Rebuild

[hadfield4wd]

Looking at wiseco piston and athena gaskets. Any reason not to?

1999 ec 250

Thanks.

[GGRider01]

What do you mean?

Those are both fine products, if that's what you're asking. Check your cylinder for a letter, either A, B or C. Get the corresponding piston.

[Zman]

I agree.

[hadfield4wd]

Oh What is the difference between a, b and c? I've used many wiseco's just never worked on a gg didn't know if there was any special snake oil. Like you said the letter thanks.

Wiseco only lists one piston

[GGRider01]

S3 makes the GasGas OEM piston, if I recall - they have A, B and C pistons. Most any Japanese and European two stroke uses that same lettering system. It denotes, I think, an increase of .01mm. A heavily used A cylinder may measure out to be a B cylinder, but without precision measuring, why take the risk of accelerating the wear of an already used cylinder? Granted, there is a bit of leeway here, and many people go up a size with each rebuild. I think it may be even more critical when unsure of cylinder size to get your ring gap set correctly.

The original cylinder on my GasGas was unmarked. It also had spots of aluminum showing through, so being impatient I just replaced it. I was sent an A cylinder and ran an A piston.

Here are the Wiseco part numbers for the EC 250. The last letter indicates size. I added the size next to the part number to show the difference.

01.7307.A - 66.33mm
01.7307.B - 66.34mm
01.7307.C - 66.35mm

If you haven't already found a source for the gasket kit, this one is what you need and the price is fair. It doesn't take them long to get it in and ship it to you either. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[12Bravo]

Originally Posted by hadfield4wd

Oh What is the difference between a, b and c? I've used many wiseco's just never worked on a gg didn't know if there was any special snake oil. Like you said the letter thanks.

Wiseco only lists one piston

While I have an EC200 I am following your progress. Pictures and some videos would be great! I'm learning and need to replace my top end soon.

Keep us posted.

[hadfield4wd]

Originally Posted by 12Bravo

While I have an EC200 I am following your progress. Pictures and some videos would be great! I'm learning and need to replace my top end soon.

Keep us posted.

Well I'm not sure that I'll get video. I'll take pictures. This is not my first rodeo. I've rebuilt dozens of bikes/atvs. This is just my first GG. So I want to learn as much specific stuff I can.

Originally Posted by GGRider01

S3 makes the GasGas OEM piston, if I recall - they have A, B and C pistons. Most any Japanese and European two stroke uses that same lettering system. It denotes, I think, an increase of .01mm. A heavily used A cylinder may measure out to be a B cylinder, but without precision measuring, why take the risk of accelerating the wear of an already used cylinder? Granted, there is a bit of leeway here, and many people go up a size with each rebuild. I think it may be even more critical when unsure of cylinder size to get your ring gap set correctly.

The original cylinder on my GasGas was unmarked. It also had spots of aluminum showing through, so being impatient I just replaced it. I was sent an A cylinder and ran an A piston.

Here are the Wiseco part numbers for the EC 250. The last letter indicates size. I added the size next to the part number to show the difference.

01.7307.A - 66.33mm
01.7307.B - 66.34mm
01.7307.C - 66.35mm

If you haven't already found a source for the gasket kit, this one is what you need and the price is fair. It doesn't take them long to get it in and ship it to you either. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

So I was hoping to order the piston today. However I'm out of town till Friday. So you're basically saying to pull the piston to check the letter and get the same? I don't think it's that worn, there is no discernable issues, however it's the original piston on a low hour bike, this is preventative and piece of mind for my.

Also is the cylinder nikasil'd.

I really appreciate the knowledge on this site.

[GGRider01]

No need to pull the piston. The letter will be stamped on the outside of the cylinder, unless like mine it isn't. I don't know if they used nikasil or something else, but it is plated.

[TheLetterJ]

The cylinders are plated. The letter (if present) will be at the rear of the cylinder, all the way near the bottom where it meets the cases, should be visible with cylinder still installed.

I actually intentionally ordered a "C" piston for my ~200hr "A" cylinder and it fit PERFECT... but in the end, I just wasn't comfortable with the condition of the plating so now I'm sending it off to have it re-plated anyway... should have just bought an "A", oh well.

On a similar note, A, B, and C pistons all use the same rings. I did not have to file my rings to get the proper end gap, but with a new A cylinder you probably would need to.

[nknudsen]

Originally Posted by hadfield4wd

Well I'm not sure that I'll get video. I'll take pictures. This is not my first rodeo. I've rebuilt dozens of bikes/atvs. This is just my first GG. So I want to learn as much specific stuff I can.





So I was hoping to order the piston today. However I'm out of town till Friday. So you're basically saying to pull the piston to check the letter and get the same? I don't think it's that worn, there is no discernable issues, however it's the original piston on a low hour bike, this is preventative and piece of mind for my.

Also is the cylinder nikasil'd.

I really appreciate the knowledge on this site.

If the engine sounds good and is a low hour unit I don't feel it's worth it to pull it down for piece of mind. Run it. Mine was a low hr 2000' when I got it and still has the oe top end w/no issues. BTW I am a preventive maintenance kind of guy when needed. What is the comp. psi?