INSTRUCTIONS:
PROPER MAINTENANCE OF YOUR NEW STOCKER
You have just purchased the finest Briggs and Stratton racing engine on the market. Years and years of research and development on the racetrack and on the dynamometer have gone into making your new racing engine extremely competitive. The following is a guide to maintaining a high performance level, and understanding your engine. You must follow these several basic rules to consistently have a fast racing engine.
First Practice Session On Your New Gecker Engine
This step is very critical to the life and seal ability of your engine. For the first two practice sessions with your fresh engine, run 14 ounces of Cool Power Green Medium. Before the first heat, drain the oil and replace with 12 ounces of Thor Oil. During these practice sessions, run methanol fuel. We perform this routine to ensure that that the piston rings are broken in for sure as there have been issues with seal on the new Briggs scraper and oil rings.
Oil
After running your fresh engine with the above combination, drain and add straight synthetic oil. We recommend running Thor Racing Oil in Light or Medium for the best durability. Drain and add fresh synthetic oil after two heat races.
Note: Never run automotive style synthetic oils.
Fuel
Always use clean and fresh methanol. Methanol attracts water: this makes it very important to keep fresh. We recommend using a filter to screen the fuel entering the gas tank on the engine as you are filling it. It is most beneficial to only fill the fuel tank to 1/2 inch above the tank seam (unless you are running an Enduro event). Overfilling can result in poor performance during turning. At the end of each race day or any other time where the engine is run on methanol, it is very important to drain the methanol fuel and run WD 40 through the engine. Methanol is very corrosive and can cause severe damage to aluminum components. You can also remove the plug and spray WD 40 down the cylinder. When done running your engine, make sure the piston is at TDC with both valves closed in an attempt to preserve valve spring life.
Jetting
Precision reamed jets are essential to smooth fuel flow in the primary and secondary circuits. Always carry a supply of jets from .049” to .0584 (.063 controlled engines). To correctly monitor jet sizing you must pay close attention to the cylinder head temperature (CHT) gauge and Exhaust Gas Temperature (EGT). A memory gauge can aid in tuning your combination. If your engine cuts out at the end of the longest straight or appears sluggish in the mid range you need to decrease the jet size. This is usually visible on the CHT/EGT gauge.
CHT and EGT
It is important to keep the CHT on stockers to less than 440. On purple plate restricted engines, CHT may be as hot as 420. The CHT can be monitored by increasing to a larger jet size or by moving to a colder heat range spark plug. It is very important to always insure that a higher CHT number cannot be associated to a bound up," tight or poor handling chassis. Often, the CHT can help to indicate chassis problems. Regardless of the engine type, Gecker Engines operate with the most amount of horsepower at approximately 1300 degrees in EGT. Moderation of temperature can also be accomplished by using tape on the blower housing screen. Keep the tape on if the temperatures are low. Take it off if they get hot. If you qualify, always tape the engine up solid so that it can get to temperature immediately.
Spark Plug
We recommend using several plugs: a Nippon Denso W-24 through 31 FSU or ZU fine wire, Autolite 411 or similar reach and heat range spark plug. If your engine is a Controlled Stock or a Limited, you can use a 292 Autolite plug. Utilize .028” to .032” spark plug gap. Use spark plug to moderate CHT. If the engine is hot, go to a colder range and/or larger jet size. Replace spark plug every two to three race days. Spark plugs can perform poorly due to methanol fatigue, with no visual signs. It is very critical that the spark plug is indexed (open end of the gap) toward the intake valve. In order to get this right, you will need some copper spark plug washers. Washers come with the engien and are available at every kart shop.
Air Filter
Always run an air filter and filter cup on your engine. There is no loss of performance by running an air filter. Running without and air filter can cause significant loss of cylinder seal and can shorten the life and the performance of the engine. If you are running on real dusty tracks, use a K & N filter instead of the S & B filter.
Note: On each race day on dirt, you should change the filter once. It is a good idea to have an extra filter cleaned, oiled and ready to go so that you can change it after your last practice. It is also necessary to use an Outerwear pre-filter if running on the dirt. If your dirt is really dusty, use a foam pre filter and stay on top of it.
Clutch
Your clutch engagement is as follows:
Purple Plate-3500 RPM
IKF Blue Plate-3625
Gold Plate-3850RPM
Unrestricted Stock-3900 RPM
Limited-5100 RPM
Animal-4100 RPM
Carb
It is necessary to replace the carb diaphragm every race day. Always ensure that the carb stays clean and free of debris. Running a carb and tank support has proven affective against breakage. Always remember that good running carbs are often “hard to come by.
Header
We highly recommend using the header or header with muffler combination that is recommended for that engine/camshaft as developed on the dyno by us. This does not restrict you from testing other header combinations. It gives you what we have found to be the best combination.
When Do I get The Engine Freshened ?
Through our experience, an engine can begin to fall from its performance potential after approximately 3 to 5 full race days. In some situations, race engines may go just past this point before the performance level will fall off. To maintain a high performance level, it is necessary to refreshen the engine.