What would you do different building an engine for dragging or for hill shooting? Different cams, piston, porting, valves, or carbs, and why do it that way? Thanks.

 

the stroke on the hill is nice, but the flats it isn't as noticed.

 

Where has this question been?! I thought you'd never ask..... or, maybe I was hoping nobody would ask, because that means they are thinking and might figure some important things out!

But....right now, supper is calling me....

Bill- are you sure?

222

 

i know the non stroker hangs a lot closer on the flats than the hill, i have a few strokers i run with i'm in the game on the flats the hill they just out pull me. but then i'm not as informed on all combination as you guys[img]i/expressions/face-icon-small-smile.gif[/img] so there is always other ways of getting some where. didn't you guys run some non stroked thing guinness or something that was working over the stroke engines.

 

Heck maybe we will see one here thats fit for both!! From what I gather people are getting pretty serious about ds days. I dont know how im gonna compete with my little motor....[img]i/expressions/face-icon-small-blush.gif[/img]


Ah heck maybe ill have to get one of those lightweight FSR hpr pistons and a new air filter and let yall know.

 

I like a good torque curve for a hill shooter. If you have enough power to keep it at peak power consistently, then you have no worrys. But most of these bikes cannot do that, and if they are, they are losing speed at the bottom. But this is on the big hills, it might not matter on the smaller hills.

 

the mountain is a whole nother world from the flats, alot of guys are gonna get schooled at dsdays!
IMO setup is just as if not more important than motor - gearing, tire choice, etc. - but the longer your curve maintains peek power the more forgiving it will be. you won't hold the same exact rpm the whole climb, the grade varies, so if you got a curve that peeks and drops quick then you have little room for error and rpm fluctuation will hurt worse but if it holds a steady line longer at peak and you gear for the middle then you got lots of room to keep from falling on your face.

 

Good torque is what is needed to climb hills.

For example a motor making somewhere in the 40's for torque but turns a lot of RPM making peak power of around 80HP near 10,000RPM, may do very very well on flat drags, but not as well on the hill due to lack of torque.

If a different motor setup was making 70 for torque but still around 80-90HP at a lower peak RPM, it would perform better on the hill because of the torque.

But you can go too far with emphasizing torque and have all low end torque and no upper RPM power - like a harley motor, that's not what you want either. Wheel speed and a wide enough power band also is needed in sand.

 

so what is it 222? we all are interested to hear your take, as the rotax engine is moded, you guys keep finding things that are very interesting. as we all have found the weight issue of the ds has been holding us back for years. Imagine if we had had 400 pound machines to start with, you bomb dealers would have been able to retire with all the machines you sold.

 

question: line up a 2 stroke and a 4 stroke of equal weight and equal peak horsepower. All other factors being as equal as possible, which one wins?