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I'm gauging interest in a good forged high compression piston kit for the 143cc big bore z125 kit, I have in the past had custom pistons made and the smallest quantity that I could have made was at least four. I am planning the 143cc kit for my bike and I cant find anyone willing to sell a forged piston for these bikes,I refuse to put a cheap Chinese piece of junk piston and rings and pin in my bike, I also know that there are companies that are buying them from Wiseco, JE, etc (I can tell by the pictures of the pistons in their built engines) but they wont sell them to the public for some stupid reason, (likely greed), instead they want you to buy an entire engine build from them for thousands of dollars to get a hundred dollar good piston.

This is my first post but to give some background, I am a dealer lead tech, have been in four bike shops and two car dealerships as well as having held an AMA pro MX license, I am not new to the industry nor racing nor engine building. I dont race bikes these days although I still have them, I drag race a 1000hp 4 cylinder big turbo car for cheap thrills instead.

It seems ridiculous to me that there are not barely any aftermarket parts for this model vs the Grom, I am not a Grom fan at all, they are cheaper in quality than the Z125, like most things Honda these past few years. If we want these bikes to grow rather than stagnate like they have been we need to push ahead on good quality products whether we have to have them made ourselves or not, its not a big deal for me, it can be done.
 

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Hey Bishilvr. Is the idea that we're all pooling in for 4 quantities of a 143cc big bore kit (Z125 pro) that we'll split 4 ways? Or are you trying to do like a business-like venture from this?

As for the lack of aftermarket parts- that's just supply and demand. The Grom has a bigger following so innovation will flow towards where the money is. It's kinda sad with the lack of parts we have (mostly generic chinese brand parts and a few headlight/rack options). I don't think there's a big market for 143cc bore kits especially looking at the demographic of Z125 owners and the hardcore/technical scene but I don't think it'd be hard to find a 4 way split if that's what you're proposing.
 

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@Bishilvr I'm curious what you have in mind. There were some forged pistons made by JE a while back and I jumped on one of those (time will tell if that was a good idea or not). I'm just curious what you plan to have made...
 

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Discussion Starter #5
Hey Bishilvr. Is the idea that we're all pooling in for 4 quantities of a 143cc big bore kit (Z125 pro) that we'll split 4 ways? Or are you trying to do like a business-like venture from this?

As for the lack of aftermarket parts- that's just supply and demand. The Grom has a bigger following so innovation will flow towards where the money is. It's kinda sad with the lack of parts we have (mostly generic chinese brand parts and a few headlight/rack options). I don't think there's a big market for 143cc bore kits especially looking at the demographic of Z125 owners and the hardcore/technical scene but I don't think it'd be hard to find a 4 way split if that's what you're proposing.
I am just looking to find out if anyone wants to go in on a single run of four pistons so that I can have one myself without being stuck with four of them, for that matter we could go to a bigger bore if anyone wants to do that instead, but seeing as the 143cc is as big as you go before case boring comes into play I am figuring that the 143cc would be more likely to have interest in it, I am not a big fan of JE but they are owned by Wiseco now and should have gotten better in quality, so either them, Wiseco, or one of the other companies I have had custom ones made by in the past, we could have whatever compression ratio we wanted, coated or non coated, etc but seeing as Wiseco already lists a piston for the 110cc version of this engine it shouldn't take much to have something in a larger bore made up from that basic form that already exists.
 

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Discussion Starter #6
@Bishilvr I'm curious what you have in mind. There were some forged pistons made by JE a while back and I jumped on one of those (time will tell if that was a good idea or not). I'm just curious what you plan to have made...

I wasn't able to find a single forged piston for the Z125 from any manufacturer in my research, did JE have the 143cc version or just the stock sizes? if they have the forgings for the 143cc then it wouldn't take much to have them make a batch for us I wouldn't think, I've been in the Wiseco plant and they have the ability to turn things around pretty quick and seeing as they own JE these days that gives us some options maybe.
 

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I'll bite. I'm interested in one. Don't have a 143 but I've been where you are before, and the 143 is probably where I'll end up soon anyways. Depending on the price this sounds like a good idea. I'd like to hear where you are sourcing this, what the timeline is, and specs.

Billet vs forged? It's been a very long time since I brushed up on metallurgy. Billet is not inferior. Forged is a substantial improvement on billet. Forging has a similar effect as polymerizing does to plastic (that's kind of the way my brain processes it). Not any harder, just less brittle. More dense, but not heavier.
 

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So if they offered a machined piston, would that be good enough? I have a Wisco machined piston in my KAYO, the thing looked like a little jewel when I took it out of it's little fabric bag. It is the high compression from one of the Yamaha quads, but it fits really nice in the TTR engine, 13:1 rated and it's a screamer compared to stock, but still a 125cc engine to stay in the class.

I'm guessing that JE forges an oversized blank that fits several different applications, and then machines down to what you need.

I wonder if you could get a similar affect if you shot blasted the oversized rough machined part with heavy shot, then went and cleaned it up to final dimensions.

I'd probably go with a coating or anodize on anything I had made, it will be tougher if it is an alloy that can be anodized.
 

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Discussion Starter #11
I would think that a better wrist pin also should be with the kit, I will need to see whats available for the pins.
 

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I contacted Steve at JE awhile back and he quoted a price of 795-850 per set of 4. Coatings etc might be extra. I was just going to send him my old TB 60mm high compression (11:1 I think) cast piston for him to get the measurements etc. I could spring for the initial purchase, but would like to sell the other 2-3? Anyone interested still?
 

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I'm interested also. Let me know $, timeline etc whey you can.
I'll send him a new piston set to copy. TB...it may be a 12:1 CR? Price would be at least 200.00 best guess as he initially quoted me around 800.00 for a set of 4. Will update.
 
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