Unorthodox for Hardline: XR80 YerfDog

My 7 year old son Cory is building this Yerf Dog, after he grenaded the Tecumseh 6.5 that was in it. We figured we'd find something they still made parts for so I went to Cycle One in Knoxville and dropped a buck or a hundred and fifty and came out with a nearly-complete Honad XR80 motor. Took her home and found out quickly it wouldn't be a simple bolt-in. With the motor all the way against the seat, the bike sprocket sat 1/2" in front of the axle centerline. So I started hacking the frame to stretch the wheelbase and drop the eng sprocket low enough not to eat up the case with the chain. By the way, I still have to do all the welding, he's not a fan of spatter burns.

Wasn't gonna work.

Easiest way to remove the frame.

Removed the bar that mounts the frame to the rest of the buggy.

Started welding in some squarr...

Re-used the rear portion... Dunno why.

Put in the crossmember for the engine mounts and gusseted the heck out of 'er.

Another angle. The boy LOOOVES Wes Kean's buggy's open headers, so we tried to copy it.... as much as one can copy a big-block open header to a lil ricer-bike.

wooompoww lookin good

Go-kart racing fuel tank I scored... FO FREE

Mounted an ammo box to carry recovery essentials. You know, like a juice box, a slingshot, Nintendo DS...

Note: hillbilly intake- radiator hose and SBC valve cover breather thingy... Heck, I don't even own a Chebby!


Much thanks to lil brother for the help! Teachin' the boys how to wrench!
Only things left are clutch, throttle and brake cables, plumbing and wiring, and put a chain on 'er! Then time for some bounty hills and lotsa WOOPOW!

Wish I had one of those when I was 7! Looks pretty cool.

Need to turn him loose with a groover on those rear tires!

Looks good, what's the HP rating on an xr80?

TBItoy said:

Need to turn him loose with a groover on those rear tires!

Looks good, what's the HP rating on an xr80?

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Oh, you'd better believe they're getting a Tennessee cut! Hmm, hp on an 80 is.... Not enough for that boy, I can promise you that! He'd drive it like a dirt late model with the 6.5 on it, burp the throttle to set it up, flatfoot it and countersteer all the way around the corner! Proud pappy here!

Great job Cory!

I bet that things gonna rip up the yard. ;D Gonna need some video there Dad!

Probably have to do a.rejet on the carb with that new intake design. Look up on thumpertalk what the guys are running with open exhaust and airbox mods. If not she is going to be waaaay to lean

That thing is flat out cool!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
That bad boy needs a set of these on it!!!!

Thanks for the tip CheapJ7! Those paddles might be out of the budget haha!

Cool! My 7 yr old has a Yerf too. His is the 3206 where yours is the 3203. Have you upgraded the front ball joints and spindles yet? Those are very week on these carts. I haven't on ours yet but our balljoints could go at any time considering we're running 23x8-11 MudHooks on the front. :****: It's a fun cart. I still need to put a bigger sprocket on rear to make up for the 25x12-9 tires on back.


If you haven't found them already, check out www.buggymasters.com, www.bmikarts.com and www.buggydepot.com for lots of parts and information.

The best setup I could find was a 105 main jet, stock pilot, and drop the clip one or two notches on the needle. fuel air screw 1 3/4 turns out from full seat.
May still have a small off idle stumble when you crack the throttle fast from idle to wide open due to those non pumper carbs needing a little more back pressure than you are giving it.

Should be fine thought rolling into it, or it will be so small you shouldn't notice.

Sweet! See if you can come up with a set of Honda ATV wheels and tires like jpony did, then hit up Interco's blem page for some cheap meats for that thing.

grcthird said:

Sweet! See if you can come up with a set of Honda ATV wheels and tires like jpony did, then hit up Interco's blem page for some cheap meats for that thing.

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The originals just used a spindle bolt so you'll have to put hubs on the front. Hard to find 4x110 but you can redrill some 4x4s like I did. 4x110 fits perfect on the rear with no mods.

Those 25s are really too big for it because I need to go to a 45T sprocket which will require relocating my rear axle. Everyone on BuggyMasters swears by the 22x8-10 with a 39T sprocket.

HOLY CRAP he is gonna have fun in that thang man

I know an old school XR80 engine is tough as hell, "also see I would like to know just exactly how many miles I put on an XR80 I had as a kid" :****:

keep us updated

ETO said:

That thing is flat out cool!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
That bad boy needs a set of these on it!!!!

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where did you find these tires at and what sizes do they come in?

ridenrace6 said:

where did you find these tires at and what sizes do they come in?

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They are Interco Auquatorque tires. They only come in one size it is a 25/12/9 and they are kinda high for a ATV tire around $150 each but damn they are some bad looking tires.

Thanks for all the advice, fellers! Very helpful links too, jpony! I'm about to head down to the bike shop where I bought the motor to ask how to hook up that little coil doober. I have absolutely ZERO knowlege about a bike, except how to ride one...... and barely at that! The boy thanks you too!

RobbyBobby will be extremely jealous of this monster1 :****:

jayphizzle said:

RobbyBobby will be extremely jealous of this monster1 :****:

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Big Bird #2!

Anyhoo, progress-

Nifty little air cleaner I built from a 4" to 1 1/4" PVC adapter and a 6" cut down to 5" air cleaner top. Uses a 4" filter. Held on with radiator hose.

Coil holder-onner-doober from scrap piece of polished treadplate.

Had 2 shifters, connected by linkage. Having Precision Machine whittle me out 2 billet shifters and one will say "Cory" on it.

The motor swap stretched the wheelbase out a little more than I would have liked, but it just means room for bigger meats! Maybe some of them Robby Bobby Thornyburgs with a Tennessee cut!