What makes an engine need race gas ???

[KX Newfie]

What mods are done to some K 5's that will only allow them to burn high octane fuels

I'm building another motor. The cylinder is ported, & it came with a high compression piston............do i need to burn race gas

My current K-5 seems to have the same engine setup aside from the carb which is an electron carb.

The built motor has a stock carb.

[stewart]

all the wiesco pistons are stock compression  ..the heads are moddified for higher compression  by cutting and reshaping  them to a smaller cc volume,,stock heads are 42cc  ,,moddified  heads are less like 35cc  must run high octane or it will damage piston from spark knock  or detanation

[bigbellybob]

octane rating is the fuels ability to resist detonation. as compression goes up the octane requirement goes up. 12:1 is about all the compression pump gas can handle. RPM and spark timing also affect your octane requirements or fuel selection. some high octane fuels burn to slow for high RPM motor if your still burning the fuel mix past 20 degrees after TDC its not contributing to the force push down the piston. and not helping make power.

how high do you think the compression will be?

[KX Newfie]

Not sure how high the compression will be.

My cylinder head at the moment has many dings in it from a cracked ring.

I'm dying to ride, but only have one head  ....& snow is coming in less then a month 

The piston that came with my other engine is definately more beefy then a stock wiesco.
Not sure what it is, but it looks wicked strong 

Anybody got a cylinder head for sale......perferably modded

[stewart]

we have heads stock or modd ..in stock

[mysnykkx500]

stuart You need your own store.. LOl Maybe They can make you one on here to show what all you have for sale.