Piston Stop Tool

[OCD Solutions]

The instructions that came with my TBM Flywheel reccomended using one of these tools. I had to change out a Bendix this weekend and since I already had the tool I figured, why not finally try it? :dunno:

I have used the rope method before but more recently have been using an AC flywheel tool to hold the crank from spinning but this workd so slick I will def use it again.

I placed the piston at BDC and ran the tool in till only 2 threads were showing.

Why is everyone so scared to use these tools? I could see that if the bolt was seized on one could put more strain on the piston dome that it could handle or possibly bend a rod but I would think that for most cases this method would be very safe.

Anyways, what are your opinions? Anyone got a crappy engine we can experiment on to see how much force it takes to cause damage?

 

[steveyz250fpilot]

I wouldn't use it....that's just my pessimism though! I'd hate to hear a piston go pop.

 

[Mark44]

I use an impact and don't have to hold a thing.

Mark44

 

[OCD Solutions]

I wouldn't use it....that's just my pessimism though! I'd hate to hear a piston go pop.

#1) I used it on my backu...I mean Jen's ski. :biggrin:
and #2) I am just looking for a reason to swap in a ported 760 topend I have sitting on the shelf.

It was by far the fastest and easiest method i have used to date. 15 minutes start to finish to swap out a bendix, even with pulling the tank. Not once did it even feel like it was risking the piston.

 

[OCD Solutions]

I guess this really isn't the first time I used it, just the first time on my Yamaha engines. I tested the crap out of it when i parted my Seadoo 951 motor and it didn't leave a mark in the pistons or touch a bearing, that's what made me wanna try it this weekend.

 

[steveyz250fpilot]

It's not the mark that you can't see...but the stress you can't see either!

 

[nightrider05]

I don't understand why people are afraid of all of the methods including piston stop, rope down the spark plug and so on.

The rope down the cylinder trick is actually recommended by manufacturers.

We used piston stops in school..never had any issues.

 

[OCD Solutions]

I just can't see companies like TBM reccomending you use a tool that can cause engine damage, that opens them up to way too much liability. They are legitimate tools use on engines all over the world, why not ours? 75ft/lbs has to be peanuts compared to some of the other stresses our engines see.

nightrider05; TBM also mentions the use of the rope trick in the same instructions. :biggrin:

 

[tightithrash]

all i know is my buddy put a rope down is cylinder and now his rod is bent.....after seeing that there is no way id do something like that again.....

too sketchy imo when you can use a proper tool or an impact, not saying that tbm piece isnt a proper tool, just to sketchy for me.

 

[steveyz250fpilot]

I roll with the rope!

 

[Mark44]

I really wouldn't have an issue with either method just find it easier to use an impact.

Mark44

 

[OCD Solutions]

not saying that tbm piece isnt a proper tool, just to sketchy for me.

Better clarify here, TBM doesn't make the tool, just the flywheel. I bought the tool seperately online. I actually bought two of them thinking that i would spread the stress out on two pistons at once but one seems to be more than adequate.

I like hearing peoples opinions but I so far I have only heard 1 actual bad experience and it was against the rope trick.

Keep one thing in mind folks, I don't think that it matters what method you use for those ultra stubborn flywheels or couplers. That much overtorque is going to mess up something regardless of what method you are using, including the flywheel stop tool.

 

[DangerBoy]

A piston stop as pictured in the first post is a safe stop, provided it is used properly and is not used on offset chamber designs and is of good quality

The difference between it and a rope is that this tool applies the force to the CENTER of the piston at Bottom Dead Center. a rope will not allow for equal pressure which than tries to tilt the piston which can cause damage to the piston skirts, and you cannot set the piston to BDC which than applies force to the Rod, this tool could also cause this issue if not exactly on center

not to mention the potential to shear a piece of the rope off in the cylinder

We still recommend Our specific flywheel lock as the safest method

Db

 

[orangefinger]

impact bam done

 

[OCD Solutions]

I will have to try the Impact method one day, tried it on my Sled Clutches a couple time but unless you have a really good one it didn't have the snap to "snatch" the bolt loose.

Impact $50 for the cheapest one? Cordless? 24V $$$??

Piston stop tool, $4.95 plus S&H. not relying on battery charge or requiring 120 volts, priceless!!

I paid $14.95 for 2 of these tools shipped.

 

[Waternut]

Why is everyone so afraid to put force on the crankshaft and pistons when removing parts? Unless you really dick it up like put a HUGE rope in place that stops the crankshaft in mid stroke, you're putting exactly the same forces on everything that they're designed to withstand. The head is designed to contain the combustion and therefore can take being pushed up, the piston is designed to be pushed down, and the crank/rods is a monster that is designed to be pushed on as well.

Think about it another way, you torque the flywheel to 51 ft-lbs but inevitably use a little more force to remove it. However, a lightly modified engine can produce more torque than that and that's when things are being subjected to 1500°F+ instead of a nice cool 70°F in your workshop.

 

[nightrider05]

I just can't see companies like TBM reccomending you use a tool that can cause engine damage, that opens them up to way too much liability. They are legitimate tools use on engines all over the world, why not ours? 75ft/lbs has to be peanuts compared to some of the other stresses our engines see.

nightrider05; TBM also mentions the use of the rope trick in the same instructions. :biggrin:

I have used the Rope trick on tons of motors with ZERO problems. It was a way I was taught in school and was told its one of the safest ways(along with the piston stop tool)...however I don't have a piston stop tool in my collection.

all i know is my buddy put a rope down is cylinder and now his rod is bent.....after seeing that there is no way id do something like that again.....

too sketchy imo when you can use a proper tool or an impact, not saying that tbm piece isnt a proper tool, just to sketchy for me.

You would have to be doing something crazy to bend a rod...sure he didn't bend a rod by sucking in water?

Why is everyone so afraid to put force on the crankshaft and pistons when removing parts? Unless you really dick it up like put a HUGE rope in place that stops the crankshaft in mid stroke, you're putting exactly the same forces on everything that they're designed to withstand. The head is designed to contain the combustion and therefore can take being pushed up, the piston is designed to be pushed down, and the crank/rods is a monster that is designed to be pushed on as well.

Think about it another way, you torque the flywheel to 51 ft-lbs but inevitably use a little more force to remove it. However, a lightly modified engine can produce more torque than that and that's when things are being subjected to 1500°F+ instead of a nice cool 70°F in your workshop.

x2..the force created by the exploding air/fuel mixture is going to be greater than the small amount of force you are putting on the piston through either of the mentioned methods

 

[WILKEY]

rope trick all the way

 

[ATS_Aaron]

Tbm is f)$;:ing dumb. A piston stop tool will damage a piston. Believe me it's a sh!TTY feelng when the previously stopped engine suddenly rotates over.

TBM for the loss again.

Aaron

 

[ATS_Aaron]

I had to put down the iPhone and get out the laptop to update this one...

Piston stop tools are used for finding EXACT top dead center. NOT FOR HOLDING THE ENGINE WHILE YOU TORQUE ON/OFF A FLYWHEEL OR COUPLER. TBM is straight up retarded for recommending this.

The correct use of a piston stop tool goes like this:

1. remove flywheel cover

2. make a pointer. I use a paper clip and a short 10mm bolt (actually a 6mm x1.0 bolt, but it used a 10mm socket) that I screw into the top hole.

3. install piston stop in #1 spark plug hole and set it so the piston stops just before TDC. (turn the engine over by hand) Make this point on your flywheel at the pointer.

4. turn the engine over the opposite direction until the piston gently hits the stop again. Make another mark.

5. measure between the two marks and mark the MIDDLE. This is your EXACT TDC.

For some dumbass reason I used a piston stop while installing my new Cold Fusion couplers. I knew better but I was being lazy. The piston stop damaged the top of my front piston.

Aaron