Stock vs. wiseco piston

[festerovic]

So I have the cyclinder off my KX250, and I'm inspecting for cylinder and piston wear. Everything looks OK, no rough spots or obvious wear on anything. I have heard that its a good idea to put new rings on a piston every now and then, so I went to order some new ones.

Turns out, you can buy the stock rings, or get Wiseco replacement rings, but they are not compatible with each other's pistons (according to wiseco). So I'm looking all over the piston for some kind of ID, so I can tell if its stock or wiseco, and there isn't any.

The bike was purchased used, there were a bunch of wiseco stickers on it, and since its a 98 hopefully a new piston went in at some point. Is there any way to ID which one is which? Thanks for any help.

[Faded]

Most, if not all the Wisecos have the part number stamped on the crown.

[KX02]

Most stock Japanese pistons are made by ART. If you look on the bottom side of the piston and see ART somewhere it is a stocker.

[The Baron]

A Wiseco piston is forged, not cast so you should be able to tel by just looking at it from the underside, plus Wisecos normally have an arrow stamped ont he top to indicate the front of the piston.

[festerovic]

Awesome! Thanks for the quick replies guys, now I can get my parts and get back to riding.

[mxracr121]

Stick a new piston in too. Your already there, just make life easier on yourself. You'll be good for another 40+ hours or so.

[pdxjim]

Vertex pistons are cast like the stockers, and not forged like the Wisecos.

Cast warms up quicker and is less prone to problems if you just get on and ride without adequate warm-up.

[festerovic]

Ok, so I looked at the piston to see what model #s or ID there was, I got this:

C00C4 8005 72 95mm

I can't tell if there is a decimal point between the 72 and the 95. There are no numbers that match up to Vertex or Wiseco pistons, at least that I can tell.

The bore and stroke on the bike is supposed to be 66.4 x 72 mm. The 72.95 is weird. Also, the head gasket(I replaced it a trip ago) overlaps the cylinder bore by about 2 mm.

Where can I find out what piston I have? Should I just bring the cylinder to a place that can measure the current bore and go off of that, or if the piston needs to be .95mm longer, can I get a regular one?

I'm really confused...

[quadfather03]

Im gonna make this as simple as possible for you [Only registered and activated users can see links. ] visit this site and order the Vertex piston kit it comes with everything you need to do the top end including my favorite and the only gaskets i touch cometic. I have done enough of these to know that its no fun any other way. Unless you do like i just did and mail you cylinder to phathead racing and get it bumped up to 265cc big bore with phat head and optional domes, thats about 600.00. The vertex kit if in stock is only like 139.99 as opossed to the wiseco at 129.99. Shipping is free over 100.00 and its 2 day shipping so you get it quick. Worth the time to make this piston change. I dont even do ring changes any more with pistons as cheap as they are i do a vertex kit every year just once and i know my bike will performe flawlessly throughout the season.

Now on the subject of are you overboared that is hard to say on any bike. Those bikes have to either be sleeved to be over from what im told however you can take it to your local kawasaki shop and just let them look at the piston/cylinder and they can tell you then just walk out thats what i do. They make their money of people who cant work on their own bike not me i just use them for advice kinda like a help line. Hope this helps.

[KX02]

+1 for the Vertex kit from Motosport outlet. I just got one for my bike. I really like the Vertex pistons, they hold up really well and run smooth.

[festerovic]

Okay, so I went to the service dept. of the dealership that I trust. He immediately recognized the cylinder as a kx250, but also that it was way bored out. It was 72.95mm bore, and 72mm stroke, to make a 301 cc bike. Also, he told me it had been ported, and nicely done at that. The nikasil was mostly gone, and he told me it needed replating or to be bored and resleeved. Also he verified it was a Wiseco piston (they have a W symbol on the bottom).

When I asked for a new piston kit, thats where there was trouble. There are no pistons with the dimensions listed above available from wiseco. They had no idea what to put in this bike. So they told me to get it sleeved, and then put a stock sized piston (wiseco, stock, or vertex) and then I could use stock sized parts again.

So, now the kicker is, is the over bore too large for a sleeve? Like, is there enough mass in the cylinder still to add a sleeve and be snug? I' have no idea how thick the sleeves are, and how much of a bore you have to do on a stock size cylinder to get it to fit. Somebody tell me I'm worrying for nothing.

I guess my other option is to find a piston kit that works, but that will probably be the hardest route. Probably cheaper if I just get a new cylinder, but I want the big bore performance if I could keep it.

Let me know what you guys think. And Happy St. Pattys Day!

[mxracr121]

Originally Posted by festerovic

Okay, so I went to the service dept. of the dealership that I trust. He immediately recognized the cylinder as a kx250, but also that it was way bored out. It was 72.95mm bore, and 72mm stroke, to make a 301 cc bike. Also, he told me it had been ported, and nicely done at that. The nikasil was mostly gone, and he told me it needed replating or to be bored and resleeved. Also he verified it was a Wiseco piston (they have a W symbol on the bottom).

When I asked for a new piston kit, thats where there was trouble. There are no pistons with the dimensions listed above available from wiseco. They had no idea what to put in this bike. So they told me to get it sleeved, and then put a stock sized piston (wiseco, stock, or vertex) and then I could use stock sized parts again.

So, now the kicker is, is the over bore too large for a sleeve? Like, is there enough mass in the cylinder still to add a sleeve and be snug? I' have no idea how thick the sleeves are, and how much of a bore you have to do on a stock size cylinder to get it to fit. Somebody tell me I'm worrying for nothing.

I guess my other option is to find a piston kit that works, but that will probably be the hardest route. Probably cheaper if I just get a new cylinder, but I want the big bore performance if I could keep it.

Let me know what you guys think. And Happy St. Pattys Day!

I'd call RPM for help. I think they actually sold the 2-stroke oversized division to another company, but I think they are still in the same building together, or can at least tell you who to call. They did probably 95% of the overbore kits out there and should be able to help you. Look for their ad in the back of motorcycle mags or google Rick Peterson Motosports.

[cory326]

I guess the next question would be, do you want to run your bike as a 300? If not get it re-sleeved if possible or, if thats not a smart thing to do, get a new jug and start over with stock. Ossa or one of the other more mechanic minded guys would know more.

[twostroker]

Since my bike is an 84 and many parts are discontinued i decided to send the cylinder off and get it bored and a new wiseco sleeve, piston, and rings. What year is your bike? if its generally new i recommend you go with the big bore, but if its old and lots of discoed parts stick with stock, the cylinder will last longer.

[festerovic]

So, I checked with a couple shops that told me that it was not bored too large. I can get a sleeve that puts the cylinder anywhere from stock to 285cc. I think I'm going to go with 265, since it's alot easier to get the tope end kit for this size than the others. Ultimately, I want things to be easy.

thanks for all the help, everyone, now go ride some for me until the Beast is back in effect!