Murray Hard Drive Project

[Hollowlog]

Just picked this up a week ago. It would run briefly on starter fluid. We installed a new carburetor, cleaned up the spark plug and have it running well. Also installed a new clutch and throttle cable. We then found out the small gear on the jack shaft is spent so we are in the process of rebuilding that whole assembly since you can’t just buy a replacement. Also throwing new chains on it. Not a rust bucket but not a cream puff. Hopefully my son will finally get to ride it sometime this week.

 

[Grizzlymi]

Very cool kart! Should be a fun and enjoyable project. Looking forward to its progress.

 

[Whitetrashrocker]

Man I need to find one of those. Thats nice.

 

[panchothedog]

That's a nice find. He should have a blast driving it. Ah maybe you too Dad.

 

[Hellion]

We then found out the small gear on the jack shaft is spent so we are in the process of rebuilding that whole assembly since you can’t just buy a replacement.

Would love to see that process (photos please) and the condition of the original assembly. We like mechanical post-mortem autopsies and maximum excruciating, nauseating detail. Someone here said it better than me though

Aside from that you appear to be having no problems. Born with a silver wrench in your mouth?

Your kart is quite a find in that condition. If it’s Bubba-bombed in rattle can paint and mismatched, non-OEM parts, no matter how well done, I don’t want it.

 

[Hollowlog]

Haha, I will post some pics and also the parts he purchased to rebuild the rear gear assembly. I am glad to hear that you think it is in good shape. I believe it is all stock from what I can see from the diagram I found online. My son wants to clean it all up and give it a new paint job but I think he will wait to do that until next year. We will probably just clean up and paint the areas with minor rust to slow down the rusting process.

My other son is still looking for a go kart and now after picking up this one, I will be better prepared for what to look for.

 

[electricgokart]

Just picked this up a week ago. It would run briefly on starter fluid. We installed a new carburetor, cleaned up the spark plug and have it running well. Also installed a new clutch and throttle cable. We then found out the small gear on the jack shaft is spent so we are in the process of rebuilding that whole assembly since you can’t just buy a replacement. Also throwing new chains on it. Not a rust bucket but not a cream puff. Hopefully my son will finally get to ride it sometime this week.

Super excited to see this complete. Are you going to repaint it?

 

[Hollowlog]

Thanks for sharing in the enthusiasm! Yes, my son would like to paint it. I suggested getting it up and running and ride it a bit first, then take the time to disassemble and give it a proper paint job. I think he would like to make it look as nice as possible.

 

[Denny]

Make it reliable then blow it apart for paint.

 

[Hollowlog]

Parts came yesterday and we assembled as much as we could after dinner and before bedtime for my son. The Jackshaft is rebuilt with really the only difference that the spokes we found did not match exactly. Instead of a 26 tooth sprocket, which connects to the 10t sprocket on the centrifugal clutch, we have a 20t. Hopefully that will be okay. Chain is all hooked up, however, we need to move the engine forward to get the appropriate tension on that chain. Fingers crossed, he will be taking it for his first ride tonight.

 

[Whitetrashrocker]

Looking good.
Whats the tooth count on all 4 sprockets and the tire diameter.
That 6 tooth difference could change the gearing quit a bit.

 

[Hollowlog]

Thanks!

Clutch to Jackshaft is 10t to 20t, respectively
Jackshaft to axle is 10t to 36t
Tire diameter is 16”

 

[Whitetrashrocker]

If my math is correct that is a 7.2:1ratio.

Wheres bobO when we need him. He would tell you the actual top speeds.

That should be a good start. Not to fast and will be quick off the line.

You can always get different tooth sprockets later to tune the gearing later as needed.

 

[Hollowlog]

I think your math is spot on. I just did a google search and sounds like the typical full throttle of the 206cc Tecumseh engine is 3600rpm so should peak somewhere around 7.5mph with the current setup.

 

[JimD]

You are wrong on your speed, it would be 23.8mph at 3,600rpm. which is typical for kart speeds back in the day when they were made in the USA. Would recommend full face helmet, teeth are damn expensive today. If you want to slow it down you have to increase the size of the 36 tooth sprocket. I can forward you a speed calculation program we wrote to give people a quick answer when they asked how fast will they be going. Just send me an e-mail at Max-Torque. It takes into consideration engine rpm, tire size, and the 4 sprockets being used.

 

[Hellion]

Jim, you need Max-Torque in your avatar and your official title under your name. Then again you may not fly under the radar as much anymore.

 

[Hollowlog]

Awesome, I was thinking the speed that showed on the calculator was pretty slow. Yes, he will be wearing a full face helmet…much more protection than what I used as a kid. What is the full email? I am attaching a photo from the website I used…just curious where I went wrong.

Thanks!