Why is it that a 500cc power valved, high strung two stroke dirtbike only puts out 65 horsepower and only lasts 5 races before a recommended piston change.

And my 600cc powervalved two stroke snowmobile puts out 126 horsepower and will easily last 10,000 miles before even needing rings!

Are motorcycles really that [sm=lame.gif]?

 

I have no idea, but I'm going to take a guess...

(1) The dirtbike only has 65hp because 126 would be unmanageable.
(2) The dirtbike doesn't "need" a new piston after 5 races, the racer is not willing to risk any loss of power or mechanical breakdown during a race.
(3) Since a snowmobile is operated at temperatures below freezing (and often below zero), engine cooling is phenomenal! Heat and dirt damage motors, there'slittle heat and no dust while operating a snowmobile.

Did I get any of them right?

 

i'll go with the heat being a major factor.

 

I was thinking the cold temps would definately be a factor. How about oil injection versus mixture? Also aren't most snowmobiles rotax engines? I don't really know much about the newer sleds.[:-]

 

The snowmobile is a multiple cylinder I presume so there is a big part of the power. 65 HP sounds like at the wheel for the bike after a transmission, chain, etc. 126 is at the crank since there is no tranny on the mobile except the CVT which they would not take a reading out of that.

The 500 will last alot longer than 5 races reguardless of what the manual says.

 

I disagree with the premise of your post. My 2001 KDX200 has never had a piston or ring change and I've ridden it hard last season on the track, racing other bikes and in the wilderness on multiple occasions. The bike still screams... Who says you have to change out the piston or rings every five races?

Mike

 

Are you really saying a 600cc engine has 126 HP?
Wow that seem like a lot. Whats the HP of a 600cc superbike?
Is your snowmobile a 4 cyl?

 

the kx500 is severly restricted of the line to. since most will be riding in a tree-heavy area kawi and the gov think 65hp is enough. sleds are ran on lakes and fields so they are almost maxed out off the line. if you were to put aftermarket things like a pipe, jets, reeds, high volt stator, air filter, arrestor and maybe a new plug it will bolw 65hp out of the water. kinda like the banshee, stock it does 70 sompething (pathetic for a 350 twin) but after just fmf dualies and proper jets it will push 90+[8D]

also, sleds are twins and triples (and sometimes quads[&:]) that makes a big difference to, think about it. why would a 600twin get beat up and down the lake by a 600 triple? 600 triples can take most 700 twins[8D] more cylinders = more power.... to an extent.

 

[sm=exactly.gif] the 5 race thing is for racers that think every .006hp will really mean the race[8D] a crf250x recommends a new topend something like every 20hrs[sm=bangbang.gif] ive run my xr on the same crap (other than the stroker kit after like 50hrs) since i bought it and that has several THOUSAND miles on it and i havent noticed a difference.



p.s. i cant wait until 2smoke bikes get fuel injection.[&:] im gonna throw a party when that happens

 

You guys have also forgotten that the KX is OOOOLD tech, while i'm willing to be that the snowmobile gets major R&D every year.