How You Mount Your 206 Engine Can Cost You Precious Time


From the desk of @BriggsRacing.

As the 206 program continues to grow so does the need to revisit past subjects from time to time as new racers enter the ranks.

One fundamental: How you install your engine WILL impact performance and life.

Just like a house built on only half a foundation will have issues so will a racer following suit with their engine. As I walked through the pits at a recent race one thing that I noticed was that every front runner had their engines mounted with little to no offset. That isn’t a coincidence.

In a class of equal power, SETUP including the engine installation IS the difference.

Tip #1: Always Keep motor offset to a minimum.

When an engine is offset from the base plate it creates an unnatural dynamic where vibration and torsional stresses are amplified. Flywheel vibration and cylinder movement increases. Imagine you are on a diving board. The same energy at the first step of the board at the fulcrum moves the board very little but that same energy at the end of the board amplifies movement dramatically. The principle is the same. The greater your engine offset from the mounting base plate (fulcrum) the more amplified the vibration (harmonics) and torsional stresses become.

Tip #2: Excessive Motor Mount Offset is Reducing the Life of Your Engine.

Over time this instability helps accelerates wear and component fatigue. Wear can lead to more clearance which in turn is likely to create more vibration so now you are still on the end of the diving board but adding even more energy. This flexing can create internal binding robbing you of power. The distortion of the block can also lead to a side gasket failure, rod thrust face wear and more. While the 206 is engineered for racing giving us a large safety factor installation is a key to engine performance and life.

Tip #3: Excessive Motor Mount Offset is hurting your LAPTIMES

In vibration lab testing simulating excessive engine offset negatively impacted fuel metering causing performance loss as well.

We have had racers see REAL gains just from reinstalling their engine correctly.

In a world were racers want to believe that oil or someone’s sales pitch makes an impact properly mounting your engine truly IS your easiest gain. Not to mention that you are extending the life of your engine.

Just because a mount allows for substantial offset doesn’t mean you should do it!

Tip #4: Relocate your seat bracket if you have to

“Well my welded seat strut gets in the way” is a common response. Just like a racer has to bend a strut to adjust for a seat size they also need to adjust their seat location to allow the engine to be properly mounted. Another option is to remove the welded struts and install adjustable seat struts which are readily available.

Some chassis manufacturers have truly engineered a 4-stroke chassis (we have a list here on the forums) so they already come with adjustable seat struts and/or have shifted welded strut locations. In the end they understand that the performance gained also helps to sell their chassis. On older karts or on karts with manufacturers slow to adapt a racer needs to make this adjustment to get the most out of their engine.

See also: CRITICAL success tips download our top do’s and don’ts list HERE.

Summary: Essential Mounting Tips to Ensure Maximum Life and Performance of your Briggs 206:

  • Never use a motor mount plate that is LESS than ¾” thick. Thinner plates do not offer enough rigidity.

  • Just because an engine mount allows for excessive offset doesn’t mean that you should. Basic engine mounts are generic and allow for flexibility beyond recommendation.

  • If your kart has welded seat struts they can be bent as designed to minimize engine offset.

  • Adjustable clamp on seat struts are also an easy solution.

  • Another hint not mentioned: Running your clutch inboard (sprocket closest to the side cover) further lowers crank forces and engine stresses.

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I like how their ultimate line is: “Cut your chassis if it doesn’t work with our motor.” Kind of a cop out IMO. But there are some horrific motor mounts out there. Most of the time you can make a minimal offset work some way somehow without having to get out the torch and hack saw.

Is that the ultimate line though? That’s not how I read it at all. It was the last in the list of tips to be fair?

To me it seemed like a last resort… should you even have to resort to it. It was a much more common problem when the 206 first came around just under a decade ago, but nowadays, with beefier mounts on the market more people have been able to make it work without modifying the seat bracket.

Gentlemen, can I jump in here with a question that is close to the same subject.
What are your thoughts on 15 degree mount vs 7 degrees?

Depends on how much clearance you want between the air filter and rear wheels. 15deg will give you more leeway, just make sure you level the float bowl to compensate.

I am looking to dabble in 206 sometime this season and came across this old thread. I never had considered the “cost” of offsetting the motor. I will have to fit a larger seat (freeline 4) on a Compkart chassis and just assumed I would need to find a mount that would hang the motor out far enough but now I’m not so sure. So…

Is this information still current?

What is consdidered the centerline?

How far can you go with offset? Or I guess would it be better to mount the seat and adjust the motor or mount the motor and adjust the seat location?

You can always bend the left seat post over. It allows you to get motor centered over the rails.

On our OTK, we moved it 1.25” over which got motor over 2” or so and now run clutch inboard. Also allows for better weight distribution.

Jim Scatena is a dealer for the Comp 4r and has a good tutorial on how far to move the post over. Reach out to him on FB and I’m sure he’d be happy to share.

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4 posts were split to a new topic: Seat Bracket Adjustment (Bending)

Sooo… I just checked mine. Is this bad?

Yes and no. There are plenty of karts that run with the engine set far to the right. It’s not ideal but it still works. VLR is one chassis that does so due to the right seat post design.

If you can get your corner weights correct, I wouldn’t worry too much about the offset.

One draw back of the mount you have is flex. The Burris tends to flex quite a bit. I now only use Odenthal for 206. The JTP is also a good piece. We used to run a Burris and a Mega mount. Mega mount was even worse than the Burris.

When your engine is back on the kart, grab the pipe and try to rock the engine side to side. You’ll be surprised at how much movement there is. There is zero to near zero with odenthal. All that movement is wasted energy.

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I had a cheap offset mount for my son’s kart when he started 4 years ago, it was made of thin aluminum plate. We were constantly throwing chains, having the clamps loosen etc. Totally unacceptable.

I have the advantage of being a tool and die maker and engineering technologist, so i made a sliding mount, very similar in concept to the Odenthal/JTP style mounts. I used a 1" thick base plate, and since moving to this style of mount, we haven’t tossed a chain, or had the clamps loosen during a race weekend. I’d definitely suggest the Odenthal or similar to get a good solid setup.

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I’m concerned primarily about performance and reliability. Since I have yet to throw a chain or have anything break, I don’t really want to change motor mounts unless there is a risk to performance and/or reliability. If the flex in my motor is costing me lap times or risking motor lifespan then I do want to look into the others.

Do you think I’m costing myself in lap times due to this amount of offset? If so, I definitely want to move it as much as I can.

If your chassis is not scaling correctly, absolutely costing lap time. At that point, it’s more about getting the engine moved over.

If it is scaling correctly, it may be costing you time but hard to quantify an amount it’s costing you.

What chassis are you on?

2015ish Kosmic. 30mm. I’m definitely right-rear heavy 10-20lbs. I will try to bend the seat posts a bit to shift weight and get motor mount centered more. I’m still around .9-1 second slower than the leader so any little thing I can do, I would like to try so I can eliminate that variable. Weight distribution seems like a big one.

I’d like at getting the chassis tables before you go trying to bend struts for no reason. The engineers put the right side strut where it is for a reason.

Being right rear heavy doesn’t mean a ton until you look at the overall picture. Front/rear/cross is way more important than thinking your engine placement is causing you an issue.

Do you have any weight on the kart?

Don can you clarify this point. It seems to me with the motor where it is, even centered on the frame your right rear will always be heavy.

Have you scaled with the motor centered vs fully offset that many mounts offer? Do you even see a difference?

Significant difference when moved over.

At my current weight, I can add 10lbs of lead. I put it at the front between my feet to try to get a better front to back percentage. With the 10lbs on the front, I’m 58% rearward bias. By the next race I might be able to add another 5lbs on the left side of the seat.

My general opinion is that the usual 43%F/57%R weight distribution is too much rear weight for the 206. 206 generally runs hard tires and you’re constantly trying to find a way to free it up because getting the inside rear to pick up is difficult at low speed and low grip. I think 45/55 is a much better starting point. It’s easier to move weight backward than forward anyhow.