Mounting a Briggs LO206 on a sprint kart

Right now the Briggs & Stratton LO206 is the karting craze sweeping the nation.  As a matter of fact, so many tracks are adopting the concept that Briggs can barely keep up with demand.  And that popularity means that many racers are putting the package on that old chassis that’s been sitting in the garage for a few years, or buying a used roller that spent its previous life as a 2-stroke TaG kart.  The LO206 is by-and-large one of the easiest engines i’ve ever mounted to a kart (and boy have I done a bunch), but its very design means that there are a few things to take into consideration before heading to the track.  By simply making sure you have a few key items when putting it all together, you can be out of the box and ready to go in under a couple hours.

 

Pretty much everything you need to mount up an LO206

Pretty much everything you need to mount up an LO206

From Briggs, the LO206 is sold as the engine only…aside from some paperwork, that’s all thats in the box.  Hopefully the shop you buy your engine from is able to supply a complete turn-key kit, but if not (as in my case), there’s a few small important pieces you’ll need to buy.  Don’t worry though, while this walk through is not intended to be a comprehensive, step-by-step guide, it should cover everything you need to get your installation going without many surprises.

 

Also, don’t forget to read through the LO206 rule set just so you’re clear on what you can and cannot do.  It’s a quick read.

 

Motor Mounts: Don’t cut your seat strut yet!

 

By far, the biggest hurdle there is when mounting the LO206 is clearance; namely the right side seat strut, rear chassis cross-bar, and right rear tire.   The LO206 (and all other 4-strokes) is inboard drive, meaning that the clutch faces toward the driver, unlike a 2-stroke TaG where the clutch is outboard.  Running the chain inboard means that you have to clear the seat strut, and sometimes it means that you’re going to have to offset the engine a bit to do so.

 

A 4-stroke specific chassis is designed to take all of this into consideration, but if you’re like many people out there (myself included) you’re using a 2-stroke chassis that was designed for that outboard drive.  Lots of people seem to think that the best way to do this is to cut off and move the seat struts, but you should only be doing that as an absolute last resort option as it’s going to have a big effect on the way your kart handles.  Instead, you need to choose the right motor mount.  There are plenty of options out there – a popular one is the Burris mount that allows you to adjust the engine to clear the seat strut, or the Odenthal EZ Set.  I had an old mount from a Parilla Peopard, so I just had one of the local kart shops machine a plate that would allow the necessary clearance between the seat and seat strut.  So that’s an option too, if your kart shop has the means.

 

My custom aluminum plate from Billet Performance Karting.  Bolts directly to an old Leopard mount (in black).

My custom aluminum plate from Billet Performance Karting. Bolts directly to an old Leopard mount (in black).

Something else you need to take into consideration is the clearance to the right rear tire.  My air filter runs pretty close to the tire, and you’ll likely want at least a 5º tilt in your mount to get a bit of clearance.

 

Don’t forget about the rear cross bar, either.  Once you get the rear sprocket inboard you may find that that too large a gear will rub on the bar.  This is totally dependent on chassis design and short of changing your gearing or axle diameter, there’s unfortunately not many ways around this.  However, I haven’t really seen it be an issue, unless you’re running a very large rear sprocket.

 

Once you get all of these clearance issues sorted, the rest is easy-peasey.

 

Clutch

 

Whatever clutch you end up using, it’s absolutely imperative that you also use the appropriate radius washer between the clutch and crankshaft.  You’ll notice when test fitting your clutch on the engine that theres a decent amount of play (about 1/8″) between the clutch and end of the crankshaft.  The radius washer has a special chamfered edge that matches the machined edge of the crankshaft and the flat edge of the clutch to eliminate this play.  It is normal to have a tiny bit of play in the clutch drum, so don’t worry about that.  Not running the radius washer can cause severe damage in a short time to your crankshaft, and you could end up  having to buy a brand new short block if the damage is bad enough.  A radius washer (if it didn’t come with your clutch) is about $1….so don’t do that.

 

About $5 in essential clutch hardware that I had to purchase separately.  From left to right: Max Torque Clutch radius washer, 5/16" fender washer, 5/16" lock washer, and 5/16"-24 bolt

About $5 in essential clutch hardware that I had to purchase separately. From left to right: Max Torque Clutch radius washer, 5/16″ fender washer, 5/16″ lock washer, and 5/16″-24 bolt

 

Briggs has put together a pretty useful video on this topic, its definitely worth 3 minutes of your time.

 

 

(Pro Tip: if you don’t have a strap wrench as shown in the video, you can use the starter cord to prevent the engine from turning over backwards.  Simply pull the cord out until you feel resistance and tighten the clutch bolt, just don’t pull too hard!)

 

Fuel Pump

 

Plumbing the fuel pump couldn’t be easier.  Note the small arrows on the pump body and follow their directions.  One line in, one line out, and one line for the pulse fitting.  Don’t forget that you need to supply your own pulse fitting, fortunately there are some nice machined aluminum ones – that replace one of the oil fill plugs – available for under $10.

 

The fuel pump. The yellow line on the left side of the photo is the 'out' which goes to the carburetor.  The yellow line on the right is the 'in' line feed from the tank, and the blue line is the pulse line to the side cover fitting.

The fuel pump. The yellow line on the left side of the photo is the ‘out’ which goes to the carburetor. The yellow line on the right is the ‘in’ line feed from the tank, and the blue line is the pulse line to the side cover fitting.

 

Fuel pump pulse fitting, that replaces one of the yellow oil fill plugs on the side cover.

Fuel pump pulse fitting that replaces one of the yellow oil fill plugs on the side cover.

Exhaust

 

The LO206 exhaust is spec, and comes in two different flavors; the RLV 5506 or 5507.   In this era of plastic rear bumpers, you’re going to be better off with the RLV 5507 as it curves away from the bumper and won’t melt it (ask me how I know!).  The muffler is spec as well, and it needs to be clamped to the header with some pretty substantial force, so I would highly recommend a heavy duty clamp like the RLV model (pictured) as opposed to a cheap radiator hose clamp.  These come loose constantly, so don’t forget to check tightness before every on track session.

 

Note placement of safety wire & RLV exhaust clamp

Note placement of safety wire & RLV exhaust clamp

Your club rules may differ, but mine requires me to safety wire the muffler to the header bracket through the muffler baffles.  I also made sure to safety wire through the baffles welded onto the outside of the muffler as well.  RLV also suggests using a steel strap and hose clamps to secure the two pieces.  So far, my double safety wire system is working and i haven’t lost a muffler yet!

 

You’ll also need to wrap a portion of the exhaust with header wrap (check your club rules).  Need help on how to wrap header wrap?  It’s just like wrapping the handlebars on a road bike.  You can secure the wrap at either end with some hose clamps.

 

Check with your local club and/or sanctioning body on header wrap requirements - most require a full wrap of the exhaust.  You can use hose clamps to secure the wrap.

Check with your local club and/or sanctioning body on header wrap requirements – most require a full wrap of the exhaust. You can use hose clamps to secure the wrap.

You will probably notice when you go to mount the header that the bracket perfectly matches up with a hole on the cylinder head, but there are no threads in that hole for a bolt.  Strangely enough, that’s how it comes from Briggs and you have to tap the hole yourself.  If you’ve never done this before its pretty easy, but will require a tap set… use a 6mm or 1/4″ tap, and secure with the appropriate bolt and lock washer.  Please don’t skip this step; its a bit annoying that you have to do it, but it’s going to ensure a significantly longer life for your header.

 

Tapping the threads for the exhaust bracket bolt

Tapping the threads for the exhaust bracket bolt

Finally, don’t forget to buy an exhaust gasket and safety wire drilled bolts to secure the header to the cylinder head.  Fortunately, Comet Kart Sales sells the perfect little kit just for this purpose.

 

Misc exhaust hardware.  From left to right: safety wire drilled header bolts, exhaust gasket, RLV exhaust clamp

Misc exhaust hardware. From left to right: safety wire drilled header bolts, exhaust gasket, RLV exhaust clamp

 

Setting up the Carburetor

 

The only thing you should really need to do to the Carb out of the box is set the float height.  It sounds intimidating, but it’s quite easy…and made even easier with this handy instructional video from Briggs.

 

 

Briggs also has a handy Carburetor tuning guide that’s worth a read.

 

 

Engine break in

 

So you’re ready to hit the track, but before you get too far don’t forget that you need to properly break in your engine ensure best performance and a long life.  There are quite a few different schools of thought on how to best break in an engine, but I follow the Briggs recommended procedure (which also happens to be how I break in all of my engines), and i’ve had good results so far.  Ideally, you’ll want to use a ‘break in oil’ thats designed for the job, but in a pinch you can use a quality non-synthetic SAE-rated 30 weight motor oil; use 14-16 ounces.  Here’s what you do…

 

(These engines are shipped dry from Briggs, so don’t forget that you have to put oil in them before you start it up for the first time!)

 

  1. Start the engine and let run at idle (1,700-2,000 RPM) until operating temperature is reached…that’s about 5-8 minutes.   Shut the engine off and let it cool to ambient temperature.
  2. Repeat step 1
  3. Drain oil while it’s still warm from step 2.  Refill with 14-16oz your non-synthetic break in oil.  Allow engine to cool to ambient temperature before proceeding to step 4.
  4. For this step you’ll need to run the kart on the track for about 10 minutes.  It’s best to run the engine through a wide RPM range (don’t drive it like you’re qualifying); take a few laps at low-mid RPM, a few at mid-high, and run the last couple at a fast pace.  Don’t be afraid to run it up to the 6,100 RPM rev limiter!  As always, let the engine cool to ambient temperature before running it again.
  5. Do another 10 minutes on the track; take a couple laps to gently bring the engine up to temperature, and then drive it like you’re qualifying.  This step is completely optional, but it’s what I do.
  6. Drain oil while its still warm.  Refill with 14-16 oz of your synthetic race oil.  Briggs recommends Amsoil Briggs & Stratton 4T Racing Oil, and that’s what I use as it’s specifically formulated for the unique demands of these engines.

 

And that’s it!  If you want to speed up the process a bit, you can run steps 1-3 at home before you head to the track.

 

All in all, the Briggs & Stratton LO206 is a dead simple engine to mount, and you truly can be out of the box and running in a couple hours if you have all of the parts and know what you need to do.  I can’t say that about most racing engines!  It truly is kartings ‘easy button’ even from when you open the box.  Add gas, pull the cord and go racing!

 

Got any questions or comments?  Share them in the comments below!

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