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THE RACERS EDGE

SETTING UP A BASIC BRIGGS & STRATTON F200 ENGINE
By John Nuttall, Burris National Speedway Series

The project before us is to build a Burris National Speedway Series (BSNN) legal F200 for a Junior 1 racer using a Briggs and Stratton 206 Intek engine. This engine is intended for a rookie racer using basic tools common in every racer’s toolbox. The engine is built to be budget minded, reliable and competitive, without the need of a machine shop.

As the driver develops more skills, the crew will learn more about engine building. Of course, there is more horsepower to be found with more advanced equipment, skills and budget.

Tools needed:
Meter socket set
Metric open end wrench set
Small flat screw driver
Set of flat feeler gauges
Impact wrench
Torque wrench in inches pound
Ring compressor
Rotary Grinder

Parts needed:
Part      Price
B&S 206 Intek Engine Northern Tools $250
B&S 190 Camshaft Sears Parts $ 75
Dyno 275 Intek Camshaft   $100
Animal Value Springs Kit B&S Part $ 24
ARC Billet Rod    $ 89
F200 Tillotson Carb .635 venturi (EC Birt) $106
EC Britt intake manifold   $ 50
GEM Filter Cup    $ 20
GEM linkage kit    $ 30
GEM Air Cleaner    $ 12
Robertson Exhaust Header   $ 45
Gasket Kit     $ 15
Total      $816

Step 1 - Disassemble the Engine

We will need change the crankshaft in this engine to get it under the 200 cc engine limit for the F200 Class so we need to disassemble the Intek Engine. Remove the sheet metal, muffler, fuel tank, carburetor, value cover and fuel tank bracket.

TIP: Many of these parts will be reused so take care removing and storing them.

Step 2 - Remove the Flywheel

Next, remove of the flywheel using an impact wrench. To loosen the flywheel from the crankshaft place socket a few sizes smaller than the nut, strike the socket with firmly with a hammer. Remove the side cover of engine, and head. Save these parts for later use.

TIP: Do not use a socket wrench with a screw driver to hold the flywheel. It’s dangerous and can damage the flywheel.

Step 3 - Check the Tolerances

Before starting the assembly process, we need to check the tolerances of the piston to wall clearance and rings.

Begin by removing the rings from the piston. The top ring is the compression ring, the middle ring is the scraper ring and the bottom ring is the oil ring. Identify the compression ring by its black color. The scraper (middle) ring is polished. The oil ring (bottom) is a 2-piece ring. The tensioning spring behind the oil ring will not be needed again. Mark rings for easy identification in the assembly process.

Next, check the piston to cylinder wall clearance. An engine shop would use a micrometer to check the piston diameter. An inside micrometer is used to check the cylinder bore. We did this by putting the piston in the cylinder and using a flat feeler gauge to measure the space between the block and the piston. Remember to remove the piston rings carefully first. The measurement should be .004 to .006 inches.

Next check the ring end gaps. The compression should be greater than .008 and less the .012 inches. If the ring end gap is too small, file the end of the ring to get to the minimum gap. If the ring end gap is too large, buy a new ring.

TIP: Clean the block with carburetor cleaner or your parts washer. Make sure every part going into the engine is clean and free of debris.

Step 4 - Assemble the Block

Install the piston on the new rod. The new rod is longer than the stock Intek 206 rod. There is an arrow on the top of the piston that points to the flywheel side of the engine. This ensures proper alignment. Insert the wrist pin and the retainer. The wrist pin will only go in from one side.

TIP: Use plenty of oil on each part you install.

Install the rings on the piston. Put the oil ring, scraper ring and compression ring on the piston with the oil ring at the bottom. We will not be reusing the tension spring. Then slide the piston into the cylinder bore, using the ring compressor tool. Be careful not to damage the cylinder walls.

Remove the rod cap. Most after market billet rods come with a replaceable bearing insert. Install the bearing inserts now.

Install the crankshaft. Attach the rod with the bearing insert to the crankshaft. There is a ROD TORQUE requirement in the package with your new rod. Torque the bolts. Normally the torque is 150 inch pounds.

Install the camshaft and lifters. Use lots of oil. Make sure the timing mark on the crankshaft lines up with the timing mark on the camshaft.

The last step before putting on the side cover is to make sure every thing is clean. No dust, dirt, or metal shavings.

Insert the side cover and gasket on the engine. Make sure the crankshaft turns freely and easily. Install the side cover bolts torque to 100 inch pounds. Studs may be used to replace the side cover bolts.

TIP: If you have a dial indicator now would be a good time to check the piston pop up. There is NO piston pop up rule in the F200 format, but you may need to correct the combustion chamber volume later. Decking the block is one way to lower the combustion chamber volume.

Step 5 - Install the Flywheel

Install the flywheel and cooling fins on the end on the crankshaft using a 4 degree offset key. This will advance the timing to approximately 20 degrees.

Install the flywheel nut and torque to 150 foot/pounds. If you are planning on using an electric starter, replace the factory nut with an electric started nut. Remove the starter assembly from the fan housing and install a flywheel fan screen.

Install the ignition coil using a .020 to .025 inch feeler gauge to set the gap between the flywheel and the ignition coil.

TIP: Use an impact wrench to tighten the nut. The flywheel key is used to align the flywheel but doesn’t actually hold anything. The nut must be tight.

Step 6 - Assemble the Cylinder Head

If you want to do some basic porting on you cylinder head, there is a good article at www.sa-motorsports.com. Basic cylinder head porting will improve the performance of any production cylinder head by removing flaws that come through mass production. Basic porting does not attempt to correct any design or engineering deficiencies. Once your porting project turns to that, you're beyond the scope of basic porting techniques.

After you are done porting, clean every part before assembly. Special care should be taken to remove old Loctite from rocker arm adjusters.

If you are doing head porting, use bluing to mark the cylinder head so you can match the intake of intake manifold to the intake port.

Install the carburetor and intake manifold. Check the alignment carefully. You don’t want the gaskets acting as restrictor plates. Use a shape razor knife to cut gaskets.

Test fit the temperature gauge sensor under the spark plug. Trim the head fins as needed to get a proper fit.

Test fit the exhaust header. Trim the fins as needed for a smooth fit.

Step 7 - Install the Cylinder Head

Install the head and head gasket using the factory head bolt or studs. Some people say studs save wear and tear on the block. The cylinder head must be torque to 170 inch pounds. Use an X crossing pattern to tighten the bolts.

Step 8 - Adjusting the Valves

The camshaft manufacturer includes value lash adjustment number with the cam. Write this number inside the value cover with black marker.

Set the engine to top dead center. The magnet on the flywheel will be pointed at the coil. Both valves should be fully closed. Set the valve lash to the cam manufacturer specifications. Use a box end wrench to hold the tappet adjusting nut and an Allen wrench to lock the set screw in place.

TIP: Setting the valve lash is an important part of weekly engine maintenance.

Step 9 - Installing the Carburetor

Install the carburetor and gasket onto the intake manifold. The carburetor will need an extra pulse hole if you’re using a remote fuel tank. See the photo for the correct hole to drill. The drill size is .140 inch.

There is a small pulse hole on the upper left hand side of the gasket. It must line up with the pulse hole on the intake manifold.

Install the linkage on the air horn. Check linkage to make sure the butterfly opens all the way.

Step 10 - Finish Up

Install the exhaust header. The attaching bolts must be drilled and safety wired.
Install the valve cover.
Install the fan cover and air shields.
Install kill switch to the coil wire.

Step 11 - Breaking in the Engine

With the engine setting flat, fill the crank case with good 30 wt engine oil. Do not use synthetic or racing oil. Fill the crank case to the top of the drain hole.

Start the engine. Let it run on idle to low Ram’s for 15 to 20 minutes until the engine has reached full operating temperature.

Repeat the process under load using low to moderate speeds. Under load means on the kart.

Step 12 - Go Racing!
This engine is intended for a JR 1 rookie racer. It will produce more horsepower than the driver’s skill for many weeks or months of racing. It meets all of our basic goals of a budget minded, reliable and competitive, without the need of a machine shop.

The engine should be taken to track tech inspector to have the combustion chamber cc’ed. You will be able to add some power the engine by increasing the compression ratio to near the F200 limits.

TIP: Oval Kart racing is not about horsepower, it's about kart set-up. Although horsepower is important, it doesn’t help unless it gets to the ground to make the kart turn. Spend your rookie season learning about kart set-up not just horsepower.

What happens next depends on your driver and your budget. As the drivers’ skills improve and the crew chief learns the fine points of kart setup there will come a time when you’re ready for more horsepower. As with all OHV engine the biggest gain in horse power will be in the engine heads. Improvement in flow of air and fuel into engine and the flow of exhaust gases out will increase the horsepower the engine makes.

The next steps in your engine package should be race prepared cylinder heads with larger sized valves, blueprinted carburetor, tuned exhausts, and lighter rotating parts. You could expect to pay an engine builder $400 to $500 to prepared the head, blueprint the carburetor to get maximum performance.

END

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