Sandrail/go kart project

[Hunter65]

So the other day i got an old rotax 440 2 stroke and my friend and i got it to run. And it just so happens that i got some old fourtraxs the other day and we cut off the front end of one and we decided to start building. So far i have the plastic stripped off and i lowered the handlebars. Today im going to put a steering wheel on and start to build the frame. If i get that done im gonna start to build the rear swingarm. I will probably need some pointers with this. Also im not really sure how thick i should make my axle since this is a pretty powerful engine? I will post pictures of progress later tonight.

 

[weirdarmadillo]

cant wait for pictures...

 

[modelengineer]

The axle should be 1 1/4" or 1 1/2" high tensile 4140 chromoly, precision ground. Should handle the power. I'm using 1 1/4" with ~50hp and a big gap between the wheels and the bearings (puts more stress on the axle)

 

[Hunter65]

haha well i only have a forney stick welder thats about 60 billion years old so i have to take time and do my welds right. Also does anyone know the specific horsepower on my rotax 440? Its a 1971 free air. its got two cylinders but only one carb but thats how its supposed to be.

Oops sorry its fan cooled not free air.

 

[Kaptain Krunch]

Being that old and a free air, no more than 30hp, my F/C 1990 440 is only around 45hp.

 

[Hunter65]

How much would an axle like that cost about 4 feet wide? along with pillow blocks?

 

[Hunter65]

Ok so i guess its still a go kart since i think a sand rail is 35 hp or more.

 

[freakboy]

a sand rail is pretty much any buggy with long suspention and sand paddles...

 

[Hunter65]

Ok well its got the front suspension of a four wheeler im not really sure how long the travel is. And i will use it at some sand dunes in the summer but till than it will have four wheeler tires on it.

 

[freakboy]

i would extend the arms out more. get some more width in the front there.

 

[Hunter65]

Ok that seems like a good idea but i dunno exactly how to do that. And also i would need longer tie rods right?

 

[freakboy]

Longer a arms in general just the main tubes would all need to be longer a eaqual length.

 

[Kaptain Krunch]

I wouldnt lengthen the a-arms, i would widen the part of the frame that the a-arms are attached too, that way you dont change the leverage on the shocks.

 

[Hunter65]

Ok i like Kaptian's idea. Well im going out to work on it now so i will post pics in a few hours. They wont be the best though cuz i have to use my phone.

 

[That One Guy]

Man! That's EXACTLY what I wanted to do! I found a 1987 suzuki trailsport 230 for 300 bucks! But my parents wouldn't let me buy it because the people who own it are rednecks. They said that all the engine needed to run, was a new ignition coil, which costs 55 bucks. and EVEN IF the engine didnt run, I could still use EVERYTHING else on it. All the parts from my local supplier are going to cost me $787 without shipping or tax, and that's not including a battery, lights, or other things.

 

[Hunter65]

Haha well i didnt get much done tonight but here are some pics.

 

[That One Guy]

Are you gonna leave that front bumper on it?

 

[Hunter65]

Well im not sure yet. If i do i probably want to lower it down a few inches.

 

[That One Guy]

Good idea, that's kinda what I was thinkin'. That thing's gonna be a beast.

 

[Hunter65]

Ya but it probably wont be finished for awhile. I need to get a bucket seat to finish my front end than i can start on a swing arm. My biggest problem though is getting money to buy the axle and pillow blocks. But im probably going to sell the rest of my quad parts and frames and than i should be able to buy the axle. But im hoping to get a lot of speed out of it since it wont weigh as much as the snowmobile it came out of and its a pretty big engine.