Looking help with Clutch Engagement speed


Can someone please give me the ins and outs of clutch tuning. I have a Hillard Inferno Fire clutch for my Briggs Lo206 and I’m having a tough time understanding what RPM to set the clutch engagement speed.

Ive read you want to set it for peak torque which for the black slide is 2500-3000RPM. So is it that simple?

What are the advantages to setting it at a lower RPM or a higher RPM? Does having the clutch fully engaged gong thru a corner cause a drag thus it would be better to set the Clutch engagement RPM higher so it disengages as the RPM fall off.

The Hillard chart shows 4 black spring begins to touch the drum at 3500rpm? So is it another 200-300 RPM before it begins to lock up?

Thanks, I just really want to get this cleared up.


A version of this question was just posted. You want the clutch to engage at or just under peak torque for maximum acceleration. Its that simple. Someone with hillard expertise can help you get to the 2900 range.

Yes I saw that thread. My issue do I just set the clutch for peak torque and thats it.

The black slide shows between 2500-3000 rpm. When would I ever set it higher than that 500rpm window.

It does require a little bit of testing. Most recommend running all black or black and white springs. I will say it definitely depends on the track, lowest RPM, how many times the clutch will lock and unlock throughout the lap. If you set it too high then your clutch will slip too much or engage late and you’ll be killed off the slow corners. The opposite effect can happen if you put too soft of springs in, the engine can’t get any RPM’s up before the clutch locks and will bog way down.

I’ve been testing with mine a bit and fount that black and yellows work great at my track. But I would recommend starting out with black and white springs first. That’s a pretty good starting point. Also another big tip is make sure your shoes are in the leading orientation (toe of the shoe forward). Your shoes will last longer and you’ll get a better lock up.

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You want the clutch to hold the engine at “peak torque” at the start and coming off a corner. If the clutch is holding the engine at peak torque RPM, that torque is transferred through the chain to the rear axle. With maximum torque at the rear axle, you have maximum horsepower at the axle. It’s different between the engine and the axle until the axle RPM, multiplied by the gear ratio, is the same as the engine. Clutch lockup. Use a bathroom scale, positioned between a strong wall and the front of your kart. The highest reading on the scale is where you want your clutch to hold the engine on the starts. It takes some time, don’t burn up the clutch, 2 or 3 seconds per test should be enough.

Where do you race? I race at 103rd in Jacksonville, Florida.