Wiseco K810 Piston Clearance

Hello, I am a long time lurker and first time poster. I was not able to find the information I’m seeking via search so hopefully this will work.

I currently have a set of KZ750 jugs sent out to a friend who is a reputable sprint car engine builder and nitrous 2 stroke builder. He has a considerable amount of power sport experience, but not any in the KZ world. He is in the process of boring out my cylinders, and has a question on fitment.

The Wiseco product literature and website all state that “piston clearance is built in” and boring to size will be sufficient, however by his measurements that will allow for .0025” piston to wall clearance on most cylinders and .0015” on the largest piston. In his mind, this is not enough clearance for an air cooled motor.

Is there anybody who has experience with this kit and can speak to minimum/necessary piston to wall clearance?

Thanks!

i would set them at .003 thousandths piston to cylinder wall clearance if i was just handing it off to someone else to break in.
if i was breaking it in myself i would set it closer to the .0025 clearance and be very mindful of my break in procedure.

that's my .02 fwiw.
hth,

leon

Bore clearance is 0.051mm = 2 thou for the Wiseco pistons.

www.750turbo.com/forum/viewtopic.php?f=2&t=11185

Thanks for the help guys! Appreciate the input, he's much more at ease now and is finishing the job this weekend.

What clearance did you guys decide on? I've got that same kit and a cylinder that needs to be bored. I was thinking .0025"

On all the bigger 1075 etc Wiseco kits I've fitted , including the 250hp Turbo drag bike I've gone 2 thou with no issues.

I've always thought .002" was the standard for air cooled engines. Out here in the heat I wouldn't want to go smaller clearances.
Steve

This guy's funny but he has some good points

My Zephyr 750 ran more than 70000km on Wiseco K810 kit without any issues. Cylinder-to-piston clearance was set to that recommend by Wiseco: 0.051mm (0.0020) .

Anyone know how the 810 pistons compare to stock in terms of weight, and would the engine vibrate more with the 810 kit installed?

Don't know about the weight difference for the 810 but these 4 cylinder engines are self balancing so you won't get anything more than the normal buzz unless the crank was twisted.

How does self balancing work? I thought any time the piston weight changed, the counter weight needed to change because the counter weight counters the weight of the piston, rod, and crank throw.