49mm piston question.

[Trek 700c 100cc]

Hello, My piston likes to scuff the cylinder when operating at high rpm.

The cause of this , I think, is cheap quality piston that expands too much under heat.

I heard a china doll 49mm piston has more thickness thus having less expansion.

I don't know where to get one of these pistons, any suggestion would be helpful.

 

[francisjohn]

Im confused. What bore do you currently have? I ran the 49mm for awhile and I can tell you now that 49mm Pistons are a hit or miss when it comes to availability

 

[Trek 700c 100cc]

Thanks for reply. I have a 100cc engine, that how it was listed when I bought it.

But its not 100cc because it's 49mm bore. It's just a way for them to sell more motors I think(to say 100cc!!!)

 

[GW's Motorized]

Thanks for reply. I have a 100cc engine, that how it was listed when I bought it.

But its not 100cc because it's 49mm bore. It's just a way for them to sell more motors I think(to say 100cc!!!)

Yup, its all marketing gimmicks

 

[francisjohn]

Thanks for reply. I have a 100cc engine, that how it was listed when I bought it.

But its not 100cc because it's 49mm bore. It's just a way for them to sell more motors I think(to say 100cc!!!)

Uhhhh ok let me try and explaining this differently.

Yes, it is a "100cc" because it's a 49mm bore. Just as if someone said "I have an 80cc" we would know it's a 47mm. Even though none of these engines list their true displacement, if someone says "I have a 100cc" then you know it's a 49mm. The only other option is a 50mm, but those are categorized as "YD100" where people will just flat out say "I have a YD100"

Do you have a link? Because even though the YD100 is a "brand term" used by CDH, similar to how there is no such thing as a CDH110, but CDH sells the 85cc "110cc" and then CDH just resold it with their name in the title.

Link would help. If you have a round head, then it's 49mm. If it's a one piece cylinder (no removable head) and is square at the top, it's a 50mm "YD100" and even then, there are tons of kits that are "YD100" but are sold as a "100cc"

This is why I was asking if it's 49mm or not. There is a way to tell. The fake displacement listed is the way to know bore size, there aren't many models, it isn't too hard to figure out.

 

[motorized Chuck]

Yup, its all marketing gimmicks

That is based on Chinese measurements. Your actual CC's, depending on actual rod stroke attached is likely a 72.5cc to 76.
Just ask Google gaga bore and stroke calculator.
To further show that Chinese measurements are full of §¥|@, a 38mm stroke by 47mm bore if actually around 68-68.2-5cc. That's 68.2-68.5cc's. not 66-80.
Only the phantom ZT MOTO is close to the actual 85cc. That is, if it is truly a 40mm stroke from BDC to TDC. I tore a brand new 1 down, mic'd it out and it was a 39mm stroke. That being said, was a 82 CC engine!