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Right-o, I took delivery this week of one NOS std 61mm piston and two Wiseco pistons, they are a pretty thing eh? They come in a wee velvet back like something precious from a jeweler! So today I took everything thing in to my local machine shop including my cylinders of course to get measured up. I'll wait and see how that turns out! We did strike one issue. The gudgion pins of the Wiseco's appear to be 14mm, I was expecting them to be 15mm as per the stock item so we will have to sort something there. I'm thinking the men can bore the pistons out for a 15mm pin and add a groove for the stock clips. Any thoughts on that idea or other suggestions?

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Mismatched pistons? Weigh them to be sure.
Steve

No, I have 2 Wiseco's. I basically bought the NOS piston for reference.

I see. Good luck.
Steve

Rustyhama wrote: The gudgion pins of the Wiseco's appear to be 14mm, I was expecting them to be 15mm as per the stock item so we will have to sort something there. I'm thinking the men can bore the pistons out for a 15mm pin and add a groove for the stock clips. Any thoughts on that idea or other suggestions?

Well, the fella at E&S head services says my bores are all good and within spec so the Wiseco's will work. There just the little hurdle mentioned above. Apparently they won't be able to do the work required on the pistons to allow them to take a 15mm piston pin so they have to send them to Christchurch (my old home town 4 1/2 hours up SH1) something about being too small and needing a mill??? They've asked that I supply them with the new, stock pins so I've ordered a pair and a set of snap rings from Partzilla today. Can anyone think of another way to do this? A 0.5mm 'tubular' shim on the 14mm piston pin to go through the 15mm hole in the conrod? I'm guessing that would wear through and find it's way into my bottom end pretty quick - bad idea, I think I'll stick with my first idea. Just looking for a couple o' thumbs up here...

No eBay APP ID and/or Cert ID defined in Kunena configuration

TexasKZ wrote: While you may actually find a piston solution, please be aware that there is much more to consider than just the diameter. The wrist pin diameter, dome height, valve cut outs, distance between the wrist pin and piston top, and the skirt to crank clearance must be compatible.

This.

There is quite a lot more involved in here than just boring out. Distance between wrist pin and top of piston crown for example.

Do your research first as I said earlier, last thing you want is a motor that wont even turn over when the head is fitted.

Your machinist is only looking at his part of the job, you need to look at the whole design together.

I incorrectly mentioned a 13mm pin size, it is 14mm - the same a same as a lot of these GY6 Chinese scooters. It is ok to change plans if you need to, before spending a lot on machining.

I'm pretty confident that the Wiseco's will be an excellent match. I've ordered some 15x47mm wrist pins from Wiseco, and I had a chat with a guy there who thinks what I'm trying to do is feasible as long a small the machine shop can get it right, I'll trust that they can as that is their business. Below is a photo of the Wiseco next to the NOS piston. and one from above

Just to finish this thread off. I got my pistons back. The fella who did the work, Bob Denton apparently helped John Britten with his early engine work. He did an amazing job. When I put the pistons on the bike, the pins went in perfectly and snap ring locked in like a factory job. So now I have a Wiseco piston upgrade on the mighty KZ 305!

Cheers
Hama
82 KZ 305 - Hamasaki cafe racer
80 KZ 750 - banished
06 KDX 200