Why do so many people use Yerfs for their Frankenbuggys

[toomanytoys2]

Just curious about this. Is it because it has such a simple cage to graft on to? Not trying to be a or condensending, but it just seems like there are better quality buggys to start with. Or is it just the shear joy of taking a backyard buggy and turning it into something serious?

[Masteryota]

I think it has a lot to do with availability. I have found at least 4 more spiderbox's around me for cheap with a blown out front or ball joints, and all of them still run! I have seen hammer heads, Tomberlines, and a Carter or two, but they want way too much. Plus, the spider's start out a simple forward only, light chassis, and seems easily modded to add reverse, bigger engine, better suspension, etc..

I can say this, it is much easier to mod a front end with equal length control arms and a simple steering knuckle instead of the unequal length set ups I see on the hammer heads with the tall steering knuckle, while more stable and better steering, the angles are easily mucked up once you start changing it.

[x-bird]

ditto the above, plus the simplicity of the front cage allows a lot of room for additional tubing and freedom of design. overall it's also a better looking design --- ;~) around me though, the spiderboxes are too scarce and pricey.

[ckau]

[QUOTE=toomanytoys2;33494 it just seems like there are better quality buggys to start with. Or is it just the shear joy of taking a backyard buggy and turning it into something serious?[/QUOTE]

I had wanted to build something along these lines since quads and 4-wheelers first came upon the scene. A cross between a quad and a go-cart.
The first time I ever laid eyes on a yerf, two things immediately popped in my mind.. Hey! That's' what I envisioned and ... Shortcut! Here's a unit already working I can fiddle with. A huge part of the work has already been done!
I bought it on the spot. paid like 1,300 and some change for a new yerf. That's a cheap price to pay for a working/ rolling chassis. There were other buggys out there but the main reason I and most others were and still are, drawn to these types is the price. Two thirds less than any quad or 4-wheeler. These buggy allows most of us folks with not so deep pockets the ability to purchase a toy the whole family can use. There are other more quality buggys out there but the initial investment escalates dramatically.

[toomanytoys2]

I am defiantly kicking myself now. I had an almost roller Spiderbox that I sold the frame for cheap. The next week, I fell into a Joyner 650 that doesn’t run. As soon as I saw the Joyner, I could envision a way to graft the front end to the Yerf frame, but alas, it was gone. I currently have a Hammer Head 150, and after the engine mods, I am fairly well pleased. However, the suspension is lacking, so I was thinking of upgrading it. However, 2 things came up.

1st – The wife said no (she likes it the way it is).
2nd – It looks like too much would be involved to convert over to a good A-arm system.

So I intend to part out the Joyner to make $ for my build. But what am I going to build? I am thinking about getting another Yerf and putting the Joyner suspension on it, or Finding a blown 250 with independent rear suspension and redoing the front, plus I have a good ATC 200 engine that is begging for a home, but now I would need a reverse box. Since I am a teacher, I have more free time than most, but since my wife doesn’t work, not that much free $. Plus, I have the what if syndrome. What if I do this, what if I do that – Which I fully blame you nice folks for.

[Masteryota]

Blame?? Yeah ok, we kinda do that too, lol. What model atc 200 do you have? I am using a 200s engine in mine, its a moderate upgrade, but should be more than enough for me, for now.

I'm in the same boat, I'm a wrench, so the mods and work come naturally, but being a wrench, living on the flat rate system makes for inconsistent paychecks, and the wife stays home as well.

[toomanytoys2]

Not sure what model the engine is, but I believe that it must have been one of the first, since there is no suspension on the ATC. When I got it I thought it was a 185 until I noticed the compression release and looked on the cylinder and it said it was a 200.

[Masteryota]

Is it a pull start only? if so, its a 200s, 200x has a kickstart(higher compression), and 200e ans m have electric start. They are all almost identical engines, but the s has the least amount of power(13.5hp). I am replacing the 200s piston with the 200x for more squeeze, hope I can get about 15hp out of it with open intake and exhaust.

[toomanytoys2]

Pull start only, so it must be an s. What are you going to do for reverse? Are you going to use some sort of gearbox, or just leave off reverse. I also read somewhere that you can use a cam from an XR200 and get more power. I'll see if I can find that article.

[Masteryota]

Well, seeing as the yerf did not come with reverse, I'm not heart broken about it. Using a separate gear box to add reverse would soak up too much hp, if that engine put out around 20 or so, it wouldn't be so bad. If I decide to add reverse later, it will likely be a starter and flywheel style mated to the jack shaft, but thats like very last on my list of things to do.

I heard the same thing about the xr200, and the 200x cam, but all the specs I have found indicate the power gain is marginal, and its all in the top end, I want the low end grunt for mine, part of the reason I did not opt for a sportbike engine. I almost bought a complete ninja 250 engine for this thing, but the power doesn't come in till after 6k RPM.

Bumping the compression will increase power throughout the entire RPM range, but you have to be careful about heat, increased compression will result in more heat generated. I plan to use a 14" radiator fan behind the seats to help cool it off.

I did look at the Wiseco pistons, but at $120 for a piston, and the likelyhood of breaking the recoil rope on the trails seemed too big of a risk. The stock runs at 7.6:1, the x model piston runs 9.6:1, the race piston is 10.25:1.

[x-bird]

Originally Posted by Masteryota

Bumping the compression will increase power throughout the entire RPM range, but you have to be careful about heat, increased compression will result in more heat generated. I plan to use a 14" radiator fan behind the seats to help cool it off.

I did look at the Wiseco pistons, but at $120 for a piston, and the likelyhood of breaking the recoil rope on the trails seemed too big of a risk. The stock runs at 7.6:1, the x model piston runs 9.6:1, the race piston is 10.25:1.

After my first test run, a heat shield between the headpipes and the seat is a must --fan idea is a good one too. ...it started getting pretty warm on the backside. been thinking along the same lines about shaving the head or deck a bit, going .010 or .020 over and throwing another rod into it--but again air-cooled design comes into play ...

[Masteryota]

Originally Posted by x-bird

After my first test run, a heat shield between the headpipes and the seat is a must --fan idea is a good one too. ...it started getting pretty warm on the backside. been thinking along the same lines about shaving the head or deck a bit, going .010 or .020 over and throwing another rod into it--but again air-cooled design comes into play ...

My head pipe is in pretty rough shape, and when I make one, or have one made, I will be using a header wrap to help shield the heat away from the riders, and move it to the muffler, which ever muffler I decide to use.

[toomanytoys2]

I agree with the header wrap. That stuff is amazing. I use it on my VW's headers because the oil lines run very close to them and I was getting heat soak into my oil. You can touch the header briefly when at operating temps with the heat wrap on, but you would fry your fingers without it. It also dropped my oil temp 30 degrees.

[n1kogr]

not to jack your thread but i used a yerf as a base just because i got a comlete roller for 100 bucks then sold the complete rear end for 100 so it was a free platform. Im still not done with it but its now a single seat irs with a 2005 kfx 400 engine 5spdw reverse.

[toomanytoys2]

N1kogr,

I would love to see pics of your irs setup when you get it done. I am thinking along the same lines.

David