Piston:Cast or Forged?

[motoxvet]

I'm about to do the top end on my '80 Suzuki TS-250. So I guess the choice is between OEM and Wiseco. I use the bike for off road only-fire roads, some single track but not much. I hear and read some not so good things about forged pistons like long term durability. But then I read that OEM pistons will EXPLODE when their life is done. The small price difference is not a factor. Someone told me that Wiseco's were indestructable (almost) but I BROKE one once so I'm gun-shy. The skirt broke off, rode around on the crank until it finally took out the bottom of the sleeve. I ride the bike pretty hard and I also wouldn't mind a little longer warm-up. I always did it with my race bikes. So I'd like some opinions.

THANKS!

[CamP]

I'm an OEM piston guy and they've never failed me yet. Lately, I've stocked up on a few OEM '82 RM250 pistons for less than $20 each on ebay.

[scalejockey]

For a vintage air cooled motor? OEM ALL the way! The newer stuff i always use Wiseco.

It's all about the way those(forged) pistons act in the air cooled motors.We used to call them Seizeco pistons in the 70s'

[Tom68]

Lightest piston strong enough to do the job thats readily available. A cast piston made correctly is fine, i.e OEM.

The little bit of experience I have with Wiseco is the're dam heavy unless the one you want is available in a Pro light.

Forged Wossner piston for my XR500 is very very good and light.

[Huskychuck]

if you use a Wiseco, go just a little bigger then they say, out youll have some heat and lock up issues.

[scalejockey]

if you use a Wiseco, go just a little bigger then they say, out youll have some heat and lock up issues.

Exactly! if your bore is a bit worn and you don't want to bore it oversized. Slap in a wiseco and let it rattle a little.At least it won't break skirt like a cast piston.

[jleblanc]

go wisco, forged is better because they heat up more evenly, have a good machinist bore the cylinder, run it lose for aircooled 3-5 thousands is good, also some older oem pistons are bad becasue they sat on a shelf for so long they become fatigued, broke way more cast than forged

[CamP]

Pistons don't go bad from sitting on the shelf.

[500XC]

Forged! Strangely enough, I'm doing the same thing on a 1981 DS250 that gave me, my uncle, dad, sisters, friends and grandpa almost 10 years of continuous service with minimal care!

I have a Wiseco in my 81 PE250, and I pulled the top end after 65 hours, and threw in a new set of rings after I threw a chain and broke the case. Verdict: Still good, still in there, 25 more hours! Another pull down is sceduled for 100 hours.

Use a good machinist, one that has old timers still hanging around, and does the whole job properly (Torque plate, buying the piston FIRST then measuring and setting the ring gap for proper expansion)

Also, might I suggest something with a bit less painfull suspension?

[jleblanc]

Pistons don't go bad from sitting on the shelf.

i beg to differ from 30 years of changing temperatures metal can fatigue much less the fact that it has probably been dropped several times scratched and way not, the time it spent on a shelf is not good, plus it was most likely a cast piston which is not very good anyway. stock is good but come on people we have better processes for making things now.

[CamP]

i beg to differ from 30 years of changing temperatures metal can fatigue much less the fact that it has probably been dropped several times scratched and way not, the time it spent on a shelf is not good, plus it was most likely a cast piston which is not very good anyway. stock is good but come on people we have better processes for making things now.

I'm sorry son, but you really don't know what you are talking about here. An aluminum piston, whether it be cast or forged, has an almost infinite shelf life as long as it is stored properly. I'd suggest that you stop talking advice from whomever told you that.

[RacerXr]

...30 years of changing temperatures metal can fatigue much less the fact that it has probably been dropped several times scratched and way not, the time it spent on a shelf is not good, plus it was most likely a cast piston which is not very good anyway. stock is good but come on people we have better processes for making things now.

Changing (room) temps ? Dropped several times ? Forging is a new process ? Huh ?

This makes no sense to me. But, what do I know ? I'm an old engineer/vintage MX'r, I'm probably close to death anyway :-)

[Tom68]

Cast Pistons are ideal for two stroke because they fit with close tolerances that are relatively constant with temp' change, two advantages of this are minimal piston slap even when cold and better sealing of port openings in the cylinder walls.

Manufacturing wise a cast piston can have its material thickness controlled and be made appropriate throughout. A forged piston to be reliable and light has to be followed up with a lot of machining due to the limitations of the forging process.

[Wiseco]

Hammer test.

https://www.thumpertalk.com/forum/showthread.php?t=854456&highlight=cast

[CamP]

Hammer test.

https://www.thumpertalk.com/forum/showthread.php?t=854456&highlight=cast

That hammer test was idiotic. A piston never sees any forces like that when it is running.

A two stroke piston has long skirts to distribute the thrust forces against and forging is not required. Only in a short stroke four stroke engine like the modern 4T race bikes does a forged piston become necessary because the piston skirts are so short.

I'm thinking of boycotting Wiseco products for posting this BS misinformation spam. Why do you need two TT accounts to pump this crap? It's obvious that you and CBDaddy are the same person because you are both from OlieO and both have the same bike in your TT garage.

Edited December 8, 2009 by CamP

[pwrpapa]

I always run cast oem pistons when possible, I'm not really a wiseco koolaid drinker.

[Wiseco]

That hammer test was idiotic. A piston never sees any forces like that when it is running.

A two stroke piston has long skirts to distribute the thrust forces against and forging is not required. Only in a short stroke four stroke engine like the modern 4T race bikes does a forged piston become necessary because the piston skirts are so short.

I'm thinking of boycotting Wiseco products for posting this BS misinformation spam. Why do you need two TT accounts to pump this crap? It's obvious that you and CBDaddy are the same person because you are both from OlieO and both have the same bike in your TT garage.

Lighten up a little. There was nothing in that thread that made anything a Wiseco commercial. It even went above and beyond to say CRUDE on it so it didn't try and indicate that it represented any real life forces that a piston sees in an engine. It was just a side by side comparison of what a cast part does vs a forged part when forces were applied to it. Maybe next time it will be a couple of aluminum faucet handles or something - one forged and one cast, to make the comparison and not piss anyone off. The metallurgical validity of the point is still valid. Nobody is pumping anything. Geeze.

[CamP]

Lighten up a little. There was nothing in that thread that made anything a Wiseco commercial. It even went above and beyond to say CRUDE on it so it didn't try and indicate that it represented any real life forces that a piston sees in an engine. It was just a side by side comparison of what a cast part does vs a forged part when forces were applied to it. Maybe next time it will be a couple of aluminum faucet handles or something - one forged and one cast, to make the comparison and not piss anyone off. The metallurgical validity of the point is still valid. Nobody is pumping anything. Geeze.

Young impressionable riders see BS like that and the next thing you know the message spreads like wild fire that cast pistons are brittle and will explode in your bike. I think it's irresponsible of you to put that crap out there. You are seen as an untrustworthy snake oil salesman by knowledgeable people with messages like that.

[Wiseco]

Young impressionable riders see BS like that and the next thing you know the message spreads like wild fire that cast pistons are brittle and will explode in your bike. I think it's irresponsible of you to put that crap out there. You are seen as an untrustworthy snake oil salesman by knowledgeable people with messages like that.

I think you are being overly critical and have an axe to grind for some reason. I give TT'ers more credit than to see a smashed part and assume that is true in all cases for all cast pistons. These forums are full of discussions on this topic, with a whole lot worse said and shown than a simple side by side photograph. As I said right in the thread, there are pro's and con's to both types of pistons.

[scalejockey]

I have a simple list that i use.

Air cooled 2-stroke....use oem cast. Have seen too many seizes with air cooled and wiseco pistons over the years.

Water cooled..... (without a steel liner)wiseco or oem cast if "that"person is good on keeping a fresh piston in.

New "modern" 4-stroke stroke...OEM.or what ever the customer wants.The valves will need done before the piston goes,unless some dirt has gotten by.

I go off of what iv'e seen in years and piles of old pistons. And yes a wiseco piston can crack i have one right now.But it was so loose that the ring caught on the exhast port.LOL!