206 Questions

So I finally bought a 206, about 4 years late to the party. I know nothing, so I have many questions, most of which have probably already been answered so sorry in advance if I’m repeating others.

  1. How do you determine gearing? I ran a 206 race a month ago and missed the gearing by like 4 teeth. I’m used to figuring out gearing by either minimum RPM (in KA100) or maximum RPM (back in Yamaha). The problem is the 206 has a rev limiter for the high RPM and a high-stall clutch which means I can’t find minimum RPM either.

  2. What’s the clutch maintenance like? The clutch seems weird since it starts engaging, revs higher as it’s slipping, and then the RPM’s drop as it fully engages. Is that normal?

  3. Are the tire pressures any different? I imagine you have to run higher tire pressures than in a 2-stroke since the kart isn’t working the tires as much, but they run the same tires in 206 and KA out here, would you just run the same pressures in both?

  4. What general engine maintenance has to be done on the 206? I had the float set before I ran it, is that all? What about oil changes?

Also, unrelated, but I’ve been referred to as Aaron from KartPulse at the track before. I just find that mildly amusing.

  1. I struggled with this, but really is the same as any class. Balance acceleration against top end. Don’t be bothered by getting into rev limiter. We are in rev limiter at our track about 10-15% of straight away. The top end loss at our track is acceptable for improved acceleration.

  2. I run hilliard flame clutch. I clean groves after most races with dremel wheel and replace spring

  3. I am not sure. I think you are on the right path

  4. Virtually none. I check the leakdown once a year. I probably should check the valve adjustment more often, but do not. As I say that I will probably check it every other oil change. Oil change I do every other weekend. I check the case side bolts when I have the clutch off. I think that is it. Much less work than I did in KT100

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As one of the guys that refers to you as “Aaron from kartpulse”, welcome to the 4 cycle world.

Stop by garage 32 next time you are at Whiteland and ask away. We’d be glad to help you out.

-Derek (many times referred to as “the other guy at Ghost Racing”)

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Is yours the Ghost Racing that provided the Stahl family with engines?

Yes, sir. It is myself and @Matt_Geist. The Stahl Family are great people and we are very happy to be a part of their program.

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Here is what I did with my 206:

  1. I just go talk to track mechanics and other people on the track what gear they are using and go from there. I usually run 1 teeth up due to heavier weight. The rev is limit to 6100rpm and low rpm is based on your clutch spring setup.

  2. I am using hilliard flame clutch as well. The maintenance is just to clean the clutch with WD40 and sanding drum and shoe, also clean roves. Check spring and replace as needed. Your spring setup will determine your clutch engaging point. I have two black and two white which should give me somewhere around 3400rpm.

  3. We have MG yellow, people are running similar tire pressure between KA and 206, but if you check the field, the tire pressure people runs is always all over the place.

  4. Oil change every race weekend and that’s pretty much it.

Love their show and great to see you here on KP.

Grease the clutch bearing every few days. I have only changed the springs once and I’m not sure it made a difference. Running the Hillard Fire. Oil the change, change the oil and that’s about it.

As for gearing its something I struggle with as well. I did cheat a little bit, by asking the guy who I bought the kart from what he ran at a list of nearby tracks. So that way I was at least close. He and I were very close in size (height/weight)

I hit the clutch (Hillard Flame) with brake cleaner every other race or so and oil the bearings. After about 6-8 races I replace the clutch springs unless I feel the need to do it sooner. Two black, two white springs.

As for oil, I change it after each race.

Tire pressure where I run is best at around 10-12 pounds. Depending where I run I’ve run upwards of 14 pounds, but never higher than that personally. I run MG Reds normally, unless I have to switch to Vega Reds for certain races.

I would want to get the limiter before the end of the straight. Just exactly how much before the end to be determined.

That RPM drop when the clutch engages, it’s been my experience, is caused by the engine going lean on the low-speed. How you fix that on the L0206 I have no idea. It’s my understanding you can’t change jets, which you should do, change the low-speed jet’s, make it richer, at least one size, maybe more. It might make it hard to idle, race engines are supposed to idle! lol

That’s how I had it geared, but the track had so much infield that I was losing more time coming out of the corners than I was gaining from the top end. I was moreso asking if there was an easy(ish) way to figure that out before getting to the track. I don’t have 2 piece sprockets, so I set the gearing when I move the hub over to the inboard position while changing over from KA. I’m not pulling apart my axle assebly at the track just to change the gearing.

You cannot change the jet on a 206, but I’m not sure if there’s a different adjustment that you can make on the carb to have the same effect.

You can play with float height.

Really though with the throttle fully open, the idle circuit plays a very small part with the 206. It doesn’t have the same influence and overlap with the high circuit that a low screw would on a KA or TaG for example.

Adjusting the position of the needle clip will modify the fuel ratio at part throttle. That is your best adjustment for lower RPM. You want everything else optimized for high RPM. At least that has been my experience. YMMV…

And you would be surprised at how much more the engine needs to be rich on the low-speed. When you think about and, the engine reaches peak torque at a very low RPM, it gets hot and, it needs more fuel. I remember the day I discovered that with my McCullough’s, it was a real eye opener.

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I’ve experienced that too with my two strokes, it’s easy to go too lean when really they are demanding more fuel

But there’s really no crossover between a two stroke McCullough running a butterfly diaphragm pump carb and a Briggs 206 four stroke running a slide carb with a float.

The idle circuit on the 206 (Which is controlled by air, not fuel) doesn’t have anywhere near the same influence on the fuel curve.

I’d almost wager you could close the circuit down and have no impact on peak torque.

Keep in mind that the torque curve (therefore fuel demand curve) of these engines is very different too. The McCullough demands fuel in a much more acute way at peak torque compared to the 206 which is a low output engine with a very flat torque curve.

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The rev drop on lock up is just how these crap drum clutches work.

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I started racing with tthese crap drum clutches in 1966, I thought the same thing, until I learned better.

I know!, It’s just too much trouble to try it!