Author Topic: New addition to the family! Gotta rebuild the brakes... (Read 2853 times)

nobody · « **on:** July 03, 2009, 12:24:22 PM »

So after a bit of looking and wondering if I'd find something good I finally have. A 1978 cb750f that's been sitting for like six months in the back of some shop owners shed. He said he thought it ran but it had no title, hopefully it won't be a huge hassle to get a new title. So we hooked it up to his shop truck (no battery in the bike) and the thing started right up and ran clean and smooth. The front brake fluid is gummed up and doesn't work, needs new tires, a handful of other things but all in all a good score at $600. Come winter it'll be torn down and turned into a cafe bike but for now I'll just try to get it back on the road.

right side... I don't know what kind of exhaust that is but holy crap it's ugly. I picked up some black kerkers to replace it.

left side

check out the clock... SICK!!!!!!!

a touch of class from a previous owner

aged like a fine wine

some pictures of it's big brother waiting for the engine to be pulled, been dragging my feet getting the transmission rebuilt.

j-conn · « **Reply #1 on:** July 03, 2009, 12:26:50 PM »

hmmm... more toys!

Alan F. · « **Reply #2 on:** July 03, 2009, 01:35:18 PM »

Good score for 6 bills! That muffler almost looks like a cherry bomb that's been slash cut, how's it sound?

robe0531 · « **Reply #3 on:** July 03, 2009, 01:38:18 PM »

very good score

HavocTurbo · « **Reply #4 on:** July 03, 2009, 02:11:28 PM »

Either that or a truck muffler from a dual set-up.

I'm curious as to the sound as well.

Quote from: Alan F. on July 03, 2009, 01:35:18 PM

Good score for 6 bills! That muffler almost looks like a cherry bomb that's been slash cut, how's it sound?

nobody · « **Reply #5 on:** July 03, 2009, 02:21:04 PM »

It actually sounds really good, very deep and loud. Kinda like straight pipes but cleaner. It's just too ugly to keep on the bike though, hopefully the kerker maintains some of the meanness that it currently has.

Dave-and-his-550 · « **Reply #6 on:** July 03, 2009, 02:32:33 PM »

I think the pipe looks good. Is it rusted through or something? I say paint the whole thing flat black.

Toxic · « **Reply #7 on:** July 03, 2009, 03:00:12 PM »

Anyone can have a Kerker, that pipe looks great.

+1 on keeping it and painting it flat black, maybe some black header wrap to.

Alan F. · « **Reply #8 on:** July 03, 2009, 03:03:00 PM »

Yuck, header wrap...

nobody · « **Reply #9 on:** July 03, 2009, 03:48:28 PM »

I don't know, I think the exhaust is plain old ugly. I might try chopping it or something but I think Kerkers would look better, probably perform better too. The jury is still out on the header wrap, I guess that depends on how the bike looks when I actually start putting it back together next spring.

nobody · « **Reply #10 on:** July 04, 2009, 12:18:03 PM »

What would be the best way to clean the gelatinous goop that once was my brake fluid out?

Frankenkit · « **Reply #11 on:** July 04, 2009, 12:31:38 PM »

take off your caliper and MC and blast them all out with brake parts cleaner.

nobody · « **Reply #12 on:** July 04, 2009, 01:26:32 PM »

So I should probably buy a couple front caliper rebuild kits then?

Frankenkit · « **Reply #13 on:** July 04, 2009, 01:30:20 PM »

yup and make sure you don't have *any* pitting in your piston, or you're asking for problems. (that said, I have a little but my brakes are still good. Would go for a new brake piston, but 650 pistons are pretty near unobtanium.

rebuild your master cylinder, too. there are tiny, tiny orifices that clog easily and cause major problems.

nobody · « **Reply #14 on:** July 04, 2009, 01:55:11 PM »

Where can I get a master cylinder rebuild kit? I found a kit for the front calipers but not the master...

http://www.oldbikebarn.com/Honda-CB750-F-Front-Brake-Caliper-Rebuild-Kit-cb750-f?sc=12&category=52301

Alan F. · « **Reply #15 on:** July 04, 2009, 03:56:48 PM »

Get your M/C rebuild kits directly from Honda. Price isn't that high, besides it's not something to skimp on to save a few bucks.

nobody · « **Reply #16 on:** July 04, 2009, 05:31:09 PM »

So I pulled the calipers and master cylinder off the bike completely. All the bolts were finger tight and there were no brake pads on either side, they must have started a brake job and changed their minds. Both calipers seem to be seized, I can't get either piston out of the caliper. I know you can pop them out with compressed air or with hydraulic pressure pretty easily. The problem is I don't have an air compressor and I don't think the master cylinder is working well enough to pop it out. With the master cylinder off of the bike and the reservoir full should it spray fluid out when pumping the piston? I'm only getting a dribble.

Old Scrambler · « **Reply #17 on:** July 04, 2009, 06:46:18 PM »

Don't pump it until you have removed and cleaned all of the old gunk. Put a heavy plastic bag on the MC with a big rubberband....punch some small air-bleed holes........then get some compressed air and blow the lines out in the opposite direction. Then rinse with brake cleaning fluid and re-attach the line to the calipers. Install new fluid and press out the pucks............works for me.........

Frankenkit · « **Reply #18 on:** July 04, 2009, 09:51:05 PM »

I would recommend against ordering from OBB. It's rare when a person gets what they want when they want it from them. I'd try partsnmore, actually, and z1 enterprises.

nobody · « **Reply #19 on:** July 04, 2009, 11:06:34 PM »

I was thinking about upgrading to steel lines while I have it apart but can't find them on either z1 or partsnmore... any idea where I could find them?

Frankenkit · « **Reply #20 on:** July 04, 2009, 11:11:05 PM »

go to your local harley dealership... the ones around here have pre-measured pre-manufactured lengths of ss lines in black or steel grey, along with all the necessary banjo bolts and copper washers.

nobody · « **Reply #21 on:** July 05, 2009, 09:05:32 PM »

At a Harley dealership? They won't laugh at me when I ask for honda parts?

Frankenkit · « **Reply #22 on:** July 05, 2009, 09:14:28 PM »

I didn't even have to ask. They were just hanging up. I just measured mine for reference and brought the banjo bolts to make sure they're the same size. If you need to ask anyone for advice, ask the oldest guys. The young guys don't know crap and are too full of themselves to care. The young guys remember their old jap bikes from 'back in the day' and are often quite willing to help you.

nobody · « **Reply #23 on:** July 06, 2009, 05:47:47 PM »

I found some places online too. I might hold off on the stainless lines until I get my clip-ons (this winter). Don't want to waste money on lines that I'll only use a few months.

nobody · « **Reply #24 on:** July 07, 2009, 07:30:26 PM »

So I popped the pistons out of the calipers, there was a ton of gunk in there just like in the reservoir, not super surprising. The pistons have a little pitting and may need to be replaced, I'm a noob though so you tell me. The calipers don't look too bad, maybe a good cleaning will bring them back. I'm a little worried that maybe the lines have some gummy goop in them as well but I can't tell, nothing dribbled out of any of the hoses when I removed banjo bolts. I stuck a Q tip in the splitter joint to see if any gunk was in there but it didn't look too dirty. Again, noob, you tell me...

HavocTurbo · « **Reply #25 on:** July 08, 2009, 12:05:00 AM »

If you're worried about gunk....

take some brake cleaner spray and spray it into the lines, then take an air nozzle and shoot some compressed air in there.

Cleans them right out.

nobody · « **Reply #26 on:** July 08, 2009, 06:10:33 PM »

Cool, I'll have to try that. Where would be a good place to buy new brake pistons? Can't find them on partsnmore or z1. Honda has them but they're $107 each.

Frankenkit · « **Reply #27 on:** July 08, 2009, 06:13:41 PM »

You have a 750, the world is your oyster when it comes to brake pistons. Look at phenolic ones- they'll never rust/pit.

nobody · « **Reply #28 on:** July 08, 2009, 06:26:21 PM »

I just read somewhere that 80-82 750f calipers will fit my bike, confirm or deny?

nobody · « **Reply #29 on:** July 17, 2009, 05:32:25 PM »

So I got the 81f calipers, was only able to pop one piston out of each caliper. Any ideas how to get the second one out? Do motorcycle shops have some sort of piston extracting tool? Secondly, The calipers were missing two pieces (a rod and a bracket, the others are pictured below), I've contacted the ebay seller but chances are that they got lost somehow. Any idea where I could pick up these pieces without having to buy another caliper? I could probably check the junkyard but they might not have the 80-82 750f. Could they be bought individually? Oh, and upon further inspection I found a huge cluster of disconnected wires... FUN!

HavocTurbo · « **Reply #30 on:** July 20, 2009, 11:51:07 AM »

IF you cannot find replacements...

Let me know and I'll make them for you.

Grab yourself some padded channel locks and pull the other pistons out. Should be relatively easy.

nobody · « **Reply #31 on:** July 29, 2009, 07:24:04 PM »

Thanks Havoc, the pistons inside the 81 f calipers are perfect, the bore isn't too bad either. I'm repainting them while I wait on the rebuild kits.

nobody · « **Reply #32 on:** August 25, 2009, 08:00:08 AM »

So I'm putting this bike on hold. The brakes don't fit right because the wheel won't sit straight, I'm going to rebuild the wheels and see if that fixes it. I gave it new plugs, fresh gas, clean oil and it wouldn't run anymore. I think the gas may have gone bad. So I pulled the carbs, broke a rusty throttle cable in the process and a rusty choke cable. Pulled the float bowls off and inspected them but can't see anything blatently wrong. I sprayed some carb cleaner and some air into tiny parts but have yet to reconnect them as I no longer have cables to make them work...

All in all this project is making itself a noble adversary. Since I'm moving in a few weeks I've no money to continue working on it right now. Once I get my new shop set up at the new apartment I'll start it up again. I'm just going to dive into the neo classic cafe racer build instead of trying to make it road worthy and get it titled right now. Maybe I'll put the 74k on the front burner and see if I can't fix the tranny first. Either way I'll probably just start a new thread in the projects section. Thanks to those who've answered questions and tried to help me out with this thing. I'll be back soon with more progress to show. (hopefully)

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Author Topic: New addition to the family! Gotta rebuild the brakes... (Read 2853 times)