What is everyone's thoughts on AIP pistons?

[Freakingstang]

Just like the question in the thread title, What is everyone's thoughts on AIP pistons?

Dean, please do not partake in this thread for a while. I had a bad experience with one in an 066, but would like to hear what everyone elses experience has been with AIP. I have pics of some damage of a piston, but will wait a couple days to post pics. I am not hear to rag on AIP, but more of trying to find out if there have been any other problems.

-thanks
Steve

 

[04ultra]

Dr.Freak I have one sitting on top my computer as we speak...Havent had to use it yet..

 

[Freakingstang]

Dr.Freak I have one sitting on top my computer as we speak...Havent had to use it yet..

After what I had happen....I wouldn't use it. A bottom end isn't worth saving 50 bucks or so....

 

[NWCS]

i have one thats been sitting here on my desk a while. what damage happened? sure it wasnt an airleak or something else that got it? post some pics

 

[Freakingstang]

Positive it wasn't an air leak... Lets just say that these pistons are cast, not forged. I am still picking pieces out of the crankcase. The saw wasn't even running when the damage happened.


I was removing the Clutch assy to access the oiler. I had 3/8" rope in the combustion chamber. (piston stop). Yes the piston was above the port openings in the clylinder. When breaking the clutch lose, I heard a pop, and naturally thought it was the clutch releasing.....Took the clutch off, and went to turn the motor slightly to remove the rope....It wouldn't turn. The piston pretty much exploded. The center support for the wrist pin is gone, and both skirts broke off. The top of the piston looks fine. go figure.

Before you bash me, I have used this technique on at least 15 other saws, still with the factory mahale pistons, and never had a problem. I do not use and actual piston stop, because that too can cause damage even with a good piston.

I'll get pics up later when I have the saw in front of me.

-Steve

 

[THALL10326]

Positive it wasn't an air leak... Lets just say that these pistons are cast, not forged. I am still picking pieces out of the crankcase. The saw wasn't even running when the damage happened.


I was removing the Clutch assy to access the oiler. I had 3/8" rope in the combustion chamber. (piston stop). Yes the piston was above the port openings in the clylinder. When breaking the clutch lose, I heard a pop, and naturally thought it was the clutch releasing.....Took the clutch off, and went to turn the motor slightly to remove the rope....It wouldn't turn. The piston pretty much exploded. The center support for the wrist pin is gone, and both skirts broke off. The top of the piston looks fine. go figure.

Before you bash me, I have used this technique on at least 15 other saws, still with the factory mahale pistons, and never had a problem. I do not use and actual piston stop, because that too can cause damage even with a good piston.

I'll get pics up later when I have the saw in front of me.

-Steve

Yikes, not good. The way you broke the clutch loose is the way most everyone does it. I've use a plastic piston stop and have crushed them removing clutches but have never damaged a piston. That piston your speaking of doesn't sound too good although I admit I've never seen one or had any dealings with one. I'm factory all the way, no Stihl logo on the part no go in the saw. I read a thread awhile back where someone cracked a piston in a Poulan saw while getting the clutch off so I guess it does happen.
Post those pics Stang, I'd like to see that piston.....

 

[NWCS]

i recently did the same thing with one of my husky 181s. good thing i have spare pistons. did get me to come up with a safer way to pull the clutch on saws. after this happened i did split the case and replace the crank bearings for safety.

http://www.nwchainsaw.com/piston.jpg

 

[Lakeside53]

i recently did the same thing with one of my husky 181s. good thing i have spare pistons. did get me to come up with a safer way to pull the clutch on saws. after this happened i did split the case and replace the crank bearings for safety.

http://www.nwchainsaw.com/piston.jpg

So what's your safer way?


I use the rope method (tired of the plastic thingies breaking) and never have had a problem. Taken off some real brutes this way.

 

[NWCS]

Lakeside: the husky 181 has a pretty thin delicate piston in the first place. i milled a chunk of UHMW plastic to put between the crank weights and the case to pull the clutch and flywheel on the 181. part of the problem was the clutch was on REAL tight.

 

[Big Woody]

Important equation

part of the problem was the clutch was on REAL tight

= 1/2" Impact wrench

Or make yourself a Virginia Wife Beater (AKA custom long handled clutch removal tool)

http://www.arboristsite.com/showthread.php?t=31654&highlight=makita+clutch+removal

 

[Lakeside53]

Lakeside: the husky 181 has a pretty thin delicate piston in the first place. i milled a chunk of UHMW plastic to put between the crank weights and the case to pull the clutch and flywheel on the 181. part of the problem was the clutch was on REAL tight.

Ha! I use the Stihl square plastic Carb screwdrivers for the same thing - They slide nicely down the sides of the open crankcase and lock the crank weights! Some get bent up real good, but...

 

[cord arrow]

yep. heavy glove holding drum, one super quick triggger pull, done. on or off.

never lost a drum, never broke a piston, never had an issue.

torque? coupla quick hits with the brake at full throttle. easy. perfect.

never really understood this nonsense...

 

[Freakingstang]

yep. heavy glove holding drum, one super quick triggger pull, done. on or off.

never lost a drum, never broke a piston, never had an issue.

torque? coupla quick hits with the brake at full throttle. easy. perfect.

never really understood this nonsense...

You serious? Maybe if you tried this on a large saw that had some serious torque holding the clutch or flywheel on. This isn't your average 55 rancher. It is an 066 that has been together since, 1991 or so. I have broke many of starter paws trying to do what you described. But it does work on the smaller saws, like a 55 rancher, or ms290.

 

[Lakeside53]

yep. heavy glove holding drum, one super quick triggger pull, done. on or off.

never lost a drum, never broke a piston, never had an issue.

torque? coupla quick hits with the brake at full throttle. easy. perfect.

never really understood this nonsense...

Good luck on a modern Stihl... How ya going to hold the drum on an in-board drum system???

And... they should be torqued... The correct torque will allow it to be undone without excessive force. Put it on loose and then hit the brake - you will invariably over-torque the clutch.

The reason a correctly torqued clutch does not over-tighten by the same brake appication is that the break-away torque is much higher then the dynamic torque applied when tightening. That why you should never stop when nearly torqued and then attempt to keep going without backing off the clutch - i.e. one smooth motion to the correct torque.

As for an outboard clutch hand held... I had an 051 that needed nearly 140 ft'lbs to break way...

 

[Lakeside53]

You serious? Maybe if you tried this on a large saw that had some serious torque holding the clutch or flywheel on. This isn't your average 55 rancher. It is an 066 that has been together since, 1991 or so. I have broke many of starter paws trying to do what you described. But it does work on the smaller saws, like a 55 rancher, or ms290.

Uh... the MS290 has an inboard clutch...

 

[Freakingstang]

Uh... the MS290 has an inboard clutch...

Ooops. You got me there Andy...I was going off of memory...You're right, it does, and i must not have done that on that saw..

Anyways, pics will be here in a few...


-Steve

 

[Freakingstang]

here are a couple pics. I can get more later if needed.

First pic. Piston is broke in this pic, but I "assembled" the broken pieces to show you the top of the piston. There isn't a bit a damage or marring to the top of the piston. There is also a piece of the rope that caused the damaged. it is 3/8" cotton rope.

Pic two shows some of the pieces that came out of the case.

pic three is the underside of the piston.

These pistons are obviously cheaply manufactured. From the break being so clean, it leads me to believe that these are cast instead of forged. Forged pistons do not break clean. They can break, but it usually distorts the piston, looking much more like severe beating damage than a clean break.

 

[NWCS]

Freakingstang: DANG that does look pretty bad. i have never seen a piston that bad! yeah i would have to agree there is something wrong there with the alloy used. i have put the baileys pistons through some heavy stress and come out with flying colors. looks like a bomb went off in that piston.

 

[Dan Forsh]

Freak, why don't you contact the manufacturer?

www.aippistons.com

They claim they are ISO 9001 and their site goes to great lengths to stress (sorry bad choice of word) the quality of their products.

If they are a serious business I would think that they'd take interest in your findings.

There is a feedback section on the website.

Dan

 

[Lakeside53]

The ISO9001 doesn't mean they are as good as OEM - it just means that the factory has QC and QA in place such that everything coming off the line is built to the standards they put in place. Question is : what are those standards?

I haven't seen any pistons from Stihl that are forged. They are all "cast". The question for the aftermarket pistons is "what are they cast from" .... recycled aluminum or virgin 2021 (or whatever Mahle uses) alloy, and what heat treatment was done after casting and then (sometimes) after machining.

I'm sure the manf. would give you a new piston, but would you feel comfortable in using it?

Mahle is one of the the world's largest piston manufacturers. The 066 has pushed them to the limit - even their pistons have had problems with heat and have been revised a couple of times. The 084/088 have an iron heat disk cast in to the piston to alleviate this issue, and that engine isn't a huge leap in HP over the 066 Dual port Magnum (7.7 to 8.7), roughly. I'd be suspicious of any aftermarket piston in large saw.

Freaken: How tight was your wrist pin fit? I've noticed many of the aftermarket piston pins are really loose. The Stihl/Mahle fit is an extremely very tight specification: Bore +0.002mm to +0.006mm -> figure that in 10,000ths of an inch!. It's a narrow range tight interference fit often requiring heating of the piston in hot water for easy insertion. If your pin was loose, even up to 1 thousandth of an inch, it could have fractured the piston from vibration. As the piston gets hotter, the fit gets looser as the piston alloy expands faster than the steel pin. I see you used the AIP pin. The Stihl pin has a ground taper bore to reduce weight and possibly thermal considerations. The AIP is a straight bore weighing considerably more.