Building a Race Kart

[Mammoth]

There's a couple motors out there that I don't see very often, but I always keep my eyes peeled in case one should happen by.
I recently came across these 2 engines that I would have never guessed they'd cross my path here in the U.S.
They are 2 stroke 685cc torque monsters built for sidecar motocross over in Europe.
They came with two extra cylinders/heads, a box full of gaskets and 5 pistons.

Finally in my possession after years of watching and waiting I knew exactly where these were going.
Around here they race winged outlaw karts and thats the plan for these.
With no hesitation progress began. Purchased a 2014 QRC Area 51 open roller from a local racer.

Built a mount for the engine. Making the engine sit as low as possible keeping the weight close to the ground.

And here it is in its new mount. The first thing people notice about these is how massive the cylinder really is.

---------- Post added at 11:04 AM ---------- Previous post was at 10:46 AM ----------

The size of the reed cage made me think that this thing is starving for air, so I purchased the largest reed cage they make. It was supposed to go on a Z1000 snowmobile, but it will work well for this.
The intake was smaller than the new reed cage, and it was at an angle to fit into a motorcycle frame. I milled it flat in order to straighten out the air flow and then added a bunch of aluminum to the left side.

Then the grinding and porting began. The side ports really got opened up.
Made a bracket for the reeds to bolt on to.

Here is the reed mounting bracket over the stock intake for size comparison.

After it was opened up.

Reeds in place.

 

[ezcome-ezgo]

Keep these updates coming. This looks awesome.

 

[Mammoth]

Got a 54mm Lectron Carburetor. Then made an intake for it.

Took 3 days working on the seat getting it as low and as far to the left as the kart would allow. Ended up cutting the seat in so many pieces I didn't know if it would get back together again.
Hard to explain everything in writing, but here is the gist of it.

Narrowed the whole seat by 1-1/4". Layed it way back.
Cut out the bottom back corner which was now dragging the ground after laying it back.
Welded in a new bottom back panel parallel to the ground.
Cut out the left side of the seat floor so the frame would clear after pushing it to the left. Then rewelded a new piece around the frame.

Had to move the seat mount farther to the left.
In the end the seat was moved to the left about 3 inches and my body now sits way lower.
Moving everything to the left and lower will make a big improvement when making left turns, because turning left is all these karts are designed to do.

Mounted the motor as far forward and to the left as possible. Had to cut a hole in the right side of the seat to clear the water pump.
The motor now sits 4" to the left from the stock position.

---------- Post added at 11:44 AM ---------- Previous post was at 11:34 AM ----------

My friend designed an expansion chamber for this motor.
He opened a book with the instructions on how to make patterns for the cones.
I followed the writings and drew up the patterns on paper.
Then I cut them out of sheet steel.

Rolled them in a roller.

Then started welding.

 

[ultralight01]

Awesome!!!

 

[Arkparkp4]

Man I wish I could make my own mounts... It's hard to come by for my engine.

 

[bob58o]

You win best engine category already! lol

Very Very Cool!

 

[Mammoth]

Man I wish I could make my own mounts... It's hard to come by for my engine.

You could build one just like it without any fancy tools. The majority of the work was done with a hacksaw and files.

I made some templets for the side plates out of thick paper. Transferred it to aluminum, and then cut them out with a hack saw.

Cleaned up all the edges with files and sandpaper. Used round files in each 90* corner to prevent cracks.

Drilled out the holes, and welded them to a plate.
If you don't have a welder or drill you could probably find someone who does.

I ordered the aluminum from eBay, but it could be made from steel as well.

 

[chancer]

This is cool stuff!
I wish Brett was here to appreciate it!

 

[not_a_bot]

Daaamn. I envy your machinery, but I envy your skills more. Thanks for sharing this fun beast's evolution.

 

[chancer]

How did you come up with the lengths and cone sizes for the Expansion chamber?
I do not personally know how, but from what I understand it makes a big difference in getting it all right.

 

[Flyinhillbilly]

Way cool.

 

[Mammoth]

How did you come up with the lengths and cone sizes for the Expansion chamber?
I do not personally know how, but from what I understand it makes a big difference in getting it all right.

My friend Craig designed the expansion chamber using his 50 years of racing knoledge and two books.
Gordon Jennings Two Stroke Tuners Handbook and Axlender Gram Bell Two Stroke Performance Tuning.

Using the web Opfermanmotors told me what the dyno numbers were, and with that info Craig thought about it for several days and then drew it up.

We checked the port timing and this motor is set to have all the power at a lower rpm. Something equal to a trials bike.

Since its for such a low rpm the pipe has to be real long, and with the displacement being so high the pipe has to be real wide.
5.2 inches in diameter in the middle.

It's big.

When I first met Craig 20 years ago and started asking him questions about how to get more horsepower from engines he said "the best $300 dollars you can spend on engines is on books"


.

---------- Post added at 11:59 PM ---------- Previous post was at 11:52 PM ----------

New intake on the left and stock on the right. It's a lot smoother in person. The camera doesn't pick it up very well.

Here is a shot of the seat. You can see all the welds.

 

[chancer]

Cool sounds like you are on the right track. Like I said I do not personally know. We used to have a member here who was a 2 stroke guru and he built some cool pipes that he designed with a computer model and built them same as you did. Your right they get really BIG when done right. It was all over my head but he was a joy to watch.

 

[Mammoth]

With those two books I could design a pipe, but would have to get it on a dyno to verify the work.
Craig has the years of collected knoledge to be sure of what he is doing.

I just purchased a dyno and hope to mess with this engine on it, but I'm really limited on time with my work schedule, and the kart race season is already in full swing so I need to get it on the track.

 

[mckutzy]

Have you tried the pressure washer method(hydroforming) for puffing the exhaust opposed to welding all the sections together?

 

[Mammoth]

Have you tried the pressure washer method(hydroforming) for puffing the exhaust opposed to welding all the sections together?

Yes, that's the next step in the process after i figure out how it will shape around the kart.
Then it could be made with thinner steel making it lighter. It's .040 steel right now and when hydroformed it can be .030

After testing the engine we might change the dementions a little to fine tune it.

 

[chancer]

Here is the Thread by Desertduler I was referring to, He has some info on the Pipe design. Cool stuff!
http://www.diygokarts.com/vb/showthread.php?t=24346

also here is the program he used:
http://www.buildandclick.com/html/tuned_pipe.html

 

[Mammoth]

Good stuff.
Makes me wish my invader was running so I could tear around like he is doing in the videos.
What happened to desertduler?

 

[chancer]

Long story I guess. He decided to move on from this forum. I actually invited him back just to see your thread. He responded but respectfully told me he was not going to continue to be part of the forum. Anyway we have the info here that he did share.

 

[Mammoth]

Took lots of work getting the pipe shaped and welded, but its almost done.

Bought the biggest air filter that would fit on the 54mm Lectron which was a 7"x7" K&N.

It still wasn't big enough so I added another K&N to the top.

Now its about big enough. With air filters the saying goes the bigger the better. You don't want any resistance.
Here it is stuffed in there.

Here's the flange welded on one end and brazed on the other to prevent cracking.