GPZ750/810 racer running....

After doing a lot of talking, here are the first steps in my Vintage racer build.

It's going to compete in the open class in the Italian Vintage championship. It's going to be up against big 1100 Zed's and Sozooks but as we dont have many horsepower tracks in the calendar, hopefully the quicker, more modern handking handling will make a difference.

Let's start with some frame bracing then?

bottom top tubes are now braced to the top one and also felt like adding to side supports to the steering head that was sticking out so much

another shot showing smal triangulation under new tubes

planning to use the two bottom holes in the cases (they will bolt to those two new ears) as well as going for rigid mounts instead of the rubber ones

above the rear cross tube i welded four ears. gonna bolt to them a1/8" ally plate to make that area more rigid, that plate will serve also as the carrier for the total loss ignition battery

last, never like the idea of the left engine spacer being bent by the chain tension, ite welded to the frame now + a msall bracket transfer loads to the rear cross tube.

all in all, about 1 pound of gusseting added, but have removed about 3 with all the those brackets and spacially THAT side stand bracket!

bosses for the race stand bobbins welded to the s'arm...

last, whiel at the welder's, filled up the side chamfers in the combustion chmaber, effectively "bathtubing" the chambers. this will let me to control better the squish areas as well as making them wider. as a bonus, chamber volume is smaller so yiu can get away with a less bumpy piston. head has been surfaced already, have to reprofile the inner side now.

KZ750 or 83-85 GPz750 head?

gpz 83

turboguzzi wrote:

last, whiel at the welder's, filled up the side chamfers in the combustion chmaber, effectively "bathtubing" the chambers. this will let me to control better the squish areas as well as making them wider. as a bonus, chamber volume is smaller so yiu can get away with a less bumpy piston. head has been surfaced already, have to reprofile the inner side now.

Also a great way to screw up pressure recovery in the cylinder.

I know what you're trying to accomplish but there's a down side to every up side & sometimes the hoped for improvement cancels out other important characteristics. JMO

Not trying to be a dink to you, it's obvious you're not a hack. Just something for an intelligent guy like yourself to consider...

Larry C

x

hi larry

not sure i understand what you mean by pressure recovery. can you explain?

I had pretty good results with a similar operation on my 500/4 racer, built a 0.2" wide, 0.03" thick squish area and was able to run 13:1 CR, 28-30 degs advance without any detonation. see pic

Would be interested to hear your recommendation regarding max CR for a road racing 810. We are allowed to use only pump super premium 98 octane + some additive, so all in all about 100 octane.

injected, not a bad idea, lets see if i find the place to do it.

Sure, if i had the means to scan the CC and then CNC each piston accordingly it could be great, but well above my means now. with this approach all i have to do is turn the pistons on a lathe for a flat external ring and then deck them to the desired squish.

TG