Scared of Wiseco - long

[mprest4]

i have a 95 200 that is just getting its first (apparently) top end ever. i have a B cylinder. i ordered a wiseco kit after the tech i talked to over the phone said the wiseco would be just fine, no clearance problems (and they don't make different sizes).

well the wiseco piston says 66 mm on the box and my service manual says the standard inside diameter of the cylinder is 66.026mm - 66.041mm with a 66.1mm service limit. the manual says the clearance range is 0.079mm - 0.089mm with no service limit. sorry to bring math into this but i don't think i'm going to have enough clearance with the wiseco piston. 66.041 minus 66.0 equals .041 which is roughly half of the recommended range.

i took it to a machine shop to get the cylinder and the old and new piston measured (in case the wiseco isn't 66) but what do you guys think?

 

[Boot]

Don't know about the figures, but I do know that a lot of motorcycle people I've talked to lately do not think much of Wiseco pistons. They apparently have a reputation for expanding more than the stock ones.

This was news to me. I'd always thought that Wiseco was a top aftermarket company. Having just seized a new Wiseco piston in my 240, the message has been driven home, though in fairness to the company an aftermarket iron sleeve was also involved (but with a generous 3 thou clearance).

Suggest you try to find a Pro-X piston? These are made by Japanese OEM manufacturers and are excellent.

 

[BRush]

The stock piston is a cast piston. The Wiseco is a forged piston. While forged pistons are stronger than cast pistons, forged pistons do expand more than cast pistons and allowances for this must be made when determining what clearance is correct. The clearance in the service manual is for the stocker and will not be appropriate for the Wiseco. The Wiseco should come with an instruction insert that will tell you how to figure the required clearance. Forged pistons also require more careful warmup than cast pistons. Kicking a cold engine to life and then pinning the throttle on a fire road 10 seconds later is an invitation to trouble.

More reading:

http://dirtrider.net/forums3/showthread.php?s=&threadid=35945&highlight=forged

 

[shr]

Note! To All,

Pro X makes a very good piston and they do come in a; "A", "B", "C", and "D" size.

It is my opinion that the Pro X pistons are better than the stock Kawasaki piston.

I have also been told by the Wiseco customer service department, that their pistons are made to the "A" size stock pistons. The "A" piston is the smallest size.

 

[BRush]

According to EG's book Pro-X does not actually make pistons, but is a marketing company that sells surplus ART pistons. ART being the company that manufactures all the Japanese OEM cast pistons.

 

[yzeater]

It is my opinion that the Pro X pistons are better than the stock Kawasaki piston.

Everybody is right (except shr), the Pro X is EXACTLY the same as the stock

 

[shr]

The Nik's Pro X pistons are made in Japan, but they are not surplus pistons from Art!

Also they are not exactly the same as stock! As the are permanent mold cast pistons that say PRO X inside the skirt of the piston!

Sheesh.... I just tried to give a little helpful information to you, mostly to let you know that you can buy an after market piston that comes in a A B C or D size.

So let the games begin!

 

[Robcolo]

MPREST4 -- If you do use the Wiseco, read my post on the other piston thread "New Top End....which Brand"

 

[mprest4]

well i got the numbers back from the machine shop. the wiseco measured exactly the same as the stock piston that was in there. top and bottom. so i guess this wiseco was a B size. it also probably means that i could have just replaced the rings.

i looked at both pistons and pins and bearings to give them an eyeball quality comparision and heres what i found. no noticeable difference in weight. stock has 4 oil holes around the pin compared to two on the wiseco. stock pin is thicker than wiseco. wiseco needle bearing was too big ID for the pin. at least compared to the stock. i could push it on one side while it was on the pin and see a good size gap between them. i didn't like that so i used the stock needle bearing.

i will replace the wiseco with a pro-x/OEM next time.

thanks to all for your advice.

 

[WoodsRider]

I've been using Wiseco pistons for close to 10 years in various Japanese and European bikes I've owned, and have never experienced a catastrophic failure. Wiseco is the factory piston for GasGas. I have seen failures where the circlip that holds the piston pin in place has popped out and damaged the cylinder. However this problem is associated with improper installation of circlips as opposed to a defective piston.

I've got nothing against stock pistons either, except for the price. The stock KDX220 pistons do have some issues with thin walls which results in a cracked piston skirt.

To maximize piston life do the proper maintenance. Replace the rings, annually for the Sunday trail rider and at least every six months for the hard-core racer. Replace the entire piston assembly (piston, rings, piston pin, circlips and pin bearing) after it's second set of rings.

Most piston failures I have seen were the result of something else like too lean of jetting, lack of lubrication or poor air filtration. Always follow the piston manufacturers guidelines for "breaking-in" a new piston and seating the rings.