Topic: 1978 CB750F3 Cafe Racer Project...just starting...

[quebec_monstro]

Hi everyone, i just bought myself a little project in wich I'm gonna spend a lot of time...

i decided that I would have my own built thread so I could benefit from all of your good comments and advices....

So here is the bike just arrived at my house :





So here are the big lines of this project :

I'm used to modern sports bike so solid handling will be in my top priorities

I do not want futur problems with electrical stuff so I'll be renewing all electrical...this will also permits me to learn on that field...

As for the engine....well this will depends on my budget...but probably only overhauling it without performamce upgrade...only esthetics and reliability upgrades...

So till next time ... 

[70CB750]

Swing arm bushings were plastic from the factory, you should replace those with bronze. Stearing head - there is an All Balls bearing kit for that. Cheapest on Amazon. That will do the most for solid handling unless you got wheel bearing issues or such.

The engine, now that can be trouble. This model is known for eating valve guides between 20000 and 30000 miles and replacing those could mean complete valve job and new valves. To keep your guides happy and last stick to 20W50 oil all the time.

[calj737]

Welcome. Some particular tips that you may find very helpful in managing the engine maintenance, or rebuild, is to install a "frame kit". It allows servicing of the top end of the motorcycle without removal from the frame. See this link, and his signature at the bottom has info on how to obtain it: http://forums.sohc4.net/index.php?action=profile;u=6664

Here's a great build thread for you to read and bookmark about servicing the top end, and assembling for a permanently leak-free solution (these motors are notorious for developing small oil leaks in the most unusual places) : http://forums.sohc4.net/index.php?topic=107040.0

A for handling improvements and modern upgrades, certainly overhaul the front forks and wheel bearings, and install proper fork oil and seals. You may prefer to install an aftermarket fork brace and steering damper to aide in the rigidity and stability. An ultimate upgrade can be to install cartridge emulators in lieu of single rate springs. Some even replace their front ends with that from a donor GL. This provides dual front discs, slightly larger forks and it bolts straight into the steering neck. And you don't lose the vintage aesthetic.

And definitely, tend to the rear of the bike as 70CB suggested. Your rear shocks look spent and the swing arm bushings want to replaced with bronze!

If you do pull the bike down to the frame, inspect it carefully for any hidden signs of rust from within and mend that. Enjoy the bike, and keep your build thread updated regularly for us "junkies" to enjoy!

[madScientist]

^^ What those two guys said :-D

I put in the frame kit in mine and it's been awesome. It lets you tend to the engine while in the bike later on down the road.

A fork brace helps out a LOT. Before I put mine on I could feel the front flex some. Wheel and steering bearings are key as well as the bushings in the swingarm. With you bike on the center stand, grab the rear wheel and pull it from side to side and you'll see what we mean.

Rear shocks, I went with IKON's...about $300 and the handling is night and day over the old ones. More expensive / better shocks are out there (read: works shocks).

Front suspension...i didn't really do anything except change the fork seals and put in dampening oil. I hear progressive springs help out but never felt the need to put them in. I might later but I'm still kicking around a GL front end swap in the possible future.

Side note...i put a steering dampener on mine recently as, when I would get over 110mph or so, the steering felt a little loose. Depending on how you ride you might give it a consideration.

The valve guides, depending on how many miles you have, are likely shot. If you're going to have to go to that length of head work you might consider having it ported by the magician Mike Rieck. There's a lot of power that can be massaged out of these heads as in most engines.

As stated keep your build thread updated and let us know if you have any questions...we like to help.

[SOHC4 Cafe Racer Fan]

What everyone else said.

IF you want the best handling and braking possible in descending order:
(1) Swap out the stock front end for a GSXR front end (see Cognitomoto.com for turnkey solutions)
(2) Swap out the stock front end for a 75-77 GL1000 front, Race Tech internals (emulators and springs) and a fork brace
(3) Upgrade your stock front end with Race Tech internals (emulators and springs) and a fork brace

[dewey4262]

From someone who is just finishing up a F3 build, I want to emphasize that you check the valve guides for play. I was lazy and chose not to do this and would later have to pull the engine again after already completing my build. I chose to switch to a K4 head and barrel, leaving the option of using the ebay 836 kit in the future. You could also get a valve job done on the F3 head but it is not cheap. In terms of suspension I went with new rear shocks; Ikon, Hagon or the like would do well. In the front I did a rebuild with new seals, etc and progressive springs. I also added a Tarozzi front brace and an NHK damper. This set up is quite capable. For even more capability you also have the options of cartridge emulators or retrofitting modern suspension, although this would cost more, and in the case of the retrofit, require more labor.

[quebec_monstro]

Swing arm bushings were plastic from the factory, you should replace those with bronze. Stearing head - there is an All Balls bearing kit for that. Cheapest on Amazon. That will do the most for solid handling unless you got wheel bearing issues or such.

The engine, now that can be trouble. This model is known for eating valve guides between 20000 and 30000 miles and replacing those could mean complete valve job and new valves. To keep your guides happy and last stick to 20W50 oil all the time.

I thank you very much for those advises but I had already those swingarm upgrades in my plans By the way, I've seen also swingarm shaft on needle bearings kit on the web...is that worth it??

And What about the boxed section swingarm that is sold by Carpy's...is that worth it??

And I thank you very much for the oil grade suggestion...I'll use that ...and also, I guess it is a good thing to use full syntethic oil....

Thank you in advance...

[quebec_monstro]

What everyone else said.

IF you want the best handling and braking possible in descending order:
(1) Swap out the stock front end for a GSXR front end (see Cognitomoto.com for turnkey solutions)
(2) Swap out the stock front end for a 75-77 GL1000 front, Race Tech internals (emulators and springs) and a fork brace
(3) Upgrade your stock front end with Race Tech internals (emulators and springs) and a fork brace

For sure i won't retrofit a GSXR front end...it is to much investment and I find that its denaturating the bike...I don't know if that word exists...hihi

What about the front fork exchange with a GL1000 first of all I have already to front disk...but maybe the diameter of the fork tubes are different...in what exactly is this an upgrade??

Thanks you all you are really awsome to have answered that quickly 

[SOHC4 Cafe Racer Fan]

What everyone else said.

IF you want the best handling and braking possible in descending order:
(1) Swap out the stock front end for a GSXR front end (see Cognitomoto.com for turnkey solutions)
(2) Swap out the stock front end for a 75-77 GL1000 front, Race Tech internals (emulators and springs) and a fork brace
(3) Upgrade your stock front end with Race Tech internals (emulators and springs) and a fork brace

For sure i won't retrofit a GSXR front end...it is to much investment and I find that its denaturating the bike...I don't know if that word exists...hihi

What about the front fork exchange with a GL1000 first of all I have already to front disk...but maybe the diameter of the fork tubes are different...in what exactly is this an upgrade??

Thanks you all you are really awsome to have answered that quickly 

The GL front end features:
(1) larger diameter fork tubes (37mm vs. 35mm) -- which provides a sturdier front (better front end feel);
(2) larger brake pistons and a ready to bolt on twin brake rotor set up mounted aft of the forks -- much better stopping power.

This modification requires nothing more than bolting on the entire front end -- forks, triple tree, brakes, entire wheel, axle.  The steering stem is the exact same size, and it uses the same bearing races (swap out the loose ball bearings for All Balls).

[martin99]

As I understand it, most people go for a GL1000 front end because it's a fairly straightforward way to convert to twin disc - which you already have.  I find the front brakes on my F2 quite adequate, especially since fitting SS lines. And I don't do 110mph (not even sure if it would do it) but I agree a fork brace makes a difference. Probably well advised if you're going the cafe route and plan to ditch the stock fender.

[quebec_monstro]

Well....this was all good answers and it lend me to my decision wich is the following :

1 - I 'll brace the fork with a tarrozzi kit. that is for sure (Where to buy for the better price??)

2 - Most probably put a stering damper...because now that I have one on my Monster900 from 1995 I know how much it helps strentening the front end 

3 - Maybe I'll put some better progressive springs also with thicker oil inside...if I can find the money depending on engine rebuilt...

I thank you all for your good comments and by the way, I'll be selling quite a few stock parts from this motorcycle...the seat for exemple and the stock gauges dash board, front light, etc...so if some of might be interested I'm open to offers 

[calj737]

Best to post your parts for sale in the For Sale section. You'll get the most visibility there.

You can try www.fastfromthepast.com for the brace and damper.

[quebec_monstro]

I would like to get your recommendations on wich engine gasket kit shoul i buy??

I've heard that the one rom AtENA is not the better quality...is that true?

I thank you all in advance...

Best regards.

[70CB750]

Lot of people go with the MLS gasket set from CycleX:

http://www.cyclexchange.net/Engine%20Parts%20%28Non-Cafe-Gaskets%29.htm

[quebec_monstro]

And what would be the down sides of buying this kit ?? :

[70CB750]

I don't think you can go wrong with anything from CycleX, they build and race CB750s.  I went with the MLS head gasket set, since that was all I needed - but the engine did not run yet; no personal experience.

[edwardmorris]

Vesrah is pretty popular, but I'm not sure if they make it for later years/Fs.

I'm going with the Vesrah kit for my K2, but I may do the MLS head gasket for the head. I had it decked, and from what I read, that's the only requirement for the MLS.

[SOHC4 Cafe Racer Fan]

Decking the mating surfaces of the cylinder, head and valve cover is a good idea.  It eliminates a leak variable.

[quebec_monstro]

Hi everyone, here is a little update of my project going on :

I've taken many parts of the bike so far and I'm alsmost at the point of getting the engine off







I've tooked the compression readings and I got 135 PSI on cylinder 1 & 4...the two other cylinder were to dificult to get good readings with the tool I have in a hand....

So probably the engine is not so bad...I hope

I do not know yet what I'll do with the engine but something is for sure I'm tearing it down in pièces to have a new painting on it...so I'll doublecheck everything while I'm there and take decision at the same time...

I've read that it is almost impossible to have slight oversized pistons for those «black engines» is that true or is there a well hidden place where I can buy some???

If I was to buy a restoration book, would you guys suggest to go with the «Clymer» one or the one published by Hayden??

I thank you in advance for your precious help

[Davidov]

I've tooked the compression readings and I got 135 PSI on cylinder 1 & 4...the two other cylinder were to dificult to get good readings with the tool I have in a hand....
So probably the engine is not so bad...I hope

If I was to buy a restoration book, would you guys suggest to go with the «Clymer» one or the one published by Hayden??

Those compression numbers are good. I would still plan on doing a top end rebuild to ensure many more miles of use. My F3 had worn guides, and a number of errors inside the engine from previous repairs.

I use the factory K8/F3 manual that can be found on this site, and the HondaMan book.

[70CB750]

+1 on Hondaman's book.

[Davidov]

I've read that it is almost impossible to have slight oversized pistons for those «black engines» is that true or is there a well hidden place where I can buy some???

I think the .25, .50., .75, 1.00 over bore sizes are hard to come by. My engine measured all within specs, so I only needed to hone/de-glaze the cylinders and install new rings. Another benefit of rebuilding before catastrophic engine failure.

You can go from mild to wild on these engines.
http://www.cyclexchange.net/Honda%20cb750%20(%2077-78%20)%20%20F%202%20Section%20Page.htm

http://www.dynoman.net/engine/pistons/custom.html
Like a big bore kit 

[quebec_monstro]

Hi everyone, my project is progressing slowly and here is where I am right now :



I've taken out most of the parts and now the engine will be coming out really soon...

I'm planing on re-using the stock carbs but to go with pods filters...I've seen many places to buy them but I would like to hear from you guys :

Where is the best place to buy them to make sure i get good quality ones?

And by what I have read, the ones I need is the 42mm ones? (I just measured the outside diam. of my carbs and I'm measuring 46mm...!!

[martin99]

You do indeed need 42mm

I think most would recommend K&N filters, I have S&B on mine, a good American make but I don't see much mention of them on here.

[SOHC4 Cafe Racer Fan]

Assuming you are keeping your Comstars, and you want to improve the handling, then you will need to stay with the stock front forks.  I would recommend rebuilding them with Race Tech internals (springs and Gold valve emulators).  In addition, you might be able to add a Tarozzi fork brace to improve the rigidity and feel of the front.  Further, If you want to improve the brakes, you can swap the calipers to a twin piston caliper that directly bolts on to your forks.  A couple of Honda models are compatible.  Run a search on the upper left and it will give you the models and date ranges.