These instructions are for EC's Denki PZ22 carburetors, which are specifically designed for industrial small engines based on the Honda GX200, such as Predator, Tillotson, Wildcat, Ducar, or the Briggs 5 hp flathead. While these instructions have general guidelines that can be used by other PZ22 carburetors or on similar or radically different engines, we can not guarantee these instructions will help you with your aftermarket carburetor or your application. For example, the Briggs LO206 uses either a Briggs or a Walbro PZ22, which are slightly different from one another, and both differ from the Denki PZ22.
For optimal performance on your Honda-Clone GX200-based or Briggs & Stratton 5hp Flathead engines, we recommend using only our PZ22 carburetors.
Please read this before mounting your carburetor.
EC is world-renowned for its carburetor expertise, with documented championships and race-winning history for over 50 years. However, performance is not a guarantee, nor does it grant a warranty on this product, since the synergy of the engine components, assembly, application, and vehicle dictates results.
Engines comprise multiple systems working together and must be assembled by builders with the tools and working knowledge to troubleshoot and adjust these systems. Many issues may result from other engine problems, such as the driveline and the handling/chassis setup.
This carburetor cannot be returned or exchanged if it is run with fuel. If you decide to return it, it will follow EC's return/exchange policy and be shipped at the customer's expense and restocking fees. Carburetors or parts bought from other retailers and dealers will follow the return policy of those companies. EC will not accept any EC product purchased through other retailers.
EC will help support their product after the sale for the original customer only; if the carburetor is bought second-hand or used by an engine builder, you will need to seek the advice of those individuals since the carburetor may not longer be in the original condition and the history of the carburetor is not clearly known.
Below are helpful troubleshooting and tuning suggestions that will help you resolve the most common issues you may experience during the carburetor's lifetime. If you need help beyond the information below, check our website and blogs for technical information, contact us through email, or call us. We will need engine specs, classes/applications, and your order/invoice number or name.
Carburetor Troubleshooting
Carburetor Blueprinting - These carburetors are developed for engines based on the GX200 Honda (e.g., Tillotson 196-268, Wildcat 223-240, Ducar 196-224, and Predator 212-224) or Briggs 5hp Flathead, both blueprints are specific to their engines and cannot be interchanged. The carburetor is tuned for performance specifically at wide-open throttle under racing conditions, which means the air-fuel ratio is tuned between 12-13:1 with high-octane pump gas. Average dew point 46, elevation 800ft, average temperature 57°F. Changes in engines, fuel, or ambient conditions may require additional tuning.
Exhaust Headers—These performance carburetors are designed for performance or racing engines. They are not blueprinted to run with headers less than .875 ID, including weenie pipes, Tillotson 225RS short-spec headers, stock exhaust, screw-on lawnmower mufflers, or other highly restrictive exhaust systems. We highly recommend using headers with .930-.990 ID with either low restrictive or no muffler.
Fuel Tank Vent – This should be checked before your carburetor is mounted. You should have a vent with a 1/4-inch hole in your fuel tank. DO NOT USE CHECK VALVES on the end of a 1/4 hose, as these restrict the vent and may not vent at all. Venting issues can range from pressurizing fuel, causing a rich condition, or creating a vacuum, especially after running. We've covered this thoroughly in our "Your Fuel Tank Sucks and It's Costing You Performance" Blog.
Fuel Pump – Depending on the fuel you are running, fuel pumps should be changed or rebuilt at least once a season. As the diaphragms wear, the carburetor will act as if it's lean. Carburetors running on any alcohol must be flushed after every race, starting with the fuel line through the pump and filters and running through the engine. Not only does the alcohol deteriorate the fuel system, but it can also cause corrosion inside the engine.
Another issue is where the pump's pulse is placed; ideally, the intake is the best location. The crankcase is the second choice, with the valve cover being last. In rare cases, the valve cover may cause issues with the fuel pump not pumping effectively.
Fuel Tank Placement - Usually, racing karts mount the tank on the floorboard with an inline fuel pump and fuel filter. Try to keep the fuel line as short as possible and keep the fuel tank as close as possible to extend your pump's lifetime and ensure the fuel pump isn't causing any issues. If you are gravity-feeding your carburetor, keep the tank less than 2ft above the carburetor. If the tank is too high, it can increase the fuel pressure and override the inlet valve, causing an uncontrollable rich condition, usually with fuel coming out of the bowl vents
Engine and Carburetor Angle/Tilt - Float bowl carburetors work best level as possible. If you have an engine mount that tilts the engine or if the chassis or vehicle changes the rake or angle of the engine, it will also change the angle of the carburetor, which can cause the carburetor to flood and act erratically.
Inlet Needle/Seat – If the carburetor is flooding and cannot be tuned, the needle valve is not closing completely. You'll notice this primarily when you are idle and at low speed. You'll start by cleaning the seat out, and if that doesn't fix the problem, you'll need a new needle valve.
Fuel is coming out of the bowl vents
1. Fuel Pressure is too high and overpowering the inlet valve (Check fuel tank vents)
2. The inlet needle/seat is leaking or not sealing due to deterioration or debris.
3. Float is hanging open, improperly set, or has a crack or damage that prevents the inlet valve from closing
4. The engine pressurizes the carburetor; the carburetor is either damaged or has a leaking valve.
Why may my brand-new blueprinted carburetor require additional tuning? Carburetors are often blueprinted for a specific class based on particular rules, components, and fuels. However, two primary reasons exist: components or engine type changes and atmospheric conditions.
First, changing significant components such as the head, camshaft, header, or displacement can change the signal to the carburetor. In other cases, varying engine types such as flathead, OHV, or the different kinds of 2-cycle engines are the most common. Each engine type has a different blueprint or setup for optimizing the carburetor.
Secondly, atmospheric conditions such as ambient temperature, humidity, barometric pressure, etc., can affect tuning. Here's our simple explanation: if you can't breathe, neither can your engine.
| Environmental Conditions | Current Tuning | Recommended Adjustments |
| High Ambient Temperature (Hotter air is less dense than cold) | Rich | - Decrease Jet Size |
| Low Ambient Temperature (Colder air is more dense than hot) | Lean | - Increase Jet Size |
| High Humidity - Wet (more accurate to use Dew Point) | Rich | - Decrease Jet Size |
| Low Humidity - Dry (more accurate to use Dew Point) | Lean | - Increase Jet Size |
| High Altitude (Approximately every 800ft) | Rich | - Decrease Jet Size |
| Low Altitude (Approximately every 800ft) | Lean | - Increase Jet Size |
Spark Plug Tuning
Spark plug tuning is often done incorrectly. Usually, there is a contradiction in the spark plug color and engine performance, typically resulting from an overly rich low-speed and idle with a very lean top end.
The plug will read rich, dark, and usually wet, which happens when the engine is idle. However, the carbon build-up doesn't clean up at high speed, where the engine could be going lean.
| Spark Plug Condition | Recommended Adjustments |
| Wet Fouling | - Low speed/idle is too rich - Check for blown head gasket/warped head - Check piston rings and cylinder bore for damage and wear |
| Dry Fouling | - Low speed/idle is too rich - Check spark plug heat range(may need hotter plug) |
| Metal Deposits | - Plug is overheating/melting (Use colder heat range) - Pre-ignition/detonation - Check piston for damage/melting (Reduce ignition timing/increase fuel octane) |
| Carbon/Other Deposits | - Check the oil level/catch can (A blown head gasket, warped cylinder head, damaged or worn piston rings, and cylinder bore). - Bad Fuel (Use non-ethanol gasoline and keep the tank with fresh gas) |
Using a sparkplug in the correct heat range of your engine is vital. Cross-reference the stock plug heat range(NGK BPR6ES) and stay within two heat ranges of this plug for any gas-powered engine. For this reason, never use the Autolite 3910X with any of our carburetors. That plug is designed for endurance engines or engines running power adders and is too cold of a heat range for engines. We recommend using a fine-wire iridium(Torch K7RTI or NGK BPR7EIX) plug gap between .026-.032" for the best performance.
Methanol engines can run colder heat ranges because they don't build up carbon like gasoline, but they can experience high combustion temperatures due to higher compression ratios and more BTU. We recommend fine-wire iridium (Torch K7RTI or NGK BPR7EIX) starting with at least one heat range colder or more than the stock plug. If in doubt, contact us for recommendations.
Tuning Notes and Considerations
The stoichiometric mixture for a gasoline engine is the ideal air-to-fuel ratio that burns all fuel with no excess air. For gasoline fuel, the stoichiometric air–fuel mixture is about 14.7:1 i.e. for every one gram of fuel, 14.7 grams of air are required. For optimal power for most gas fuels is 12.5:1 which is rich. Indications of a rich mixture is not bad unless there are performance issues. Before making tuning adjustments, talk to our technicians.
Low Speed Jet Tuning - The low speed jet influence the air-fuel mixture at idle and at low signal or air speed which can be from idle through part of the midrange around peak torque depending on the engine displacement, piston speed(stroke), camshaft timing & overlap, carburetor size, header diameter and intake port volume. That said, idle may be sacrificed for midrange torque. So you may have to choose between a clean, smokeless idle or a rich idle for strong midrange torque. These carburetors lack an acceleration pump to help off idle or on/off throttle so the pilot jet is rich to help with midrange acceleration. In modified engines, you may need to raise the stall on your clutch or torque converter, or go with a smaller carburetor.
Main Jet Tuning - Once there is enough signal or airspeed, the carburetor transitions to its main circuit, where you run the rest of the powerband. The main jet can influence air-fuel ratios from low speed to top end and is recommended as the first change if you are making tuning adjustments.
Metering Rod/Needle Jet - The Needle jet is primarily for part throttle tuning but can contribute to wide open throttle tuning with the main jet. We don’t recommend making this adjustment until you’ve talked with our technicians.
| Problem/Symptoms | Tuning Condition | Recommended Adjustment | Notes and Other Contributing Factors |
| Idling: - Unstable RPM/Revs up and down - Only runs on choke - Stalls/Doesn't stay running | Lean | - Turn Idle Air Mixture Screw in to reduce air - Decrease Idle Speed Screw to lower idle rpm - Increase Pilot/Low-Speed Jet | - Check Fuel Tank Vent(Vacuum in the tank preventing fuel flow) - Check Valve Lash (Too Tight) - Pressure Check Intake Port for Valve Leak - Check Intake, Inlet, and Gasket for Leak |
| Idling: - Stalls - Exhaust smokes black | Rich | - Turn Idle Air Mixture Screw out to increase air - Increase Idle Speed Screw to raise idle rpm - Decrease Pilot/Low-Speed Jet | - Check Fuel Tank Vent(Pressure in the tank increait'suel pressure) - Check the Choke and ensure it's off - Check ignition timing (too low) - Check Coil Gap (may change timing and spark energy) - Check Spark Plug for Fouling - Check, clean, or replace the inlet valve - Check Float Settings and for damage |
| Off Idle Acceleration, Under Load, from a dig) - Slow Acceleration - Stall and doesn't rev under load | Lean | - Turn Idle Air Mixture Screw in to reduce air - Increase Pilot/Low-Speed Jet - Lower Needle Clip - Use Narrower Metering Rod/ Needle Jet | - Check Fuel Tank Vent(Vacuum in the tank preventing fuel flow) - Check ignition timing (increase if possible) - Check Coil Gap (Ensure it is set correctly) - Check Clutch/Torque Converter stall( raise if possible) and for damage |
| Off Idle Acceleration, Under Load (from a dig) - Hesitation or Irregular Acceleration - Stalls then accelerates | Rich | - Turn Idle Air Mixture Screw out to increase air - Decrease Pilot/Low-Speed Jet - Raise Needle Clip - Use a Thicker Metering Rod/ Needle Jet | - Check Fuel Tank Vent(Pressure in the tank increase fuel pressure) - Check ignition timing (increase if possible) - Check Coil Gap (Ensure it is set correctly) - Check the Clutch/Torque Converter stall (raise if possible) and for damage |
| Acceleration at Speed (exiting a corner/cruising) - Slow Acceleration - Bogs | Lean | - Increase Main Jet First - Increase Pilot/Low-Speed Jet - Lower Needle Clip | - Check the Clutch/Torque Converter stall (raise if possible) and for damage |
| Acceleration at Speed (exiting a corner/cruising) - Erratic Acceleration(Hesitates then accelerates) - Runs Flat | Rich | - Decrease Main Jet First - Decrease Pilot/Low-Speed Jet - Raise Needle Clip | - Detonation (Reduce ignition timing, reduce compression, increase octane) - Valve Float (Check valve train, reduce valve train weight, increase spring pressure, reduce valve lift) |
| Wide Open Throttle at Max Speed/Top-End - Breaking Up(sounds like popcorn or rev limiter) | Lean | - Increase Main Jet | - Check Air Filter(Ensure its clean and not over saturated with oil) - Check ignition timing ( flywheel may have slipped and lost timing) - Blown Head Gasket or wrapped head (lost cylinder seal) |
| Wide Open Throttle at Max Speed/Top-End - High-Speed Stall (Acts like hitting the kill switch or engine turns off) | Rich | - Decrease Main Jet | - Make jet changes before other carbDon'tr changes, starting with the main jet. - Don't use other carburetors for jetting or tuning references; the emulsion tube, air bleeds, nozzles, and shape and size can influence the jetting. - Before tuning, check other possibilities such as fuel tank vent, clutch engagement" or ignition symptoms |
| Jet Changes | Use .001" increments for gas Use .002-.003 increments for methanol |
Other Engine and Performance Considerations
Camshafts - Stock Camshafts are around .220-.230 lift with around 215-225° duration with no overlap. Increasing lift, duration, and overlap will move the powerband higher, and you can start to lose drivability at low speed and off idle. You may lose the vacuum or signal to the carburetor caused by reversion, leading to hesitation or dead spots at idle and low speeds. It's essential you build your engine for the application and not solely based on the horsepower the engine can make.
Cylinder Heads - Most stock cylinder heads have between 25-27mm intake valves and 24-25mm exhaust valves. The ports are also small. Increasing valve and port sizes can also impact and hurt the signal to the carburetor and will work in conjunction with your camshaft and carburetor size.
Carburetor Sizing - For the best results, base your carburetor sizing on the inlet of the intake port. Most stock heads are between 22-23mm for "street" or low rpm/torque builds, aiming for a carburetor bore size 85% of the inlet size. In this case, 18.7-19.55mm(20mm), 90-100% for performance builds on gas and 110-115% for methanol. Airflow will vary by brand and design, but most aftermarket carburetors as low as 85% of the inlet size will generally outflow the cylinder head.
Air Cleaners - Good air filters are crucial for engine longevity. Use the best-quality air filters available and keep them clean. We recommend the Maxima Racing Oils, Air Filter Cleaner, and Filter Oil for all our air filters, carburetors, and engines. Following cleaning and oiling instructions, air filters oversaturated with filter oil may cause the carburetor to run rich.
Engine Oils - Engine oils are the last line of defense when it comes to contamination. It's essential to use high-quality racing oil and not an API or passenger car oil for your engine. It's also very important to use the right viscosity engine oil. Most clone engines have trouble with oil not draining from the valve cover back to the sump. Viscosity is the resistance to flow; higher viscosity oils worsen the problem. It's best to increase the drain back hole between the lifters to at least 1/4" and use 20wt engine oils. We highly recommend using the Maxima Racing Oil Break-In 5w16 or 10w-30 for breaking-in the engine and RS 0W-20 engine oils as your regular engine oil for the best lubrication and performance for your engine.
