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Content tagged 're-drive'

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  1. Post on Subaru EA81 in 4-strokes

    By bcbushcaddy, posted
    Hello all, 
    Not sure if I am posting this twice - just lost my sat momentarily and killed the previous post. In either case here it is again. Couple of pics below of our Subaru EA81 engine and re-drive set up. Only started flying it so too early for me to answer to many specific questions but this is what was done to the engine to modify it. Stratus profiled Cam (no longer available as far as I know, but use local engine shop), higher compression, flowed heads (flow charts to follow), stock ignition, 38 amp after-market alternator, VW Jetta radiator with stock pump and pulley regulated by 16psi cap with 190F thermostat; 
    cooling works well, PCV return (right side of re-drive) line will be changed up slightly, air filter - may go bigger, wondering if it leans me a bit too much at high power settings?, electrics - simple is good and same for ignition, points are cheap..., TBI-40 works well, but it is finicki in downdraft mode,  ...and a little glimpse of the other side of the firewall. We will try to post a few more inputs as we get them over the next little while testing this set up here. If you have questions of a similar installation with the TBI, but gear driven than Willis (Marshawk) can probably give you more feedback than "moi", I am only getting started flying it and testing it. 

    Yamaha APEX (EFI) engines, adapters, and complete FWF kits are now available, any type PSRU you want. 
    GT4 RAM and GT5 CAM clutches are now available, fits all Rotax C box installations, Air Trikes SPG4, and other PSRU types.  This is a direct swap-out replacement for the troublesome, high-maintenance RK400, Air Trikes BMW, and other centrifugal clutches sold for experimental aircraft conversion engines. 
    Both the GT4 and GT5 are self-aligning, pre-lubricated, double-sealed, and self-supported/self-aligning by means of precision deep-groove ball bearings.  No more shoes wearing out in 12-120 hrs.  No more filthy shoe dust all over the PSRU.  No more broken springs.  No more drum attachment screws coming loose and falling out.  No more impossible alignment headaches.  No more tinny, irritating, “minibike clutch” rattle on idle.  GT4 comes with a LIFETIME guarantee, GT5 comes with a 1000 hr TBO, and a 500hr/5yr guarantee.   Both clutches are rated at 6 times the torque of the YG4 engines for 1 million start-up cycles. 
    The Yamaha Apex fuel injected engine replaced the RX1 carb engines for model year 2006 when they discontinued the RX1.  As availability of good, low-mileage RX1 engines (2003-2005) wanes, Apex engines have only become more available (2006-present).  The 140 HP RX1 was an awesome engine, but refinements that came with the Apex line  made the original YG4 even more desirable.
    EFI improves ease of starting, instantaneous air density adjustment (altitude, heat, humidity) and allows precise metering of fuel delivery which allowed Yamaha to go more aggressive with ignition timing curves and cam profiles; which resulted in a 10 HP increase across the entire power band of the original RX1.  The Yamaha engineers didn’t stop there.  They reduced weight from 125# to 118# with the absence of carbs, a slightly lighter crank, and some reduction of case material.      
    Mohawk Aero Corp has been successfully fabricating adapters and installing Yamaha 4-cylinder engines on aircraft since 2012.  With an eye on the future for power enhancements such as turbo and superchargers we designed and fabricate a universal adapter suitable for use with just about any PSRU available or imaginable which could easily handle such tremendous HP.  We successfully engineered, fabricated, installed and tested our own Hy-Vo Silent Chain PSRU which bolts directly up to the crankcase with no other intermediate adapter whatsoever.  This unit reduces vibration significantly, includes a prop strike protection friction plate clutch, reduces installed weight, and reduces overall length by 2-1/2” over Rotax C and 3-1/2" over Air Trikes SPG4 gearboxes. 
    Please contact us at:
    Visit our website at: Mohawk Aero Corps
    Visit our YAMAHA AIRCRAFT ENGINES Facebook discussion group at: