To mix or not to mix..

[Motorrad]

  Soo... when I originaly colaborated with stewart I was planning on running C12 race fuel...

But have been giving it some thought.... I think I may be able to get away with a 50-50 mix of C12  and premium pump fuel (91oct)...

all my husqvarna 250cc and 400cc bikes are in the same compression range as my k5.. and they are happy on that mix... Just trying to keep it simple (same fuel mix for all bikes... and cheaper)....

I know a stock bike will ping under hard load with just pump premium... but the heads are shaped horribly.. thinking the reshape fixes that...

What ya think?  this goes out to guys like Jerry,BDI,Doldguy, etc and others that have experiance with reshaped heads, and compression...     Bike will be desert raced... so LONG STRAITS, DEEP SAND etc...



I run 40:1 oil mix....
K5 motor specs.
Head
head miked .912 thick and was 42 cc chamber volume stock  ..mikes .882  now from head  nut face to deck thats .030 of face has .040  step 86 mm dia 4 degree squish and re radiuse chamber and polish 13.5 to 1 compresion


Crank stuffers.

Window piston
ports are stock, just cleaned up.
desert gnarly pipe
40.5mm sudco carb
Kips bolt mod.
V3 reeds

[DoldGuy]

Motorad,
I have the same cut head as you & am in the learning process with it now. As posted earlier, using the Digatron to gather the info & its  teaching me quite a bit about the K5. Currently using the Q16 so obviously have not had any issues with detonation, but like you thought about the price of the race fuel versus pump & for the little amount that I use it is not an issue. If you look at the cost of C12/gallon ($8 ?) versus what you would pay for premium at the pump ($3.50 ?) you would save approximately $4.50/gallon so you would save maybe $20 (?)  in fuel cost to blend, in my opinion its not an option as the potential dollars to risk far out weighs the benefits especially running in high load areas like sand.
If it is the conveniece of having the "same" fuel to use in all bikes you could mix up a jug of straight C12 & pull from that to mix the fuel for all of the other bikes. I would also highly suggest looking into some type of data aquistion (Like the Digatron) as it will allow you to see any potential problems like detonation, running to rich (more fuel consumption), etc. especially if you do decide to blend the fuel.

Hope some of this helps!
DoldGuy

[kaw rider]

with a great cooling system you can raise your compression ratio numbers 2 points higher and run the same fuel octane. you can run pump gas with a great head design.

[Motorrad]

with a great cooling system you can raise your compression ratio numbers 2 points higher and run the same fuel octane. you can run pump gas with a great head design.

I have never seen a stock bike that wouldnt ping in the dunes on pump premium....  (california crap fuel)...



Your right Doug....
  I had a moment of lazy thinking (and cheap)...

once you do the math for $20 a quart 2 stroke oil, race fuel etc... it makes you wince.... especially at a desert race (100miles plus in a day)...

I really dont see the need for a digitron... Yes it would be cool and fun... but for those of us that jet on the "safe side" since we run miles of sand at high speed......