Author Topic: 78 CB750F Turbo, post build review  (Read 68299 times)

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Offline NitroHunter

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Re: 78 CB750F Turbo, post build review
« Reply #50 on: March 02, 2010, 09:58:47 AM »
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Offline Bamboozler

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Re: 78 CB750F Turbo, post build review
« Reply #51 on: March 07, 2010, 11:24:05 PM »
Quick update for the work done this weekend. 

Friday the intercooler was delivered and I was pleased with what Bell Intercoolers can produce. Fit and finish was spot on, the welds were as neat and perfect as you can get.  I was able to fit in the larger core request in time before they started on the IC, so the picture shows the 9x4x3.5 thick core.



I was hoping that a box would be delivered on Friday with two stainless mandrel bends and a bit of aluminum straight pipe to be used for the exhaust and IC fab.  Nothing on Friday but strangely FedEx dropped off a ground package on Saturday with the parts, sweet, weekend of fab is on. ;D

Had my friend Mark weld up the exhaust for me on Saturday.  After he welded one end of the muffler I packed it with the fiber glass and then handed it back to him for final welding.  Had a discussion and kinda thought that maybe the end caps should've been rivited on instead of welded in order for it to be repacked down the road.  But it was too late for my wondering as Mark was welding it while being discussed.  :D  If figure the sales guy that answered questions regarding how to weld up the muffler said the fiberglass 4" should last 15,000 miles.  For the $80 or so bucks in material I could just make another or hack into one side to repack; worry about that down the road.  The brushed stainless does look a bit simpler/clean with just welds.



After the exhaust was welded (and mounting tabs welded to the intercooler) the exhaust was started on using what could be saved from the prior short route exhaust.  After fitting, chopping, staring, grinding, staring/thinking, more staring, and finally tack welding into place the exhaust ready for final weld.  The exhaust should be finished being welded in a day or so and when back I'll tack the back side bracket/mount that will fasten the exhaust to the rear rider's foot peg bolt (waited just in case the heat of the final weld shifted the final resting spot).  Also will have the wide band 02's bung welded on at that time (forgot to install it).



The last thing that was done was the mounting of the intercooler and fabbing the newly routed cold side pipe.  The mounting of the intercooler was kinda a pain and time consuming. The goal was to create two small steel tabs which would be welded to the frame and then bolt the IC to them.  The difficultly was holding the IC in its final resting place.  Constantly had to recheck and verify three different IC axis while trying to take measurements or verifying changes.  My dad helped in clutch times by holding one end.  In the end it sat where it needed to be which unlocked the ability to start on the intercooler piping.  Before calling it quits the cold pipe was tacked (only has one seam) and blow off/bypass valve cut off of the prior pipe and tack into place on the new one. Next is fabbing up the hot side intercooler pipe and getting it all welded up.

'78 CB750F Turbo, 101 rwhp @ 8 PSI (Project thread)
2007 Yamaha FZ1
'78 CB750F basket case crying for a resto
'78 XL250S
'78 Suk GS750E
Digital Ignition project (Project thread)

Offline Bamboozler

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Re: 78 CB750F Turbo, post build review
« Reply #52 on: March 15, 2010, 12:55:24 AM »
Update from this week of work.  

Exhaust is welded and complete sans O2 bung.  Happy with the fit, it didn't move at all from the finishing welds.  Added the rear mounting tab for support after I got it back.  Anxious to hear what the muffler sounds like!  







The intercooler pipes are complete now as well.  Looks a bit more 'busy' up front but that's something I knew would happen and accepted the fact in order to gain the cooler.  All in all the fitment turn out well. Not liking how small the gaps are from pipe to pipe, but there aren't too many routing options with where the IC and turbo sit; keeping it compact as possible was a goal.  The pipe that cuts in between the frame and the motor shouldn't rattle on anything (knock on wood).  I left the full 5" leg on the silicone 90^ to reduce the amount of AL pipe back there, the silicone is for the most part suspended; just gently rests on the flat of a tappet cover.  One thing I noticed post welding was the blow off/bypass valve port hole sits right at the end of the straight section that just starts to bend.  I would have moved it had I seen it.  When looking inside the pipe the incoming air stream looks like it would 'fall' into the BOV's port hole instead of streaming smoothly through the bend. I don't think it should force the value open or anything, especially with only 8psi, but its not the best for the ensuring smooth flow.. but then again either does the 4 90^ tight radius 2" bends on the hot pipe side. :D Ah well, not a perfect world.

(Edited to add, 4 90^ bends, not 3)









« Last Edit: March 15, 2010, 08:12:08 AM by Bamboozler »
'78 CB750F Turbo, 101 rwhp @ 8 PSI (Project thread)
2007 Yamaha FZ1
'78 CB750F basket case crying for a resto
'78 XL250S
'78 Suk GS750E
Digital Ignition project (Project thread)

Offline BIKE

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Re: 78 CB750F Turbo, post build review
« Reply #53 on: March 15, 2010, 04:41:47 AM »
I love this thread. :)
1975 CB750 K5
1977 CB750A

Offline KB02

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Re: 78 CB750F Turbo, post build review
« Reply #54 on: March 15, 2010, 04:43:44 AM »


What is that little bracket for on the lower left side of the frame?
1978 CB750K Project
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Offline Bamboozler

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Re: 78 CB750F Turbo, post build review
« Reply #55 on: March 15, 2010, 08:17:29 AM »
Hi KB02, the bracket is for the oil cooler.  I took the guts from underneath off to check the primary chain tension and didn't yet get around to fastening the cooler and pump back on in those pictures.

Thanks for the words BIKE.

'78 CB750F Turbo, 101 rwhp @ 8 PSI (Project thread)
2007 Yamaha FZ1
'78 CB750F basket case crying for a resto
'78 XL250S
'78 Suk GS750E
Digital Ignition project (Project thread)

Offline scartail

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Re: 78 CB750F Turbo, post build review
« Reply #56 on: March 15, 2010, 01:19:13 PM »
It's looking good Bam.

So, what was the conclusion on your HP goal? Planning on splitting the case, and tossing in the suggested chain?

Just curious, slight change in engines... Is the weak point for 550's the primary chain as well?
'89 Hawk GT, newly acquired, daily beater...
'76 CB550, was my daily beater... my cafe project...
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Offline Bamboozler

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Re: 78 CB750F Turbo, post build review
« Reply #57 on: March 15, 2010, 04:00:03 PM »
Thanks Scartail. Unfortunately I can't provide you with any insight on the weak link of a 550.  You're going to have to seek the answers from some of the 550 experts here on the board, I don't have any experience with those guys (and not much with the 750s for that matter). I only would be guessing (but the primary chain does sound like a prime suspect in weakness). 

Right now I'm going to wait and see what a stock F motor thinks about being hit up with 8psi which is the lowest I can set the current system to.  I'd don't really have a HP goal in mind, just want to play with boost on a street bike for now.  I'm interested in seeing what the motor's going to think of it all before something deteriorates, or will it?  How long until,  month, two, year, more, maybe these motor are real stout if properly tuned?  As posted prior I checked the primary chain tension and it came up as a 3 on the scale of 0 (new) and 10 (replace).  After I get some time into this setup I'll check it again and post what I see.  What ever forces me to split the case first I'll hit up the maintenance items that should be replaced while in there.  I had a tentative shopping list of around a grand that was going to be pursued if the primary chain needed to be replaced (primary/cam chains, primary/cam tensioners, cush rubber, head studs, and a few 78F head items, ect.).  Back cut trans is another wait and see situation, that right there my force a case split if it proves to be a problem.  I'll monitor it all the best I can and report what I find, would like to see the stock motor take it with stride, time will tell.

I would love to drop coin on all the go fast parts to build a bullet proof motor for insurance and turn up the boost if and when I would like; but its not going to happen at moment.   As NitroHunter said, "don't rattle the motor".  If the tune is square and you don't detonate the A/F mixture causing piston lands to break or bent rods I would think you should be able to get some mileage out of the stock setup; and slightly more so with a late F model even.  Wish I had the answer of now much mileage (boost) you can reliably get. ;D
'78 CB750F Turbo, 101 rwhp @ 8 PSI (Project thread)
2007 Yamaha FZ1
'78 CB750F basket case crying for a resto
'78 XL250S
'78 Suk GS750E
Digital Ignition project (Project thread)

Offline wannabridin

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Re: 78 CB750F Turbo, post build review
« Reply #58 on: March 15, 2010, 07:01:20 PM »
amazing...  i can not WAIT for a video!!  you need to take a vid while on the bike, so we can see when boost kicks in  ;)
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Offline Bamboozler

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Re: 78 CB750F Turbo, post build review
« Reply #59 on: March 16, 2010, 08:15:54 AM »
Thanks wannabridin.  Those helmet cams are getting fairly reasonable, would be fun to play around with one, might be a possibility.  I'm wondering as much as you are how the bike will react to the earlier onset of boost.  The T3 that was on the bike really started to move when 8psi was reached, but it was quite high in the RPM range 7k or so and the delivery was very smooth because of it.  That could change a bit if 8psi is reached by 4k or so.
'78 CB750F Turbo, 101 rwhp @ 8 PSI (Project thread)
2007 Yamaha FZ1
'78 CB750F basket case crying for a resto
'78 XL250S
'78 Suk GS750E
Digital Ignition project (Project thread)

Offline scroggins5000

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Re: 78 CB750F Turbo, post build review
« Reply #60 on: March 16, 2010, 10:47:58 AM »
This build is crazy! l can't wait to read more.

Offline bmartin

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Re: 78 CB750F Turbo, post build review
« Reply #61 on: March 25, 2010, 05:15:01 PM »
Great posting - I have an old school ATP turbo on a 1969 CB750 that I've been working on for the last two years.  I expect to have it completed for this ridding season.  I'm in the process of changing over the S&S carb over to a HSR42, installing a A/F system and improving the ignition.  I've had the motor and turbo running but not on the street as of yet.

I'm just taking it slow and reading everything I can find about previous projects.  I've learned quite a bit from your posting and I thank you.  (I had was not sure about the fuel pressure that this bike should be set to...)  My bike is basically ready to go - just a few more odds and ends to finish.  I'm sure more items will pop up once the bike on the road.

I'm a newbie in this form - so keep your postings coming...


Offline Bamboozler

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Re: 78 CB750F Turbo, post build review
« Reply #62 on: March 25, 2010, 06:03:42 PM »
Sweet deal, you best get a project thread up and kickin' for your turbo bike!  Love to see what you've done with your '69 with the ATP setup.

Thanks for the words.  I started down the same path last summer, reading as much as I could to find answers to the questions I had as this project started taking shape. It helped that I had a bit of prior turbo experience in the car realm too.  I'm trying to explain everything as clear and detailed as I can with out coming across as annoying or a know it all (which I'm far from). I had the same questions myself and I'm trying to post the details that I wish I could find in one spot when starting this project; or details that someone may find useful.  Hoping to take the teeth out of a turbo project to someone who's never played with boost before.  There's more than one way to skin a cat too.  There are plenty of ways to go about things that are of different/better than I did.  I hope to help get the ideas flowing!

Off to stick some time in the bike now, been away from it for a week plus.  Seat pan, rear fender/electronic mounting, rear tail light fab, is the last barricade to getting the bike moving with the new turbo.  Should have something to post at the end of the weekend.
'78 CB750F Turbo, 101 rwhp @ 8 PSI (Project thread)
2007 Yamaha FZ1
'78 CB750F basket case crying for a resto
'78 XL250S
'78 Suk GS750E
Digital Ignition project (Project thread)

Offline Retro Rocket

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Re: 78 CB750F Turbo, post build review
« Reply #63 on: March 25, 2010, 08:22:28 PM »
Hi Guys, you may want to check these heavy duty primary chains out.

http://www.classiccyclecity.com/gallery/thumbnails.php?album=48

If interested send forum member "nippon" a PM....

http://forums.sohc4.net/index.php?action=profile;u=2494

Mick
750 K2 1000cc
750 F1 970cc
750 Bitsa 900cc
If You can't fix it with a hammer, You've got an electrical problem.

Offline Bamboozler

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Re: 78 CB750F Turbo, post build review
« Reply #64 on: March 25, 2010, 11:12:29 PM »
Thanks for the heads up Mick. 

When I'm unfortunate enough to be cracking my case open the next time (hoping later rather than sooner:) I will be sending Nippon some coin for one of those chains. Seems to be the strongest primary chain that can be had.  Thanks again for the contact info.
'78 CB750F Turbo, 101 rwhp @ 8 PSI (Project thread)
2007 Yamaha FZ1
'78 CB750F basket case crying for a resto
'78 XL250S
'78 Suk GS750E
Digital Ignition project (Project thread)

Offline Retro Rocket

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Re: 78 CB750F Turbo, post build review
« Reply #65 on: March 26, 2010, 12:07:05 AM »
Thanks for the heads up Mick. 

When I'm unfortunate enough to be cracking my case open the next time (hoping later rather than sooner:) I will be sending Nippon some coin for one of those chains. Seems to be the strongest primary chain that can be had.  Thanks again for the contact info.

No worries mate, i am ordering one next week for my 1000cc build... ;)

Mick
750 K2 1000cc
750 F1 970cc
750 Bitsa 900cc
If You can't fix it with a hammer, You've got an electrical problem.

Offline Bamboozler

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Re: 78 CB750F Turbo, post build review
« Reply #66 on: April 15, 2010, 11:34:37 PM »
Got a good amount of work pushed forward the past few weeks and found a later part of the night to chill on the PC for an update.  I should have broke this update up into smaller bits, but by the time I've been done working on the bike or taken care of other things as of late I haven't had time to throw anything up.  Been hell bent on getting the CB road worthy to enjoy, one last project yet to be completed (tail light) and its legal to be on the road.  I did get in two tuning runs on the back roads last weekend, will touch base on that in a bit.

The cafe seat is finished and I'm happy with the result. There were a few things I might try different if I were to do it again but the results fit what I was aiming for.  The CB360 gas tank was chopped at a slant and a piece of 16 gauge mild steel welded to it to form the back rest and trimmed the excess with the cutoff wheel (love that B&D angle grinder w/ cut off wheel, trimmed the excess in a minute or two). After stuffing rags under the rear tank to find its resting spot measurements were made and the seat pan cut out of the same 16 gauge mild steel and two were welded together. 







A 0.5" length of steel flat bar welded onto the side of the seat pan as trim for upholstery mounting.  The front of the pan received a crescent shaped tongue piece of steel to follow the profile of the tank and fill the void between it and the seat.  Inside of CB360 back hump two "T" (on its side) bracket were welded to secure the rear to the mounting platform that will be discussed in a bit.  Each "T" bracket got a nut welded to it in order to receive a bolt to secure it to said platform.  The welding of these brackets forced some choice words as I realized my folly for welding to the inside of the tank. ;D  I blindly welded one of the brackets on before realizing that the bleed through from the weld heat distorted the heck out of the outside of the tank... >:(  At that point I was forced to do the same to the other side in order to complete the bracket system that I was not committed to, and took it as slow as I could stitching weld onto the bracket with as minimal heat (max wait time) as I could; welding lesson reinforced. ;D  The end result is noticeable but not too bad.  I tried my best to blend/sand the dips out, the tank has other character marks from 30+ years of life, now it has more. ;D

A rattle can primer and stain black finished the seat and off to the upholster to get a seat pad made.





Can see the minor distortion from the weld.



Nothing new with the method of mounting the seat.  The bracket that locks the pan down was simple square tubing cut into a "U" channel and welded to the frame.  Nuts were welded underneath the front and back two platforms (middles skipped) and four holes were drilled into the pan so the whole works could be secured with four cheese head pan screws.  I was intending to have the upholsterer make a removable pad in order to access the Philips screws to access the battery and electronics.  Rubber washers buffer the pan to the brackets.  On the rear of the frame another long "U" bracket was welded in order to secure the electronics mounting platform and brackets that were welded into the CB360 tank.  Two holes in the middle of the platform were drilled to secure the stock plastic fender, which was nice to retain. 

The biggest reason for the mount was to relocated the wide band controller as well as have a place for the fuel pump voltage regulator, tail light, and any other stow away stuff.  This last fall two Innovate wide bands died on me, they just stopped working. I did have them warrantied and after receiving the last one the customer support guy mentioned that this would be my last replacement and to check my mounting location. The WB controller and sensor wires sat and ran about 4 inches from the coil pack and ran by a few plug wires.  We both assumed voltage spikes were induced into the sensor wires or controller itself causing the microprocessor to loose it's marbles.  The failure of both controllers was unreadable/executable firmware (processor dead in the water).  With the rear mounting of the WB I also installed a 15V transorb (similar size of a surface mount diode) on both the Vin (power line) and analog out line.  These guys will clamp voltage on what ever wire installed to 15VDC and not allow anything higher (the over 15V energy is consumed by the part).  If the line has prolonged voltage spikes above 15V it can destroy the part. May swap with some 17-18V parts to better keep out of reach of a temperamental system voltage regulator.

Pictures of seat pan brackets and mounting platform.  WB controller and fuel pump voltage regulator board mount mounted with neodymium magnets.  Magnet mounting is temporary for now, but may stay that way as it works well (Vreg needs to get a weather proof case asap).  Also mounted the HID ballast and controller with epoxied on neodymium magnets behind the metal head light brackets/arms/ears/holder things, works very well with a few 12lb pull strength magnets.









The thought for the tail light is to mount it onto the back side of the platform, that way the seat can be free of attached wires and come right off.  This will be tricky due to the loading of the suspension and having the rear tire come into contact with the light.  I would like to mount the light within the end of the seat (recess of the CB360 fuel tank, that domed cutout area).  This may require a bump stop to be add to the rear shocks to limit travel (not wanting to do), it will be very close without and time will tell if needed.  In any case the license plate needed a holder and couldn't be mounted under the tail light. With some left over 16 gauge sheet, steel tubes, and "U" channel a plate holder was made.  A small LED board is fasten on the under side of the "U" channel with three tiny neodymium magnets (love those things, check some out here www.kjmagnetics.com).  There are two LED drivers running two LEDs each at full current.  These tiny LED drivers need just a resistor to set its current.  The plate holder had to slightly bent forward in order for the light to illuminate the whole plate.  May also play with tucking/hiding a single high brightness LEDs under the seat and directing it at the plate.  Wires run up through the hollow round tube.  To make me feel better and not worry, I'm going to weld a little finger off plate holder's mounting tube (that fastens it to the end of the frame) which will prevents the plate holder from rotating into the wheel if it ever decided to loosen up on me. I don't want to hear what sounds like rocks thrown into a blender at high speed as the plate holder is twisted up into the wheel.. :D





I got the seat back from the upholsterer last week Friday just in time to take the bike out for a quick tuning run. :)  I think the upholsterer did a great job of constructing the seat pad.  I dropped off the seat pan a few days earlier with about 15 or so 1" long x 0.5" thick x 0.125" thick neodymium magnets.  If possible I wanted a pad made like a cushion that is clamped down with the magnets around the perimeter of the pan.  After talking with the upholster it came to be that the seat portion was going to be pertinently locked down and the magnets used around the curved back rest area to hold the material tight.  It was going to be a two piece design in order to access the rear two screws (abandoning the front two screws, the rear bolts that secure the seat to the platform make it very sturdy with the two rear screws, fronts not needed). It ended up that the magnets were too difficult to keep apart with sewing so velcro was used to secure the curved back rest.  I'm not a much a fan of velcro but it seems to do the job.  The only thing I like is that he made it a one piece part, no seems, which I liked seeing that the front was glued down and moisture would be trapped if caught in the rain.  All in all it turned out great and if the velcro gives grief I'll request pockets are sewn into the material before magnets are brought into the picture.

Pics of the bike with seat and few cosmetic improvements (grips, mirrors, fuel door back on, painted/polished tank emblems back on, and re-cleared the fuel tank and rear seat after 180 grit (clear was too light in some spots on the fuel tank and specs of rust started to form).  Forgot to say that a pair of Avon Roadriders are gracing the wheels as well.  Progressive front fork springs, seals, and oil are getting hit up this weekend.  I'll have to post about where the tune sits and what becomes of the LED tail light another time as its too late :)











'78 CB750F Turbo, 101 rwhp @ 8 PSI (Project thread)
2007 Yamaha FZ1
'78 CB750F basket case crying for a resto
'78 XL250S
'78 Suk GS750E
Digital Ignition project (Project thread)

Offline Retro Rocket

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Re: 78 CB750F Turbo, post build review
« Reply #67 on: April 15, 2010, 11:59:09 PM »
Looking very nice....I really like those tank seats.... ;)

Mick
750 K2 1000cc
750 F1 970cc
750 Bitsa 900cc
If You can't fix it with a hammer, You've got an electrical problem.

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Re: 78 CB750F Turbo, post build review
« Reply #68 on: April 16, 2010, 05:09:19 AM »
Wow....what a nice bike, really.

The seat really matches the lines of the tank......you see too many that don't.

~Joe

Offline scartail

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Re: 78 CB750F Turbo, post build review
« Reply #69 on: April 16, 2010, 05:45:20 PM »
Amazing Bam.

Hey, in the first page you have a scavenge pump for the oil return. Do you have it set up to be running all the time? Or do you sensor or some sort to trigger it?
'89 Hawk GT, newly acquired, daily beater...
'76 CB550, was my daily beater... my cafe project...
'72 Yamaha R5, newly acquired project... donated to my buddy...
'67 Suzuki T20, still working on her too... Currently in pieces...

Offline bradweingartner

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Re: 78 CB750F Turbo, post build review
« Reply #70 on: April 18, 2010, 06:06:35 AM »
Amazing Bam.

Hey, in the first page you have a scavenge pump for the oil return. Do you have it set up to be running all the time? Or do you sensor or some sort to trigger it?

It's wired in with the fuel pump so it runs all the time from what I remember reading.

Offline Bamboozler

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Re: 78 CB750F Turbo, post build review
« Reply #71 on: April 18, 2010, 10:19:17 AM »
Thanks for the positive comments all.  I agree with above, all the tank seats I've seen had fit the bike they where put on very well. When I first saw that CB360 tank in that CBX project link I posted on page two it was game on. :)

Hey Scar, as bradweingnartner stated both the fuel and oil scavenge pump relays turn on their pumps when the red run/off switch up by the throttle is turned on.  Didn't want to leave it up to me to remember to turn both on when firing up the bike. :) 

There are a few things i am wanting to touch on with the oil scavenge system.  One would be to monitor the current through the oil pump and while the normal cruise oil pressure is present plug off the accumulation chamber's breather port.  I would like to see if there is a big enough loading (if any) on the oil pump when vacuum is applied to the complete oil feed system to justify the chamber.  If there isn't much of any increase in current from plugging that breather/vacuum relief port I'm going to scrap the accumulation chamber all together.  I don't like the idea of having a way for oil to puke out of the bike (that breather port), if the scavenge pump should stop working.  I may not notice the problem until the red oil pressure idiot light turns on if I don't see the smoke screen behind me in time. A turbo is much easier to replace than a motor. 

I also want to add a idiot light/LED to illuminate when current stops flowing through the oil pump's wires via a current sensing circuit and relay.  That should be quicker/easier to see than the cloud of smoke behind me.:)

Lastly I would like to see if the full 12V is needed for the oil system and throw a voltage reg circuit on it like the fuel pump if its not needed. That would mean running the bike at full oil pressure and letting the oil drain from the turbo into a bucket and have the pump pull the oil out of said bucket (monitoring the oil level). Lower the current/voltage to the pump until you have enough safety margin of pump speed to be comfortable with, measure the power consumption of the pump, and make a regulator to dupe those numbers.  May be able to squeeze out an amp or two of savings.
'78 CB750F Turbo, 101 rwhp @ 8 PSI (Project thread)
2007 Yamaha FZ1
'78 CB750F basket case crying for a resto
'78 XL250S
'78 Suk GS750E
Digital Ignition project (Project thread)

Offline scartail

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Re: 78 CB750F Turbo, post build review
« Reply #72 on: April 18, 2010, 11:56:47 AM »
I can't remember why running the scavenge pump on all the time isn't a good idea. There's a company out there that does remotely mounted turbo kits for autos. I think their name is SRS or something like that. As I recall, they use a hobbs pressure sensor. It turns on the pump at like 4 psi of boost.

Anyway, keep up the good work. Your project is definitely an inspiration to us all.
'89 Hawk GT, newly acquired, daily beater...
'76 CB550, was my daily beater... my cafe project...
'72 Yamaha R5, newly acquired project... donated to my buddy...
'67 Suzuki T20, still working on her too... Currently in pieces...

Offline Porscheguy912

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Re: 78 CB750F Turbo, post build review
« Reply #73 on: April 18, 2010, 12:00:28 PM »
Friggin sweet!
I'm planning a Wisconsin ride soon. I'd love to come visit your bike.....
Current: 1978 CB750F3
Past: 1974 CB550K

Offline Bamboozler

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Re: 78 CB750F Turbo, post build review
« Reply #74 on: April 19, 2010, 08:16:39 AM »
Hey Scar, I'm wondering if you're thinking of a methanol injection kit using the hobs switch?  I did have a hobs switch that turned on a methanol injection system at xPSI on my turbo'd car (92 Mitsubishi Galant VR4, awd/turbo 980 of 1000... RIP :'().

In the CBs case if it didn't have the pump on at all times the oil would eventually back up into the center cartridge's bearing and force oil out the oil seals giving me a cloud of smoke out the tail pipe.  The pump is self priming and can be run dry if it happens to.  The oil needs to drain as easily and restriction less as possible.  If the bike would be rode for a long duration without dipping into boost the switch wouldn't turn on and back up would occur. 

I looked up SRS turbo and came up with www.ststurbo.com, thinking this is the place. I see some if not all of their kits come with pressure switches, but didn't find in a quick search of their website how it's being use.  They do offer meth injection kit and boost controllers that could use the hobs switch and it looks like they may have one right before their oil pump; not 100% how they're using it.

Porscheguy912, shoot me a PM with details of when you'll be heading up. I'd love to meet up with ya.  Haven't confirmed 100%, but a friend with a Yami RD350 and I are tentatively planning to go to Road America in early June for the classics bike weekend.  Wondering if you heard/planning on heading there?

'78 CB750F Turbo, 101 rwhp @ 8 PSI (Project thread)
2007 Yamaha FZ1
'78 CB750F basket case crying for a resto
'78 XL250S
'78 Suk GS750E
Digital Ignition project (Project thread)