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Author Topic: ANYONE EVER FITTED A TURBO TO A CB750..?  (Read 11252 times)

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UKCB750CAFERACERS

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ANYONE EVER FITTED A TURBO TO A CB750..?
« on: February 25, 2006, 10:09:31 AM »
Dear SOHCers .....

Has anyone any experience of fitting a TURBO to an SOHC CB750...?

Amongst my goodies is an IHI equipped turbo charger kit that has never been used...it has the manifolds,a huge carb,and odds and ends.

I can see how it all fits together and how it works...it has a "waste gate"or blow off valve in the manifold. ;D

Im not sure how to rig up an oil supply/return for the turbo bearings... ???

Im not looking for a huge power increase,just to get it wrenched up and fitted correctly
to a good strong lump...I havent reduced the compression ratio so far...maybe a good idea.

Any ideas,suggestions please...? (other than dont bother and maybe an asylum room being in order.. ;D ;) )

The best turbos back then were from ATP-American Turbo Pak-I think,but they were
HUGE greenbacks....Kawa ZIR TC for example.....

Ive seen quite a few old pics (back in the 70s)of CB750 Turbos...so it can be done again...I hope.....

Just another bit of fun whilst keeping these beasts on the road. ;D

Ive seen a pic of an F2 with a supercharger...!the owner described it as sounding like a helicopter on steroids..! mega power but easier than a turbo,no "lag"just kaboooom ..power!

Nostalgia is great....or maybe I should just go and buy a cheap modern scoot instaed..? ;D

Any JAPAUTO owners out there...?stories of big block lumps,huge power...almost like the RC 1litre lumps back then....

Well,back to the asylum room,nurse says no more bike stuff today...! ;D ;) :P

Thanks all


Safe rides
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Offline MRieck

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Re: ANYONE EVER FITTED A TURBO TO A CB750..?
« Reply #1 on: February 25, 2006, 11:20:06 AM »
I would take oil from the main galley block off cap and return it to the clutch cover. You'll need to drill and tap for AN fittings in both instances. Iwould think a -4 supply line and a -6 return line would be sufficent. Those old draw-through weren't very good (though they can make power) especially compared to blow-through systems with EFI. They can be better today if you use an Mikuni RS series carb. There are much better wastegates available today as well. I'd recommend better connecting rods and some other parts. You can buy Joe Haile's books which can help and contact Mr. Turbo as they do still draw-through kits for KZ1000's and some others. Rick Stetson at Harry's Machined Parts in Massachusetts knows alot about turbo's as he built the engines and was crew chief for Gary Clark( 4 time funnybike national champ and still quickest ET holder). I was at his shop a few months back and there was a cb engine there with a turbo he was going to work on.
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UKCB750CAFERACERS

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Re: ANYONE EVER FITTED A TURBO TO A CB750..?
« Reply #2 on: February 25, 2006, 12:20:19 PM »
Sincere thanks for your advice and comments....

Drliing/tappling the clutch cover should be straight forward I hope..!

Ill look for that book asap..

Thanks again,and enjoy your SOHC biking

Cheers! :)
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Offline HondaMan

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Re: ANYONE EVER FITTED A TURBO TO A CB750..?
« Reply #3 on: February 25, 2006, 06:07:34 PM »
The CB750 with turbo (can't remember the brand, but it was for a Volkswagon engine) we did "up here" (6,000 feet high, Colorado) had a surprise ending: fuel would not flow fast enough above 7500 RPM (45mm Mikuni pull-thru carbs, times 2) and it would go flat lean. We ended up with a Gold Wing fuel pump feeding the carbs through a large, single-hole fitting on the tank. Gearing went to the basement (16T front, 52T rear) and a 110/90 rear tire to get it on pavement.
Wastegate was set at 7 PSI. Compression was stock. Rods were Yoshimura roadrace rods. Bearing clearance (stock .0008") was set to .0012"-.0015". Intake valves were polished, throats of the intake tracts were opened approximately 2mm all the way to the valves. The valve springs were shimmed .010" exhaust and .020" intake, springs were Yoshimura roadrace.

Wasn't very nice on the street, but pulled into the 10s on the strip. Best I remember was a 10.29, but don't remember the speed.

I wonder where that bike is today?
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Offline cbjunkie

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Re: ANYONE EVER FITTED A TURBO TO A CB750..?
« Reply #4 on: February 25, 2006, 09:40:39 PM »
in other wrds...yes. someone HAS fitted a turbo on a 750... there is nothing new under the sun... ;) 8)
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Offline cben750f0

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Re: ANYONE EVER FITTED A TURBO TO A CB750..?
« Reply #5 on: February 26, 2006, 02:20:51 AM »
ah the dream i would like to build... turbo'd cb.....
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Offline Geeto67

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Re: ANYONE EVER FITTED A TURBO TO A CB750..?
« Reply #6 on: February 26, 2006, 04:42:02 AM »
Mr. Turbo used to sell kits for street cb750s back in the day (that black bike is a mr turbo kit). Their kits often used rayjay turbos. Not very wild but it definatly had a cool factor. I think the most you could run them was 6 psi on a stock motor. I rode one once and it was noticibly better than a stock cb750, but I have never owned one. Just make sure your kit is complete with the turbo oil feed off the oil filter, or that you have someway of feeding the turbo oil.
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Buffo

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Re: ANYONE EVER FITTED A TURBO TO A CB750..?
« Reply #7 on: February 26, 2006, 01:09:30 PM »
Check the spin on oil filter...  ;D
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Offline Jeff.Saunders

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Re: ANYONE EVER FITTED A TURBO TO A CB750..?
« Reply #8 on: February 26, 2006, 05:36:51 PM »
Quote from: Geeto67 on February 26, 2006, 04:42:02 AM
Mr. Turbo used to sell kits for street cb750s back in the day (that black bike is a mr turbo kit). Their kits often used rayjay turbos. Not very wild but it definatly had a cool factor. I think the most you could run them was 6 psi on a stock motor. I rode one once and it was noticibly better than a stock cb750, but I have never owned one. Just make sure your kit is complete with the turbo oil feed off the oil filter, or that you have someway of feeding the turbo oil.

It looks like an ATP kit in the picture - the log pipe is their trademark....  My Z1 runs an ATP kit modified to run a 42mm Mikuni flatslide (and yes you must run a fuel pump pushing approx 4-6 lbs of fuel pressure - I've emptied 3.5 US Gallons of fuel in less than 30 minutes of 'spirited' running).

Even on fairly tame boost settings, a turbo is going to put lots of stress on the stock connecting rods - if these are upgraded you'd be able to run a turbo at decent boost. Another problem is heat - turbo bikes run incredibly hot, so you have to work very hard to reduce detonation - this means running an advancer unit set back from the stock settings.  My turbo'd Z1 runs a Dyna 2000 as that system provides different retard settings for the higher rpms - currently it's set at around 32 degrees of full advance.  Ideally you run turbo pistons - not only for the lower compression, but the additional strength of forged pistons designed for the higher boost and heat issues from the turbo.

I'm not sure how best to manage an oil feed to the turbo on the Hondas - on the Z1 you tap into the oil fitting behind the cylinder block and insert a special restrictor to help divert oil to the turbo without reducing pressure significantly to the engine itself
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Offline cben750f0

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Re: ANYONE EVER FITTED A TURBO TO A CB750..?
« Reply #9 on: February 26, 2006, 11:07:02 PM »
here is a few picks of a turbo set up i found ebay a while back... thought it looked cool so kept the pics...
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Offline cben750f0

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Re: ANYONE EVER FITTED A TURBO TO A CB750..?
« Reply #10 on: February 26, 2006, 11:08:34 PM »
and the last one of the collection....
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Offline Sam Green Racing

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Re: ANYONE EVER FITTED A TURBO TO A CB750..?
« Reply #11 on: February 27, 2006, 07:11:46 PM »
What did you do with it Ben.

Sam.
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Offline cben750f0

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Re: ANYONE EVER FITTED A TURBO TO A CB750..?
« Reply #12 on: February 27, 2006, 11:23:21 PM »
mate i had $800 AUD on it and got blitzed completely... i think it went for twice that is US$... i liked it , but not THAT much ;D... BTW if anyone is interested i have an article from March '78's SuperBike mag, on a turbo'd CB750 Sidecar outfite, and an article on forced induction of 'modern' bikes.... good read... let me know and i can either talk to the moderators, or zip it to your email account... good reading...:P... peace
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you are never to old, to act like a kid... be safe
funny thing,chasing someone down hill on a bike 30 years older than theirs..
he said \\\\\\\'it was like watching a 250kg unguided weapon getting stuck up you bum\\\\\\\ http://www.bikepics.com/members/trixtrem/

Offline cb650

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Re: ANYONE EVER FITTED A TURBO TO A CB750..?
« Reply #13 on: February 28, 2006, 04:39:23 AM »
Heard when Honda was investigating the cx500 turbo they thought of doing the 650.  Went with the 500 for the water cooling. 
Is ther anything that hasnt been done to the 750?



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Offline MRieck

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Re: ANYONE EVER FITTED A TURBO TO A CB750..?
« Reply #14 on: February 28, 2006, 05:32:33 AM »
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