Sweet pickup on a early block!

[jeff kushner]

I've been keeping an eye out for a early GT750 block for a couple of months and I just scored a standard bore 72 block with the flanged intakes off of fleabay of all places for a song! Turns out the guy might be going to AMA Vintage days in July so I might not even have to take the hour & a half detour to run up to his shop outside of Cleveland on our way out to Mid-Ohio. Scott will bring it with him and I'll just get it from him at the swap meet. Saved me 350 bucks on shipping and the guy could not have been nicer on the phone. He also knows the engine and didn't try removing the block from the upper case so I know that it's in good condition. The flanged intake sure makes life a lot easier when modifying this engine. We used the same back in the day and ran into the exh port limits but found an innovative way around that too. Step by step it's coming together. Hopefully, by the time I return from Ohio in July, I'll have all the parts and pieces necessary to begin the build. I'll have a load of nice stock 74 parts for sale too<LOL>.

jeff

[Suzukidave]

We used the same back in the day and ran into the exh port limits but found an innovative way around that too.<LOL>.
jeff

Good deal Jeff are you maybe talking about a spacer to lift the block several
mm's as Cometic gaskets sells the copper head gaskets and block spacers in a variety of thicknesses.I dont think they show them in there catalog so you have to call .

[jeff kushner]

Yes, it's pretty sweet how some things turn out! Back in the day, lift kits weren't commonly used, at least in the circles that we traveled...we didn't know anything about them so we experimented with different port shapes for the exhaust and tailored one around the water jacket constraints that gave us super power for a narrow range, kind of like what that guy (I forget who it was) did who was going after the speed record but not as radical or wide as his. Even back then, rings were pretty tolerant as long as you gave them plenty of "ramp" to tuck back into the grooves and the ones that I've been getting from Wossner are much better. Of course they don't make GT750 piston kits but I have to give John or Jim a call to be sure. Sometimes things don't make it into the catalog, like the Cometic gaskets!

I like options so I've got 2 different lift plates (2 & 3.5 mm) and several base gaskets of different thicknesses and the final decisions will take place during the build. I've got to get the block, clean it and take a few measurements. I seem to remember that we found some differences between the blocks of various years in addition to the porting changes they made so I'll want to have a good idea of what I'm working with.

jeff

[tz375]

Jeff,

Jim has Wossners for the 750 in different sizes, so you should be OK there. Ports were different JKL to MAB as you know and there are pretty wide manufacturing tolerances on heads and blocks. There are other minor differences between very early part and later ones in stiffening bars but not a lot else.

As you probably found in earlier experiments, the water passage is lower on the outsides of the exhaust ports, so a nice curved top works well to avoid breakthrough.

Early blocks need to have the intake flange machined or an angled wedge inserted to tip up the carbs - or cut a hole above the clutch to clear the right carb drain screw. That's easier than machining a spigot block for sure.

[jeff kushner]

Thanks TZ, I didn't know for sure but since they are proprietary to the Gt750 & 500 , we just can't plop in any 70mm (+) side-cut piston. I'll use the angled adapters available now. We use to cut out rad hose to bump out the bottoms but now, it's fit, cut & match, smooth and bolt for stock size carbs but with the larger ones going on, it's going to involve a little more "expansion" work but still worlds better starting place then the spigots!
Here's one of the many places that carries them.....

http://www.transcanimports.com/download ... langes.pdf" onclick="window.open(this.href);return false;

On my 550 I reamed the spigots out and it was tedious work. I broke it down into 3 stages, rough, close and fine by the tools needed to do it. It took three or four hrs for each cylinder in total. I still am not sure what the final value was in terms of power but every little bit helped on that engine.


jeff

[tz375]

Intakes are a royal PIA on later models just to trim the bridge down and then the port is usually far from concentric with the spigot OD. By some happy coincidence, the early flange type block as a short bridge and less of a concentricity issue to resolve.

I have one here and I keep thinking that I want to open up the studs holes and weld them up and then machine the flanges at a new angle and add new stud holes to take either Mikuni or Suzuki inlet stubs.

Stock Suzuki are good match for a 34mm carb, but not so good for larger carbs.

Extra pairs of transfers are worth a few HP but they are cubic work and cost. Wider transfers also look like a good idea but take time to work out the horizontal port angles to point the streams where you want them to go. A boost port or two would really help, but that's even more work......

[Suzukidave]

Boost ports .. no problem