200exc piston questions

[overthebars]

Hopefully you can tell me a couple of things concerning a new piston that I got for my bike.
I decide to replace the piston in my ’03 200 EXC. The old piston looks to be in excellent shape (as does the bore), but it has 2 seasons of riding on it, and I thought I would be a conscientious owner who changes his piston before it disintegrates along the trail due to old age. I pulled the top end off. The old rings had a gap of .38mm and .50 mm. One was past the wear limit of .40mm. The piston had a “1” stamped on it, so I ordered a type 1 KTM OEM piston set via mail order. It came today, so I went to change it. Before I put it in, I noticed a couple of minor oddities that I thought I might ask about before I finish the installation.
First, there is something weird about the little pins that keep the rings in place on the new piston. They are nearly in alignment with each other! There is only a couple of degrees away from being one over the top of the other (maybe 3mm of offset). They are located between the same ports on the bore. My old piston has the ring placement pins more like 20 or 30 mm apart (one on each side of the inlet port). I have never seen a dual ring two stroke piston with the ring gap aligned one over the other like this. Is this a manufacturing screw up, or is it normal?
Secondly, my old piston has the exact size stamped on it. It is 63.95mm. It also has a .01+ stamped on it. The new one is stamped 63.94mm. The both mike out to 63.94, but the old one has a lot of miles on it. The rings on the new one have a ring gap of .35mm, which seems pretty close to the wear limit to me for new rings.
I bought my bike used. But it was in new condition. The original tires still had the dye streaks that new tires have when I bought the bike. I was told the bike was never torn down. But is this an oversized piston that it had in it? .01mm seems to be too small of an increment for an over-bore. I thought bore were usually in the .1mm increment range. With the plated bore, I would have thought it is not even feasible to bore this bike.
I am sure the new piston will work, but if it isn’t correct, I would just as soon send it back for a +.01 piston. Am I worried over nothing? Any insight on this situation?
Thanks
Tom H
:ride:

 

[elf]

Ktm makes a 1 and a 2 piston. the 2 is slightly bigger. Most guys switch to the 2 when its time to replace the piston. The slighly larger piston makes up for wear on the bore.

Don't know about the pins for the rings, Sounds like it would make getting the cylinder on easier!
If you want a tighter ring gap you can use weisco rings, I have noticed they come with a less gap than the ktm ones do.

 

[cujet]

I do not know what KTM is up to with that ring gap placement. However it cannot be better than staggering ring gaps. Some 4 stroke engines really have compression troubles if the ring gaps line up.

Chris

 

[overthebars]

Got it figured out

I took the piston to my nearest KTM dealer. After humbling myself by saying I would not buy KTM parts by mail order any more, the mechanic straightened me out.
First you are right, Elf, the #2 piston is slightly larger, and for some reason mine came with one from the factory.
Secondly, we looked a a bunch of KTM pistons, none of them had their rings line up like these did. The mechanic looked a bit closer, and noted that the ring end gap was lined up in a transfer port. If I had installed it, the ring end would have popped into the port and maybe broke a ring, or even worse, ruined the bore.
The new OEM piston was defective! He couldn't believe KTM's piston supplier screwed up like that. He had never seen it before. I returned it to the mail order supplier for credit.
To follow up, the mechanic miked my old piston and my bore, and told me I was wasting money changing my old piston, It was absolutely fine. KTM pistons are high quality units that normally last for years under normal use. It is not like a Jap bike where you do need to replace the piston just because. He sold me a set of rings, the bike is back together, and runs just fine.
The moral of the story for me is pay a few extra bucks and take care of my local dealer.

 

[elf]

Nice catch! that could have been disaster, Your luckey to have a good dealer near you. I don't think many would have taken the time to mic your piston and tell you that you didn't need a new one.

 

[mountainrider]

Has anyone else had this problem. I bought one of these pistons and when I noticed the ring gap I took it back to the dealer. They said that all the #2 200 pistons were this way and that it was OK. I installed it and it has run fine for over a year now, but seeing this thread has me worried.