This kit bumps it up to 13:1 compression. Do this motor have a beefy rod in it stock? I know that on my 416 i would want to replace the rod to go to 13:1. Anyone ever worked on these engines in a dirt bike or know enough to give me some info on this? OR any opinions?

 

The rod in this engine is much stronger than a 400ex rod. It will take the 13:1 compression with ease. My cousin has been running a 13:5 in his wr 440 for 3 years with zero problems. Sparks racing will have a 14:1 available for alcohol runners soon.

 

14:1 and alcohol..... DROOL

 

the yz450 bike has 12.5 to 1 stock. the yz400 and 426 have used that comp. ratio for years with very few problems. the biggest rod problems these motors have had was on the 98 and 99 400's where the lower rod bearing would wear out with lots of hours. but yamaha made the 426 rod bearings larger.

 

stock comp on a 450 is 11.9:1.

 

you must mean the quad, because the dirt bike is 12.5 to 1

 

i read it wrong... Bummer for me

 

So, will the bike run on premium too? Or does it need race gas?

 

the dirt bike will run on 92 or better pump gas

 

well with 13:1 you would think the bike would need to run race gas. Race gas will make a big diference in this bike no matter what compression you run.