Just Another CB750F Cafe Racer 1979 DOHC - Seattle Area

Ct.Allen253

Seattle, WA
Hello DTT Crew,

Spent a long time on here (and CB750c.com since my ideal bike was DOHC Honda) checking out the projects while actively looking for a bike that I liked, at a price I thought was good. It finally happened. Recently purchased a 1979 Honda CB750f. Only ~17,000 miles on the odometer. Very clean and runs. Have always done my own maintenance on my cars but looking forward to getting more engine knowledge/work as this project goes on.

Here's the bike. The purple will be gone away with ASAP.



Photo Jun 28, 8 25 31 PM by CT A, on Flickr

Photo Jun 28, 8 25 51 PM by CT A, on Flickr

Photo Jun 28, 8 26 21 PM by CT A, on Flickr

Ended up getting this bike a VW dealership. The previous owner had traded it in with 3 other cars. So, the FSM came with it. Along with a note with recommend maintenance and other tips. (Which I feel are pretty self explanatory but nice none the less.)

Photo Jul 07, 3 20 06 PM by CT A, on Flickr

Photo Jul 07, 3 20 21 PM by CT A, on Flickr

Photo Jul 07, 3 20 42 PM by CT A, on Flickr


-First issue is my front brakes are semi-seized, I can push the bike but it's a workout. Going to pop those open and drain them and most likely rebuild them.
 

Ct.Allen253

Seattle, WA
Re: Just Another CB750F Cafe Racer 1979 DOHC

Not much time for the project right now, been getting ready for the annual camping trip to Detroit Lake, OR. But I broke into the front brakes just a little bit to see why they're locking up. Here's what I found:

Photo Jul 08, 3 37 41 PM by CT, on Flickr

Photo Jul 08, 3 37 32 PM by CT, on Flickr


Removed the horns to access the.. spliter? Master cylinder?
Photo Jul 08, 3 39 11 PM by CT, on Flickr

Definitely been a while lol

Next to drain the system and see what the calipers and pistons look like. Also going to look into getting the hoses done to SS braided.
 

BigNickel

New Member
Re: Just Another CB750F Cafe Racer 1979 DOHC

Wow, looks like a very clean bike to start. I'm also going through a DOHC right now, I'll be following this!

Cheers
 

Ct.Allen253

Seattle, WA
Re: Just Another CB750F Cafe Racer 1979 DOHC

Thanks BigNickel. I've seen your build as well. Super jealous of the GSXR front end. I need to find one of those ASAP.
 

japstar

New Member
Re: Just Another CB750F Cafe Racer 1979 DOHC

second that, very clean bike.

The thing mounted on your lower triple between your brake lines is a splitter. The master cylinder is in the same part of the brake fluid reservoir.
 

SilkySmooth750

What does "Personal Text" mean?
Re: Just Another CB750F Cafe Racer 1979 DOHC

That's actually an incredible bike. If all those notes are true, I wouldn't mess with that thing at all but to get all the safety issues rectified. I personally don't like purple either, but man, I will shed a tear if you start tearing that bike apart.
 

XVRacer

New Member
Re: Just Another CB750F Cafe Racer 1979 DOHC

Man you've got a great baseline to begin from.

Personally I'll pull all of the maintenance and ride it for awhile. The later CBs are some of my favorite bikes.

Instead of a traditional cafe hack job, how about an early '80 AMA Superbike look?
 

adventurco

Nick Ol' Eye
DTT BOTM WINNER
Re: Just Another CB750F Cafe Racer 1979 DOHC

XVRacer said:
Instead of a traditional cafe hack job, how about an early '80 AMA Superbike look?
+1 on that

Seems like a good find, if what the notes say are true.
 

Ct.Allen253

Seattle, WA
Re: Just Another CB750F Cafe Racer 1979 DOHC

Got the front calipers pulled off. Seems that the right front caliper was the one that was seizing. Just waiting on my rebuild kits from Georgefix http://www.ebay.com/usr/georgefix. Also, ordered up a valve cover gasket and bolt grommets so I can knock out my valve clearances soon.

Photo Aug 08, 10 32 08 AM by CT, on Flickr

Left and right calipers
Photo Aug 08, 10 31 50 AM by CT, on Flickr

About to pop out the pistons, this is where I figured out that it was the right caliper that was seized due to it's non-existent actuation.

[Untitled by CT, on Flickr

Untitled by CT, on Flickr
 

Ct.Allen253

Seattle, WA
Re: Just Another CB750F Cafe Racer 1979 DOHC

Got some DOT3 fluid this morning and got straight to work. Pistons don't look as bad as expected hoping I can just clean up the outside.

As for the inside of the caliper, do you guys think I can just clean it up with some Dremel sanding buffing wheels?

Untitled by CT, on Flickr
Untitled by CT, on Flickr

Hoping I can just clean these up and don't run into issues having to replace the calipers. Didn't order replacement pistons either. Wanted to see what the current ones looked like first. There's alway a budget ;D
 

Ct.Allen253

Seattle, WA
Re: Just Another CB750F Cafe Racer 1979 DOHC

Today was valve clearance day. Here is what they're at:

Cylinder 1
Ex1: 0.11mm Ex2: 0.10mm
In1: 0.08mm In2: 0.12mm
Cylinder 2
Ex1: 0.15mm Ex2: 0.11mm
In1: 0.10mm In2: 0.11mm
Cylinder 3
Ex1: 0.08mm Ex2: 0.10mm
In1: 0.11mm In2: 0.10mm
Cylinder 4
Ex1: 0.14mm Ex2: 0.13mm
In1: 0.11mm In2: 0.10mm

What do you guys think? The guys over at www.cb750c.com recommend .004" to .006" (~.010mm - 0.15). At first I was worried about the 0.15 and 0.14mm exhaust clearances. But, with their specs I should be loosening the 0.08mm clearances.

Untitled by CT, on Flickr
Untitled by CT, on Flickr
Untitled by CT, on Flickr
-Looks like the PO used some RTV. That's a no-no :D

Untitled by CT, on Flickr
-Looks used as it should, but not to bad IMO. Anything I should be doing to this as far as cleaning?
 

adventurco

Nick Ol' Eye
DTT BOTM WINNER
Just Another CB750F Cafe Racer 1979 DOHC

As long as your Pistons don't have any pitting you're good to reuse them. You can "hone" the inside of the caliper by hand with some scotch brite pad just to clean up any oxidation. Most important thing is to pull out the rubber seal and clean the hell out of the channel that it sits in. Get some dentist tools and clean the upper and lower corners really good. Depending on the shape of those seals you may be able to reuse, but they should be available for short money on eBay for genuine NOS. I had issues with aftermarket rubber being too tight. That piece is what allows the piston to return to its resting position when you release the brake lever - it basically "twists" outwards as the piston is pushed out, and when released it pulls the piston back with it to release pressure on the pad. If there's any junk behind the seal it will create too much pressure and the piston will not be able to return correctly. Pay special attention to the side that was seized.

When installing, coat the rubber seal with brake fluid and press the piston in. There should be a bit of resistance, but you shouldn't have to force it in.

Sent from my iPhone using DO THE TON
 

Ct.Allen253

Seattle, WA
Re: Just Another CB750F Cafe Racer 1979 DOHC

Thanks adventurco.

I've been following most your builds and saw where you had an issue with the seals. I got my rebuild kits, and the pistons look good after a lil scotch bright. Already dental tooled the seal grooves. Will be putting them back together once I get the valve shims buttoned up.
 

MattCB750OT

New Member
Re: Just Another CB750F Cafe Racer 1979 DOHC

Cognito Moto sells a hoop with built in brake/turn signals. Really cleans up the rear end.
 

hillsy

Active Member
Re: Just Another CB750F Cafe Racer 1979 DOHC

If you're planning on taking the cams out then get a flat punch and whack the cam cap bolts a couple of times before you try and loosen them or you'll be buying Helicoils.
 

Ct.Allen253

Seattle, WA
Re: Just Another CB750F Cafe Racer 1979 DOHC

Finally getting back to the project cause I just want to ride!! Got the new shims in then this happened.. About to go get a E-Z Lok kit for M6x1.0 for the cam cover bolt that stripped its hole.

In the meantime going to get a new standard lead acid battery since my died while its been sitting the last two years. Also, lost my original key but luckily had a spare.

Tank doesn't look too bad inside, wondering if I should be doing one of the tank coatings or just do a gas rinse a couple times.

Going to change oil and plugs and get this baby running while there is still some sun!

Untitled by CT, on Flickr

Untitled by CT, on Flickr

Untitled by CT, on Flickr

Untitled by CT, on Flickr

Untitled by CT, on Flickr

Untitled by CT, on Flickr
New rubber.

Untitled by CT, on Flickr

Untitled by CT, on Flickr

Untitled by CT, on Flickr
 

Ct.Allen253

Seattle, WA
Got the EX-Coil into the Cam cover hole of the cam holder. Also got anew battery installed and she fired and ran.
Next is to go through the carbs as she doesn't run without full choke.

Untitled by CT, on Flickr
Prepping to drill out old threads.

Untitled by CT, on Flickr
No shavings please.

Untitled by CT, on Flickr
Untitled by CT, on Flickr
Installed here
 

pidjones

Well-Known Member
Ct.Allen253 said:
Got the carbs out and now tearing them apart. Ordered new rubber for them, also ordered all new Allen head bolts so I can get rid of the stock Philips head screws. Will get some parts cleaner and start soaking all of these parts.
They are not Philips head. They are JIS. Get a #2 and #3 JIS screwdriver (I just use JIS hex bits) and you won't be stripping the heads.
And while you have the float bowls off, fill each with 91% isopropyl alcohol to check for overflow tube leaks.
 

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