Centrifugal Clutch with Needle Bearings

[Wicked_Daddy]

Need some resource help...

I have a CC that has needle bearings between the clutch drum and the inner sleeve. It has an 18 tooth sprocket. It came with the original purchase of the used engine - no idea who makes it. While this clutch is excellent quality, I wanted something with 12 teeth. So I bought one, not realizing it has only an oil bushing. I oiled it as prescribed and it generally works OK. However, the fit of the drum on the inner sleeve is rather loose and it vibrates on the inner sleeve to the point it creates a harmonic friction that will kill the engine at idle. Maybe it's just a cheap one (I admit to getting it on Amazon).

So I am hunting for a 12 tooth CC that has the needle bearings and at this point, have been unsuccessful.

Any info is appreciated.

 

[Hellion]

What is the chain size or pitch you need?

So the tolerances of the needle bearing clutch are more precise? In my experience the common oilite bushing clutches are all a little rattly with clearances to account for heat expansion and/or manufacturing variances, but that is very interesting.

5 second search results:

12T Needle Bearing Centrifugal Clutch, #420

12T Needle Bearing Centrifugal Clutch, #420

www.studzracing.com

 

[Wicked_Daddy]

Yep, saw that but I have #35 Chain and 3/4 shaft. Coleman makes one for a 5/8 shaft. Ugh.

 

[Wicked_Daddy]

Having now done my research, I will go with a true Max-Torque clutch. I believe the real failure is not the bearing issue, but just a cheap choice from Amazon that has proven to be a waste of money and time.

 

[Denny]

The owner of Max-Torque is a friend of ours on here. DM him @JimD .

 

[JimD]

The smallest 3/4" crankshaft sprocket you can get with a needle bearing is a 13 tooth. All 12 tooth sprockets in the #35 with be a bushing. BUT neither the bushing or the needle bearing are doing anything once you are moving. They are non-functional while moving, they only come into play at idle. W stays at idle very long, very few people, its start the engine and go and when you are moving the clutch is turning as one piece of steel. You oil the bushing when you are done riding while the clutch is warm and the bushing will suck in the oil and last for years. You oil it before you go riding and you haven't done nothing except coat your kart with oil because it sure didn't stay on the bushing or chain.

If a clutch has a built-in-key then the sleeve will not be harden. The sleeve is what the drum and sprocket rotate around on. Put a file to it to see if it is hardened and if it is not then i would stay away from the needle bearing because it will gall the sleeve quickly and then the tolerances take a quick dump. The clutch with a keyway can be hardened because if it does shrink you can always hone it open but it is a throw away if it shrinks with the built-in-key because there is no way to salvage it.

Ratech made a 12 tooth needle bearing clutch that was very unique but each of the needles had to be inserted into the sprocket by hand. It was too costly and the market wasn't willing to pay for it and the fun kart market he was after doesn't make changes unless it was cheaper than what they were paying for a clutch.

 

[Wicked_Daddy]

Thank you for the thorough explanation, Jim. I purchased 2 Max Torque 12T clutches today. Hopefully, I will be ripping around on Saturday!

 

[Wicked_Daddy]

All 12 tooth sprockets in the #35 with be a bushing.

My 2 Max-Torque clutches arrived today - both 12T, #35. I have to say that I am impressed. I compared them to the one I bought off Scamazon and what a profound difference. I don't normally go cheap but I was just experimenting and luckily, that was an inexpensive lesson. The differences are night and day and I see how the hardened sleeve plays a crucial role. The oiled bushing is obvious. The Chinese clutch doesn't even have a bushing and the key is built in - no hardening! There is no wobble in the MT clutch drum, it spins smoothly and freely. I am super excited to install the MT on the Ducar that I just finished building and go for a run.

Great quality. Well done!

 

[JimD]

Thank you for the fine compliments. Wish I could take credit for the design but the original owner, George Fields, came up with that design in 1970 and it is the most copied clutch out there. My biggest competitor, Comet, copied it in 1983 and the china boys have also done the same. The heart of a clutch is the bushing and the spring. Looking at a spring you cannot tell which is music wire and which is stainless steel without dipping them in nitric acid. The one that dissolves was music wire and is what most springs are made from. The good spring made with stainless steel cost 5 times more but it also can take more than twice the heat 250F vs. 550F. Since an engine runs hotter than 250F you now know why the cheaper copy has problems. Don't dip the springs in nitric acid the fumes are not good for your health-- THEY CAN KILL YOU!!!!

 

[ezcome-ezgo]

Dang, so what am I supposed to do with all this nitric acid?

 

[JimD]

Nitric acid is used to create many different types of explosives like nitroglycerin and trinitroglycerin (TNT). These are military grade and used for national defense. Be inventive, EZCOME-EZGO you will come up with something in your lab. I got a couple bags of fertilizer you can mix with it and then .......

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[ezcome-ezgo]

Ok, so the FBI is reading this now. I will shut up.

 

[JimD]

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Very good movie that you will enjoy and a learning tool.