Best Power Plant for a Budget Drag Bike?

Hurco550

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I've had the desire floating around in the back of my head for a bit (a desire partially dredged back up to the surface by texastars recent drag bike build) to build a simple drag race bike for a few years now. I live within a short driving distance of several 1/8 mile asphalt drag strips and also every summer there is the KOI dirt drag races which travel around to different fairs and drag race a dirt track anywhere from 150 ft to 300 ft, mostly 200ft though.

The idea in my head is a rigid frame simple bike with two wheel sets and probably a set of dr350/650 cush wheels setup which will make for easy rear gearing changes and a disc rear brake. One set will have a drag slick/ street tire front an the other will have knobbies for the dirt drags.

The frame will likely be completely one off built by me, rigid rear end, simple telescoping forks out front.

The question I have for the racing gurus is what powerplant would you recommend going after with the following criteria:

1. Cheap. (I know this word is relative when talking about racing)
2. Plentiful. (easy to find parts and donors)
3. Simple. (two stroke pops into my head, but the KOI races are setup that you may run 5 or 6 runs back to back, so whatever it is needs to be able to stay cool and not meltdown with that many back to back hard runs.)

I'm also not concerned (yet) about being the fastest guy out there, I just wanna have fun.

one of the engines that has popped into my head has been the ex500 ninja lump, which hits the 3 bullet points, but I know they aren't REAL powerhouses.

Ive also thought liquid cooled two stroke snowmobile engine with a cvt setup, but im afraid that even that without a cool down cart will want to melt down with the back to back dirt drags.

So what say you? What engine would you recommend to build a drag bike around?
 
Cheap and plentiful? Predator 212 motor....lol


I'd say Kawasaki inline 4, a kz650, 750, etc... tons of parts availability including race shit
 
An engine that you know pretty well. A buddy built one for the sand/dirt out of a wrecked Yamaha FZ1. He built a chassis around the powerplant for really cheap but went with a 4 wheeler rear axle.. He is like you in the metal world, he can make anything...lol. I know you want cheap but dont overlook the wrecks out there that can be had for pretty darn cheap. My 02 GSXR 1000 was bought for 600 bucks and was a mess. I had to buy a frame and a few bits but when I got it together I went a 6.08 in the 1/8th at like 120mph. You will want to go faster no matter what you are on! If you go water cooled you can hot lap it as long as your clutch holds up.
 
canyoncarver said:
Cheap and plentiful? Predator 212 motor....lol


I'd say Kawasaki inline 4, a kz650, 750, etc... tons of parts availability including race shit

I do have that kz550 ltd hanging around out back at the buddys place. They can be a bit peppy?
 
Banshee - fully built 150 hp.... You didn't say it had to be cheap...

Any 2 stroke twin sled motor with CVT will do.
 
teazer said:
Banshee - fully built 150 hp.... You didn't say it had to be cheap...

Any 2 stroke twin sled motor with CVT will do.

haha bullet point #1 was cheap ;)
 
+1 vote for the LC sled engine, just need a big enough rad.
If people can watercross their sleds in the summer heat at WFO then a few short pulls shouldn’t hurt.
 
Dude, you and your dad collect sleds. Why is that even a question? A sled engine. Only sleds. Lead sleds. Also, you don't want cush for dirt, so get a 19" RM rear wheel. You can share the rear caliper, spacers, and axle with the DR350 wheel. The sprockets will have a different bolt pattern, tho. The overall OD of a 19" RM wheel should be about the same as a DR350 18" with slick.
 
farmer92 said:
+1 vote for the LC sled engine, just need a big enough rad.
If people can watercross their sleds in the summer heat at WFO then a few short pulls shouldn’t hurt.
irk miller said:
Dude, you and your dad collect sleds. Why is that even a question? A sled engine. Only sleds. Lead sleds. Also, you don't want cush for dirt, so get a 19" RM rear wheel. You can share the rear caliper, spacers, and axle with the DR350 wheel. The sprockets will have a different bolt pattern, tho. The overall OD of a 19" RM wheel should be about the same as a DR350 18" with slick.
Dad and I were setting up a sled for asphalt drag racing a few years ago. They hold together well, but used cool down carts (er basically an electric water pump with quick connects into the coolant hoses that pumps Ice cooled water between runs) and as far as water cross in the summer, the track is literally paddling water on the heat exchangers in the tunnel the entire time.

I haven't ruled a sled motor clear out at all, BUT I'm still a little concerned about back to back heats and getting it cooled down in time

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I wouldn't over think it or make more work than you wanted, because I know how building race bikes goes. There is always mission creep, so Here is how I would start and then I can predict where you would go from there.

First I would just keep an eye on CL and pick up the cheapest sport bike I could find. In my case there is a Ninja 600 parts bike that has been lingering for a couple of months for $300 with no title abandoned by a former buddy of the seller... etc... I could probably get it for $200 and easily sell $200 of parts off of it. I would get it down to bare frame, front end and swingarm. I would run a spool front end and an XL500S rear wheel cause I have a couple of them laying around. Since I don't have the experience to build an extended swingarm, I would just put an adjustable strut in place of the shock and that would be my bike. Stock engine, 4-1 pipe and open carbs with a rejet using the stock intake rubber velocity stacks.

Here is where I suspect your mission creep would come in. Once you start racing it, you will notice what it needs, like a longer swingarm, different steering head angle, lower CG, different controls, air shifter, smaller radiator, different frame, etc... see where it goes!!! Constant development and building things, but, at least you have a starting point that will be on the track.
 
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