Topic: CB500 -75 Battery surge & clutch problems

[Alex]

Hey!

So I've spent almost 2 years on and off rebuilding my first bike.
I ripped out the old electrical harness since it was in really bad condition, installed an m-unit and wired it just like the guys from Revival Cycles in one of their tech talks.
I've probably gone through the wiring about 6-7 times to make sure it is just like in their video and that nothing is poorly isolated.

The problem I have is this:
When I turn on the ignition, the headlight and taillight are not on, but they turn on when hitting the start button (default setting from m-unit).
So I am able to start the bike and it idles fine, but if I use the kill switch to turn it off, the battery goes down from around 12.8V to 6-8V in a matter of seconds.
Sounds like a short to me, but I can't seem to find where I've gone wrong!
I bought the battery almost 2 years ago, but haven't used it until now, but charged it before installation.

Anyone else who has experienced the same problem?

Another problem is my clutch (I think?).
Before the rebuild it all worked fine.
Now when I want to take the bike out, it feels as if the clutch is slipping around 3000-4000rpm.
I've tried to adjust the cable back and forth probably 20 times, and it gets marginally better at some points, but still slipps around the same rpm.
Ignition timeing, valves, carb sync is all done and it revs upp to 8000-9000rpm easy when in neutral.
New "rubber intakes" for the carbs, carbs are jetted to match 4into1 exhaust with pod filters.
Mixture seems to be pretty on point when looking at the spark plugs.

Has anyone experienced the same problem?

Eager to take her out on the road and extremely grateful for any help or ideas!

[calj737]

Immediately I see a few things missing, which are perhaps an oversight in your drawing, or sources of some issues.

The Reg/Rec shuold have 3 yellows, White, Green and Black (2 Greens if it’s an aftermarket unit, solid state combo). There is no Black wire in your diagram from the Regulator to the switched 12v circuits. I typically run that to AUX. This measures the voltage seen in the harness (on behalf of the battery) and controls the recharge to the battery from the Rectifier.

Your diagram shows all m-buttons terminating their ground to the m-unit ground stud. Don’t do this. Wire them to a solid frame ground. Your battery shows no connection from NEG to frame/motor.

See if this diagram helps by checking all your connections against it.

[calj737]

As for the clutch issue-

The 500 has a few common sources of issues that can be tricky to sort out. Starting from the left side, there's a cam/screw that needs to be lubricated, theres a ball bearing , then a pushrod traversing the engine. When you assembled your motor, was the ball bearing reinstalled? Is the pushrod stock and in good condition (they are a known weakness)? Are the clutch disks new or old? Did you measure the thickness of the plates and disks? What about the clutch springs?

Provide a few more details on what service or replacement was done on the clutch, and surely someone can figure it out. It does sounds as though the clutch is slipping under acceleration. Does this happen in any gear, or is it isolated to a certain RPM range?

[Alex]

Thanks for your quick response calj737!

I actually think I know what the problem is when looking at your schematics.
I MIGHT have taken the black cable from the RegRec and used as ground!
The RegRec is grounded via the green cable to the alternator, but I didn't think of it that way and used the black cable to "ground" the RegRec with.
That would maybe explain why the battery is getting drained so quickly?

I have to double check when I'm at the garage later on, but I think that might be it!
Great schematics by the way!


Regarding the clutch.
I never dissassebled that part of the engine, since it worked perfectly fine before I started the rebuild.
I took off the left crankcase cover to access and lubricate the clutch lifter, but never really touched the pushrod.
I don't think that the bearing fell out, but I have to double check that to.
And if the pushrod is weak, then something might have happened when I took the crankcase apart.
The previous owner put in new disks, so I'm guessing they're still ok, but can't hurt to check them out!


Thank you again calj737, I REALLY appreciate your pointers!
I'll get back to you with an update later!

[Alex]

Alright!

So my electrical problem is fixed!
As I thought, I had used the RegRec's black cable for ground..
Not the smartest mistake, but it's solved anyway.
Thanks calj737!

Now, I looked at the clutch issue.
The ball bearing in the clutch lifter is there.
Everything machanical about the clutch lifter seems to be right,
but the one thing I'm sceptical about is the pushrod.
When looking at pictures from cmsnl, it looks like the pushrod should be one piece.
But my pushrod seems to be in two parts.
I can take out the firts part of the pushrod, but it doesen't seem like it broke.
The end of the part I can take out looks like a bowl, like something is supposed to sit in that "bowl" (like en end of the rest of the pushrod going to the disks).

Is it normal for the cb500's to have a two-part-pushrod or could this be the problem?

[calj737]

Nope, pushrod is broken. There's your problem. As I had said, that's the achilles heel of the 500 clutch, that darn pushrod. 

[Little_Phil]

Wasn't the design similar to CB450s. They had a single material one piece rod. The 500s changed to a sandwich of different materials. I read that was to overcome cold/hot variations, but they often snapped in the ali section. Both my UK 500s had snapped rods. Standard procedure was to machine the ends and slip a ball bearing between the broken bits. Used one for 8 years like that and it didn't ever really wear down that I noticed.

[scottly]

The RegRec is grounded via the green cable to the alternator

No, both the RegRec and the alternator field coil are connected to a common ground with the stock harness, not just to each other.

[Alex]

Alright, so the clutch is now "fixed"!
I ordered a new pushrod, but it was approx. 5mm too long, but worked fine when I took out the bearing from the lifter.
Any input if removing the bearing is a bas idea?

My electrical problem has come back though.
I think I was a bit early to cheer.
Turned out my NEW reg/rec was toast. Can't tell if it was like that when I ought it or if I did anything.
I'll go with blaming myself. It's probably right.
So, I had to buy a new reg/rec, but got a different one since the original model I used was discontinued at my store.

Now I have a more universal type, but with one difference.
It has two field-cables.
One white and one black.
I'm thinking white goes to white, but what to do with the extra black field cable?
I know it's a universal part, but just want to make sure there's not a specific way to connect reg/rec's with two field-cables.