My '79 CB750f Supersport - I'll take all the help I can get

[TGreg104]

Hey guys, I've been creeping around on the forums now for a couple months, figured I'll post what I got.

So about a month ago right after the semester ended, my friend out of boredom wanted to teach me to ride his motorcycle. He clearly knows me so well because as soon as I could get the bike going and actually ride it, I was hooked. So the search began for the right bike. I looked up and down craigslist for a good month and couldn't really find anything at my price point that caught my eye, until I saw her. Now I'm not sure if it was the fact that it was a "Supersport" that was stroking my man ego or what, but I fell inlove with the bike. She was dented, rusty, had dry rotted tires, and was torn up but in my eyes, it was character. So some haggling and a handshake and I walk out of there with the bike for around $840. As soon as it was a nice day out, I took her out. She ran okay, although I had to keep the choke wide open to keep her running. I got about 3 rides in before she started to quit on me, first thing I noticed was theres something wrong with the charging system as I'd have to charge the battery after every ride. Then on my last ride, as I was pulling into my backyard, the front tire started leaking a lot of air. Thank god nothing bad happened. And she's been in the backyard now for a week or so begging for new tires.

So my plan is to work in phases to keep everything manageable.

Phase 1:
-Tires
-Check Stator and r/r to locate the problem in the charging system
-New front break pads
-Fix the back brake (I think the master just needs rebuilt)
-Rebuild/Re-jet the carbs
-Fix any odds and ends I find as I'm working (I'm sure she's full of surprises)
-Clip ons
-End Mirrors
-All new turn signals (the 80's were a dark time in automotive/motorcycle design, did they really think square lights were coool ??? )
-New seat
-Clean up all the rust
-Clean/paint as much as I can
-New exhaust

Phase 2:
-rear hoop
-cafe or brat style seat
-new wiring harness
-wire tuck
-Micro battery
-Completely disassemble, clean, re-assemble
-New headlights
-New Gauges
-Check/fix any suspension problems

Phase 3:
-Tear into the engine
-Fix it
-New suspension
-Spoked wheels
-New fuel tank
-Paint her
-Finish up any odds and ends.

Realistically, I only plan to finish Phase 1 this summer as I just want to ride. Its my first motorcycle and I figured I'd have all winter to work on the meat of it. If all goes well, I'd like to complete some things in phase 2. Phase 3 may not happen for a while but its nice to have a plan. This isn't going to be one of those "heres my bike rusty, (four posts later) and heres my bike finished" threads, I'm a broke college student. I'm open to any advice/tips/suggestions as I don't really have a theme yet.

I haven't really touched the bike yet, but as I type this I have my Clymer Manual coming in the mail. I generally like to wait for the service manual, I've learned that it saves you from a lot of headaches.

As for today, I'm about to head out to habor freight, pick up some cheap tools and get those tires off. I also want to check the stator and the r/r, can anyone explain where the three yellow wires from the stator are and explain where the r/r is? Thanks in advance

 

[TGreg104]

I have more pics to post, but I have to resize them. Ill do that later!

 

[GB400 fan]

Hi, looks like a great start, heres a link to the manual kindly put up by HD.
http://www.dotheton.com/forum/index.php?topic=44399.0

you'll find all the sections there. good plan, wish I had done that first!! but there ya go!

 

[canyoncarver]

Welcome to DTT! You have a great bike to start with, tons of knowledge about them here. Parts are relatively easy to find and usually cheaper than the SOHC 750's.

I've got an 81 model of this bike "in progress", mostly because I watch Craigslist too much.

 

[TGreg104]

Thanks guys! Yeah in that picture she looks a lot nicer than what she is haha

I tested what I believed to be the stator (right side of the engine, front most cover) today. Between two of the wires I'd get between .9-1.3 ohms which I believe is okay, but the last yellow wire would fluctuate between anywhere from .9 all the way up to 20.x. I'm assuming the stator is my culprit. I'll check the r/r as soon as I dive into that pdf manual (thank you btw!) and find out where/how to do it.

Also, I had no idea that taking the wheels off the bike would be so hard : I started with the rear and had a hell of a time since I don't have a deadblow or rubber mallet yet, so I gave up and put that back on since my rear tire is ride-able. Moved on to the front and it was going well until I had to deal with the two piece "bolt" for a lack of a better term, the one that connects the speedo. I couldn't get a good enough grip on it to get it loose. The one time my one wrench slipped off and I broke the speedo cable :-\ I swear I'm breaking more things than fixing hahaha but hey, thats half the fun right? I should probably just get the tire and hold off until my Clymer comes in.

Also did some little things like take the rear fairings off, front fender (left the brace, don't work haha). I'm chomping at the bit to order some parts for her, but I want to diagnose my charging problem first that way I can order most of my parts at once.

 

[TGreg104]

Pix

 

[TGreg104]

moar

 

[TGreg104]

:

 

[TGreg104]

Is there any way to upload more than four pictures per post..?

 

[Spalding]

Sweet, i love the comstars. Might want to put a stock airbox back on to begin with as the CV carbs are a pain in the ass with pods. Might help with the choke issue. Adjust your valves too!

 

[canyoncarver]

Get yourself a can of PB Blaster. It's a spray on penetrating lubricant. Hardware stores even carry it. Spray that stuff on anything you are going to take apart and give it about 10 minutes or so. It will really help with stuck shit and may even prevent breaking a few things.

As for the air filters, those look to be decent K&N's. Much better than the cheap ass EMGO pods. You "should" be able to get them to work with those CV carbs but it will take patience and carb setup kung-fu.

 

[TGreg104]

I love me some PB Blaster! Definitely gonna have to grab me a can. And is there any difference between cb or cv carbs? or are all carbs CV's?

 

[canyoncarver]

CV = constant velocity. Uses vacuum pressure to operate the slides instead of the direct-cable pull types. In general, older CV carbs work great with an airbox but are very picky about pod style filters.


There is a good thread here on pods.
http://www.dotheton.com/forum/index.php?topic=45863.0


and a few sticky threads on carb stuff here:
http://www.dotheton.com/forum/index.php?board=74.0


Also look for kopcicle's write up on carb cleaning:

http://www.dotheton.com/forum/index.php?topic=22587.msg246112#msg246112

 

[TGreg104]

Thanks man, I'll read up on those.

So I was trying to install the front tire and I cannot for the life of me get the brake pads to stay in place and I when they are in place I cant get the rotor between the pads. I read HD's scans of the clymer and it says right there do not operate the handle while the rotors are off. Stupid me... I reallllyyyy should just stop working on this until I get the book. Im making my life so much harder.


So any advice on getting the tire in place?

 

[cklamer]

Take a piece of cardboard and fold it up and stick it between the pads so thy are pushed back from the opening.
As you set th calipers on the rotors gradually pull the cardboard out.

 

[TGreg104]

I am so disappointed I didnt think of that myself! haha thank you, I'll try it tomorrow.

 

[TGreg104]

Yeah, I'm still having trouble. Less trouble with the pads staying in and more trouble with there being enough room for the rotor to even fit. How the eff can I get the pad to recess enough to give me the clearance I need? Thank you in advance

 

[TGreg104]

Also I finally got around to test my charging system, definitely need a new r/r. My readings were all over the place, and none of them were the same.

With the stator, I checked it again after running the engine for a little bit with my multimeter on the lowest ohms setting and got readings from 1.0-1.3 on all of the yellow wires. I thought this was okay, thinking I read somewhere that they should be between .1-1.0 ohms +/-.2 but my clymer states they should be between .41-.51 ohms.

Can anyone confirm or deny my findings? I'd love it if I didn't have to drop the 130 for a new stator, but I would love a properly running bike more

 

[AgentX]

Yeah, I'm still having trouble. Less trouble with the pads staying in and more trouble with there being enough room for the rotor to even fit. How the eff can I get the pad to recess enough to give me the clearance I need? Thank you in advance

Just push them. Use a clean tire lever, or just be careful with a big screwdriver. You can lever the pads against each other as required.

 

[Rich Ard]

I use a big C-Clamp and push the piston back in, then install the whole thing.