If you really think about it a 310r should kill a 450r. Basically you need about double the displacement for a four-stroke to be competitive, so you need atleast a 600cc four-stroke for it to keep up. I also agree that so far no one has a fully built 450r so how would any of us know what racing the two would be like. As for drag racing on flat land I think its about pointless, you could have the fastest machine in the world and still get beat by someone who's just a better rider than you. I think the best way to measure horsepower is finding the steepest longest sand dune you can find and see which quad makes it farther up.

 

I think that the old double the displacement to keep up thing is not quite true. The only thing that I have to go off is dirt bikes because they have been out longer. Ricky Carmicheal is switching from a 250 to the 450. Why because the 450 is to strong out doors where Hp really makes a big difference. And no one can say the RC 250cc two stroke is not built to it's maximum potential given the rules and all that. So Kevin's 450 would have to be at least a 500cc to compete right? At anyrate, I feel that in a year or so after the quad tuners really get into the new 450's that it will be very close between the two, given big bore kits and custom cams and all that stuff.

 

The actual ratio is something like 1.73 to 1. that means a 250cc 2 stroke should equal a 440cc 4 stroke. That said, the yfz is no stock baby. It comes from the factory with an 11.9:1 compression ratio and DOHC. Correct the timing and rejet, and you have a screamer. Now, how can you compare that to a stock R with a very restrictive exhaust? Thats why the races arent leveling out. The honda is a sohc design and lower comp, so its a little slower (supposedly) than the yfz. But its a 450cc. Drop that down 11cc and thats what the 250r is supposed to hang with.

BTW, bringing up the 310 kit is like saying that a blaster will beat a warrior with a full 240 kit. NO $H!T. comparisons like this should be stk vs stk, or in the case of 15+ year old machines, as closed as possible. My friend mx's an 87 r with a fresh 250 in it. Its got a pipe, filter an airbox, but its a closer comparison than a built 310.

 

Beech,
i agree totally.My last motor was a 310.Long time no see partner.
late,zubbeyboy

 

I own a 450r to. this weekend at dumont i could also out run the stock yzfs.there was a guy there tat had a 450r with a full fmf exhaust jetted and he could beat the pipped yzfs. dont believe what . the magazines say they . In the real world the honda is faster.

 

I agree, the new "stock" quads have way way more to them than the 80's 2 strokes out the door. They aren't your average 450cc quads.

Another reason they're fast stock is because of their carb size. I mean, a 42mm TPS carb on the 450r? thats huge.... the thing is, you could throw that carb on a 250r and go ahead and match their compression level with domes or a milled head and set yourself extremely close if not infront of those new quads, especially with exhaust

 

^^ A 42mm carb on a stock cylinder 250R is waaay overkill.

 

lol yeah...it was an example...but I think I got my point across

 

Dirt wheels said that they were almost identical in a drag race,but that the Yamaha's suspension made it's lap times better.

 

well bad news, my trike will not be done this weekend so ill be using my cousins 88 trx 250r, im sure to see some 450's there (glamis) so ill play around with them to see what they have. 88 trx only has a fmf silencer and whale.