Piston questions

[KDX220PHIL]

For anyone who is interested, here is the basics:

http://www.sheldonbrown.com/dp-forging.html

I only checked it briefly, and it seems failry consistent to what I learned in school but I wouldnt know how reliable the info is as I do not have experience in forging and casting.

[NM_KDX200]

On that flywheel thing- I think ya'll might be right there.

When you say "warm it up slowly"- what are we talking about? 1 minute? 5 minutes? 10 minutes?

No hornet's nest opened here- we're just bench racing pistons, that's all.

So- what's the purpose of the big dents in the OEM and Pro-X?

[KDX220PHIL]

The "dents"as you refer to them, are there for weight advantage. They can not be made when forging, so wiseco machines a hole to reduce weight instead.

[KDX220PHIL]

Even better, some nice pics to go with it!

http://www.carcraft.com/techarticles/77899/

[jafo]

Oh Boy......

Well it looks like I hit the old Hornets nest with a stick by giving my opinion on this subject. I have been an engine builder and machinist for over 35 years and was giving my opinion on wiseco and OEM pistons.

In the past wiseco pistons did not have the hole drilled above the piston pin hole and the machining on the inside of the skirt (which made them extremely heavy). Then they started to drill the extra holes and called them Pro-Lites and made you pay more for them (the way they should have been made from the beginning). Now wiseco only makes pro-Lite pistons (at least the ones I use on the engines I build).

Someone said that cast pistons have a grain to them...... well maybe if you want to call it a granular structure, but it has no grain to it like a piece of wood, it is more like the structure of concrete. Also note the OEM pistons use a three piece mold on the inside of the piston to under cut and rib the piston pin boss to the under side of the dome. You could never do this with a forging

Now for the wiseco's, it defiantly has a grain to them (like wood). The piston is made from a solid disk blank and then it is put into a die and under tremendous pressure and formed into a piston. This process creates tremendous heat (almost to a molten state).

This is something to think about, that forged piston has a definite grain and has a memory of the original shape. I believe this is why the engine had to be warmed up slowly as these piston distort and expand unevenly, it also has to do with the extremely thick top of the piston.

I am not recommending one piston over an other, but as an engine builder and machinist I do prefer the OEM cast pistons. Wiseco are ok and you can cut all kinds of port windows in them and make the main intake window much larger.

AGAIN....., this is my opinion and 30 plus years in the business

Ron, this is alittle off the topic subject here, but when your talking OEM factory pistons, what about the notorious KDX220 Factory piston? Have you ever explored the reason why so many of them fail? I'm not trying to be an @ss, just really curious. This topic about these certain pistons have come up and know one has found an answer. Again not trying to put you on the spot, just wonder'n. I still have'nt been able to part with the original factory one I have after I swaped it out in favor of a Wiesco instead. It still looks brand new because, well it is brand new. I just did'nt want to take the chance of ruining the new cylinder on my bike.

Thanks / Jon.

[Indawoods]

I know I have never had any issues with cast pistons as far as warming up and such... It was just an observation about my other 200 with the Wiseco that got me thinking that it may be a better choice. I then did some research on the differences and found these:

http://www.lcengineering.com/TechNotes/TechNote41.htm

http://www.tprmag.com/issue/6/6_forged_perf.shtml

Not saying one is better than the other or anything but my brother and most of his buddies who build car motors use forged pistons.... he says it's because they can handle the higher compression and revs better. I don't know myself because I was always into bikes myself.... I love these discussions!

[RBD]

jafo,

I am really sorry that I even said anything about this subject..... maybe you need to ask the resident piston expert KDX220PHIL.

OK, like everything else in life one size does not fit all. Yes I have heard all of the complaints on the 220 OEM pistons and all I can say is that there is a design problem and I do not think it has anything to do with the fact it is a cast piston. A possibility is, Kawasaki made these piston to light as to keep the weight down to it's 200 counter part (Just speculation on my part and DON'T QUOTE ME ON THIS.

If the cast pistons were such a problem, then why don't all factory bikes have a piston breakage problem too (and your car)?

There is a whole lot more to building pistons that what KDX220PHIL says. Even his own article that he posted talks about forgings be coming liquid. Also there are as many compounds and mixtures of aluminum as there are stars in the sky. I have found that cast aluminum alloys can make better heat transfer and bearing surfaces than billet and forged. Again my opinion and 35 years watching new materials come to being and doing this type of work.

The only other thing I am going to say on this subject, is use what you feel comfortable with

[IdahoCharley]

Very interesting read (for me at least) - I also liked the comment ' ...just bench racing pistons..' how true that is. Must be the season - Snowing and cold here!!!

Trivia B/S - I worked for a national laboratory research center for about a decade ('90-'99). One of the projects developed the technology for spray metal forming of dies used to create plastic and metal items to reduce the cost of manufacturing vehicles.

Another program developed some of the powder metals technology specific to high temperature heat and pressure applications. e.g. NASA program and big three engine development programs. Also used cold forging, hot forging and explosives forging of specific components

Its is interesting to me when you have a chance to reflect back and possibly see there likely was a connection between your life's work and technology used to make the toys I now enjoy!!

Bottom Line - Sharing of information is good. Keep it light and we all learn something.

[KDX220PHIL]

Hey hey now, piston expert- I am anything but. I was clearly asking advice and trying to have a non-heated discussion on the matter. I was aking people opinions and comparing that to what i have read. Little to no experience here and no need to turn this into a political debate.

"There is a whole lot more to building pistons that what KDX220PHIL says"

Maybe I should post- the links and articles posted here do not neccessarily reflect the opinions of the poster.

From what i have read, generally, high performance engines use forged pistons.

I am here to learn, share and above all have fun. Sorry if I have pissed anyone off.

[Indawoods]

Nothing of the sort.... just a good discussion!

[Matt-itude]

It has more to it than cast and forged also. Many different alloys of aluminum are used by different manf. Different casting processes and finish machining. I know in race cars forged pistons have a cooler running temp on the head of the piston. They also have to have more clearance cold, or not on some brands they use an alloy that will work with stock specs. on bikes with chrome and nickle cylinders it doesn't come into play much but on cars the harder forged pistons sometimes actually wear the bore faster, but mabe that is the finish on the pistons. OK now I am confused. I do however know that maximum effort race cars run forged pistons and almost all factory vehicles use cast ones. So is there a good answer for which is better or does it come to preference and intended use again?

[canyncarvr]

I think that comparing cast to forged and expecting a single answer that is generally applicable to everything isn't going to work.

Preference and intended use? That's a lot of it I'm sure.

Consider: 'Also there are as many compounds and mixtures of aluminum as there are stars in the sky.'

Well..th'ar 'ya go! I'm betting the result of those many compounds (the piston) is going to be as hugely varied in suitable application and use as the numbers/types of compounds used.

[jafo]

I hope I have'nt gotten anyone mad especialy Rob. Rob, I don't want you to feel like you can't interact here. Thats not where I was comming from. With your experience, I just wondered if you knew anything about the stock 220 piston. I just wanted to throw that question out there while we were on the subject of pistons.

[fulltiltboogie]

They are known as "Seizco's" for a reason.

[IdahoCharley]

Wiesco pistons are known as "Seizco's" by people who do not take the time to adequately break-in the forged piston.

While I'am certainly no expert - it is my understanding that forged pistons are cam ground eccentric and it is necessary to heat cycle the piston with limited load a few times so it will more closely conform to the cylinder bore dimensions. If this is not done correctly; then the pistons are more likely to seize than an equivalent cast piston. Once however that the forged piston is adequately heat cycled under load: forged pistons are no more subject to seizing than cast pistons.

There are techical articles on this - likely available on the internet. I would attempt to locate some but the better half is giving me crap for being on the internet on X-Mas Eve.

So I'll end with saying Hope Everyone has a Merry Christmas