Just Notes

Mark Sumpter (05/07/2016) The best analogy for a reed plate is a diode as it allows the flow of electricity in one direction much as a reed allows airflow from intake to exhaust only thus eliminating spit back through the carb and retention of more crankcase gasses ergo more efficiency.

First be aware that reeds weren’t designed for bowl and float carbs but rather for pulse carbs. Pulse carbs are more like a TPI (throttle plate injection) system than a traditional carburetor relying on gravity for metering thus doesn’t have the inherent drawbacks a normally aspirated carb does.

It is optimal that any fuel system be as close to the combustion chamber as possible to build power quickly and efficiently. I find a couple erroneous statements though about them giving better high end torque on a long intake.

The longer the intake the more distance for atomized fuel to return from its atomized condensate back to raw gas thus making tuning more difficult as when the raw gas burns off you encounter a leaning condition from unmixed atomized fuel then returning back to unburnt raw fuel as rpms decrease. It is even worse with offsets as the restriction builds barriers to deatomize the air/fuel mix.

Then you have to take into consideration distance because it amplifies vibration especially in float type carbs that have an air space above the fuel reservoir that can cause serious aeration problems in the bowl not to mention gravitational influences in the bowl that can cause leaning issues. The longer the intake tune the more amplified vibration as well for offsets made from rubber hose.


40mm stroke to degrees. 40 divided by 180 degrees = 0.22mm So 1 degree = 0.22mm. 38mm stroke to degrees. 38 divided by 180 degrees = 0.21mm. So 1degree = 0.21mm….Stuff measuring for accuracy. . A degree wheel is what is required for precision measurement and marking..



39.5mm Stroke

85mm Connecting Rod (Stamped ZL-E80)

Type B Piston (Windows Machined into Intake Side)

Jake Head (milled to correct spark plug location) 5.6 (ish) cc’s

Squish Gap = 0.024″

245psi on compression gauge with fresh rings.

Exhaust Timing = 160 Degrees (Exhaust Port Widened to 65% Bore Diameter/ Highly Elliptical Port Roof -CR Machine 1 1/4 Fire Breather Manifold)

Transfer Timing = 120 Degrees (Case transfers HEAVILY enlarged + matched to cylinder)

Intake Timing = 360 Degrees (Controlled 100% by reed valve, intake port always open Via Windows Machined into Piston -NO Boost Port/ 3rd Transfer)

RSE Reed Valve w/ NT Carburetor (14mm Bore w/ velocity stack)

NT Carb Jetting For Grange:

-Throttle Slide modified from 1mm cut-away to 2mm cut-away.

-Middle Clip Position

-#87 Main Jet

KX65 OEM Exhaust Pipe

Yamaha PW80 OEM CDI

NGK BP6HS Gapped @ 0.0210 (Side-Gapped)

VP Q16 (oxygenated/ high octane leaded race gasoline)

Maxima Castor927 (16:1 Pre-Mix Ratio)