What is the reliability of these kits?

 

It depends on some factors. The machine shop is important, so is the compression you go with. If you go to 12:1 compression you will need a stud kit, most likely. If you get a 11:1, you should be alright. You also need to be aware of heating problems, because the 89mm cylinder wall is thin and can over heat easily.

I am a believer in the 87mm (416) 11:1 compression. If I was to build another 400ex, this is the biggest I would go. With a good cam and decent port job, the quad could run with stock 450's.

 

use the oem studs!!

 

who do you think sells the best sleeve and piston combo?

 

for the 416cc

 

call powroll they are great

 

416 and 426 are done with the stock sleeve. Not until 89mm (436cc) do you need to resleeve.