i have done decided with the engine situation.. i am getting a KX500 engine there bad! i have herd there pulling like 60hp stock? and there just all around bad engines alot of dig and topend at the same time... and when i get serious im gonna stick it in a drag bike and hopp it all up and mabe ad alittle nos? i dont know yet.. but its gonna be interesting!

 

fast250x, what are you planning on putting that engine in anyways? Do you have a rolling chassis sitting around in need of a little love? I'm not sure what the aftermarket is like on those bike engines, but they do have some good power from the factory. Even more so the latest generations.

468bbc, troll? Ouch! OK, maybe I am being a little unfair to you. Personally, I didn't see the need to suggest a class of engine fast 250x wasn't considering. He could also find more HP than he would ever need in a crotch rocket motor, in fact I just saw a thread yesterday asking for advice on a CBR600 build. But that is a project that requires a lot more fab time than a dirtbike drop in. I still say converting a quad chassis to belt drive for a sled engine is a lot of fab time too. However, I suppose I may have come across a little harsh, and I apologize. Blame it o hormones I guess, lol.

One other quickie. The ports in a 2 stroke are opened and closed by the piston, and reside toward the bottom of the motor, not on top like a 4 stroke. Inherently, 2 strokes do not burn all of the fuel the first time through, and a good amount of the fuel charge is ejected into the exhaust partially used up. The design of the expansion chamber "bounces" part of the exhaust gas back towards the cylinder. Depending on the setup of the ports and expansion chamber, there is a sweet spot in the rpm range that allows fresh fuel from the intake in through the intake porting, AND some of the partially spent fuel in the exhaust system back into the engine via the exhaust ports. This is what is referred to as "coming on the pipe." The exhaust ACTUALLY DOES force fuel and air back into the cylinder, performing a similar function to a turbo or a blower. That is why when you buy a 2 stroke pipe, you look for a bottom, mid, or top end pipe depending on your needs. Most good 4 stroke pipes give you a power increase across the board because they are only opening up the air/fuel flow. A 2 stroke pipe does that, but also scavanges fuel and forces it back to the engine, but only over a certain rpm range. Sounds corny, but if you have ever hit the powerband on a Banshee, you know how effective the expansion chamber(s) can be.


Oh, and I checked, Yamaha doesn't list any forced induction on any of the '06 sleds[img]i/expressions/face-icon-small-wink.gif[/img]

 

interestinq question and not the usual "my quad is faster" and "which one is better: TRX or YFZ", "ford or chevy" etc etc etc!!!!!

wth happened to my post? i thought i posted on here?? well anyway i'll try to remember what i may have said..

i thought i had said that all the engines originally mentioned (not the yfz350 or the sled engines- though they are powerful, no doubt) werent 'bad' choices but the suzuki LT500 being designed for quad and the kawasakis prob make a good choice in either 500 or 250cc config. however, you will find some cr500r conversions on the honda but they are getting shaken pretty bad, but they will rip. you will find more stuff for a honda engine but all of them can be made to do what you want if you are willing to spend some $$$. I think the latter kawis and the suzukis were powervalved so your powerband will seem smoother and have more torque down low. i know that the LT500 had gobs of torque but i dont think it was powervalved. i know the latter lt250s were as were the tecate-4 250s. a tecate 250 will run!

well since you already decided on an engine my question is does it have a counterbalancer? prob not since its from a dirtbike and not needed. the forces the engine makes generates vibration that is dissipated to the ground and pretty much 'unfelt' on a dirtbike...on a quad you now have 2 axis to think about with having 2 sets of wheels, front and back and the vibrations arent dissipated but in simple terms rocks the bike around. you may want to try a diff engine or RUBBER MOUNT the engine to reduce this. thats what they did on the banshee. the dirtbike engines always make more power so once again kinda hard to compare them to a quad variant. a couple yrs back, service honda made a "NEW" trx250R based on the 400EX frame and NEW CR250R engine; result= fast bike but hellacious vibration due to NO counterbalancer. i dont think they sold very many of them....

The ORIGINAL TRX250Rs were counterbalanced and never powervalved but they are great bikes and can be made into whatever you want. you can get new powervalved cylinders for these from ESR, duncan, ct, etc.... PSI also makes a 425 kit for the 250r, there's one on ebay right now if the auction is still active. but i have heard mixed reviews on the PSI stuff. but with this kit they claim like 70hp(?). not bad in 330lb bike.

dude, i know the kfx is a kick **** engine. kawasakis rip. but the vibration will shake the **** out of you. i think you will be beter off like scooter said with a crotchrocket engine. ive seen several of those successfully done and dont hear of the vibration probs - not to say they dont exist - i dont know for 100%... but think of the sound it would make... it would sound better than a single 500. my .02.

btw, off topic, i wish yamaha would have at least powervalved the banshee for the last couple yrs. the RZ350 engine, if i recall correctly, was powervalved in the end of its run in the street bike usage...would have been nice.

 

the main thing i am looking for thought is an extreamly light engine that when i build it right is going to get me in the 90HP range or more and i see alot of potential in the KX engine to get me that hp... i dont want the weight of a crotch rocket engine when i can have the light bike and really hall and i know the crotch rocket engine is fast as heck but im not looking into fabbing all that stuff and making it look right.. but after i build the KX engine i am going to rubber mount it as much as i can! that means as much rubber i can get in there LOL also im gonna get the anti vibe stering stems and stuff like that to help me out.. im not looking for this machine for recreation riding just a straight line drag against cars and what ever else i can find! also people know its bad when they see u have a streetbike engine sitting in the bike... but when they see a smaller different engine thats another story! they wanna drag u b/c they think they can beat u and what ever! but then they get a large suprize! so im really wanting a Sleeper.... + i have seen banshee's smoke a 1000cc crotch rocket with nos... in the sand... so thats why also im leaning that way...

 

The KX should work well for that application, good luck with it!

 

I mean i have a cbr 600 engine at my friends house if this conversion isnt fast enouf! its the older model ones the 1994 F3 or something like that... with the double carbs and all... so who knows