Topic: Sputhe 1156 kit ?

[Hotwheelbill]

Good morning everyone. Been a while since I’ve been on but I have come across something out of my pay grade. I picked this up for a good price that’s the only reason I jumped on it. 1972 frame with a 1975 motor. CB 750. But this thing has been sitting for over 10 years and is an old-school drag bike. Pulld the valve cover and the top end looks good so oiled everything down. Transmission fluid in the spark plugs for a while and everything turns over Nicely until you put the spark plugs back in. All starter and charging system has been removed. Kickstart only , which is a pain! Told that it has a Sputhe 1156 Big bore kit. With 12 to 1 pop-up pistons. Wiseco performance clutch. Double drive chain. And sprockets. Dyna ignition. Top end has heavy duty performance springs with titanium retainers. Don’t have the specs on the Cam yet. Anyone know the specs on the 1156 kit?

[Don R]

 I don't know, but there's a Sputhe that builds some hot V twins in so cal. Maybe it's their product.
https://sputhe.com/engines/

[Hotwheelbill]

Thanks for your reply. Yeah I found out last night. I already gave him a call earlier only went to voicemail. We’ll see.

[Don R]

 That many CC requires a stroker crank. I have one that figures out to 1124cc, I believe it's 72 x 69mm although my cheap caliper isn't really up to the job.
 There is a cb900 starter that fits and has more torque than a stock starter. That may require a set of starter gears and a lightened flywheel that still has the starter clutch in place.   
 

[gschuld]

69mm stroke and 73mm pistons is 1155.17cc

Dohc 900 cranks are 69mm.  73mm pistons is pushing the limits with 2.99” OD sleeves in factory cylinders, but it’s been done many times.

70mm welded stroker crank and custom 72.5mm pistons comes out to 1155.91cc

But I’d expect it would be the DOHC crank with 73s

Dohc cranks are different on both ends of the crank than the sohc4 setup.  Easy to find that out.

George

[Tracksnblades1]

69mm stroke and 73mm pistons is 1155.17cc

Dohc 900 cranks are 69mm.  73mm pistons is pushing the limits with 2.99” OD sleeves in factory cylinders, but it’s been done many times.

70mm welded stroker crank and custom 72.5mm pistons comes out to 1155.91cc

But I’d expect it would be the DOHC crank with 73s

Dohc cranks are different on both ends of the crank than the sohc4 setup.  Easy to find that out.

George

And the center of that 900 dohc crankshaft is different with its Morse Hyvo chain sprocket with more teeth than the sohc’s..

[Hotwheelbill]

69mm stroke and 73mm pistons is 1155.17cc

Dohc 900 cranks are 69mm.  73mm pistons is pushing the limits with 2.99” OD sleeves in factory cylinders, but it’s been done many times.

70mm welded stroker crank and custom 72.5mm pistons comes out to 1155.91cc

But I’d expect it would be the DOHC crank with 73s

Dohc cranks are different on both ends of the crank than the sohc4 setup.  Easy to find that out.

George

Would this tell anything?

[Old Scrambler]

That cover indicates the starter gear is GONE............likely was started with a roller device.

[Don R]

  What does the points end of the crank look like? Or this end for that matter will tell you if it's a welded stroker or a 900 crank. The 900 has the ends swapped around a welded stroker will look stock and a starter may be fitted although it might take 24 volts to crank it.

[bear]

We started doing 69mm DOHC cranks back in the late 1980's.
I didn't know it was an American thing?
I think I would put my money on it being a welded crank.

The crank on the right is a DOHC.
The cranks on the left are a couple of our modified DOHC's ready to fit into a SOHC motor.

Second pic is the DOHC crank and rods I used for my last motor.

[Hotwheelbill]

The points side has a Dyna electric ignition. The side left side, in the picture is solid. I don’t get it the nut that you see does not turn it’s solid to this entire piece.

[Don R]

 That nut looks like a rocker cover cap. I wonder if it's locktited on? In any case you have a cb750 welded stroker crank, not really a kit motor but a pro built race engine. Often there's a reason the racer stopped racing it.

[Hotwheelbill]

So I had a phone call from a lady at Sputhe . She is the daughter in law of the man that used to build these parts for the CB750. They did in fact make a 1156 kit. They even made a 1300 kit at some point. She said she still had a couple of cases but I’m not really sure what she meant and did not elaborate on it.But all documentation has been lost in time through paper and never digital. I still have her contact and she would love to have pictures if this ends up being something of theirs from the past. But there was a question about the stock jugs on the bike. So the only way it’s going to be to tear down. But I’m going to start this beast first.

[Don R]

 It sounds like the ultra big ones may have used the RC cylinder case. 

[gschuld]

73mm pistons require sleeves of at least 2.99mm OD as was commonly used by RC Engineering and others during that time period. It’s not a simple drop deal as the factory cylinder blocks tend to breach the 1/2 3/4 cooling passages when boring for sleeves that big.  You will typically find the 1/2 3/4 air passages filled with most commonly a high temp silicone, or Epoxy, or weld. 

That’s a sure sign it’s a 70-73mm bore engine

[scottly]

Told that it has a Sputhe 1156 Big bore kit. With 12 to 1 pop-up pistons.   Anyone know the specs on the 1156 kit?

Your PO has sent you on a wild goose chase, and you wouldn't be the first to fall down this rabbit hole. Sputhe made cylinder heads and cylinders for Harley Davidson's, including the iron head Sportsters. They may have made a big-bore/stroker kit in that size for the HD XR750 flat-track bike, but most certainly not for a Honda CB 750.
As has been mentioned, if it has been bored to 73mm, the cylinder sleeves will be exposed between the cylinder fins.
BTW, my 836 with high compression was also a #$%* to kick-start; I finally re-installed the electric starter a few years ago.
With that cover removed, you may be able to re-install all the original parts? You might also want to try a bore-scope down through the spark plug holes to check the piston tops.

[MRieck]

We started doing 69mm DOHC cranks back in the late 1980's.
I didn't know it was an American thing?
I think I would put my money on it being a welded crank.

The crank on the right is a DOHC.
The cranks on the left are a couple of our modified DOHC's ready to fit into a SOHC motor.

Second pic is the DOHC crank and rods I used for my last motor.

Looks like a Falicon crank in the second pic.....no more of those being made.

[bear]

We started doing 69mm DOHC cranks back in the late 1980's.
I didn't know it was an American thing?
I think I would put my money on it being a welded crank.

The crank on the right is a DOHC.
The cranks on the left are a couple of our modified DOHC's ready to fit into a SOHC motor.

Second pic is the DOHC crank and rods I used for my last motor.

Looks like a Falicon crank in the second pic.....no more of those being made.

G'day Mike,
I hope your going well.
The rods are Falicon, but all my cranks where done by an old bloke down in Melbourne by the name of Bill White.
If I brought him a crank he would grab it by the end and give it a rap on a counter weight with a ballpeen hammer. He could tell if it had any defects just by the sound it made.

[Tracksnblades1]

We started doing 69mm DOHC cranks back in the late 1980's.
I didn't know it was an American thing?
I think I would put my money on it being a welded crank.

The crank on the right is a DOHC.
The cranks on the left are a couple of our modified DOHC's ready to fit into a SOHC motor.

Second pic is the DOHC crank and rods I used for my last motor.

Are those Falicon rods a custom length?   Looking pretty long 👀

[dragracer]

Bear,
I'm not certain if I asked this question before or missed a post on this from the old thread but how were you cranking these engines?? Did you roller start them? Was on board starting ever worked out??

We started doing 69mm DOHC cranks back in the late 1980's.
I didn't know it was an American thing?
I think I would put my money on it being a welded crank.

The crank on the right is a DOHC.
The cranks on the left are a couple of our modified DOHC's ready to fit into a SOHC motor.

Second pic is the DOHC crank and rods I used for my last motor.

Looks like a Falicon crank in the second pic.....no more of those being made.

G'day Mike,
I hope your going well.
The rods are Falicon, but all my cranks where done by an old bloke down in Melbourne by the name of Bill White.
If I brought him a crank he would grab it by the end and give it a rap on a counter weight with a ballpeen hammer. He could tell if it had any defects just by the sound it made.

[bear]

Are those Falicon rods a custom length?   Looking pretty long 👀

Well spotted!

Yes the rod's in the picture are longer than std sohc rod's, but they are not custom made. They are replacement Falicon rod's for the Honda M4 rod's used in some of Honda's CB1100 engine's. When I decided to assemble this last engine I had run out of the Honda rod's and could not track any down, so we used the Falicon rod's instead.

The reason we used the longer rod's was to maintain an optimal conrod to stroke ratio.
Because our engine's where used for road racing sidecars we needed to balance what ever horse power we could achieve with a defined standard of reliability.
That standard was one hundred hours of competition before a full inspection or disassembly.
With our early engine's one of the weak links was excessive piston and ring wear.
We solved the issue by using longer rod's.     



 

[Tracksnblades1]

Bear you’re the man…

Just like the popular surveyor’s adage.

Water is just like a good woman, she’ll follow a longer rod 😁

[bear]

Bear,
I'm not certain if I asked this question before or missed a post on this from the old thread but how were you cranking these engines?? Did you roller start them? Was on board starting ever worked out??


If the engine was cold we would use a kick starter.
Once we had heat in the engine we would bump start it.
One of us could bump start it within a meter unless there was an issue.
We did not have a powered starter, inboard or outboard.

[bear]

Bear you’re the man…

Just like the popular surveyor’s adage.

Water is just like a good woman, she’ll follow a longer rod 😁

 
I just try to "focus on the task at hand"

[NitroHunter]

I'll second that, with 240lbs cranking pressure my 836 was definitely a young man's toy. Replacing the starter with a working unit would have been an admission of testosteronal deficiency... 
With me being a kid weighing in at a buck and a quarter back then, it was all technique to get that thing kick started. It was especially fun to watch big guys give it a go, unless they'd kicked Harleys or big bore dirt bikes it was an eye opener for them.