Blog

2019

June 24/19

This winter saw me build two 750 motors and gather the part for the third. Many years ago I built a motor to install in a 1980 KZ 750 for resale. I was racing at the time and thought it best to keep all my 750 parts especially the heads for the race track. I built a motor with parts that I didnt think I would ever need. I used a standard 82 KZ 750 bottom end and pistons (less compression than 83-84 KZ 750 L or gpz750). I also used a KZ 650 cylinder head with 650 cams and 750 cam sprockets. I needed to drill out the front and rear valve cover holes(2) to fit the 750 valve cover onto the 650 head. You need the 750 valve cover for it guide when running the Hyvo 750 chain. Is used Keihin 34mm CV carbs ,stock. To my surprise the bike ran really well and was a rocket until it ran out of cam at about 8500 rpm. It wwas so responsive it made me feel like I had cable slide carbs and not CV’s. I was perplexed so I did a compression test and it was 185psi on all cylinders which was 30 psi higher than what I expected. I called a friend in the U.S (Pete) and mentioned this to him and he said that the 650 head is really responsive due to the smaller intake runners and that the ticket is to use 750 intake valves and at least 83-85 gpz 750 cams. Also the smaller combustion chamber created the higher compression. So 15 years later I’m finally building a race motor suited to short tracks using; the 650 head with 750 intakes,ported ,shaved .005-.007″,Hd valve springs, Yosh stage 1 cams, KZ 750E .5 mm oversize pistons, 550 6 speed trani, either 31mm Keihin Cr’s or 29mm Mikuni smoothbores. So that motor now sits in my 1984 red KZ 750 race/street bike and will be broken in on the street later this month June 2019.

The second motor I built was a freshened up 1982 GPZ 750 with new rings and con rod bearings. this motor will go in a 1982 KZ 750E as a daily driver.

This weekend the VRRA is heading to Calabogie Motorsports Park. I’m not racing but will be there to support my brother Jason and good friend Fernando.