Technique for Checking Clutch Engagment RPM for 206

New guy question here… Been out of the game for a couple decades now and I am trying to figure out the proper technique for testing the clutch engement. When I check it like I used to back in the day (damn I sound old) it comes in consistently 1k higher than the spring setup chart says it should (4400RPM, Hilliard Flame, 2 whites and a black). I mostly ran Yamaha back in the wet clutch days and when we checked it, I’d be on the ground, wack the throttle, it would launch, the RPM would stabalize for second before it started climbing, and thats your number. When I try the same technique, the numbers come in what I would think are high.

Before I decided to ask here, I kinda went down the rabbit hole and saw refferences to engagement RPM being separate from full lock RPM (which I was apparently measuring), but no real info of how to check the “engagment RPM”. So my ultimate question is; am I doing this wrong or do I perhaps have an issue that needs to be sorted or maybe I just need to tune the damn thing?

For background, the clutch is used, but I cleaned it all up and rebuilt it, It all seems to be in good shape, and I am fairly confident its assembled correctly. That being said, the shoes are flipped I believe, so that the skinny end, or taper of the teardrop is leading. It came that way and I left it. I am not sure if this is standard, for the wording on shoe orientation from Hilliard confused the hell out of me…

Any help, techniques or insight would be awesome.

Thanks!

Never though about checking the Engagement RPM.

Here is a link for the installation, leading is what I preferred if you are running it outboard. Trailing if inboard. You can also face the tail to each other which is not recommended, but it will give you a very hard engage.

Ultimately I think the engagement RPM does not matter too much since it should not disengaged during the runs. If you are doing standing start, simple a stopwatch should be able to show you the difference.

People say that a lot. At our track you are on the clutch about 8 out of 40 seconds. I determine clutch engagement by looking at where clutch holds during lap in the session. It typically is very close to what the chart says

Where do you race that you are on the clutch for 8 of 40 seconds?

Gateway Kartplex near St. Louis, MO. On Mychron I look for how long the RPM is at about 4100 , but kart is accelerating. It is in the 8+ second range

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Makes sense. Some layouts at gateway are tight. FWIW, I would never slip a 206 at 4100. You’re giving up a lot of peak torque.

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Thanks. It does occure to me now that is higher than I got with 4 black last year. I need to look into that

I run 2 black and 2 white springs on my clutch with no weights.

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Replying rather than starting a new thread.

In another thread, someone suggested holding the brakes on a kart stand, flooring it, and checking the rpm on the mychron. When I do that, it reads really high, like 4000+ rpm. This is with 4 white springs with 1 weight. Like the OP wrote, its about 1k higher than the chart. I’m aiming for 3400rpm or so and I’d like to dial it in. I’d rather figure this out in the garage if possible rather than having to test it on the track.

Are my springs bad, shoes bad (somewhat worn), or am I doing it wrong?

I just jump in and take off watching the tach. You’re looking for “engagement”. Engagement is when the shoes start to contact the drum and start to give you forward motion.

What you’re getting on the stand is probably “lock up”. Lock up is when the shoes are full contact and the drum is “locked” to the shoes.

Disclaimer: I could also be completely wrong. I put the springs in that everyone says to put in (2 black, 2 white) and then I ignore it all year.

Makes sense. On the stand, the wheels start spinning even at around idle (2000 rpm). I presume that means the shoes are at least slightly engaged even at only 2000 rpm, though probably not enough to move the kart with me in it. Does it make a difference on the ground?

That’s probably more of the crank/needle bearing/drum contact slightly spinning your unloaded axle.

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OK, with me sitting in it, it starts moving right around 2700-2800rpm. That’s not too far off the “chart” number. I hope that’s the right way to test because I’m about to tune it using that method.

Welp, I ended up with:

2 black 2 white - 3600 rpm
2 black 2 yellow - 3550 rpm
4 white - 2700 rpm

I’m aiming for 3400, and I think I have to mess with weights to get there. So, leaving it with 2b+2y and will figure this out some other day :-P.