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Author Topic: Modern Inline 4 Transplant into an SOHC 4 Could It Be Done!  (Read 2171 times)

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Offline BobbyR

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Modern Inline 4 Transplant into an SOHC 4 Could It Be Done!
« on: December 21, 2009, 08:27:05 AM »
I  personally could never pull this off. I was looking at all of the posts about increasing power of the existing motors. Since the modern sportbike has an inline 4, what would be involved in a transplant.

This is an intellectual exercises.  We have so much expertise here I thought it would be interesting.
« Last Edit: December 23, 2009, 10:35:42 AM by BobbyR »
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Offline mark

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #1 on: December 21, 2009, 09:39:01 AM »
Hanging the powerplant from the frame would be the easy part.....

..... getting a radiator in there somewhere without looking really tacky - there's the challenge.

Could maybe hide it in one of those big ol' '70s fairings but then you're right back to tacky.

 ;)

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Offline mystic_1

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #2 on: December 21, 2009, 10:08:05 AM »
If you could do it, would the frame be beefy enough to handle it?  CB frames from the 70's aren't the most rigid things out there, you know?

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Offline Inigo Montoya

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #3 on: December 21, 2009, 11:35:59 AM »
Not just the frame but look at the spindly forks we have. but then I guess it depends on which inline 4 is used. If a person stuffed in a 600, the weight savings would be a big help.
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Offline ColinMc

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #4 on: December 21, 2009, 11:50:32 AM »
When I was considering doing this...I was thinking a newer but still aircooled motor. That would solve a few problems from the technical side of things...
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Offline BobbyR

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #5 on: December 21, 2009, 12:51:47 PM »
This is good stuff keep it coming. Gets the creative jiuces flowing.
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Offline Inigo Montoya

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #6 on: December 22, 2009, 07:09:32 AM »
I dont know if there are many air cooled motors anymore. But a smaller motor should require a smaller radiator since there is no body work covering the engine, air cooling should be better.
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Offline mystic_1

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #7 on: December 22, 2009, 08:42:03 AM »
Exhaust port spacing will be a factor, to clear the double-downtube frame.

Also, the location of the final drive sprocket.

Also, depending on the carbs used clearance with the lower backbone rails may be an issue.

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Offline tortelvis

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #8 on: December 22, 2009, 08:46:37 AM »
I hate radiators! I would go for an older air cooled like my old GSX750ES motor. It also had a digital gear indicator which is a bonus.
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Offline HavocTurbo

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #9 on: December 22, 2009, 09:30:26 AM »
Sounds stupid I know.... Me raining on Bobby's parade.  :'(

But the 94 GSXR750 Watercooled engine weighs MORE than the CB750.

Even without all of the steel plumbing for the cooling system it weighs more.

Something to keep in mind... Bigger pistons, DOHC's, "Alternator" in a seperate housing, electronic ignition (more wiring and sensors), bigger rods, bigger crank, bigger transmission gears and shafts, insanely larger clutch assembly, and larger cases (both in size and thicknesses).

Where all of the weight was saved was in the frame and suspensions as well as unsprung weight in the wheels and the brakes.

I weighed them both drained of fluids and all non attached wiring removed.

There was about a 45lb difference.

Almost every modern I4 engine will have DOHC's and an extensively larger/beefier transmission and clutch. Those increase in weights alone will make a difference when mounting to a steel tube frame.

If anything.... we should be looking at an aluminum OEM style frame and swingarm for our bikes. That would probably help a bunch.

And now I have a new addition to my project.... thank you.  ;D ;D ;D
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Offline BobbyR

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #10 on: December 22, 2009, 09:34:04 AM »
No rain on any parade, the idea was to get people's minds working on a what if scenario. I was looking at a wrecked sportbike and noticed the inline engine.
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Offline Inigo Montoya

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #11 on: December 22, 2009, 09:36:40 AM »
That is why you use a smaller engine. Considering that many 600s generate close to 100 HP which is a significant increase over our engines, AND that some of the bikes use the engine and part of the frame so to speak. I doubt weight is that much an issue.
Also, since many of these engines are certainly no wider than ours are, it gives you some room to play around with in terms of sprocket offsets. Say you need to move the engine to the left to match the rear, that may make room to mount a radiator sideways.
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Offline HavocTurbo

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #12 on: December 22, 2009, 09:54:43 AM »
Custom radiator then?

Most are curved to accomodate the width and bodywork.

While I'd love to see it done.... it would be for asthetic purposes only. Can you imagine how it would ride? With our steel "hinge" frames? Sheesh!!!

But I suppose with nothing to do and lots of easy cash.... it would be a fun project.
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Offline Raul CB750K1

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #13 on: December 22, 2009, 12:42:37 PM »
I don't see the point. The original engine is very reliable and, in my opinion, it is powerful enough.

I could understand changing the engine for another one more reliable, to keep the bike looks. But the very charisma of the CB750 lies in the engine. Taking the annoyance of transplanting the engine seems like a waste of time, why don't just switch to a modern bike instead?

Believe me, I have other old bikes -spanish made- and they are a big PITA, not just because of engine leaks, but because of multiple small fixes in the rest of the bike systems, be it brakes, electrics, you name it. Having a CB750 is having a classic bike with the convenience of a modern one.

That being said, if I had to pick one, I would pick the CB750 Nighthawk engine. It is 73 CV, DOHC, oil radiator, inline four, and oil-actuated rockers - no adjustment ever. And, it is made by Honda, so the Heritage is not spoiled....
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Offline BobbyR

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #14 on: December 22, 2009, 03:49:52 PM »
I agree with you Raul. This is an intellectual exercise. There is a thread in which an SOHC has been grafted into a Harley. The question is if you were going to do it, what would you have to do?   
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Offline bill440cars

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #15 on: December 22, 2009, 05:02:55 PM »
Quote from: BobbyR on December 22, 2009, 03:49:52 PM
I agree with you Raul. This is an intellectual exercise. There is a thread in which an SOHC has been grafted into a Harley. The question is if you were going to do it, what would you have to do?   

           Bit of a different twist, but look what was done to an old Super Hawk.  Super Hawks ran pretty goo in the day, but now..... :o


           
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Offline Retro Rocket

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #16 on: December 22, 2009, 06:09:40 PM »
In a Brit bike mag I saw a 750/4 with an early oil cooled GSXR1100 motor in it, it looked really cool and with 120+ HP i bet it went as well.... ;)

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Offline bill440cars

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #17 on: December 22, 2009, 06:39:49 PM »
Quote from: retro rocket on December 22, 2009, 06:09:40 PM
In a Brit bike mag I saw a 750/4 with an early oil cooled GSXR1100 motor in it, it looked really cool and with 120+ HP i bet it went as well.... ;)

Mick

             I can imagine! ;D ;)
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Offline Inigo Montoya

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Re: Modern Inline 4 Transplant into an SOHC 4 Could be Done!
« Reply #18 on: December 23, 2009, 07:50:25 AM »
Another option in these bikes might be a cx motor, the sideways v-twin. that would solve any front to back clearance and is really not that wide.
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Offline tramp

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Re: Modern Inline 4 Transplant into an SOHC 4 Could It Be Done!
« Reply #19 on: December 24, 2009, 12:32:38 PM »
to save money and space why not work with the old motor
larger pistons with higher compression oil cooler and modified intake and exhaust aught to get you near 100hp no problem
and if we lost 30lbs ourselves there could be a weight savings
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Offline BobbyR

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Re: Modern Inline 4 Transplant into an SOHC 4 Could It Be Done!
« Reply #20 on: December 24, 2009, 01:08:25 PM »
Quote from: tramp on December 24, 2009, 12:32:38 PM
and if we lost 30lbs ourselves there could be a weight savings

+2 on the weight  ;D

This is just a mental and engineering exercise.
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Offline techy5025

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Re: Modern Inline 4 Transplant into an SOHC 4 Could It Be Done!
« Reply #21 on: December 24, 2009, 05:53:22 PM »
Didn't the new 750 that Honda demoed basically do this? Everything was updated, but it looked similar to the "old" 750. That engine might be a better candidate.

Jim
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Offline tramp

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Re: Modern Inline 4 Transplant into an SOHC 4 Could It Be Done!
« Reply #22 on: December 25, 2009, 01:08:59 PM »
i believe that engine is a dohc
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