Topic: why do early cb750s have........AN OIL TANK??!

[ChortlingSandcaster]

I'm familiar with the 2 strokes having an oil tank that supplies fresh 2-stroke oil to the engine.

But with the exception of my  '69 cb750, EVERY 4-stroke bike I've ever owned has no oil tank.
The oil generally is filled at a dipstick port on the right side of the motor at the clutch area.

What's up with a separate oil tank?   Do these bikes burn oil like a 2 stroke (duh, NO.)
I mean, why isn't all the oil required for the engine able to fit inside the crankcase like every other 4-cylinder 4-stroke bike I own now and in the past?

Here's my reasoning.   The oil sitting in the oil tank on the right side of my cb750 is NOT lubricating the engine.   It's sitting in the tank waiting for, what, prom night?   The way it's set up, it's like Honda was thinking 'we need extra oil ready to go in case of oil loss in the crankcase, so let's have an extra emergency supply of oil on tap for that scenario." Because motor oil sitting in that tank is not lubricating the motor.

On a 2-stroke bike like a Kawasaki triple H2-750, the oil tank is running empty constantly because the crankcase on a 2-stroke motor is not full of engine oil, the 2-stroke oil is mixed with the fuel/air mixture at the intake ports (and some is supplied to crank bearings).  The H2's oil tank supplies oil that gets burned with the fuel, as is typical with 2-strokes.

4-stroke motors have engine oil in the crankcase.   2-stroke motors don't.
So why does my '69 cb750 have a 2-stroke-like remote oil tank reservoir?

Isn't the crankcase of the cb750's full of oil just like every other 4-stroke?

CAVEAT: I am not an engine builder, I suspect someone will come back with info about
this I'm totally unaware of.

[754]

It is a dry sump engine. A few advantages thee..

 like smaller crankcases, cooler oil, less drag on crank..

  At least one other early Honda twin was dry sump..

[scottly]

I'm familiar with the 2 strokes having an oil tank that supplies fresh 2-stroke oil to the engine.

But with the exception of my  '69 cb750, EVERY 4-stroke bike I've ever owned has no oil tank.

CAVEAT: I am not an engine builder, I suspect someone will come back with info about
this I'm totally unaware of.

You are totally unaware of CB750s. Period.

[ChortlingSandcaster]

It is a dry sump engine. A few advantages thee..

 like smaller crankcases, cooler oil, less drag on crank..

  At least one other early Honda twin was dry sump..

So does this mean there's an oil pump inside the engine somewhere that pumps oil through channels/grooves/passageways inside the cb750 motor to *exactly* the right places?

Is that how a 'dry sump' engine works?  Does that mean that the cb750 oil tank has both a 'send' hose to send engine oil to the engine, and a 'return' from the engine?  i.e. is the cb750 oiling facility a 'closed loop' system?

[ChortlingSandcaster]

I'm familiar with the 2 strokes having an oil tank that supplies fresh 2-stroke oil to the engine.

But with the exception of my  '69 cb750, EVERY 4-stroke bike I've ever owned has no oil tank.

CAVEAT: I am not an engine builder, I suspect someone will come back with info about
this I'm totally unaware of.

You are totally unaware of CB750s. Period.

I doubt its a crime dude.

[scottly]

I'm familiar with the 2 strokes having an oil tank that supplies fresh 2-stroke oil to the engine.

But with the exception of my  '69 cb750, EVERY 4-stroke bike I've ever owned has no oil tank.

CAVEAT: I am not an engine builder, I suspect someone will come back with info about
this I'm totally unaware of.

You are totally unaware of CB750s. Period.

I doubt its a crime dude.

Nope, just a loud proclamation of ignorance on your part.

[Spanner 1]

'Dry sump' is a bit of a misnomer as yes, their is oil in the bottom casing ( sump ) which is picked-up by the oil pump. This oil collects there having 'fallen' from higher reaches of the motor after it's delivery by the oil pump thru' the crankshaft bearings and the upper end ( camshaft area).......

[MCRider]

It is a dry sump engine. A few advantages thee..

 like smaller crankcases, cooler oil, less drag on crank..

  At least one other early Honda twin was dry sump..

So does this mean there's an oil pump inside the engine somewhere that pumps oil through channels/grooves/passageways inside the cb750 motor to *exactly* the right places?

Is that how a 'dry sump' engine works?  Does that mean that the cb750 oil tank has both a 'send' hose to send engine oil to the engine, and a 'return' from the engine?  i.e. is the cb750 oiling facility a 'closed loop' system?

Yes is the answer to all your questions. All CB750s were dry sump.

Not so uncommon. many Harleys being the most common of 4 stroke motorcycles, are dry sump with oil tank. Most British bikes of the pre-80s era were dry sump. Triumphs BSA etc.

AS 754 alludes, the main purpose on the CB750 was to keep the size of the crankcase smaller for a lighter more compact design

Designs have evolved to where crankcases are small WITH a wet sump, so for Jap bikes at least and most modern Euro bikes I suspect have wet sumps.

The oil doesn't sit passively in the tank but is circulated by the pump. The brief time its in the tank allows it to cool a bit.  Not all of the oil in a wet sump engine is constantly providing lubrication either. A similar amount is in a "pool" in the cases waiting, just like it would be waiting if in the tank. The surfaces needing lubrication can only have a certain amount of oil on them at any one time and that doesn't add up to all the oil at once.

PS A quick google search indicates many cars are dry sump as well, Porsche 911. Has a 12 qt system with an oil tank.

[Spanner 1]

Jeez, chill-out lads...... do we all know everything ??!... The pump also delivers oil from the tank directly.....

[ChortlingSandcaster]

I'm familiar with the 2 strokes having an oil tank that supplies fresh 2-stroke oil to the engine.

But with the exception of my  '69 cb750, EVERY 4-stroke bike I've ever owned has no oil tank.

CAVEAT: I am not an engine builder, I suspect someone will come back with info about
this I'm totally unaware of.

You are totally unaware of CB750s. Period.

I doubt its a crime dude.

Nope, just a loud proclamation of ignorance on your part.

Truth be told Scottly I err on the side of humility, I love being humble.  I have failed at so much sh_t in my life at age 50 that it makes me just about sick.

 I have no problem admitting I'm a rabid idjit at various times and places.  I have never let myself feel threatened by the fact that I don't know everything, but with folks like you to straighten my dumb$ss out when I f*ck up, gives me confidence I can find them answers I need, so........keep up your fine work there son.

[scottly]

Truth be told Scottly I err on the side of humility, I love being humble.  I have failed at so much sh_t in my life at age 50 that it makes me just about sick.

 I have no problem admitting I'm a rabid idjit at various times and places.  I have never let myself feel threatened by the fact that I don't know everything, but with folks like you to straighten my dumb$ss out when I f*ck up, gives me confidence I can find them answers I need, so........keep up your fine work there son.
[/quote]
Hey, PEACE, and I'm a couple of years older than you, so don't call me son!

[dave500]

always learning,two pumps are employed at times,the full pressure pump that delivers oil to bearings and galleries,and the scavange pump that returns the fallen oil to the tank under a much lesser pressure,a check valve may also be used to prevent oil draining back when the motor is not running.

[754]

Keep in mind at the time the 750 came out no one in Japan had built a production inline four, with the four pipes on it (to be truthful no one else had shown theirs , there was one more)

 If a dry sump was used, fears of overheating were being soothed. We are talking of a time where only several years before, many riders were amazed that the 500 Titan could live with 2 huge cylinders that close together.. the Mark III really shocked them..

 More food for thought, V8s used windage trays to keep oil drag of the crank, and a lot of racers have gone to drysump engines...

[meloni.racing]

Keep in mind at the time the 750 came out no one in Japan had built a production inline four, with the four pipes on it (to be truthful no one else had shown theirs , there was one more)

Wich company had also a inline four? just curious...

[Spanner 1]

Kawasaki.... almost got to show it to the public before Honda unveiled the CB 750  ( only an hour before Kaw. ).

[754]

Kawasaki, was well on the way.. but...


 after seeing what Honda unveiled at the 68 Tokyo Motor Show.....

 and the initial heart attack.... .....

 went back to the drawing board, and had decided, they were gooing to come out with something even better...

[ChortlingSandcaster]

Kawasaki, was well on the way.. but...


 after seeing what Honda unveiled at the 68 Tokyo Motor Show.....

 and the initial heart attack.... .....

 went back to the drawing board, and had decided, they were gooing to come out with something even better...

H1-500 triple!!!!!!

The triples are exciting machines.   In fact the power-come-on of a 2stroke with the piston firing every time it hits TDC is enough to make ya hate them tree-huggers who forced 2-stroke street bikes off our shores.

I have a gray-market Suzuki RGV250 imported from Australia puts out around 60hp, pretty light machine.  '89 bike.  My assumption is 21 years on, a 2010 250cc 2-stroke water cooled street bike is putting out around 100hp, 250lb dry weight.  Thank you tree huggers.

The H1-500 ruled the world starting in 1969.

*Except* for the cb750 of course.

[paulages]

Kawasaki, was well on the way.. but...


 after seeing what Honda unveiled at the 68 Tokyo Motor Show.....

 and the initial heart attack.... .....

 went back to the drawing board, and had decided, they were gooing to come out with something even better...

H1-500 triple!!!!!!

The triples are exciting machines.   In fact the power-come-on of a 2stroke with the piston firing every time it hits TDC is enough to make ya hate them tree-huggers who forced 2-stroke street bikes off our shores.

I have a gray-market Suzuki RGV250 imported from Australia puts out around 60hp, pretty light machine.  '89 bike.  My assumption is 21 years on, a 2010 250cc 2-stroke water cooled street bike is putting out around 100hp, 250lb dry weight.  Thank you tree huggers.

The H1-500 ruled the world starting in 1969.

*Except* for the cb750 of course.

the Z1 was the bike Kawa was planning to introduce, actually. the triples are beasts though.

[srook]

Kawasaki had actually mocked up a single overhead cam 750 to display.  When they got word that Honda had a production ready SOHC 750 they shelved it and built the Z1.  There is a picture of the single cam Kawasaki in Motorcycle Classics (not sure the date) it may be available on thier website.
Scott

[ChortlingSandcaster]

Kawasaki had actually mocked up a single overhead cam 750 to display.  When they got word that Honda had a production ready SOHC 750 they shelved it and built the Z1.  There is a picture of the single cam Kawasaki in Motorcycle Classics (not sure the date) it may be available on thier website.
Scott

Well I was hoping, I checked http://cu.motorcycleclassics.com  and www.motorcycleclassics.com
the latter was a subscription site, the former -- I searched on 'kawasaki 750' and it didnt come up,

if anyone finds that link POST IT!  Never had heard that Kaw was so competitive with Honda to just drop an entire bike because they couldn't get there first, in my mind a Kaw 750-4 in 1968-69 would have sped up the 4-cylinder development, more choices. 

I would love to see that 750-4 kaw.   As it is they waited, what -- 10 years or more before launching one?  By then the history of the cb750 was solidified.  Although Kaw took the 2-stroke triple category over that time period hands down.

[HondaMan]

Kawasaki had actually mocked up a single overhead cam 750 to display.  When they got word that Honda had a production ready SOHC 750 they shelved it and built the Z1.  There is a picture of the single cam Kawasaki in Motorcycle Classics (not sure the date) it may be available on thier website.
Scott

Well I was hoping, I checked http://cu.motorcycleclassics.com  and www.motorcycleclassics.com
the latter was a subscription site, the former -- I searched on 'kawasaki 750' and it didnt come up,

if anyone finds that link POST IT!  Never had heard that Kaw was so competitive with Honda to just drop an entire bike because they couldn't get there first, in my mind a Kaw 750-4 in 1968-69 would have sped up the 4-cylinder development, more choices. 

I would love to see that 750-4 kaw.   As it is they waited, what -- 10 years or more before launching one?  By then the history of the cb750 was solidified.  Although Kaw took the 2-stroke triple category over that time period hands down.

The Kawis guys were pretty frustrated by it, but they also did not wish to go heads-up against their already-senior in the Japanese marketplace. So, to avoid a direct head-to-head competition, they made it a DOHC and increased the size to 903cc. But, they forgot to make the frame stronger, or brakes important, and the Z1 became the quickest, scariest 4 to ride, ever, in 1972. By 1973 they started making significant numbers of them, pushing the CB750 out of the "hottest bike" slot.

My hobby became (and has remained) beating the Z1 in street races with the 750.

I just read the Wikipedia entry on the Z1: boy, they've got it wrong. Typical Wiki writers: they weren't there, haven't asked anyone who was, and just write it out as the ultimate authority... 

[droopy]

http://thekneeslider.com/archives/2006/01/27/prototype-kawasaki-1970-750cc-z1/

[754]

 The Z1 was released around end of 72 or had been shown.


 The triple Kaw left a big mark for sure, but it was not a refined motorcycle , like the CB 750 and Z1 were..

[scrapvalue]

Anyone here have any experience with the Yamaha TX 750?
It was twin cyl. with an internal balancer. It didn't viberate like the XS650's do.
They were produced in 1973 and 1974. I owned a 1974 and that thing was fast.
Ran it against a 500 Kawaski triple and pulled him. Not by a ton, but still was ahead.
Also ran it against 1 CB750 and that was apretty even race.
I know rider iput has alot to do with it, but that TX was a nice bike.
Not sure why they discontinued it.

Hers a picture.

[scottly]

Anyone here have any experience with the Yamaha TX 750?
It was twin cyl. with an internal balancer. It didn't viberate like the XS650's do.
They were produced in 1973 and 1974. I owned a 1974 and that thing was fast.
Ran it against a 500 Kawaski triple and pulled him. Not by a ton, but still was ahead.
Also ran it against 1 CB750 and that was apretty even race.
I know rider iput has alot to do with it, but that TX was a nice bike.
Not sure why they discontinued it.

Hers a picture.

Yeah, I had an early one. Biggest POS bike I ever owned. The first models had no chain adjusters for the counter-balancer, which made it noisy as hell, leaked oil worse than either of my BSA's, and later made it to one of the bike magazine's "10 worst bikes ever made list". The Yamaha dealer in SLO told me he had been in a warehouse stacked floor to ceiling with recalled TX motors. They were a miserable failure. Even when my bike was running well, no way it could keep up with a Kawi or a Honda. (Note to self; breath deep, suppress the horrible memories again....)