Last top end was 1200 miles ago (late Feb.). The Wiseco revs quicker, and is a little noisier than stock. I am going to put in a fresh top end in late Sept. I am going to use Vertex then. I can then be more versed on how each one of the pistons perform, and their longevity.
I used a Wiseco piston for the last 150 engine hours (this for the rumours that its last less then OEM), on my KTM360 '96, and then sell the bike :-), but it's was great, the engine was running great, no heating problems, no special noise or other issues. For the performance... the bike run much better, but be ware that Eric gorr done some good work on it, so I'm not sure it's because the piston.
If the clearance is set up right, and their broken in correctly, their great. Like Strick's KTM, the Wiseco in my GasGas is still going strong at over 1200mi. No blowby, noise, or other problems at a recent inspection. For fatigue reasons, I'll change it at the end of this season.
I have heard mixed reports on Vertex. Some say its not designed for longevity. However, Vertex is OEM on TMs, and these are very durable. I do know that an OEM TM 250 piston works very well and lasts long, in a GasGas 250 as a Wiseco alternative. Maybe there are are two diffferent Vertex piston designs. Anyone?
Funny you should mention the additional noise when using a wiseco piston. I just changed the top end in my sons bike and because of the overbore used a wiseco. Eric Gorr did the work. It appears to operate fine but I questioned my mechanical skills at first crank up. There is a notable change in the sound at idle, once underway it's masked over, is this common?
I read somewhere on a post here that when they did their first topend on a KTM the factory piston was a Vertex, so if KTM uses Vertex as factory, they must be a good piston. I replaced the factory piston in my 97 KDX220 with a pro-lite from Wiseco and rode it a year before I sold it with no problems.
I put a Wiseco piston in my '94 KTM 300 a year ago. The cylinder showed no wear after two years on an OEM piston. The piston was OK, but rather than just replace the rings, I decided I decided to use a complete Wiseco piston kit, which cost almost the same as a pair of OEM rings. I wish I hadn't. It didn't last a year before the rings wore out, the piston scored, and the blowby ruined the bottom end. If you use Wiseco, you can expect a shorter life-span than the OEM, and I would regularly check compression and clearances. I'm going back to OEM on this rebuild.
It depends on the size KTM and year. The 300s use an excellent ($$) forged ELKO piston. The others are cast, but I'm not sure of the supplier. If you want to use the Wiseco, just make sure the clearance will be OK. I don't think Wiseco makes 2 sizes like the KTM OEM #1 and #2. For GasGas OEM, they make 4 sizes to precisely fit the bore. I think this makes a big difference, as my top end is very quiet. If you start with a sloppy #2 bore size in your KTM the Wiseco may not be a good choice, you just have to measure and decide.
I just did the top end on my '99 300exc with a Wiseco kit. It does rev faster. My bore is #1 and it fits great. No extra noise. Don't have enough time on it to tell how long it will last but I've been using Wiseco piston kits since '88 when I got my first 2 smoker and have never had a problem.
I put a Wiseco set of piston and rings in my bike back in April. It replaced the stock Elko piston that was in there (although that was the second piston in the bike since new). My bike is a '98 300 M/XC. I bought the piston, rings, and bearings, from Eric Gorr after he did some work on my cylinder. I have about 40 hours on my bike since then and have not noticed any particular increase or decrease in performance. I read up a lot on this subject before doing the top-end and the concensus seemed to be that OEM is better primarily because of longevity, but a lot of people have used Wiseco's without a lot of problems. As with anything, you will get people who have had both good and bad experiences. As for me.....no problems so far.