Yerfdog Meet CBR 600

[jbmatth]

I thought I had posted my build here previously but I suppose I never did, so here goes. I started with a Yerfdog my cousin gifted my brothers and me in ~2002 when he worked for them. It was initially to test the strength of the parts as R&D for them and he would send us parts as we broke them. There are 6 brothers so there was no shortage of broken parts, roll overs, etc. When he left the company the free parts dried up and we pretty well parked it the last 15 or more years. I pulled it home around 2017 and worked on the spider box some and noticed the tank was trashed so stopped working on it in favor of other projects.






This past winter I found a wrecked 1997 Honda CBR 600 that was to be the donor for the engine, trans, and fuel system. Pulled them both apart and it was interesting pulling the engine from the bike frame but it worked out:


Cut, grind, weld, repeat:


Test fit on the cart rev. 1, so far so good:


Next up radiator and fan mounts:


TBC...

JB

 

[jbmatth]

Next came the air box and some wiring mounting:


Brake/tail light and rear blinkers came next, why would I do that you ask? Well Oklahoma has some pretty lax laws on registering and I planned to get a tag for it.


I had a set of C4 Corvette seats I'd been using as shop seating and decided to try them on for size, surprisingly they fit perfect:


Computer and relay wiring mounted, I also took this oportunity to clean up some of the wiring and add new wiring loom:


Then the batter mount was modified and mounted back in the factory cart location:


Overview of where that got me:


TBC...

JB

 

[jbmatth]

I hooked the CBR throttle cable up to the cart pedal pretty easy:


Then came the shifter, using a few bell crank type levers it was pretty easy, I had to buy a few different cable to get the hand clutch to work but it now does and works great:


The location is not ideal and I plan to eventually modify it to be in a better location for when I'm ripping through the gears. I then used stainless braided AN line to make the rear break work:


Finished the C4 seat mounts:


Then it was the cage, fuel tank, and some 5 point harnesses:


TBC...

JB

 

[jbmatth]

That was it, it was all ready to take for a rip around, here is the drivable product:






From start to finish it took about 1.5 months working about an hour a day and a few hours each weekend. Sadly, that is the condition it is still in, once it was running and driving I took it for a few spins and it honestly made me think I was going to kill myself or at least maim me. I do have two 5 point harnesses in it now and have a few things on the punch list. It needs more rear spring, a chain tensioner, better steering is a must, and I need to mount all of the controls and gauge cluster on the front cross bar somewhere. To say this thing is a blast and fun to drive is an understatement, it'll go 45 on gravel and blow the tires off like they aren't even there. On pavement the entire thing is scary and all over the road. Now that winter is here and some other projects are done like my Gambler 500 lifted Festiva, tractor, farm truck, v8 S10, etc. I would like to finely finish this to either drive more or sell. Let me know what you think I'm curious what feedback I'll receive.

JB

 

[ezcome-ezgo]

Looks sketchy and dangerous. I love it.

 

[gegcorp2012]

I think it's great !!

Nice work on the mechanical as well, and to have something drivable in a month and a half is a great accomplishment.

@Joe-405 has The fastest Yerf Dog on the planet and won the 2018 Build Off with his work. Check out his build thread to see what he did. He has a scary story or two for you, I bet.

Also seen another build recently with a 500 CC Ninja in it, but not as many construction photos.

BTW, Thanks for posting pictures of how you built your mini buggy.

 

[jbmatth]

Looks sketchy and dangerous. I love it.

It is all of the above and I really enjoy it as well.

I think it's great !!

Nice work on the mechanical as well, and to have something drivable in a month and a half is a great accomplishment.

@Joe-405 has The fastest Yerf Dog on the planet and won the 2018 Build Off with his work. Check out his build thread to see what he did. He has a scary story or two for you, I bet.

Also seen another build recently with a 500 CC Ninja in it, but not as many construction photos.

BTW, Thanks for posting pictures of how you built your mini buggy.

I read his thread last year before deciding to build mine, he did a fantastic job, mine is not in the same league. I build a lot of crazy stuff and usually jump from project to project quickly when I'm 90% complete but tired of spending money on it. If you would like to see more photos just ask, I have plenty more I didn't post.

JB

 

[Joe-405]

I tried my shocks where the factory spot was. That was part of the reason for the new bars around my engine for better placement more towards the rear. I tried 4 stronger shocks also. Still didn’t work.

good job tho figuring it all out.

 

[jbmatth]

I tried my shocks where the factory spot was. That was part of the reason for the new bars around my engine for better placement more towards the rear. I tried 4 stronger shocks also. Still didn’t work.

good job tho figuring it all out.

The shocks work, but I just don't have enough spring in the rear especially since I now have a swing arm back there about a foot longer than stock. I have an idea on the shocks/springs I want to use but just have to get it back in the working bay of the shop.

In other news I'm putting a predator engine in my little mini bike sans governor this evening hopefully so maybe the cart will make it to the top of the list soon.

JB

 

[Joe-405]

Your not seeing what I’m saying. The geometry is so far off and when the rear is pushed away it will never work. Even if you did find a strong enough shock/coil over it will snap the mounts off.

I know I tried about 15 different ones. And I even put 4 to try it also. Never had enough placement cause the mounts were too far forward.

 

[jbmatth]

@Joe-405 I see what you mean now, yes with all of that extra leverage from the extension there is likely to be no go cart coilover strong enough to get what I need. Especially with as how thin the tubing is on the cage of these things. It now just becomes a math problem, well I guess more of a statics equation to determine what spring rates I would need at any given location. I suppose I could go crazy and use a set of QA1 coilovers I have left over from my cobra build, they may even be single adjustable as well as height and preload. Might be overkill for a cart I only have $700 or so in now.

JB

 

[Joe-405]

If you just run a u shaped bar around the engine area and just tie it in your current cage then you could relocate the shocks more to the rear. It’s would really only be 2 bends and a couple straight pieces. It would look like what I did but simplified.

you don’t have to go to the extreme I did with a full cage from a chassis shop. Mine was meant for grudge racing on a drag strip so I needed extra to be safe.

 

[jbmatth]

Many ways to skin this cat, it'll depend on the shocks and springs I use then the math will tell me the rest. Luckily I have a tubing bender I bought to build the cage for my Gambler 500 car this past winter and I have some left over metal from that as well.

In truth when you or I in this case put this much power in a go cart the factory "brush cage" is no where near strong enough to keep the occupants safe in the event of a wreck. I suspect I'll get it done and the kinks mostly worked out and sell it down the road.

JB