Dyno Tuning Briggs 206 (LO206)

First of all I want to say how great of a forum this is. Thanks for all the contributions that are helping people like me have a chance at the track.

A little background first. I purchased a Kart from a season winning Sr. for my son who is racing it in the JR. 2 4-Cycle class out at UMC in Utah. I’m trying to lean as much about Kart setup and tuning as possible and I have a couple questions I was unable to find answers on while searching the forums so I thought I would ask here.

The Lo206 I purchased on the Kart had a slight oil leak on the bottom end from day 1 so we have been running it and lap times have been okay. Some days we are fast and others we are not so quick. I pulled the trigger on a new motor last race and have yet to install it as I may wait to start using it next season. Looking over these forums it seems that if you want the best out of your motors you should have them sent out and put on a dyno for tuning. I’m not sure exactly what the tuning and setup is doing to these motors and carbs as we break down and clean the carbs often and then re-installing. So that makes me think the carb adjustments wont be permanent from the motor builder anyways. Is this correct?

Also if we are adjusting valve lifters when they come out of spec from heat cycling, those also are not a permanent "tweak’ to the motor that would be something the motor builders lock in. “For a lack of better words.”

So what exactly is getting done from the builders that is so beneficial? I feel we are constantly tuning these carbs for weather conditions, and the blocks are being left alone.

What am I missing?

Thanks in advance.

I think in 206 the general rebuild and blueprints is just going through carb and head, there’s people who win on box stock motors, I use an engine builder for peace of mind. (I haven’t touched the carb settings all year and we have one of the fastest karts in my club)

There’s definitely people on here to speak on what is actually being done, I just pay the man!

Didn’t know how to quote it but here’s a great explanation from @fatboy1dh

Do you or your son have the experience to understand if that variability is due to driving/atmospheric inconsistencies?

In early days, it can seem like one is “down on power” relative to others. But, more often than not, that discrepancy is due to the newness of the driver and the fact that they aren’t as efficient/early to throttle and can’t get as good a run as a more experienced driver.

For me, I like going with built engines. I’d rather pay a pro to make sure I’m running as good as I can and focus on my racing. I like the peace of mind, without the effort or responsibility lol.

But, many really enjoy wrenching. Either way is good. Built lo206 vs unbuilt is pretty insignificant. If you are running national races of course go built but as a hobbyist, don’t sweat that you will be “slow”. You can’t make the lo206 into a rocket ship for sealed Briggs racing. (This changes entirely in dirt 4-stroke classes where builders rule, I think.)

@fatboy1dh do you concur?

According to the thread linked below, the long-term performance of a new engine can be influenced by how the engine is broken-in. So that might be one big advantage of using a builder (at least initially) because they can control the break-in process very carefully with their dynos.

I look at it as being a final QC check and a support plan for the days where things are not going so well. Peace of mind. Some desire that, some don’t. It seems like success happens either way.

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I love this answer. I figured gap on ignition timing may be a factor but never back pressures on an exhaust could come into play. For as much as I am learning these motors and taking parts on and off, I think my next season will be racing the motor right out of the box.

I believe setup of chassis and driver coaching is going to pick up more time at the end of the day than how far a muffler sits on the exhaust pipe.

Driving is worth seconds.
Chassis tuning is worth tenths.
Engine is worth hundredths.

Prioritize accordingly.


A data point. This is my first season karting. I’ve done two practice sessions and one race. Second race is this weekend (can’t wait).

We took the engine out of the box. Installed it in the kart following the ‘206 Briggs Assembly Guide’ here: Go Kart Shop |Go Kart Parts | Karts for Sale |Tillett Seats. It so happens I bought the engine from them. We did the break-in using the instructions to.

The race was in the wet, so, I changed the oil after that. I didn’t change the oil after the practice sessions. I do have a magnetic oil drain plug and we’ve seen nothing on it. The oil has been extremely clean. I haven’t decided what the oil change regiment is going to be. Probably once or twice a season; but definitely after rain.

This past weekend, the club members were coaching me on what I needed to do to improve. So, at practice, three experienced and top drivers from our club drove the kart. It performed well for them. The fastest was 0.7 seconds slower than their own kart - they were not happy with the seat position and the gear ratio was different than their kart. They commented that the engine was strong.

Based on the instructions from Briggs, we went to adjust the valve lash and found it was very close to the target, so, we didn’t touch it. We didn’t bother with the float because it was running very well.

This is the most accurate thing I have seen. If you’re chasing those last couple hundredths, absolutely pay for the best. Otherwise, if you’re comfortable with some basic set up and maintenance, use that money on practice days and driver coaching


@tjkoyen you should have shirts made with this statement on them, along with your coaching business name & contact info, and give them to the drivers you are coaching (and their parents when applicable). :wink:


Personally I change my oil after every day at the track. Every session in rain as well. Just a piece of mind thing for me.


Oil is cheap compared to short blocks. Every track day and any rain session is a good solid strategy.

Funny thing is I never changed the oil in our 206 but maybe once every 15 track days. Was fast too, and sold 2 years after I bought it for twice what it costs new to a guy that had to have it. The beauty of a 206 is that everything is so dumbed down your changes do nothing, and they just run.

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