Race fuel, pump gas or a mix of the two?
Here at Redo Banshee Parts and Accessories we get calls almost every day from someone that has lost a top end on a bike after only short time of riding. Usually it is someone that has bought a Banshee, takes it out for the first time to the dunes and doesn’t know how the motor was built or was misinformed by the previous owner. Many times this blown top end is a result of not running the correct fuel for the way the motor has been modified and could have been avoided. We want to help people avoid this costly little oversight so let’s take a look at why this happens.
The type of fuel that you need to run will be a factor of Compression/Compression ratio, altitude, squish band, and timing. The most common problem we see is people build Banshee motors with higher compression, tighter squish tolerances and advanced timing and then feed them low octane pump gas at sea level and BOOM…… you lost a piston or two.
DO A LITTLE DUE DILLIGENCE ON YOUR BANSHEE BEFORE RIDING IT.
You need to determine your compression by using a screw in compression gauge. Remember when checking your compression to hold the throttle wide open and give it 15-20 kicks. Depending on your elevation the compression can be a little different, at sea level the compression will ALWAYS BE HIGHER so keep that in mind.
Next, you should take the stator cover off and see where the timing is set at. If the bike has an adjustable timing plate you will notice a bunch of numbers and hash marks on the right side of the stator plate just above the little black box on the stator (pulse coil). If you have a timing plate with numbers on it, the number hash mark lining up with where the cases split in half will be where the timing is set at.
The most common advanced timing on the majority of Banshee motors will 4-5 degrees advanced. If you do not have a timing plate with numbers on it, take a look at the stator plate where it bolts to the cases (three bolts) and see if it looks like those mounting holes have been ovaled out. This is the cheap way to advance the timing and can typically get you around 4 degrees advance. If the holes are oval, check to see if the plate has been rotated clockwise.
You will be able to tell this if there is some mounting hole visible to the right of the bolt. If there is no adjustable stator plate and the holes have not been ovaled out then the timing is more than likely stock. The last factor is squish band, however that is a little more technical and less likely to be a factor for this post so we will skip that one.
What fuel should I be running???
Here’s a simple formula we use at Redo Banshee Parts to determine what kind of fuel to run & it has worked great for us for years on 99% of the machines we run.
IF THE COMPRESSION IS UNDER 150 lbs AT SEA LEVEL — you are more than likely safe to run 92 octane pump gas.
IF THE COMPRESSION IS 150 lbs to 165 lbs AT SEA LEVEL — you should run a minimum of 50/50 110 octane race fuel and 92 octane pump gas, but would be fine to also run straight race fuel.
IF THE COMPRESSION IS GREATER THAN 165 lbs AT SEA LEVEL — you should use straight 110 octane race fuel.
SIDE NOTE: if you have a low compression engine (120-140 lbs) using race fuel or a combination of race fuel and pump gas will not only cost you more money but will also cause your engine to have DECREASED performance.
Please understand that this is just a recommendation that we have had success with here at Redo Banshee Parts and is not the cure all for every top end failure on the banshee. This is definitely a great place to start though for getting the correct fuel selected and avoiding detonation. We hope you enjoyed this info, from all of us here at Redo…..keep those motors turning!