Finally the NSR Frankenbike is ready to go. stock MC24 engine except for after market spannies, derestricted PGM II. Planning to keep the jetting on the fat side because too lazy to change jets. Track, race use only with a not very fast old geezer in the saddle. My buddy wants to run a mix of 50/50 pump AKI 93 (same as RON98) and avgas (leaded). I'm not sure we need the avgas. any downside to avgas? Thoughts?
I've had people tell me the bike shouldn't be running on avgas when tuned for racing but..... my HRC manual says otherwise. What kind of squish clearance are you running? And you're right, you might not need avgas. There is a big advantage of avgas, its got a long shelf life. _________________ MC28SP, '16 KTM 500EXC, '16 Beta Xtrainer, '07 BMW 1200GS, '96 Ducati 900SS
As Rob says, the best pump fuel you can get, with the lowest ethanol content.
AVGAS mix is OK, but straight AVGAS isn't the magic ingredient people think it is. You need the AVGAS jet kit, and the HRC/adjustable ignition to get even close to making use of it, plus a lot of compression.* Most people in our experience go backwards on AVGAS! Add to that it's not always easy (in the UK at least) to get it, and the compression and ignition required to get it to work make the motor totally incompatible with U/L fuel, so it can really ruin your day/weekend if you run out.
My MC21 makes 67rwhp on pump unleaded, StephenRC45's F3 made 74rwhp on pump unleaded. He has finally set it up for AVGAS now (after 20 years!), and found another 1-2hp, but I don't know the exact figure as I've not spoken to him for a long time.
*I strongly advise NOT messing with the NSRs compression. The MC21 and MC28 are already right on the edge of what's acceptable, and often extremely close to detonating as it is. That's why a drop of AVGAS isn't bad, but its slow burn rate really plays havoc with the jetting and timing. It simply isn't worth it in my personal opinion. YMMV
The best thing about AVGAS is it's crank seal and bearing friendly... the NSR's Achilles heel. _________________ Andy.
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