I've never seen this referred to before, apparently it was developed alongside the Z1 in the mid to late 70's but never made it to production. What a beast. Thought some may like to drool over it.
Upt'North.
Upt'North.
Square Four 750.
- Thread starter Upt' North
- Start date
- Joined
- Jun 21, 2011
- Messages
- 1,117
- Age
- 71
- Location
- Ada ( Grand Rapids ) Michigan
- Bike
- '07 ST 1300 & '91 GW
- STOC #
- 8421
At least it is water cooled , addressed the problem the Ariel square 4 had....
There were several square 4 2 strokes used for road racing back in the 70s. Suzuki RG500 Gamma comes to mind, which they sold a street-legal version of. Smokin' fast!
bdalameda
PaleoCyclist
At the same time as this Yamaha unveiled a inline 4 cylinder two-stroke prototype. I did not make it to production either due to smog requirements.
OP
OP
Who knows, Honda may be working on a new ST right now? Or not.At the same time as this Yamaha unveiled a inline 4 cylinder two-stroke prototype. I did not make it to production either due to smog requirements.
Upt'North.
ST1500? Oh, boy!
I always thought it was a V4 but never looked under the fairing on the few that I came across. That, plus the RGV500 GP bike that actually was a V4 added to the confusion, so thanks for pointing that out.
Not a square for but the GT750 Water Buffalo comes to my mind when I see that Kawasaki
A riding buddy had this. I never stopped giving him grief until the day it was stolen. We were both happy.
A riding buddy had this. I never stopped giving him grief until the day it was stolen. We were both happy.
bdalameda
PaleoCyclist
I had a GT750 just like this one, I called it Moby Grape! I was a Suzuki Mechanic at the time. These were solid reliable motorcycles - I have seen these old two-strokes with over a 100K miles on them untouched. I rode mine all over the US and Canada and had a lot of miles on it when I finally sold it. It never let me down - practically bulletproof like an ST1100. I also owned a couple of later model GT750 L and M models.Not a square for but the GT750 Water Buffalo comes to my mind when I see that Kawasaki
A riding buddy had this. I never stopped giving him grief until the day it was stolen. We were both happy.
Well I did like Moby Grape especially 8:05. 
OP
OP
They are nice aren't they, but I prefer the cleaner lines of the later models. My chum is rebuilding a GT750A, they are worth serious money over here now. They always had a reputation for being fragile over here, I wonder if it might be down to winter lay ups and crank seals etc. Lovely to see the piccies. I can smell the Castrol R from here. You never used to see many touring either.
Upt'North.
I can't quite visualize the crankshaft arrangement. Were there 2 crankshafts?I've never seen this referred to before, apparently it was developed alongside the Z1 in the mid to late 70's but never made it to production. What a beast. Thought some may like to drool over it.
Upt'North.
OP
OP
I don't know but from the cases I would guess not. More research required me thinks.
Upt'North.
OP
OP
It might say here, but my Japanese is a little rusty. If it did have two crankshafts as I think the Ariel did, from memory I think they are referred to as U engines, or in this case I suppose a U4.
Upt'North.
Upt'North.
bdalameda
PaleoCyclist
No it did not have two cranks but a strange y shaped connecting rod for each side for two pistons to be connected to a single crank pin. It also had a single carb feeding two cylinders on each side through a common interconnected intake tract. They were working on a fuel injected version when the project was dropped.
That's interesting. Ordinary connecting rods have to deal with extraordinary stresses, imagine the lateral stresses on an angular connecting rod.
bdalameda
PaleoCyclist
The old Puch 250 "Twingle"(twin single) engines also had a Y shaped connecting rod as well as early Triumphs.. These strange engines were made this way mostly due to the metallurgy available in these earlier times, because they could not control the expansion rate of the pistons if they built one larger piston, on an air cooled two stroke, but could in effect have an engine that operated like a big single with two smaller pistons. The Japanese pioneered, along with help from an early German DKW engine designer, the use of silicone alloy aluminum which allowed larger more cam ground tapered pistons that allowed higher horsepower and larger cylinder bores without the heat related piston seizure issues with earlier two-stroke engine designs. This was a total game changer, making the higher horsepower high performance motorcycle engines possible. This new engine design philosophy made the entire Japanese Motorcycle industry domination possible back in the 1970's.
Last edited: