Are there any others floating around there? I'm going to do a tracing of a stock 72 engine when I get back out to the garage (its -5F now, so a bit too cold out there)
1954 Harley ST165 basket in the attic
1972 Suzuki GT750 project in the works
1981 Honda CB750-1000 driver
1982 Honda GL500 easy project
Interesting port plots. That J is really different to the last one I looked at belonging to a certain Mr Dave. Your J has an exhaust that at 41mm down is 1.5 to 2.0mm taller than most and taller than Dave's. It's also much wider at 47mm than stock at around 43mm.
How tall is that block overall compared with the 75? have either been machined down at all?
The 75 looks like it is stock.
For a nice street motor peaking at say 7,000 you need the exhaust at say 37mm down (36 min), transfers should go up 1.5 to 2.0mm and both should be wider than stock but angles in vertical and horizontal planes should stay the same.
tz375 wrote:
How tall is that block overall compared with the 75? have either been machined down at all?
The 75 looks like it is stock.
The 72 is on standard bore, but I got the engine off craigslist by itself so who knows where it's been. The cylinder was stuck pretty hard so if it was ported it was ported a while ago. It doesn't appear to have been planed top or bottom. There were some grinder marks on the aluminum of the intake, but the liner didn't appear to have any sloppy porting marks on it at least. Top or bottom don't appear to be planed.
I didn't traced the other stock 72 buffalo I had; and I didn't trace the 72 jugs I got before I sent them down to Eric; so I don't have anything to compare them to.
Anybody have another set of stock 72 tracings, or a stock 72 to trace?
tz375 wrote:Arne,
How much different is the new block?
The new block is between 75 and full TZ specs with some pretty nice liner work. (I'm actually pretty bummed that I started this CB750 to a CB1000 conversion project when I really want to be working on the GT!) I guess we'll see how it does soon enough.
1954 Harley ST165 basket in the attic
1972 Suzuki GT750 project in the works
1981 Honda CB750-1000 driver
1982 Honda GL500 easy project
I have a stock 72 cylinder off, just give me a couple of days to check it out. Had a fire sprinkler system break at work and flooded three floors of student housing.
"If you keep hitting your head against the wall you will eventually put a hole in the wall or your head"
Arne, the SCR tracings from Alan's bike are 73 (K) or late 72 (J) with intake spigots.
Your L may well turn out to be stock. So far I have only seen two early J blocks. Dave's had tall transfers and yours appears to have an extra tall exhaust port. I wonder if Suzuki had casting problems or if some of them were deliberately different say for road testing purposes.
Later barrels appear to hold tolerances quite well, apart from bolt hole placement relative to the bores.
It will be interesting to see what Eric's stock 72 looks like.
There's a Suzuki service bulletin that tells the changes between early and later cylinder porting. The 75 model had the ports raised by 5mm from the original porting. There were other changes.
Lane
If you stroke it more than twice; you're playing with it.
Too many bikes, too much time, ENOUGH SPACE, FINALLY! Never enough money.........
rngdng wrote:There's a Suzuki service bulletin that tells the changes between early and later cylinder porting. The 75 model had the ports raised by 5mm from the original porting. There were other changes.
Dont we need to be careful about porting width relative to bore diameter.
As an example, the first plot reference TR Porting but the exhaust width looks like the piston might just fall out if that was a 70mm bore. Now McCann may have been using 75mm(?) pistons for their big bore modifications.
Isnt there suppose to be a width ratio relative to the bore diameter that the porting (particularly exhaust) needs to stay below?
I thought 52mm was getting dicey and the plot that Arne provided is nearly 55mm. What would keep the ring in place with that kind of width?
