single ring 250 piston

[2strokeman]

I have one of Ezra Lusk's KX250 engines build by Team Kawasaki, it runs but the powervalves needed cleaning from being stored for so long. [Its a 99 or 00] anyway when we pulled it apart we found that it has a single ring piston, like a 125. I know its for heat reasons, and they get replaced after about every other race, but can you buy them anywhere? I have never seen one offered. I did see a Wiseco HP advertised and the piston in the pic showed only one ring groove, but I figured the pic was generic and was of a 125. Anyone ever found one? Or used a Wiseco HP [high performance]?

[2strokeman]

Im asking if anyone offers one for an R, not a Kawasaki. Just wanted to clear that up.

For my 363R, BDT-M used a special ordered Wossner with the top & bottom rings & ring groves thinner and made from a different ring material. This was done to match up with the custom made Aluninum Sleeve & Hard Chrome plated bore.

My point is you can have your builder order you custom made piston kits from Wossner, you can also call Wossner USA direct or call BDT-M…

Carlos.

[2strokeman]

I build my own, we also do a lot of custom work on 2 strokes for a slim number of our customers. I refuse to work on the new HIGH TECH thumpers, I call them Big Red's, that's what they sound like to me. Lol. Will Wossner build one for me, or would I have to have a middle man?

The problem with Wossner and custom orders is minimums; they will not entertain an order unless you purchase 4 piston kits or more of the same size. The 4 piston kits must fall within the standard Wossner piston line, unless you are willing to pay considerably more for to have them make 4 of a kind.

A “middle man” who deals with Wossner will be your best bet; the only 2 sources I know besides going direct to Wossner are LA Sleeves and BDT Motorsports…

Carlos.

[2strokeman]

Ok, thanks for the info, my sister talked to Ezra today and he is out of the loop so Im on my own. As many pistons as I go thru 4 isnt a big deal. I like trying diff set ups, even tried some porting, TRICKY! Thanks again.

[cannondale27]

If I remember right my old 265R used a RM dirtbike piston.I believe it was single ring.

You guys already know single ring pistons or running a set of thinner rings has its advantages and disadvantages…

On the advantage side:

A single ring 2 stroke piston has less frictional drag than two rings, cooler running, you can accomplish a reduction in friction by running a set of thinner rings like BDT-M did on my Wossner Custom Pistons for the 3330R & 363R, going overly thin causes excessive ring flutter and shortened ring life among a few other ills.

On the engine Dyno and on the track; single ring pistons show a reduction in piston heat, produce more HP, and therefore faster lap times. The main reason you do not see more single ring or two sets of thin ringed pistons is longevity, and the warranty & maintenance issues it presents to manufactures.

Disadvantages:

Higher maintenance and the need to replace the single ring frequently is the obvious one, the not so obvious is that fine tuning becomes more critical, more emphasis on proper jetting, fuel mixture, and more sensitivity to over compression.

Ideally, in a perfect world, we would have a ring-less piston, running in a near frictionless bore, the piston seal would be provided by the oil film thickness…the problem with this scenario, is the bore & piston tolerances for roundness, concentricity and taper would need to be held in the .000050” range…that my friends is in the millions of an inch and very difficult to sustain in a manufacturing environment.

Food for thought…

Carlos.

[2strokeman]

I have actually ran one ring on a 2 ring piston, it was either do that or not ride at all for the weekend! I was surprised at how little difference it made. Then when I saw the FACTORY set up in Yogi's KX- I got curious about finding one. What about these Wiseco HP pistons? Any better than a regular wiseco?

Just think how much better your engine would have performed if the second piston ring grove was not circumventing charge out the exhaust…single ring pistons run quite well.

Carlos.

[Dave83]

Originally posted by acecarlos
You guys already know single ring pistons or running a set of thinner rings has its advantages and disadvantages…

On the advantage side:

A single ring 2 stroke piston has less frictional drag than two rings, cooler running, you can accomplish a reduction in friction by running a set of thinner rings like BDT-M did on my Wossner Custom Pistons for the 3330R & 363R, going overly thin causes excessive ring flutter and shortened ring life among a few other ills.

On the engine Dyno and on the track; single ring pistons show a reduction in piston heat, produce more HP, and therefore faster lap times. The main reason you do not see more single ring or two sets of thin ringed pistons is longevity, and the warranty & maintenance issues it presents to manufactures.

Disadvantages:

Higher maintenance and the need to replace the single ring frequently is the obvious one, the not so obvious is that fine tuning becomes more critical, more emphasis on proper jetting, fuel mixture, and more sensitivity to over compression.

Ideally, in a perfect world, we would have a ring-less piston, running in a near frictionless bore, the piston seal would be provided by the oil film thickness…the problem with this scenario, is the bore & piston tolerances for roundness, concentricity and taper would need to be held in the .000050” range…that my friends is in the millions of an inch and very difficult to sustain in a manufacturing environment.

Food for thought…

Carlos.
I had model aircraft engines that were of the ABC design(Aluminum,Brass and Chrome if i recall)They had no rings and were way more powerful than ringed versions of the same engine.I always wondered why this wouldnt work for our quads?

Dave83:

You hit it right on the money…it has been tried on larger displacement engines; like I said:

“Ideally, in a perfect world, we would have a ring-less piston, running in a near frictionless bore, the piston seal would be provided by the oil film thickness…the problem with this scenario, is the bore & piston tolerances for roundness, concentricity and taper would need to be held in the .000050” range…that my friends is in the millions of an inch and very difficult to sustain in a manufacturing environment”

Here is your ring-less ABC engine…

Carlos.

[Dave83]

They do it everyday for the r/c world.I know its a much smaller bore but a tolerance of .000050 is the same on a bore the size of a dime as it is on a bore the size of a coffee can.As I mentioned,the ABC engines made considerable more power than an engine of the same displacement using rings.They actually were very durable provided you ran the proper breakin and fuels with correct lube/nitro packages. Might be a PITA to kick start a 310cc ABC cylinder engine,lol.

Super seal, a ton of compression, yes a bear to kick start.

Totally different concept, however; like I said it has been done & tried on larger displacements running Aluminum sleeves with good results, however; at a large $$$ cost…not cost effective as a manufacturing process.

The two positives were increased HP, better heat transfer to the sleeve, therefore cooler running engines.

The negative was obviously the manufacturing costs, the hard chromed plated Aluminum sleeves are very expensive, and if not set-up just perfect; complete top end destruction.

I would love to see the concept carried further into 250R’s, however; just is not going to happen, at least not from the top manufactures…

Carlos.