Topic: CB500 Turbo kit

[garretcb750]

I recently picked up a 71 CB500 with an aftermerket turbo kit made by ATP. These are rare I am told.
the cb500 engine is in peices. I was debating on whether to build a little bobber out of the cb500 or build a new header and modifiy the intake to work on my CB750. It uses a bentick zenith carb. Will this carb supply my cb750 engine with a sufficient air/fuel mixture? I figure it will because the 750 will just pull more air/fuel. Will it?

[Loas 78 CB750K]

I have no idea but it sounds cool. Pics?

[TwoTired]

Which side of the turbo is the carb on?  And, is it pressurized?

[dusterdude]

that is enough carb,it may be too much,the only ones i ever saw were on harleys,i think the smallest made was around 34mm.

[Geeto67]

Those ATP kits were rare for 750s but even rarer for the 500/550s. Personally I would try and trade it to someone with a cb750 kit first before I started hacking away, but that is just me...

Personally if you are willing to spend the money modern turbos are so much more efficient than these old monsters that you might as well use the old system as pattern for the layout and get something like a small garrett ball bearing turbo (or a rayjay modern sportbike turbo).

Those old systems usually put out about 6-8 psi at most. Anymore than that and you are going to have to make significant changes to the timing curve. To be on the safe side I would run a dyna 2000 since it has a setting for boosted applications (I am pretty sure anyway) and is somewhat programable.

those old zeinith carbs will do the job, most of those old systems were kind of over carbed anyway. For a better carb, I would look for one of the old Mukuni VMs that some of the ironhead sportys used to run, more tunable and better suited as a draw through carb (I am assuming your system is draw through and not blow through).

Or you could send it to me and I could put it on my cb550 chopper 

[garretcb750]

The turbo draws the air/fuel mixture through the turbo. Very cool setup.


Ya I would deffinatly be interested in trading the CB500 turbo kit for a 750 Kit. But what are the chances of me finding someone with one, wanting a 500 kit. The kit itself is hardly used. Just dirty from sitting around. I was told it was one of the first kits made by ATP for a 500. The owner was a guy who owns the local honda shop, he said the bike would go and go and go. But it never had a wastegate so i am guessing it would over spool. I was going to use a wastegateo from a car kit at about 4 or 5 psi. About 60 bucks on ebay.

I am missing the tail pipe but I have a flange to bolt to the turbo to make one. The end of the header pipe is abit bent up. Just need to weld in a straight piece of pipe to connect it to the turbo pipe. Easy stuff.

[edbikerii]

come on, please post some pics of that setup, even if disassembled.  I'm very curious, and I've got a cb550.

[garretcb750]

OK.. its not much but considering the hole bike was givin to me because I bugged the hell out of the guy... I think its a good deal.  The bike had a dunstall fairing, dunstall rearsets, a lockhart oil cooler that now resides on my 750, and the turbo kit... GREAT FIND.

the motor top end was in peices and missing parts but all the major turbo parts are there, and the bottom end of the motor is very clean and seems tight.

[edbikerii]

So that rectangular area is the intake manifold?

[garretcb750]

yes.. bolts directly to the head and there is an opening for the turbo to bolt on the backside of it. here is a better picture

[Tommy Neimeyer]

Is there a tag on the compressor (air) side of the turbo?  If so, what does it say?  It might say something like 301BB25 or 307FF40.  I have a lot of information about these early Rajay turbos including a rebuild manual if you need one.  I have compressor maps also.  If there is no tag, I can give you the dimensions of the compressor inlet and the turbine outlet and from that you can determine which one it is.  The A/R should be stamped/cast into the inside of the turbine inlet.

The most common sizes are "B", "F" & "E" I have heard of "A" size but never found one.  Most people consider a "B" to be for a 750 cc motor and a "F" for a 1000 cc motor however, these are rough guidelines and there are a lot of variables.  You find the "E" models on cars or all out large displacement drag bikes.  I have considered turbo'n a 550 but I felt the turbo (BB25) would be too big.

Congrat's, great find.

Tom

[designsincoldsteel]

is this still happening???

how is the build going?

i've been thinkin of doing something similar to my cb500.