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sad part is that all of those parts individually would bring super huge money on ebay, espically that crazy frame and that coffin tank. That is not just a weld on hardtail - that frame was fabbed around a stock neck. Cb350 chp frames are rare - there were some made but not many survived.

Take off all that hardware store brass, put a proper tank on it,saw the pipes off, throw out that windsheild, and bring the front end up three inches and you would actually have a decent chopper.

personally something this weird would actually be worth $1500 to me (if I had two nickels to rub together) - but I am a fucking weirdo as it is.

http://cgi.ebay.com/ebaymotors/Hond...5QQihZ016QQcategoryZ80647QQrdZ1QQcmdZViewItem
 

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quote:
quote:
Turbo Honda engine DOHC
I have the same engine, or similar ( It could be a 900 or a 1100, mine is a 750) but that turbo is amazing....would that be difficult to build??<img src=icon_smile_shock.gif border=0 align=middle>

Cafe racer DOHC CB750F

http://cardomain.com/id/jaimesix

Edited by - jaimesix on Sep 21 2006 03:26:07 AM
It is not a 900 or an 1100 - it is a 1980 750cc DOHC. The bike looks to be built out of a K bike.

They still sell turbo kits for DOHC cb750s overseas, I believe they are just the old Mr. turbo kits from the early 80's. Back then there were quite a few turbo kits for bikes, and it was not oncommon to see one - these days the only turbo bikes you see are new sportbikes.I am pretty sure the bike above uses an old draw through kit (a single carb is attached to the turbo instead of the turbo forcing air into the carbs.

Turbos on early DOHC honda were so popular that Revell even made models of turbo cb750Fs.

Making you own is fairly straight forward if you know your way around a welder. You need a header to drive the turbo, a steady stream of oil to feed the turbo bearings, a wastegate, an intake that will bolt up to the turbo, and a single carb that can handle the turbo. That hardest part is finding room for everything. Remember that Forced induction is "forced" so strange angles in the tubing is not as big a concern as it would be with N/A motors.

Wayne and sons makes a log manifold for SOHC 750s, he may also make them for DOHCs or he can custom make you one. With all the little turbo pocket rocket cars coming out of the factories these days it shouldn't be hard to find a small turbo in the junkyard (Subaru WRX, VW GTI, Mitsu Evo, Dodge SRT4, etc...) or on the message boards. I got a friend who works at a subaru dealer and they take off stock turbos all the time. Old harley sportsters used to use a huge (40+mm)mukuni VM carb that would be easy to setup for a draw through application - my local harley guy throws these old carbs out so I have a few sitting around.

come to think of it....why am I not building my own turbo
 

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...i've got a '79 750K cafe project in the process of becoming turbo charged as we speak.

as far as placement goes, i want the turbo hanging out there in your face...as it'll be muffled through the turbo and finished with a tiny cookie cutter, it'll look as sinister as it sounds! as of right now, it's gonna go rearward, right behind the left shock near the end of the seat tubes. it may sound slightly bizarre, but it works...well. the pipes will then be long and tucked and when wrapped, will look equally killer.

i've got some photos of the very initial mock up, but don't know how to post an image. can somebody throw me a bone?
 

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Nice use of a cb350F tank.

That is going to take a lot of piping to run that turbo, more than is usually in a car (with the exception of that kit for trans ams and camaros that mounts them back behind the axle). I don't think your cb750K engine is going to have enough exhaust velocity to spool that turbo properly - I.E. you are going to have major amounts of lag. Modern turbos are efficient but I don't think they are that efficient.

With a turboed bike you want things as simple as possible: Short tubes, one draw through carb, keep it tight and neat. Blow through setups are not as efficient as draw through because in the later you are using the turbo to mix the fuel as well as the in rushing air, in the former you are just asking a carb to do it's normal functions but at a higher pressure.

Also you are running those Stock CV carbs - which will make it a bitch to dial in that turbo. The Stock CV carbs didn't work all that great when new and un turboed, through boost through them is going to make the slides act as an on off switch. You are probably going to have to switch to a set of CR39 flatslides.

I almost forgot: Supercharged and turboed bikes are loud as fuck. Don't think because you have a turbo on there it will act like a muffler - it wont. On the Supercharged harley, we run Python 3 pipes (double walled) with mufflers and the decibel levels are still louder than an N/A evo with open drag pipes.

other than that cool project, lets see some more pics.



Edited by - Geeto67 on Sep 21 2006 11:24:58 AM
 

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it looks to be in german, but here is a site that looks to still have cb750/900/1100 turbo kits available:

http://www.zedbike.de/Special Parts/Rajay_MR_Turbo_Turbolader.htm

quote: Geeto...I think someone just zip tied a turbo to the bike. It's a joke. I hope.
JohnnyB
I don't think so since catboy has mentioned building a turbo cb750 before. If it is a joke I got hooked and hooked hard.

anybody considering building their own turbo system should read this book:

Motorcycle Turbocharging, Supercharging, & Nitrous Oxide: A Complete Guide to Forced Induction and its use on Modern Motorcycle Engines (Paperback)

http://www.amazon.com/Motorcycle-Tu...=pd_bbs_1/104-5349686-1941520?ie=UTF8&s=books

it is not a how to but will give you enough of the basic theories to get you in to trouble.

This is also a great basic book to get you thinking:

http://www.amazon.com/Turbochargers...ef=sr_1_3/104-5349686-1941520?ie=UTF8&s=books

There I go again, assuming this motley bunch can read.....

I keep thinking I am going to build a turbo cb750 one of these days but I never get around to it. Mostly because I also have this pipe dream that I would fuel inject it using a megasquirt controler for the computer and a car throttle body to control airflow (most likely pirated from a civic, probably use the injectors and rail too). There I go dreaming again.

in case anybody want's to try their hand at FI here is the Megasquirt FAQ:

http://www.megasquirt.info/

Edited by - Geeto67 on Sep 21 2006 12:11:43 PM
 

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I hope it's a joke because the exhaust will have lost half it's heat energy by the time it gets back to that turbo...it will be lucky to make more power than a stock engine.
I suppose with a ton of heat wrap, and a very long warm up it could run at Bonneville ok.....assume there is enough room there for the turbo to finally kick in :)
JohnnyB
 

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quote:
I hope it's a joke because the exhaust will have lost half it's heat energy by the time it gets back to that turbo...it will be lucky to make more power than a stock engine.
I suppose with a ton of heat wrap, and a very long warm up it could run at Bonneville ok.....assume there is enough room there for the turbo to finally kick in :)
JohnnyB
that was my original point. Also if you look the turbo is zip tied backwards with the exhaust rotor toward the rear of the bike. Uber bad idea - The exhaust is here you want the least amount of bends so it does not lose its velocity and energy, routing it to the back like that will take a lot of bends and also pass it clost to the intake rotor where I am sure there will be significant heat transfer.

The basic concept of turboing a cb750 is a great idea - the point is to execute it properly so it will actually work.

Looking at that setup I had a crazy idea. What if instead of a turbo a centrifugal supercharger is used instead. You could get one of those dual sprockets kits they used to sell in the 70's, use one sprocket to run the rear wheel and the other to power the supercharger via chain. Turbo location could be the same, and there is no longer hot pipes running every which way but loose.


...ok....I have to lay off the drugs....
 

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this was interesting too:

http://forums.corner-carvers.com/archive/index.php/t-2309.html

1. Length of exhaust tubing from exhaust port to turbo; generally shorter is better.
2. Turbo size, larger generally takes longer to spool up, inertia being what it is; it's possible that two smaller turbos are better than one large unit.
3. Volume of intake from turbo to intake port. Note that the intake must be able to support flow at higher RPMs.
4. Inlet tubing bends, generally larger radius bends flow better.

To be honest, this makes Nitrous look like a better idea everyday.

Get some NAAHWS, dawg!
 

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it's not a joke (although in hindsight, i can see where the zip tie mount job seems coould make it seem pretty convincing!)

lemme preface by sayiing that i'm not nearly as familiar with turbochargers as some of you clearly seem to be! very cool! this is a learning experience for me anyway. yeah, so, my pops is lending pretty credible leadership with the project. he's a field engineer for garrett and has been working with turbo's his entire adult life, both professional and recreationally. (my pop is a fuckin' genius)

anyway, this is not going to be a "proper" install in the truest technical sense of the word. all technical discussions aside, he's mentioned many of the same issues you brought up concerning boost, lag, flow, etc. however, the objective isn't a genuine, brutally fast racer (although, he's certainly more than capable of most at doing that). it's just gonna be a wickedly kick ass street toy with plenty of looks to match the devistating sound. on a stripped frame, that base 750 engine will be more than strong enough to make up for the lag on the street. so really, you can imagine the freedom all this allows.

like that tank huh? me too! great lines! yeah, bilateral sectioning will bring the proportions up to the size of that larger frame...about 6" back, 3" up, and 3" wide...with deep knee and bar scallops, it should make a pretty wicked fuckin' tank. at least, the one in my head is pretty tight...
 
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