Go Kart 800 rear axle setup

[Rick Steed]

I'm trying to get parts together for the rear axle. The axle on my GK800 is bent and rusty. So is everything on it. The sprocket hub, axle bearings, and brakes look like crap and I'm not even sure they'll come off the axle. So I'm expecting to replace the whole setup. 

The axle that's on the kart has 34 inch track width, center of tire to center (step to step), but the original specs are for 32 inches. So should I get a 36 inch axle with 2 inch steps, which should produce a 32 inch track width? I'm looking at the Azusa catalog and they have "standard steel" and "flexpruf". I'm assuming I should get the flexpruf one.

On the sprocket hub... the old hub on the axle looks like the Azusa Mark IV vari-hub. Is this the one I should get? 

Azusa sells two types of sprockets for #35 chain: the .160 inch thick TNT and .125 TAL.  Should I be getting the thicker ones? What would be a reasonable assortment of sprockets? I'm planning on getting an inboard Max-Torque clutch for my new MC49. How many teeth should I get for the drive gear? Or should I get an assortment for that as well?

I'm planning on running the kart at whatever vintage events I can find in the Pacific Northwest. I have no idea what tracks that might include, so I suppose some good general purpose gears would do for now. I'll be doing all my testing on the street in front of my house or in the parking garage at work on the weekends until I find a race/meet.

Thanks!
-Rick

[steve miller]

..might wanna try don axe for an axle ..
clutch with a 49 id prolly get a 9 and start with 68-70 on bottom ..
keep eye out on craigslist local tracks for race buy outs ..lots times get whole stacks sprockets etc.. save 100,s
I use the thick sprockets good chain ..

[doug tenney]

The straightness on Azusa axles isn't the best. But, the application matters. Something good enough for a sprint kart is often unusable on an enduro. This includes wheel ba1ance and.axle run-out.
Just starting out, with an Mc49 on a sprint kart, I think you'll be fine with an Azusa axle. I never priced one from Don Axe, but I know guys say there's no comparison on straightness. With Azusa, most chose the Flexproof type.
As you probably know, axle width is a key tuning parameter for making the handle to your liking. Wider axle = looser, but beyond that, I defer to the other guys on here.
For width measrements, be sure if the width listed by the mfr includes the stub ends or not!

You'll want a 9-tooth clutch for this application, and for most sprint tracks, you'll want a ratio somewhere around 7.3:1. That translates to a 66-tooth axle sprocket. You should have at least one spare sprocket, in case you put the RR wheel off into the dirt and whack the sprocket on the edge of the pavement. I would go with the wider (standard) sprocket thickness, split aluminum for sure.

The Varihub is widely used, period correct and despised by many. That's because it shifts to the side when you tighten it. It's up to you. If you need to replace it, there are several billet hub choices...
Toss the axle bearing set screws in favor of split collars to secure your new axle laterally. They're more reliable and won't put burrs all over the axle, making maintenance miserable later.

[ted johnson]

I guess it all depends on how worried you are about originality. REMEMBER, a whole lot of us replaced things like axles, sprocket hubs and sprockets and wheels before the kart even hit the track. Anything you want to upgrade is fine, as long as it is period correct. The original 800 rear axles were weird, with a 7/8" step in there. Only the original style Azusa wheels will fit that axle. I find that the Azusa Flexpruf axles are fine. They have improved their runout greatly. I have one in the Photon, and it works very well. Don't buy the standard Azusa axle, it's not as strong, nor is it drilled for the mandatory cotter pins. I prefer good quality .156 thick sprockets like Horstman, RLV or Williams over Azusa, and I prefer a clamp style hub like Horstman or Comet Kart Sales' proprietary clamp hub-it's so much easier to align your axle sprocket to your clutch sprocket. RLV chain or equal, too. TJ

[Jim Waltz]

It also is not a bad idea to go to some events and see what others have done.

The GK 800's and 1200's are fairly common, so chances are you'd see at least a couple at almost any event.

And, ANYONE you ask will tell you everything they know.  We're those kind of folks.

Teddy is right about the original axle being stepped from 1" to 7/8" then to 3/4".  The only wheels you can run are the original Azusa wheels made for Go Kart.

If you are not in a hurry (and I mean really not in a hurry) I could potentially set you up with a full set of these wheels in moderately good (not "show") condition.

You might want to check out the GK800 I put together for my buddy Tim, which appears in the Member Collections page here on the Forum.  I'd be glad to measure and/or photograph anything you want on the kart.  Again, as long as you are patient.  I still work (two jobs) and have a disabled wife, so I operate on 30 cycle rather than 60 cycle power.

[David Luciani]

i'm an expert in wrecking weekends with stupid missed details.

so i can assure you it's better to use reliable drive train bits and  parts on a runner.

sogo with the best axle you can reasonably afford.
don makes a great product i'm told.
if you don't the loosening of your teeth fillings from a "slightly" out of true axle will surely convince you to upgrade later!

if you use the original hub be prepared to be annoyed with it fairly often at the track.
tossing a chain on a hard corner when you're moving through the pack is a terrible lesson to learn.
the old school hubs are/were poorly produced so they tend to get out of perfect square as you tighten them. 
if you have lath skill you can correct a great deal of the poor machining but it's still a b!#th to align.
i prefer the clamp style by horstman or comet myself.

in choosing your parts as far as originality goes you need to consider what you're doing with the kart.

if it's primarally a show kart you'd be wise to use the crappy 1960 chain and correct sprocket.
some of the karts we judge are so close to perfect that points get lost on minor details.

if you intend to run it a considered approach to keeping it original looking with modern convenience is the way to go.
 i hate seeing rear karts with totally modern brakes or sprockets or rims (annodized is a particular pet peeve)
 modern parts with a vintage look and vib are fine by me and most others.

[Rick Steed]

Thanks for the feedback. Since this kart will be primarily a runner not a show queen I'll probably get stuff that is readily available and replaceable. I think this rules out hunting for original wheels and getting a custom made axle at this stage. I'll definitely use split collars to locate the axle. And if I stick with the Azusa vari-hub I'll dial it in on my lathe to make sure everything is true. At least it uses a split collar flange to mount to the axle.

[ted johnson]

The Azusa Vari-Hub sprocket hub has a tapered flanged bushing which clamps the hub to the axle. As you tighten the three or four bolts in the tapered bushing, the sprocket hub moves axially. This is a PITA. Once you've tried a single screw clamp hub such as Horstman's or Comet Kart Sales', you won't go back.
https://cometkartsales.com/Sprocket-Hubs/
the hub at the top of the page, is an especially good one. I have them on all three karts. They run true, look nice and are light.  Where you tighten the clamp screw, the sprocket stays. No creep, no misalignment. We quit using taper lock sprocket hubs in 1960, when Reed Engineering first brought out their clamp hub. TJ

[Rick Steed]

Thanks Ted. I missed that one when searching. I still haven't been able to locate a Horstman hub online yet.

[ted johnson]

The Horstman hubs come on eBay seldom. I don't know who makes clamp hubs nowdays except for Comet, and maybe Appco? BE CERTAIN the one you're looking at is for the 1" axle. I see Comet offers an Appco hub, but I noticed it was 1-1/4". Maybe call Steve Alexander at Comet and ask him about the Appco 1". It's not quite as nice as the Comet hub, but is a lot cheaper and I used to use them in days gone by with success. Ted