Brand new clutch fried after first run? Why, oh why?

Dan1980

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Hey everyone, everywhere, anywhere!

The kart can be seen at our other post here.



Here goes.

Being that this is our first time ever replacing a clutch maybe we got the wrong one or maybe we put it on wrong. Thought it was on well enough so we had fun for about an hour or so tearing up the property. It started smoking a good bit so I figured it was just the light oil burning off and generally getting broke in. Seemed all was fine until the next day we tried starting up and it was groaning really bad. Pulled it off and the brass bearing is all cracked up. So obviously it went bad. The thing is supposed to be heavy duty. What did we do? It's a Hillard brand with no setscrew. The original did have a setscrew. It was mounted too far inboard to line up with the drive sprocket perfectly but it lasted quite a while before it finally lost grip. It also had no outer bolt holding it in place- only the setscrew.

First off we had to mount it with an outboard orientation. It also needed to be moved over sideways away from the motor a bit to better line up with the drive sprocket. The instructions for this clutch only show it mounted with it completely riding on the shaft and seem to call for a 1/32" to 1/16" gap between the outer edge of the clutch and the outer edge of the shaft. Naturally, that wouldn't have been enough adjustment; so, with the clutch sprocket fully in line with the drive sprocket the clutch ended up being about a quarter inch past the end of the shaft. We were worried that could be a problem so we scoured the internet and didn't come up with an answer except that it seems lots of folks have their clutches mounted somewhat off the shaft with no problem. Seems they just use longer bolts on the end of the output shaft. The clutch came with a short cheap zinc bolt and cheapo washers so I knew we would need a longer bolt. Could't wait of course so we went ahead and just used the short one and it actually stayed on the entire time and without getting loose, no Locktite.

So from start to finish we cleaned/polished the output shaft and key-way. Lubed up the clutch bearing with light oil. In order to move the sprocket over in line with the drive sprocket we had to install it with two large brass washers on the inner motor side of the shaft which left it sitting out past the shaft. This is where my son thinks the problem lies. I didn't find out the torque value for the shaft bolt but figured it just needed to be real tight so I tightened it by hand until the motor spun freely over. Then I had him pull on the starter cord while I tightened it and it got so tight it bent and pulled/drew the cheapo washer it came with up into the clutch hole towards the shaft. That was one thin, flimsy washer. The clutch sprocket still spun freely because all the pressure was only on the brass bushing that it rides on. So, I thought everything was okay. We went to test ride and ended up not because there was trash in the carb which we didn't get to until the next day. So we didn't actually ride it with the bolt that tight Then, after watching a video of how tight someone else got their bolt under the same circumstance of having the clutch out past the shaft I had second thoughts about the tightness of the bolt. So, the next day, we loosened the bolt and only got it tightened down a hair past when the motor starts spinning. Got the carb cleaned up and drove it like that without issue -until now.

So, did my initial possible over-tightening of that clutch brass bearing weaken it to the point of going bad early? Did I order the wrong clutch? One that can't handle being installed out past the end of the shaft? I wish the shaft was longer because our research seems to conclude that the clutch needs a bit of wiggle room, a space to free float back and forth on the output shaft as the chain goes round and round. And just so you know we're using the Predator 212.

Sorry this is so long winded. I really tried. Thanksies!
 

JTSpeedDemon

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You're over-thinking it, it sounds almost certainly like a case of too tall gearing. That's a 10 tooth sprocket, what is your tooth count on your axle? Depending on your tire size you want around a 6:1 to 8:1 final drive.
 

Denny

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Gearing, weight and tire size. That is what we need. While you gave a lot of information it was just not the right stuff.
 

Dan1980

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You're over-thinking it, it sounds almost certainly like a case of too tall gearing. That's a 10 tooth sprocket, what is your tooth count on your axle? Depending on your tire size you want around a 6:1 to 8:1 final drive.
had the same issue it was the gearing
Gearing, weight and tire size. That is what we need. While you gave a lot of information it was just not the right stuff.

Sorry it took so long to get back. Finally got the time.

As you know the output sprocket is a 10 tooth. The drive wheel axle sprocket has 54 teeth. And the tire size is about 13.75 inches in diameter. Don't know the overall weight but it's just a standard steel frame, one seater. The engines rated RPM is 3800. The Gear Ratio Calculator on bmikarts.com shows this thing as currently having a ratio of 5.400.

Does that mean it has a 5 to 1 Ratio?

But I don't see how the gearing could be that far off to cause harm to the clutch. The older used clutch lasted quite a long time before it started slipping.

Thanks

 

Denny

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It should be working fine with that gearing unless you do a lot of on and off the throttle. Try a better brand of clutches. Or drop axle sprocket to 60 tooth. My way of thinking. If riding in wide open paved spaces like race track or huge parking lot where there is not a lot of on/off the gas or stopping and starting. The centrifugal clutch works fine. If riding off road, grass, gravel, dirt, mud and streams or any combination. Use a cvt. If on/off the gas a lot use a cvt.
 
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madprofessor

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If on/off the gas a lot use a cvt.
Firstly, your "5.400" question means your gear ratio is 5.4:1, because your 54 tooth axle sprocket divided by your 10-tooth clutch sprocket (54 divided by 10) goes into it 5.4 times, hence the 5.4:1 ratio. Denny's mention of a 60-tooth would give you a 6:1 ratio. (60 divided by 10).
About the CVT: I agree, and so do most everybody that knows what the CVT does. It accelerates you to a speed where the clutch becomes fully engaged (beyond the slipping point) much faster than straight chain drive, saving much slippage and therefore clutch wear. Note that a CVT comes with a new clutch as the "driver" pulley that belt-drives the larger "driven" pulley. So decide yea/nay on a CVT before you buy another clutch.
 

mckutzy

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Oil the clutch bushing every 2 hrs of use.. A couple of drops...
Oil a good amount when new.
Smoke is not a good thing....

Id say up the rear sprocket tooth count to at least a 60... if not might have to put a jackahaft to augment the ratio... tire are big, so thats the real issue..
 

JTSpeedDemon

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I don't think it's necessarily the gearing, I have 5.5/1 gearing on the Hothead and I don't have any problems with the clutch, I actually have traction problems instead since it wants to peel out.
"The older used clutch lasted quite a long time before it started slipping." This makes it sound like it's just a faulty clutch, make sure you get a quality Max-Torque SS or a Hilliard clutch, or consider a CVT.
And like Denny mentioned, watch how you managed the throttle. You should NOT be slipping the clutch for extended periods pretty much ever, there's only some odd situations where you might be forced to. I tend to adopt a habit of pedal to the metal or nothing at all and my old beat up SS clutch has been holding up like a champ. Another method is to listen for where the clutch is locked up and the engine RPMs climb freely, once you've got the clutch locked up you can do pretty much whatever you want with the throttle.
 

Dan1980

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Great help! Thanks everyone!

At this point I'm leaning towards the idea that it must have been a combination of a faulty clutch with a lot of on/off the gas action. A couple of you suggested a higher quality clutch but as stated this one was supposed to be a so called heavy duty Hilliard. I feel that just one hour of driving alone wouldn't have cracked the bushing. It must have been defective from the get go. That bushing is a replaceable part. I'm going to see if I can just order that instead of a whole new one. If so, we'll retest as before and see what happens.
It should be working fine with that gearing unless you do a lot of on and off the throttle. Try a better brand of clutches. Or drop axle sprocket to 60 tooth. My way of thinking. If riding in wide open paved spaces like race track or huge parking lot where there is not a lot of on/off the gas or stopping and starting. The centrifugal clutch works fine. If riding off road, grass, gravel, dirt, mud and streams or any combination. Use a cvt. If on/off the gas a lot use a cvt.
Thanks. We were already well aware that a lot of on/off clutch action wasn't the greatest but at the time we didn't have a choice. We had/have plans on going with a torque converter. Is that what a CVT is?
 

madprofessor

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Yes, TC (Torque Converter) and CVT (Constant Variable Transmission) are the same item, it's just semantics what to call it.
I personally prefer CVT because it's a much more technically accurate description. Meanwhile, my favorite tech reference to send people to for info about them calls them TC's (gokartsupply.com).
 

Dan1980

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Hey! Gotta update everyone. We know now what caused the bearing failure. Got in touch with Hilliard and their particular clutch brass bearing/bushing has to have a minimum gap between it's outer edge and the holding bolt. Clamping against it flush will keep it from expanding laterally and instead force it to expand and bulge in the middle when it heats up. Just not use to this type. Apparently, it only needs Locktite to hold it on. I tightened the bolt just at snug when we tore up the grass that day and it ruined the bearing. Good news is Hilliard considers it a replaceable part and they sent me a link to it on BMI Karts and we already ordered one. Excited to go from there. I'm glad we were able to wrap this up together and that we're able to post the final conclusion here for anyone in the future who might experience this problem. Case Closed. Thanks to everyone! Happy Karting!!!
 
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