You must have the older high compression .80. They will not run good with 18% oil and 15%nitro. Try some 10% nitro 4 cycle fuel with no more than 15% oil. The combination of high compression and 18% oil on this 4 cycle engine is causing the plug to cool down and not fire at lower revs. Make sure the glow plug is the one saito says to use with this engine. Oh, and watch out this engine will throw props if run too lean.