Here's a good read on thumper talk...I hope the link works.
6 years on the same piston! - ThumperTalk
6 years on the same piston! - ThumperTalk
Joeak47's thread on cast piston VS wiseco forged piston.
- Thread starter joeak47
- Start date
If the arguement about less noise and less thermal expansion are true, why are you running the piston to cylinder clearance more on the cast than the forged? The yamaha factory service manual recommends no more than .0016" of piston to cylinder clearance for a stock "ART" piston (cast).
Manufacturers do build engines with cast pistons. Manufacturers do worry about longevity and their name. Manufacturers will also make silly insane decisions to save a few dollars during manufacturing (drum brakes on the blaster versus hydraulic!!!!).
Also, ART is made in Japan (direct source for the manufacturers over there) while wiseco is made in the USA....
Cast pistons (when their clearance is set correctly) DO make less noise and aren't TOTAL bunk (they can run quite well). However, it's what happens when they come apart that means I will run a forged piston only in my motors.
Manufacturers do build engines with cast pistons. Manufacturers do worry about longevity and their name. Manufacturers will also make silly insane decisions to save a few dollars during manufacturing (drum brakes on the blaster versus hydraulic!!!!).
Also, ART is made in Japan (direct source for the manufacturers over there) while wiseco is made in the USA....
Cast pistons (when their clearance is set correctly) DO make less noise and aren't TOTAL bunk (they can run quite well). However, it's what happens when they come apart that means I will run a forged piston only in my motors.
yea i agree with sivic. if im running a cast piston, and i have the power gain and everything, u check it, leak test comp test. yada yada... but edventually something may happen when ur riding where the piston will jusst break. and usually on cast pistons, its the skirt and that drops into the bottom end and destroys it. forged dont break that eaisly. so for the little power loss or worse ring design, the fact that if the piston breaks, it usually cracks, and shuts off. but 90% of the time they dont drop into the bottom end. BUT when they do, like slick said, its probs garenteed to do more damage then cast. so therefore the peace of mind knowing i dont have to worrie about a bottom end getting destroyed if the piston blows, its worth the extra 10$ and little power loss.
but awesome testing! I:I
but awesome testing! I:I
I totally get what your saying.
However...I set the clearances within the manufacture's recommendations. Actually I fudged a bit extra on the wiseco by an extra .001, because I like to compensate for the added expansion (they need it). Wiseco says the clearance should be .002 (on the box), That in my opinion isn't enough,and I guarantee the scuffing would have been much worse than it was,if not locked up in the bore. Even wiseco's "old school" recommended clearances for the piston would have been .003 to .004
I totally get and know that the factory recommends .0014 to .0016 clearances on the factory yamaha piston that is made in japan (ART).
However... The WSM pistons are not made in japan. They are made in taiwan... Like I said, I was doing this test with a cheap cast piston. The recommended clearance for the WSM piston is between .0028 to .0035 ,so I decided to put it in the middle of they're recommended clearances.
If I was doing this test with an oem yamaha piston (japan) I would have set up the clearances at .0015 like the factory recommends. Maybe even at .002 because of the heat I run in. Factory wear limits are .004
I'm going to run this piston for a while,then I'm going to pull the cylinder to check it out. We'll see how it looks when it comes out. Who knows...that cheap cast piston just might explode and create a mushroom cloud that rolls out from under my fuel tank (doubt it). In the end game its fun to experiment and see what happens. Thats what this is all about. Its fun to learn.
Remember all the old wives tales and myths that were out there before the "Mythbusters" came about? They proved and disproved many of them. Its fun what people use to beleive was the truth.
Anyway here's some more pictures...
Wiseco clearances on the box
WSM's recomended clearances
This is the "Old School" instructions that wiseco use to include with they're pistons.
Like I said before, wiseco make a good piston. Always have. I've run them before. This experiment (that I'm not done with) is to test all sorts of things.
The ring design that the wiseco piston uses is a good design and works well. I just think that the keystone design tends to seal a bit better.
I hear you when you talk about the breakage and case damage. Hopefully that won't happen. If it does,then I'll go with an OEM cast piston thats made in japan (ART).
Here's a nice one. Amazing what happens when some jackwagon doesn't add oil to his fuel,or forgets to fill his oil tank.
No oil = lots of problems
This one probably could have gone a few more years if there was lubrication
I use one of those cheap,wobbly,three finger hones from walmart. They're not as bad as people say. It works great! Its completely adjustable. I highly recommend it! This is the one I have....
Disclaimer: >>> KEEP READING... KEEP READING ALL THE WAY DOWN TO THE BOTTOM
Actually I have access to a sunnen AN-111, ammco 3950,and had the pleasure of using a buddy's sunnen ck-10. The key,in my opinion is to have long stones,or longer that cylinder is tall. the AN-111 staones are about 4" long. The ammco's is around 3 1/2". If I need a sleeve done he has the kwik-way boring machine. The portables (AN-111,and Ammco 3950) are rigid,positive pressure hones.
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I use one of those cheap,wobbly,three finger hones from walmart. They're not as bad as people say. It works great! Its completely adjustable. I highly recommend it! This is the one I have....
Actually I have access to a sunnen AN-111, ammco 3950,and had the pleasure of using a buddy's sunnen ck-10. The key,in my opinion is to have long stones,or longer that cylinder is tall. the AN-111 staones are about 4" long. The ammco's is around 3 1/2". If I need a sleeve done he has the kwik-way boring machine. The portables (AN-111,and Ammco 3950) are rigid,positive pressure hones.
You use a Spring loaded hone to Bore ?
Yeah Joe, I bought a 2000 KTM 125 and ran it 6-7 years with the stock cast piston. Never a problem. Unfortunately I swamped it and it pinched the ring, otherwise I'd STILL be running the same piston. Short on money and time, I filed the ring groove clear and drove it another year. Swamped it yet again (same run, same hole, sort of like this: KTM through deep water. | Facebook Quads are better at hitting hidden logs under water) and drove it 80 kms home before replacing it. The KTM 125 pistons are short and have well webbed skirts, not prone to cracking (they have but not often or severe) and rarely break.
Incidentally, a nice thing about small displacement bikes: with no compression, ring completely pinched in, a two stroke will start and run if turned over fast enough. My 125 would not start on the kicker, but could be pushed in gear and started. It would not idle even with the screw turned up, but it ran fine at reduced power and took me home at road speeds on the highway. A larger displacement bike would have dragged the tire if you tried to push start it, although it might start on a tow in a higher gear. Neil rode his Blaster home with a hole in the bottom of the case. Awsome machines 2 strokes!
This is a well worn KTM 125 cast piston with many highway miles on it. Note the erosion where the gasses have actually eaten a groove in the piston at the ring gap, and yet the piston skirt is still fine. Highway rode 2000-3000kms/yr for 2-3 years before I opened it up here for an inspection:
This piston was worn too small at the skirt and was replaced with a Wiseco. A few months later the Wiseco seized up 2 miles (3kms) from home while I was accelerating around a corner at 65mph. The back tire locked up and I went down and slid across the oncoming traffic lane. Bike had been warmed up for several minutes although I had been using only the rear tank so the carb may have leaned out. Piston showed a 4 square cold seizure. That was about 3 years ago and I am back to running cast pistons in the KTM 125 with no problems since.
See here what the back tank is and how it could starve the carb under strong acceleration:
So, we have practical experience of cracked and broken Blaster pistons, and them breaking into bits.
We have experience of broken Blaster piston skirts being punched out of the bottom of the engine.
We have true experience of other cast pistons lasting many years of hard use.
I have experience of properly fitted Wiseco pistons cold (4 square) seizing in bikes, snowmobiles and jet-skis.
Cast pistons do not tend to cold seize. Forged pistons do not tend to crack or break but tend to smear.
For anyone looking on not understanding, here are some pictures of what we are talking about:
Cracked and broken cast piston on the left, cold seized forged (I believe) piston on the right.
Note the unscuffed skirts of the piston on the right. This is typical of a cold seize. The piston grew larger in diameter than the bore of the cylinder and rubbed hard in the 4 corners rather than the skirt. Notice the scuffing on the broken piston on the left? That is a sign the skirt took some abuse, whether from heat expansion, detonation, too much clearance or no lube, cannot tell from the photo.
Forged pistons really do resist shattering. That is their ace in the hole, but note too the rings on the right piston are stuck hard into the grooves. Forged pistons smear and coat the bore with smeared aluminum that has to be removed chemically when they fail.
Again, we may not be comparing apples to apples. Both these pistons show obvious signs of abuse. The one on the left has been running hard on its skirts for quite a while. Worn out and sloppy? Detonation? Over revved? Overheated? We know if you don't have these conditions this piston could have run many years. I think we can safely say that a forged piston would probably have eventually failed here too, but would not have broke. It may have seized, knocked, smeared the bore, cold seized, or lost compression, but it likely would not have broke.
The piston on right has been run hard when the engine was cold. It has happened to me many times unfortunately. "Warm up" has to become a religion if you are running forged pistons. "When in doubt, go slow" is not inspiring from a performance perspective, whereas any idiot can jump on a cold cast piston and give it hell. It will stand it for many years.
I am thinking that the tall windowed skirt of Blasters and YZ Yamahas are prone to cracks and breaking (Neil had a YZ125 and DT200 that do this too) whereas the shorter KTM cast pistons are more stout. This would make running a forged piston in my KTM pointless, but a serious consideration for a Blaster or YZ.
I am thinking that the trouble free (warm up not essential) nature of the cast pistons, combined with their less noise and potentially more power is worth having, but warrants some investigation about cracking, what is causing it? Or is it just the nature of this cast piston design to crack?
So, can you make 30-40hp in a Blaster while watching the bore clearance, detonation and heat (all of which will kill a forged piston too) and have a cast piston live a long life?
Set our opinions aside, Joe is on the way to answer that question. Thanks Joe.
Incidentally, a nice thing about small displacement bikes: with no compression, ring completely pinched in, a two stroke will start and run if turned over fast enough. My 125 would not start on the kicker, but could be pushed in gear and started. It would not idle even with the screw turned up, but it ran fine at reduced power and took me home at road speeds on the highway. A larger displacement bike would have dragged the tire if you tried to push start it, although it might start on a tow in a higher gear. Neil rode his Blaster home with a hole in the bottom of the case. Awsome machines 2 strokes!
This is a well worn KTM 125 cast piston with many highway miles on it. Note the erosion where the gasses have actually eaten a groove in the piston at the ring gap, and yet the piston skirt is still fine. Highway rode 2000-3000kms/yr for 2-3 years before I opened it up here for an inspection:
This piston was worn too small at the skirt and was replaced with a Wiseco. A few months later the Wiseco seized up 2 miles (3kms) from home while I was accelerating around a corner at 65mph. The back tire locked up and I went down and slid across the oncoming traffic lane. Bike had been warmed up for several minutes although I had been using only the rear tank so the carb may have leaned out. Piston showed a 4 square cold seizure. That was about 3 years ago and I am back to running cast pistons in the KTM 125 with no problems since.
See here what the back tank is and how it could starve the carb under strong acceleration:
So, we have practical experience of cracked and broken Blaster pistons, and them breaking into bits.
We have experience of broken Blaster piston skirts being punched out of the bottom of the engine.
We have true experience of other cast pistons lasting many years of hard use.
I have experience of properly fitted Wiseco pistons cold (4 square) seizing in bikes, snowmobiles and jet-skis.
Cast pistons do not tend to cold seize. Forged pistons do not tend to crack or break but tend to smear.
For anyone looking on not understanding, here are some pictures of what we are talking about:
Cracked and broken cast piston on the left, cold seized forged (I believe) piston on the right.
Note the unscuffed skirts of the piston on the right. This is typical of a cold seize. The piston grew larger in diameter than the bore of the cylinder and rubbed hard in the 4 corners rather than the skirt. Notice the scuffing on the broken piston on the left? That is a sign the skirt took some abuse, whether from heat expansion, detonation, too much clearance or no lube, cannot tell from the photo.
Forged pistons really do resist shattering. That is their ace in the hole, but note too the rings on the right piston are stuck hard into the grooves. Forged pistons smear and coat the bore with smeared aluminum that has to be removed chemically when they fail.
Again, we may not be comparing apples to apples. Both these pistons show obvious signs of abuse. The one on the left has been running hard on its skirts for quite a while. Worn out and sloppy? Detonation? Over revved? Overheated? We know if you don't have these conditions this piston could have run many years. I think we can safely say that a forged piston would probably have eventually failed here too, but would not have broke. It may have seized, knocked, smeared the bore, cold seized, or lost compression, but it likely would not have broke.
The piston on right has been run hard when the engine was cold. It has happened to me many times unfortunately. "Warm up" has to become a religion if you are running forged pistons. "When in doubt, go slow" is not inspiring from a performance perspective, whereas any idiot can jump on a cold cast piston and give it hell. It will stand it for many years.
I am thinking that the tall windowed skirt of Blasters and YZ Yamahas are prone to cracks and breaking (Neil had a YZ125 and DT200 that do this too) whereas the shorter KTM cast pistons are more stout. This would make running a forged piston in my KTM pointless, but a serious consideration for a Blaster or YZ.
I am thinking that the trouble free (warm up not essential) nature of the cast pistons, combined with their less noise and potentially more power is worth having, but warrants some investigation about cracking, what is causing it? Or is it just the nature of this cast piston design to crack?
So, can you make 30-40hp in a Blaster while watching the bore clearance, detonation and heat (all of which will kill a forged piston too) and have a cast piston live a long life?
Set our opinions aside, Joe is on the way to answer that question. Thanks Joe.
I have a rigid hone that I bore (wrong word) my cylinders with.
Even with the rigid hone you have to reverse the stones or cylinder to avoid taper.
Before I bought the rigid hone or for tiny cylinders I still use a flexible hone.
You have to know what you are doing and watch carefully, measure often.
Not the ideal set up, but workable to a good machinist.
Heck, I have used wooden blocks and sandpaper before.
We are only jumping up 0.025" at a time and often the ring groove is already there.
Just have to square up the bore. You cannot take this little off with a boring bar, maybe a grinder?
This said, I do not recommend everyone can do their next oversize with a Walmart hone.
It is an expedient for the expert, nothing but trouble for the novice.
Picture stone snagging on skirt, grabbing cylinder and flinging it across the room!
Even with the rigid hone you have to reverse the stones or cylinder to avoid taper.
Before I bought the rigid hone or for tiny cylinders I still use a flexible hone.
You have to know what you are doing and watch carefully, measure often.
Not the ideal set up, but workable to a good machinist.
Heck, I have used wooden blocks and sandpaper before.
We are only jumping up 0.025" at a time and often the ring groove is already there.
Just have to square up the bore. You cannot take this little off with a boring bar, maybe a grinder?
This said, I do not recommend everyone can do their next oversize with a Walmart hone.
It is an expedient for the expert, nothing but trouble for the novice.
Picture stone snagging on skirt, grabbing cylinder and flinging it across the room!
BlasterBruce...I didn't think anybody was going to fall for that one.
You have to read all the way down to the bottom. I was being sarcastice. I would never use one of those cheap,wobbly,spring loaded hones from walmart. It was a joke.
I thought a picture of one of those would freak people out.
I use rigid positive pressure hones.
HMM well i was completely interested in this thread and thought that joe was doing a great job researching and testing the differences in these pistons until i saw you bore your cylinder with a freakin hone. I will no longer be tuning in to this thread. boring your cyliner with a hone is complete jackleggery
What the fu.....two people fell for that picture???
scotj77...go back and read the post with the picture of the hone. Read all the way down to the bottom.
I use rigid,positive pressure hones. I use rigid,positive pressure hones. I use rigid,positive pressure hones. I use rigid,positive pressure hones. I use rigid,positive pressure hones. I promise!
scotj77...go back and read the post with the picture of the hone. Read all the way down to the bottom.
I use rigid,positive pressure hones. I use rigid,positive pressure hones. I use rigid,positive pressure hones. I use rigid,positive pressure hones. I use rigid,positive pressure hones. I promise!
ok not trying to be an ass here but if i am..... i don't appologize. lol a "possitive pressure" hone is still just a hone correct? as far as i know boring a cylinder is done with a lathe and that is the only "proper" way to do it.
ALRIGHT.... Who else fell for that? I went back and edited the post with the picture of the "cheap,wobbly,spring loaded hone" and added a disclaimer.
I couldn't help myself... I do have to exercise my sense of humor once in a while.
I appologize to all reading the thread.
OK back to being serious....
Just for the heck of it,what was your first reaction when you saw the picture of the "cheap,wobbly,spring loaded walmart hone"?
I couldn't help myself... I do have to exercise my sense of humor once in a while.
I appologize to all reading the thread.
OK back to being serious....
Just for the heck of it,what was your first reaction when you saw the picture of the "cheap,wobbly,spring loaded walmart hone"?
My hats off to you joeak47, great job and ALOT of good info!!! Some green for the work!!!
And I think you should've used a picture with the 80grit!!! Lmfao!!!
And I think you should've used a picture with the 80grit!!! Lmfao!!!
Depends on what you have to do...
If you are taking a a 66mm virgin cylinder and want to open it up to 68mm (8 over sizes,or .080,then I would lathe it,but leave enough material to finish with the hone. You've got to remember (and I know you know this) that every over bore is a measley .010 of an inch...or .005 all the way around the cylinder. As an example,a piece of printer paper measures .003 to .004 thick. Its very little material. Its like taking off a paper thickness all the way around the cylinder.
Your not going to want to use a rigid,positive pressure hone to hone that virgin 66mm cylinder to 68mm. It would take you a while. Pack a lunch. If you're going up one oversize at a time,its no issue. You would do the same on a $30,000 sunnen ck-10. Taking .010 off with that thing is a fart in the wind.
Whats important is that the cylinder is ROUND with no taper. Thats where those wonderful bore gauges come in handy. Check that cylinder everywhere,and check it again!
I never hog out a cylinder to the maximum,just so I can say I have a
"Big bore". You won't notice anything,and you just wasted all those precious over sizes.
As for positive pressure hones,they can correct... out of round,and taper conditions with ease. The stones can start from 60 grit (looks like pavement) and go all the way down in grit to baby bunny soft (exaggerating).
If you've ever used one,you will notice that they "act" a lot like a cam chain tensioner on a four stroke motorcycle engine. In other words,ounce it takes up the slack,it won't give it back. When you use one,you can "feel" the "cut".
Proper opperation it is essential. In other words measure the cylinder often during the honing process. They do a very accurate job! I suggest getting one. You'll thank yourself.
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