SMC Gold axle clutch

racer223

Member
Hello. I am new to the SMC axle clutch world. I recently purchased a Gold clutch second hand. I understand that it is a 4 disc and is only good for "some" horsepower. Is there any way to increase its capabilities? I am a dirt speedway guy and want to try getting away from the dry 4 disk clutches. Thanks in advance.
 

Chris Cooper

Premium User
Rainman is spot on - how much horsepower (really torque) ? The weak point would be the pins that locate the steel floaters. You can minimize the issues by having another six drive pins inserted in the housing. It's not difficult if you have a mill and rotary table.
 

Phiddy

Member
Outside of having to change the stall setting every time you change gear, it should handle your X30 fine. I talked to Tom once, and he said they were designed for up to 40hp. I can tell you it did not hold up well on my twin with two open reedjets, but could have if it had more RPM's. I was asking it to do the impossible. The SMC is a solid clutch, keep clean oil in it and inspect it often in the beginning. And like any clutch don't overheat it.
 

yamadog35

Member
I've run the 3-disc Gold enduro clutch several times with a BRC 150 on a laydown enduro kart. On the road course tracks we run, gear ratios between 4.0 and 5.0 Long hard pulls on the clutch when coming off of the tighter turns. The BRC in the configuration I'm running is somewhere around 45hp. I'm not questioning what Tom told Phiddy, but Tom told me each friction disc can take 15hp so approx 45hp in a 3-disc clutch so the BRC is right at the limit. When I've had the proper gear ratio on the kart the clutch came through a 30 minute enduro race just fine. The oil was still red(ish) and didn't smell burnt. Like Phiddy said, change the oil often, keep an eye on things, don't over heat it.
 

racer223

Member
How bout daul X30's? Not set to kill, race gas, single tilly 191's, IAME KF clutch pipes (they look like DD pipes, but are not)
 

Phiddy

Member
How bout daul X30's? Not set to kill, race gas, single tilly 191's, IAME KF clutch pipes (they look like DD pipes, but are not)
You might get away with it road racing, but I bet not on the dirt. The more RPM's that the clutch is spinning the easier it is on it. A speedway kart doesn't really have all that much axle RPM's, and the torque is what will kill the clutch. A pair of almost anything has pretty good torque and more weight too. Give it a shot, I bet I can tell you what, and in what order you will wreck in that clutch. I will post some pics later of the one I modified when I am on my home computer. My recommendation is if you gonna have two engines, have two clutches.
SMC is a great choice.
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rainman

Premium User
I know they keep together well with stock Sudan's. Never run my stroker 131 Sudan with an SMC but I know some people has done it. For duals you might need 2 SMCs unless you plan on running them together through the cracks but that might be too much torque for a single SMC.
 
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Phiddy

Member
Yup, I'm back from where you are going. It was fun, and expensive. I ended up with a 450 and a newer chassis.
1- Buy a strong axle with good fitting keys w/ a center support bearing
2- Find the best chain you can (if you plan on running 35)
3- Build a chain guide for the bottom like a mx bike
4- The most important thing, Have fun!
One more question. How much is it and you gonna weigh?
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racer223

Member
They are mild 125's. I told the motor builder I wanted them to start and idle. They will be fed by Tilly 191's, and the squish was set up so I could run 110 octane. The motors that these pipes came off of were clutch engines, and the factory engagement was in the 4k rpm range. I was thinking about starting in the 5k range. I will likely be in the 430-440 pound area.... I think. I have future plans to install onboard starting. Since the bottom ends of these motors past life was an IAME Leopard. They still have the bosses for the electric starters. If this clutch doesn't work out then I might look for an axle clutch that will work.
Phiddy, did the modification you made in the pictures above seem to work well?
 

nobozos

Member
P, nice job on that smc been running them since 89 dirt and enduro. Try four friction disks might surprise ya especially on the twin works for me Chuck
 

racer223

Member
P, nice job on that smc been running them since 89 dirt and enduro. Try four friction disks might surprise ya especially on the twin works for me Chuck
What sort of modifications do you make to your SMC's to make them live? I got my hands on mine for pretty cheap, and kind of want to try and make it work..
 
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