220 Top End Rebuild

[ROOK-E-RIDE-R]

I have a question regarding a top end rebuild for a “00 KDX 220. I have read numerous times in this forum to go with the WEISCO (forged?) piston vs. the OEM Kawasaki piston, but my brother in law (who I bought the bike from) is trying to steer me away from WEISCO as he's heard that they have tendency to expand. I just called my local Kawi dealer and they said the same thing… “avoid WEISCO unless you have no other choice” and they recommend the PRO X 1 (cast) piston, which I believe is the same company Kawi used for their OEM piston.

My questions are:

•What are the differences between cast and forged pistons?
•Are there any special warm-up procedures on a forged piston vs. a cast piston?
•Is the typical 10 to 15 hr break-in period the same on both?
•Has anyone with a cast piston had any problems?
•Anyone with a forged piston had any problems?
•Any recommendations?

Thanks,
ROOK-E-RIDE-R

 

[ridejunky]

When I did my top end, I had no problems with the stock piston and aside from little carbon buildup it was still pretty good. after hearing the horror stories about grenading
stock pistons I chose the wiesco. If you put the two together though, the stock seems to be a little crude compared to the weisco. Do a search on stock 220 pistons and you will see enough evidence to make you want to take it out asap.

 

[Lambkawi]

You might want to do a search on break-in procedures to it will save you about 10-14.5 hours of breaking in your new piston.

 

[Green Hornet]

same break in. Wiesco piston is lighter also. Mine works great.

 

[adam728]

I have a question regarding a top end rebuild for a “00 KDX 220. I have read numerous times in this forum to go with the WEISCO (forged?) piston vs. the OEM Kawasaki piston, but my brother in law (who I bought the bike from) is trying to steer me away from WEISCO as he's heard that they have tendency to expand. I just called my local Kawi dealer and they said the same thing… “avoid WEISCO unless you have no other choice” and they recommend the PRO X 1 (cast) piston, which I believe is the same company Kawi used for their OEM piston.

My opinion (everyone will have different ones).
I would go Wiseco long before going cast. It's just a better / stronger / lighter product with tighter tolerances.

My questions are:

•What are the differences between cast and forged pistons?

Well of course there is the way they are manufactured for one. Cast pistons have much larger tolerances than a forged piston. The grain structure of the aluminum is also different, the biggest reason a forged piston is stronger.

•Are there any special warm-up procedures on a forged piston vs. a cast piston?

Both types should be warmed up well. I believe forged are a little more forgiving because of their better controled dimensions and skirt thickness, as well as the grain structure thing again.

•Is the typical 10 to 15 hr break-in period the same on both?

Like stated above, 10-15 hours of break in is 9-14 hours too long. I typically to the warm-up cool-down thing about 3 times, then just ride it fairly easily for the first 45 minutes to an hour. I will pin it during that time, but only breifly. I say no wide open top speed runs. But, like everything else, you'll get 15 different opinions from 15 different people on this subject. I'm just old school.

•Has anyone with a cast piston had any problems?

I've read of a few problems on this board with the stock piston. Mine had the ring locating pin back out and destroy a cylinder. I got free stuff under warrentee, and after looking at how pitted and nasty looking the new stock piston was I bought a Wiseco. There are just too many places in the cast stocker to act as stress risers and increase the chance of breaking a skirt.

•Anyone with a forged piston had any problems?

Yup, stuck a ring on my Wiseco and peeled some plating off the cylinder. I say my fault though. Was running Klotz Supertechniplate while dual sporting (over the course of many many months). That stuff doesn't burn too clean and it really gummed things up, basically gluing the rings in place.

•Any recommendations?

Wiseco. If I remember correctly Pro-X doesn't make a piston for the 220, only the 200.

 

[markmad]

IMO you are actually bedding your rings into the sleeve and not the piston, and a KDX does not really rev that high to warrant a forged piston.
Im not saying don't buy forged but don't be sold on peoples hype because at the end of the day no one has taken the time to analize the material differences in the 3 different pistons.

 

[adam728]

IMO you are actually bedding your rings into the sleeve and not the piston, and a KDX does not really rev that high to warrant a forged piston.
Im not saying don't buy forged but don't be sold on peoples hype because at the end of the day no one has taken the time to analize the material differences in the 3 different pistons.

Maybe no one has gone through all the testing for this particular application, but it has been proven many times that forged pistons are lighter / stronger and just plain better than cast. Casting is a cheap way to get a decent product. Forging is much more expensive but gives much better dimensional and surface finish control, as well as control of the material's grain structure. Cast parts will always be heavier and weaker than a properly forged part.

There's also the whole quality thing. Look at a stock 220 piston next to anything and you can see it is crap. I'll have to take some pics of mine some day. The casting is very poor, especially for a part as critical as a piston. Mine was FREE and I won't run it, as I can envision one of the skirts breaking off as I kick the engine over.

As the the whole "doesn't rev high enough to warrent it", well, depends on the mods. My bike revs out pretty good, although I don't know the exact rpm. But lets say this. Stone stock, reved completly out in 6th I went 71.9 mph. After all my mods I went up 2 teeth on the rear sprocket, which should drop top speed. I pulled off something around 83 mph. It revs now, and I definitly would not want the low quality stock piston in there waiting to ruin my day.

On many bikes the stocker is just fine, and some racers even perfer them over aftermarket pistons. But the KDX220's piston is a well known weakness. After studying a new one up close and personal I would recommend everyone change it out for something better!

By the way, there is only 2 different pistons, stock, and Wiseco. Pro X only makes pistons for the 200. You could use one, but it might fit a little on the loose side. :rotfl:

 

[markmad]

Point taken adam didn't mean to sound as if i am against it,I don't own a 220 so i have never seen the piston,but i will be sure to try the 200 piston in a 220 one day sounds like it could be a bit of a slapper.LOL

 

[adam728]

Point taken adam didn't mean to sound as if i am against it,I don't own a 220 so i have never seen the piston,but i will be sure to try the 200 piston in a 220 one day sounds like it could be a bit of a slapper.LOL

If you are worried about slapping, just run a 220 piston in your 200. You'll need a little butter to lube it up, and a 15-20 pound sledge, but it should fit nice and snug. :cool:

One day I'll post pics of my new stock piston for everyone to see. Problem is right now I am in Mexico and the pics are on my laptop in Georgia. It'll be about 4 weeks before I am home to get it.