New guy old kart

[Cowinthefog]

Hello go kart wizards!

I have an older Murray Explorer I just purchased, I believe it is a 1999. I have posted some pictures. The keen observer will notice there are no tires on the rear rims. There are two pictures of the engine simply sitting on the plate two different directions. This unit has a jack shaft, which appears to be in good shape. The motor on it is NOT the stock motor. It is, I believe, a 10 HP B&S from a generator. It does not have the proper fuel tank on it which I am not concerned about. The rear tires are off so I can try and creatively remove the rims that are SUPER frozen on. Also not a big concern. I have been trying to do some research on drive systems and such. It had a 6.5 HP motor and a centrifugal clutch from the manufacturer. I would like to keep the 10 HP motor, which I believe would do better with a torque converter set up. I think this means getting rid of the clutch, which I do wonder about. Also I have read that a 40 series TC set up is the most efficient way to go. I don't know if I need to (or should?) use the jack shaft or bypass it, hence the pictures of the motor facing two ways. The motor seems to run fine, so I will use it unless it totally won't work. It has a 7/8 tapered shaft which is long enough to cut off the tapered portion off and weld an adapter sleeve on to make it 1" and go with a standard TC setup. The jack shaft is a 3/4" diameter. I can sort out the gas tank and the tires. I will be upgrading the brakes to a hydraulic system. I plan to cut and re weld the exhaust pipe pointed a sensible direction. My burning questions are, do I need to use the jack shaft (which way should the motor face) and if not, what is the recommended way of getting rid of the clutch? All my other questions relate to gearing and which way the motor faces. The tires are 18x9.5x8. Yes, the front tires are slicks. Always having traction is predictable and boring..... I also wonder about chain sizing, I tried reading about the differences but haven't found much helpful info yet. Please let me know if I need to post more pictures. Thanks!

Josh

 

[Denny]

Aaahh gwas hoppa, you have much to learn. That kart probably came with a 20 series CVT when new. Stepping up to a 40 with the 10 hp is a wise decision. But you may need to step up to a longer shaft for the jack shaft. That’s OK and easy to change. BMI, GoKart Supply, OMB, Go Power Sports and MFG Supply are parts suppliers with high quality parts and should have all you may need for this project. Also check the Jungle store! Don’t be surprised if you end up having to cut the axle because you can’t get the rims off. Heat, beat and penetrating oil are your friends in this endeavor! That should be enough to get you frustrated for now!

 

[Cowinthefog]

Aaahh gwas hoppa, you have much to learn. That kart probably came with a 20 series CVT when new. Stepping up to a 40 with the 10 hp is a wise decision. But you may need to step up to a longer shaft for the jack shaft. That’s OK and easy to change. BMI, GoKart Supply, OMB, Go Power Sports and MFG Supply are parts suppliers with high quality parts and should have all you may need for this project. Also check the Jungle store! Don’t be surprised if you end up having to cut the axle because you can’t get the rims off. Heat, beat and penetrating oil are your friends in this endeavor! That should be enough to get you frustrated for now!

But sensei, how will I know if the jack shaft is too short?

 

[Cowinthefog]

And do I need to keep it? I'm trying to figure out if the driven clutch bore diameter matters (is it common to the jack shaft?). It looks like a chain connects the driven clutch to the jack shaft in videos I've seen. But if I don't NEED the jack shaft, I can probably spin the motor around and put the crankshaft almost right above the axle sprocket. I don't know if one way is preferable or simply more effective. Thanks for the help!

 

[Denny]

You need to spin the engine around unless you like driving around backwards. Keep the jackshaft! You need it for the 40 series! You may need to change the diameter of the shaft to suit the driven diameter.

 

[Cowinthefog]

Doh! Thanks for the common sense shoulder punch. I totally didn't think of that...buuuut I see it now. So, that is my last big question-I'm not grasping the mechanical connections here. I THINK-engine crankshaft connected to drive pulley of torque converter-belt connects drive pulley to driven pulley-sprocket behind driven pulley connects to jackshaft with a chain-opposite end of jack shaft sprocket connects to axle sprocket via a chain. Yes?

 

[Denny]

Something like that. Your catching on.

 

[panchothedog]

Standard size for the driven clutch on a 40 series torque converter is 3/4" . So your current jack shaft should work fine.

 

[Cowinthefog]

So, I discovered the driven shaft on my torque converter is 7/8 through the bearings and 3/4 outside the bearings. This tells me I can't use my existing jack shaft or even buy another without accomodating the different diameter. I would prefer to avoid that if possible. Also, I had to jack the motor up 4.5 inches for the backing plate to clear the jack shaft housing and line up the sprockets. Even if I try to find a longer compatible jack shaft, the motor would have to sit way off to the left to line up the shaft bores of the torque converter and jack shaft...what are my options at this point? Do I relly NEED the jack shaft? Does it serve a mechanical purpose besides moving the drive sprocket to the other side? I don't know...the wood is for mock up purposes...

 

[Cowinthefog]

What if I make a base platform roughly where the motor is sitting, bypass (or remove) the jack shaft and go straight down to the drive sprocket, having moved it to the same side? It looks like it would work? What don't I see? If I remove the JS, I can lower the motor a couple inches. Yes, the brake disc is on the same side, but it looks like there is room.

 

[Denny]

If you removed the unnecessary and crappy style locking collar you could slide the sprocket over on the jack shaft. Things look like they should line up then? Or just move the engine over.

 

[qtband]

Here is what the original setup looks like. I just started restoring this one today.

 

[qtband]

Lose that backing plate.

 

[Cowinthefog]

Alright, I got everything placed, attached, connected, etc. The carb was junk, Nikki version, so I got a Chinese/Amazon version that seems ok, except it runs lean. It will only idle with the choke plate closed. Any tricks to get a bit more fuel through these little things?

 

[Cowinthefog]

Drill the idle metering jet a touch bigger?

 

[Cowinthefog]

 

[Cowinthefog]

So, left to my own devices, this is what I came up with. I appreciate the advice given. But I always have sooo many questions. I couldn't see a way to make the engine work with the jack shaft and that engine and the torque converter. So I removed the jack shaft and swapped sides with the axle sprocket and brake disc. I didn't understand the hydraulic brake set up I bought was for handle bar mounted brakes so I attached it in the back to work with the rod I already had. Maybe not my best ideas, but it all looks to work well enough to test and hey, it's not going to the moon, right?

 

[Cowinthefog]

Would you believe I let a blind kid do the welding? ....

 

[Denny]

Yes, yes I would.