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Hi all! Anyone have or use a piston stop when working on their mowers or other lawn equipment? I have done the rope in the cylinder trick when trying to remove a clutch on a 2 cycle trimmer but thought for the cost investment it might be nice to buy one of these. They are listed as no longer available as a Lawnboy part but I have been able to find a lot of aftermarket ones. I see some have a center adjustment feature as well. Any thoughts whether these are worth having. I know when trying to remove the blade on a mower the "hold the blade with a rag method while turning the nut" isn't always the best choice and I have tried the "wedge a piece of wood in there method" and that doesn't always work either. How do you know what length to buy or are they standard or would the adjustable one be a better choice and if so, why. Also, while on the subject of service tools, I have been thinking of some additional specialty tools to have for servicing the mowers. I would really like a seal puller although I don't do enough seals to warrant buying one at this time. I know a lot of you use a piece of pipe to set your seals and I have done this but the Lawnboy tool sets the depth the same all the time. I may try to find a way to modify my seal setting pipe so it has a depth stop. Also would really like a small tach for checking the mowers. I have researched and have seen everything from $150.00 handheld digital tachs to the mechanical Vibratach. Have see a few that look like they are supposed to be mounted to the equipment and give RPM and hours. The wire wraps around the plug wire and the unit is grounded. Anyone use one of these as they appear to be a good value for the price but I don't think they are resettable. Give me your thoughts as to the best and most accurate and easy to use tach for the best price. Thanks, Bill
 

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If you can't get the blade nut off using a 2 by 4 for a stop and a 1/2'' breaker bar,
don't try to use a piston stop.
Take the mower to a garage and have them get the nut off with an impact gun.
Experience taught me a hard lesson years ago.
 

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Discussion Starter #4
If you can't get the blade nut off using a 2 by 4 for a stop and a 1/2'' breaker bar,
don't try to use a piston stop.
Take the mower to a garage and have them get the nut off with an impact gun.
Experience taught me a hard lesson years ago.
Thanks for the info Ron! I have an impact gun but have never needed to use it on a mower. I have always been able to get the blade nut off using one of the before mentioned methods although it is not always the easiest. Also when reinstalling the blade collar and blade the crankshaft has a tendency to turn until you get the nut on far enough that the collar grabs so I thought the piston stop would work well for this as well. I used a piece of rope on the last mower to keep the piston held until the blade collar was snug enough to tighten all the way. Thanks, Bill
 

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You're right the piston stop will help you get the blade collar locked on the taper, though it's not necessary. With the collar locked to the crankshaft I usually torque my blade nut with the mower laying on it's side (empty fuel tank) by holding the blade with one hand (heavy rag of course) and the torque wrench or breaker bar with the other. You should be able to loosen the blade nut this way, if not it may have been overtightened. Also, always use never-seeze on the threads. Torque to 525-650 in lbs.(manual). Remember the collar is supposed to slip on the crankshaft if you hit a pipe or other immovable object. The Lawn Boy piston stop holds the piston at about mid stroke,you don't want to hold the piston very close to tdc or bdc since with enough torque in may pass by. Needless to say I don't use the piston stop when tightening the blade, but I sometimes use it for tightening the flywheel. A adjustable piston stop is useful if you check your timing with a degree wheel, which I don't think anyone does. As for tachometers I bought the Tech Tach tt-20k. It was worth the price since it does exactly what I want: press the button, hold near the spark plug and read the RPM.
As far as other special tools go, everyone usually gets what they think they need. I don't have all the factory Lawn Boy tools, but I do have many specially made for my own use.
 

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I was always too afraid to use a piston stop as it would create too much pressure on the piston and bearing behind.

I made one that could be used as a piston stop from an old spark plug with the ceramic busted out then I welded a nut on and threaded a bolt through the nut.
I mainly use it to find true tdc on my VW's though but it technically could be used as a piston stop.

Not real pretty but it works....
 

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Discussion Starter #7
Hi Guys! Thanks for all the useful info. I may pick one up for the trimmer clutches and maybe to remove the flywheel on the mower or to get the blade collar snug before tightening. Bill
 

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For what it is worth, I also put some lithium grease on the threads and that helps it when removing it. I do the same thing on the threads of my car lag nuts when I rotate tires. Never had a problem.

As far as the flywheel removal I use a Sears rubber adjustable strap and it is easy to remove the flywheel.
 

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Discussion Starter #12
:ditto: :ditto:

The steel will damage the soft aluminum piston!:Stop::Stop:
Hi! I wonder why the online Lawnboy service web site still shows the piston stop being used although they are only showing it for flywheel removal and not blade removal which would put a lot of pressure on a concentrated area. I have also seen the devices that clamp onto the housing and hold the blade from turning but I may try an old style wooden double handle screw clamp just to hold the blade to get the nut broke loose. If the collar is not taken loose then reinstalling the blade is not a problem however if the collar is loose the crankshaft turns because of the locking feature of the nut before you can get enough pressure on the tapered collar to tighten the nut without the crankshaft spinning. I may have to use the rope method to hold the piston or just use very little pressure with a piston stop just to get the nut snug and then remove the piston stop and tighten the rest of the way. I will not use the stop to remove the blade based on all the information I have received from the members here on the forum. Thanks to everyone for weighing in on this question. All of your input is greatly appreciated. Bill
 

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Hi Bill, I've always used the rope method myself. I'd rather have the cushioning effect of the rope as it compresses. I've used a large vise grip clamped onto the deck to hold the blade in place much like that contraption shown above, or I've just put my foot on the lower rim of the deck and turned the blade up to my booted foot to hold it. Either way, the spark plug is out of the mower and across the room on the work bench, of course. I gotta' get me a tach and an impact someday though.
 

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I just impact them off, if that doesnt work the 2 by 4 comes out along with the breaker bar and the nut usually comes off. Those blade adapters can be a pita, but if they dont pop off i usually wind up cutting the collar off. One time i had to cut the crank on a mower but it was for parts anyway LOL.

To remove clutches and flywheels on saws i take have a black plastic piston stop and they come off.
 
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