Topic: CB750f. Parts bike or project? Pic heavy thread. Need opinions.

[b1jackson]

Hi all.  I'm back again!

.Barn find bike that's been sitting a good long while but at some point (80s maybe?) a sort of attempted cafe job was done and some engine hop ups and bling added.  Here is what I know.

- engine not seized.  Kicks over fine.
- missing seat and muffler rotted off.
- some front signal bits missing and headlight looks funny as a fairing was on it at one point.
- tank obviously home painted but sound and fairly clean.
- no side covers or air box or chain guard

And here is what's different compared to my other supersport (same year)

There is a yoshi cam in it.  The part # is 111-00 and according to a search this is the "road special" version whatever that means??

Someone had the engine out and chromed some bits.  These actually still look very nice considering I haven't even polished them yet. They attempted some engine paint too which now looks like crap.  I assume all this effort was at the same time the cam went in.

The front end....notice my spare rotor? I have no idea what this may be off of. Were they going to put a dual brake set up at some point or?  Also, I wonder if the entire fork set up is non original.  Ideas?

An extra oil cooler added (plus a side guage).  Not sure what that's about but it's piped in just below the oil filter housing.

Rear shocks!  Some sort of 80s sport performance?

Here are some pics of my treasure.  I bought this as a parts bike for some tail end pieces but the cam upgrade and other ad ons kind of make me think someone loved this old beast at some point and perhaps it's a diamond in the rough!

Appreciate any insight!



Oil cooler





Focus on the shiny valve cover and not the #$%*ty tank paint job!





Rotted off exhaust but perhaps enough headed left for an add-on.

"Performance" shocks?  Please enlighten me on this 80s upgrade.



Nice chromed bits!  Distract from the ugly!



Front end





Cam upgrade

[b1jackson]

Carbs are off.  Let's just say....very green and nasty.  Nothing even remotely left that looks like fuel.

[Jerry Rxman Griffin aka MuthaF'er]

Early 75 model. 1/75 or 2/75 probably. Could only make out the CB750F-1xxxxxx. That and the rear master cylinder with the nylon reservoir are the 2 tips. MANY non 75F parts. The Yoshimura Road Special cam was the street version, not the full race Daytona version that I used for my street version. Better low and mid-range vs top end power mainly above 7000 rpm. Looks like the front fork lowers have been painted but may be original and the PO tried to do a double disc upgrade. That entire headlight 'thing' has been rigged up. If you have a bore scope take a look and post up some pictures. It may also have the Yoshi 812 kit inside. It would also be interesting to see inside the intake and exhaust holes. Seats both original and after market are available as well as repro side covers. The headlight stuff can be sourced with a little more difficulty. If the dual front brake has been done properly just add some calipers. The rear brake can be an iffy subject but a full redbuild kit is available from SiriusConInc close to you.   

[bill440cars]

       Nice to see another SOHC 750 being rescued and especially an "F" model. Sounds like you are going to work with it, instead of parting, as originally thought? 

[palepainter]

It looks like a great project to complete and not part out.  It is way more together than what I started with. It looks like someone put some time into it at one point in its life.

[b1jackson]

Early 75 model. 1/75 or 2/75 probably. Could only make out the CB750F-1xxxxxx. That and the rear master cylinder with the nylon reservoir are the 2 tips. MANY non 75F parts. The Yoshimura Road Special cam was the street version, not the full race Daytona version that I used for my street version. Better low and mid-range vs top end power mainly above 7000 rpm. Looks like the front fork lowers have been painted but may be original and the PO tried to do a double disc upgrade. That entire headlight 'thing' has been rigged up. If you have a bore scope take a look and post up some pictures. It may also have the Yoshi 812 kit inside. It would also be interesting to see inside the intake and exhaust holes. Seats both original and after market are available as well as repro side covers. The headlight stuff can be sourced with a little more difficulty. If the dual front brake has been done properly just add some calipers. The rear brake can be an iffy subject but a full redbuild kit is available from SiriusConInc close to you.

It's a 1/75 on the steering stem plate. Good idea on the bore scope.  A Xmas gift perhaps!  Yes, the PO tore off the fairing and left the gawky headlight bit sticking out.

[Jerry Rxman Griffin aka MuthaF'er]

You can get a CHEAP scope on Banggood.com outta China as much as I hate that. May take 3 weeks? Plug into your phone or laptop. We should be able to distinguish stock pistons from aftermarket.

Were you able to get the stock cam too? Hotter than most stockers. Mine is a 1/75 also. When I measured the lobe heights of the stock cam and 2 other stockers I discovered my exhaust lobes are 0.1mm taller than the K8 and the F2 cams.

[b1jackson]

Yes, I have the original cam stuffed in the yoshi box

[Jerry Rxman Griffin aka MuthaF'er]

There is a fair amount of difference between that stock cam and the Yoshi cam. My Yoshi Daytona shows quite a bit of difference over all 3 stock cams I have. You may find a needy K3 - K6 SOHC4'er that might want your stock cam.

[b1jackson]

Good to know.  Thanks.  My cheap bore scope has been ordered too!

[SOHC4 Cafe Racer Fan]

Dig those finds with period go fast parts.  I'm also a fan of the spoked 75-76 Super Sports.

[b1jackson]

Any thoughts on those rear shocks?

[754]

Stock Japan shocks off later model..
You got a great start there, well worth finishing that one up..

[b1jackson]

Thanks.    . I know there is a great group here.  Scottly saved me from going insane on some issues on my other bike.  Hopeful he is an active spectator on this one as well!

Carb bowls are off and man, are things dirty!  #2 looks like it has tar in in its so nasty.

[seanbarney41]

Any thoughts on those rear shocks?

shocks are from cb900f, kinda ironic, since I think I see a 900c in the background.  They could be from a dohc 750f as well.  I have used them on a couple different sohc cb750s and I think they work very good on the longer swingarmed sohc 750f's.  A lot of guys criticize them for heating up and fading.  Even when they fade they are much better than stock sohc shocks.  They are also longer than stock so they will slightly steepen rake angle, shorten trail, and generally quicken turn in.


If that chrome stator cover is as nice as the valve cover, I will trade ya for an unchromed one and throw in $80 cash.

[b1jackson]

shocks are from cb900f, kinda ironic, since I think I see a 900c in the background.  They could be from a dohc 750f as well. 


If that chrome stator cover is as nice as the valve cover, I will trade ya for an unchromed one and throw in $80 cash.

Hey, good to know re: shocks. The 900c was bought as a non runner a few weeks back but with a simple carb clean, it was running. Something I will likely sell come spring.

And I won't be trading off any of the chrome bling as this is my second supersport so will be swapping onto the best bike.

[Jerry Rxman Griffin aka MuthaF'er]

Everybody needs 2 Super Sports! 

[Scott S]

 I kinda dig the patina on the tank, in a weird way.

[b1jackson]

Early 75 model. 1/75 or 2/75 probably. Could only make out the CB750F-1xxxxxx. That and the rear master cylinder with the nylon reservoir are the 2 tips.

Do you know of any other differnces between the 1/75 and 2/75 models?  I noticed my other bike is a 2/75 and I noticed the rear master cylinder you mentioned.

. I'm not good at those "spot the differences" puzzles!

[bill440cars]

Everybody needs 2 Super Sports! 

            Myself, I'd settle for just one. 

[Jerry Rxman Griffin aka MuthaF'er]

Early 75 model. 1/75 or 2/75 probably. Could only make out the CB750F-1xxxxxx. That and the rear master cylinder with the nylon reservoir are the 2 tips.

Do you know of any other differnces between the 1/75 and 2/75 models?  I noticed my other bike is a 2/75 and I noticed the rear master cylinder you mentioned.

. I'm not good at those "spot the differences" puzzles!

The rear masters changed over at ~7000 and change. That's it for 75. Colors changed for 76 in April. VERY LATE 76 used different rings (thinner top and middle). 

[b1jackson]

Ok.  Good to know that little tidbit.

Question about the oil cooler add-on.  I went to remove the oil filter and noticed that there is a different base plate for the filter housing to mount to and this base plate is where one of the cooler lines taps into.  The bike at one time had some sort of fairing on it and I wonder if it was common to add oil coolers when fairings were added since perhaps the fairing impacted air cooling ability some what?   Recall this was likely in the 80s.  The oil cooler certainly isn't a stylish add on and likely was mainly hidden with the fairing on.  Or did someone actually think they needed the "performance" upgrade of an oil cooler.

[Jerry Rxman Griffin aka MuthaF'er]

There is NORMALLY an electrical junction box residing where your oil cooler is. Curious about the wiring since I don't see the junction box?

Oil coolers are cool and/or they cool the oil. No sense in adding one unless extreme temps or high performance engine.

[b1jackson]

Yes, the junction box is there as well.

[b1jackson]

Since this is a project thread, I should add what kept me occupied today.  Carb clean!

Man, they were nasty.  On top of fuel varnish from the 80s, the carbs had been painted black when the engine was and was half peeling and have stuck.  I pulled them all apart and gave the bodies a hot bath in simple green (diluted first) then a second concentrated bath.  Nice and clean now.  Had to bath with the floats in as the pins were stuck good.  The spring loaded awl and heat trick worked good.

One of the pins got a bit bent and roughed up by the pliers when removing it so I'll have to fix that up or get a replacement.