I bought a 1981 yamaha srx ice drag sled. I did some riding on it and it ran great no overheating. I checked the compression with my friends junk $10.00 tester and it said 130 psi. So I thought it could run on 93 oct. fuel. I put the 93 oct. in and the sled drove for 10 min. and the temp was 230's. and the cly. were 900-1000f. So I got home and checked the compression with my snap-on tester and the compression was 165psi. So my question is did the 93 oct. cause it to get hot or do I have another problem? Does race fuel cause the motor to run cooler if the motor has high compression?
sandmanmike1
New member
Silly question but did you run pre-mix in it. Most race sleds have the oil injection blocked off and premix there fuels.
Race fuel (110 octane) actually acts as a coolant along with being a propellant. Where as the 93 octane will start to detonate(spontainiously combust)under compression as the temps rise in the cylinders, meaning that the heat and compression are making the fuel/air charge combust before the plug fires at the proper time causing lots of heat and reduced power. If you don't already kow it you are VEEERRRYYYY close to a burn down. What fuel mixture was in it before the 93 octane, 110?
If so, then I will presume that the machine is set up and jetted for 110 vs 93 octane. It is possible to run 93 octane but that motor will require a bit more fuel, if you know what I mean. Hope this helps. T
If so, then I will presume that the machine is set up and jetted for 110 vs 93 octane. It is possible to run 93 octane but that motor will require a bit more fuel, if you know what I mean. Hope this helps. T
oldsleder said: