outside nut with a wrench or something, depending on which way it's threaded. on the clutch side, what are you guys using to hold onto the clutch?

If you do that, you will stretch the threads.

I use rope, and air wrench, never had problems with this method.

I have had the best luck bringing it to my dealer. Hey Ed why is your phone always busy

See, you asked and I listened only one smiley per post.......

Timothy, please re-think the idea of using the flywheel end of the crank in any way to remove the clutch. The threads on the flywheel side are usually smaller than the clutch side.

Marky Mark said:

Hey Ed why is your phone always busy

Click to expand...

I think he has call display now
John

Gypo and you call me a trouble maker, wrong.
No I donot have call display,
Marky the odd person phones here wouldn't you know but that is a good thing

To bad its not a Mac because they have a hole in the flywheel and a hole in the flywheel cover so you can lock it with a screwdriver But I gues that was old school now they want you to buy a tool or take it to your dealer

Hi Lakeside53, welcome to the Chainsaw Forum!

The plastic "screw in" stops are not meant for angled plug holes like you will find on a vertically mounted cylinder. Side loading has caused them to break and leave chunks in the engine.

Steel threaded stops or the plastic spoon type are the factory alternatives for angled plug holes. The threaded plastic stops are commonly used for horizontal cylinder saws where the plug hole is square to the piston face.

My next coment is in reference to your`s regarding "constant pressure with a breaker bar", Lakeside53, but it is offered as food for thought to all advocates of this method who also all seem to be naysayers regarding the use of an impact wrench.

How many bolts, studs, threaded rods, etc.... have been twisted off using a breaker bar vs how many stuck nuts are successfully broken free with an impact? I agree, at a given amount of torque the clutch will spin free. On the other hand, reattaching the clutch using the impact could easily overtorque the crank because there is no "breakout".

I don`t believe that any bearings in good condition, which means minimal clearance and adquate radial support, are any more damaged by an impact wrench during clutch removal than they would be by the same amount of force delivered by a breaker bar. In fact I think that an argument could be made that an impact wrench and rope in the cylinder is easier on the bearings because a significant portion of the torque applied is depleted between overcoming the inertia of the static crank/con rod/piston/clutch assembly then further disappated by compression of the semi-resilient rope rather than coming up hard against a piston locking device. Also, spreading the load vs point loading is always beneficial in this case.

I also believe that the dynamic load of the alternating hammering applied in this case, because of the inertia of the crank assembly and compressability and momentary expansion of the stop, will ultimately deliver less force to the bearings, of course I turn the pressure down on the wrench as well.

There now, this should provide enough fodder for someone to jump me since this place is in need of some lively debate.

BTW, I saw Ed`s caller ID when I was at his house. I don`t know why he is avoiding you Mark?

Russ

When using the rope method, be careful not to lower the piston too far. That will avoid getting the rope into the open ports with the risk of shearing a piece off.

I prefer the rope method over the stops, I've seen pistons get damaged using those stops. I put a bight in the rope instead of just using the end of a rope. I stuck the end of a rope in a cylinder once, got it hung in port and almost sheared the rope, had a hard time getting it out, after that started using the bight method and never had a problem. Experience is the best teacher on clutch jobs, especially with a bigger saw and a stubborn clutch.

Larry

Rope-A-dope it!

Lakeside, Russ made the point already but.......Impact wrenches loosen frozen fasteners that a cheater bar wont budge or simple will break. The reasons have to do with the energy transfer via sudden impact and vibrational patterns set up by multiple impacts etc. -Bottomline is -Anyone who has worked on a bunch of stubborn bolts with both tools knows that the impact is more likely to get things loose without breaking something.