Z500 for racing

not easy to diagnose form miles away, but things i would check:

quality fuel? i run all my race engines on 98-100 octane which you can find in some italian stations, if not try to put some octane aditive.

igntion timing? my CB500 and GPz550 racers run best at max 28 degrees

good fuel supply? take out the drain plug from the first carburetor bowl, open the tap, and see that it flows freely out. do the same for all cyilinders

hows the plug colors? show signs of too lean?




 

I didn’t have time to test anymore before the race but I changed to a smaller fuel filter and moved it away from the engine. 
it has run perfect all race weekend. Or maybe it’s the German 102 octane fuel I found at a gas station 🙂

Thanks for the input on the ignition. I never tested it but I will check when I get home Ignition is all standard.
My 650/750 it set to 35 after recommendations from this website  members.tripod.com/gpz_rider/technical/FAQ2000.htm

higher octane will surely cure many problems

timing depends a lot on what you done to the combustion chamber and piston crown, if there is squish or not.... the 35 is a quite standard figure for a street bike, might or might not be the best for your specific engine 

my racers always have some squish built into the combustion chamber so needed less max advance and that makes the engine more efficient and less prone to overheating/detoante

the only way to find out is to do some runs on the dyno and see what timing works best

search for "minimum best torque" timing, also known as MBT