TOPIC:

DON'T SAND. USE A HONE.
Steve

If you re-bore go the next size up, as i do not know what bike you have i cannot recommend exactly what you need, also what country are you in, if the US Z1 enterprises would be a good place to go.

No eBay APP ID and/or Cert ID defined in Kunena configurationNo eBay APP ID and/or Cert ID defined in Kunena configurationPiston options are limited.

OEM oversize pistons and rings were discontinued and very hard to find.

There is a place in England that sells .5mm oversize pistons and rings (look on ebay). They are pretty expensive and I suspect, the pistons/rings are made in China, but not positive.

Wiseco big bore kit - +3mm. Available everywhere. Good quality but expensive.

Cruzin Image big bore kit - +3mm. Dirt cheap. Most reviews are pretty good though. These might be your best bet if money is important.

I got a set of the IMD pistons for my KZP. I believe they are made in India. Seem to be of decent quality, at least my machinist thought so.

ThatGPzGuy wrote: I got a set of the IMD pistons for my KZP. I believe they are made in India. Seem to be of decent quality, at least my machinist thought so.

Where did you purchase them +0,5mm ?

Today I just tried to sand (just some), and it didn't improve anything, see attached picture.

I have more options then how to proceed as I understand from you.

I have talked with my local workshop, and he said from the picture it looks like honing is not enough, and he could
"raw" borr the cylinder +0,4mm to see if the cylinders are fine before I order any pistons.

Data:
Engine: 81 750-4
Carbs: VM24


If I goes up to big bore with 69mm piston what will the result be?
1. Only re jetting to get the bike running fine (my carbs is from 650CC engine same year)?
2. How much more power will I get approx, will it be a big difference in the driving experience much more acceleration?
3. What is the side effect? will the gear box or something get errors quicker/earlier? Do I need to rebuild more of the engine?

Thank you all for your inputs.

I bored rusty 750 barrels out to 1000 and still saw staining. They are cast iron and very porous. I ran them for two years. No problems. If yours are not pitted, I'd hone them, install new rings and RIDE THE PISS OUT OF IT.
Steve

I think I will go for the "raw" bore on 0,4mm to see what happens...
What steps do I`have if 0,4mm is not enough to i need to whole way to 69mm ? what steps do I have ?

Somebody know what impact big bore 69mm will have for me when it comes to get the engine running fine after these upgrade?

I have created a separate thread when it comes to the valves:
kzrider.com/forum/2-engine/607490-valves#775716

Keep in mind while doing a rough overbore.. Without having the new pistons in the hand of your machinist. That you should take out as little material as needed to do the bore cleanup.
Your machinist can then check the actual size of your new pistons to then finish bore or hone your cylinders to the exact right size to achieve the recommended piston to cylinder wall clearance
Dave

.4mm over bore is a fine idea. That will allow you to see if the bores clean up and still allow a few thousands for the final hone to size after you get the pistons.
I'm pretty sure you will be fine with .5mm.

gordone wrote:

ThatGPzGuy wrote: I got a set of the IMD pistons for my KZP. I believe they are made in India. Seem to be of decent quality, at least my machinist thought so.

Where did you purchase them +0,5mm ?

eBay. stores.ebay.com/imdpistons/

No eBay APP ID and/or Cert ID defined in Kunena configurationI`m so grateful for your feedback !

I have good references on the machinist person, cross my fingers 0,4mm is enough

If so is the next question what oversize +0,5mm piston I shall purchase...

And there are only one option as I understand?