Author Topic: 71' CB750 ..I'm hooked! but trouble in paridise? (Read 4553 times)

750four · « **on:** June 05, 2011, 08:01:02 PM »

Picked up a 1970 cb750 with a K1 engine in it a awhile ago. Had not been fired for 10? years. So I've been tinkering on this bike for awhile now. It's been on the backburner a couple of times due to ..well... life.

Anyhow the big pay off came yesterday, my tlc has payed me back. Starts first kick and it's a blast to ride! I've updated a lot over the time it's been sitting. Went through the head, installed new APE valve springs, lapped valves, new rick's reg/rec combo, Dyna s ignition and green coils, dyna wires. Cylcex dual carb system. new tires, wheel bearings, new chain...etc.

So after running about for around 45 minutes it starts to poop out on me. I have a backpack on me full of wrenches and misc tools. 1 of which is my multimeter. It drained the battery down to 6 volts! Luckily the battery charged itself back up enough for me to start and limp home. Also seems when I check the charge on the battery with the key on it's 1/2 of that. 3ish.

I've check cont' of the yellow stator wires and they're all good. The other 2 wires are showing 7.2 ohms resistance. Which is right on spec via my manual. Not sure if maybe the reg/rec is hooked up wrong or maybe my stator/ rotor is bad.

How do you wire the reg/rec to the battery and ignition? What is the difference in the black and white wire on the unit? I had landed the white one on the key switch with the battery +. and the black I had landed on the key switch to the acc. for some reason, maybe it should be on ignition. I don't see what difference it would make though.

Are there any other ways to check the charging system while the bikes not running. For some reason my mutilmeter wigs out when the bike is fired up. I think it may have something to do with my loud ass pipes....thats another project though

Toxic · « **Reply #1 on:** June 06, 2011, 04:01:48 AM »

free bump so the e-gurus can help you out. Now post a pic of your bike. I want to see the dual carb set up, thanks

750four · « **Reply #2 on:** June 06, 2011, 10:01:20 AM »

Hey thanks, I'll get some newer pics soon. Last pic is my avatar. Come a long way since last week, then I got set back by this ordeal. No worries though, my charging system is one of the only things I really haven't revamped. Well, aside from the Rick's reg/rec combo.

Bankerdanny · « **Reply #3 on:** June 06, 2011, 10:35:32 AM »

Did you attach your meter at the battery while running to see what kind of voltage you are getting? you can also wire a cheap ammeter from the auto parts store temporarily to see if the alternator is pumping out any juice.

You mention you replaced the regulator. Personally I'm not a fan of replacing stuff like that until I know for sure it isn't working. You know, the old if it ain't broke, don't fix it school.

scottly · « **Reply #4 on:** June 06, 2011, 06:50:24 PM »

The 2 wires that you read 7.2 ohms on are the field coil. One is white, and one is green, although with age it may not look like it. The regulator controls the current through the field coil to regulate the voltage fed to the battery. The green field wire is connected to ground, and the white field wire is connected to the regulator white. The black reg should be connected to the ignition on terminal. This assumes the Rick's combo uses the same color codes as Honda.

750four · « **Reply #5 on:** June 06, 2011, 08:05:31 PM »

I think I'm going to run the white wire directly to the terminal on the battery + and the black will go to the key switch ignition. Just wonder where it would be best to tie in the coil power to. black I assume?
I've tried to measure the charge with my multimeter, but it wigs out anywhere within a 3' radius while running. hints the weak attempt at baffles. 1 feel out on the ride LOL.

Here are a few pics. some of thereg/rec, cyclex carb system and various other stew.

greenjeans · « **Reply #6 on:** June 07, 2011, 11:21:17 AM »

Good lord - gimme a side shot of that bike. Those 3/4 shots look #$%*in'

wixil · « **Reply #7 on:** June 07, 2011, 02:23:32 PM »

+1 on the side shot.

750four · « **Reply #8 on:** June 08, 2011, 04:06:11 PM »

So the reg/rec is a rick's unit 10-100. It does mention not grounding. So if I run the ground from it to the battery than I can't ground my battery to the frame? I need to redo some wiring now.

scottly · « **Reply #9 on:** June 08, 2011, 06:59:05 PM »

Can you post the instructions for installing the reg, or a link to the instructions?

750four · « **Reply #10 on:** June 09, 2011, 09:25:39 AM »

There really aren't any instructions, comes as a plug and play deal. but I have rewired my 750. Including the Dyna S ignition, dyna coils, and new key switch( bat, ign, acc.).

750four · « **Reply #11 on:** June 09, 2011, 09:31:31 AM »

Please do the following BEFORE installing Rectifier/Regulator

· Check the AC output of the stator (I think I had 7.2 ohms)

· Check that the stator is not grounded

· Replace any burned or corroded connectors on stator & rec/reg

· Check & repair any melted wiring

· Use hi-Temp Dielectric grease on all connectors

scottly · « **Reply #12 on:** June 09, 2011, 10:28:08 AM »

The white wire from the reg connects to the white wire on the field coil. The black wire from the reg connects to the ign sw. Both green wires on the reg, and the green field wire connect to chassis ground. The red wire from the reg connects to battery+.

Syscrush · « **Reply #13 on:** June 09, 2011, 11:10:56 AM »

Quote from: 750four on June 08, 2011, 04:06:11 PM

So the reg/rec is a rick's unit 10-100. It does mention not grounding. So if I run the ground from it to the battery than I can't ground my battery to the frame? I need to redo some wiring now.

No R/R will require you to not run a ground strap.

750four · « **Reply #14 on:** June 09, 2011, 06:56:45 PM »

Check the pic above. I have the red going to the field + and the green to the ground in the field. The white is ran to the battery terminal and the black goes to the key switch ignition. We all know where the yellas go. The other green ground is not tied down at the moment.

Because...I tried to ground it to the battery and not ground the battery to the frame. That didn't work. So I grounded the battery to the frame and the reg ground is free. Still runs when its grounded also.

also on another fun note. I did try a honda chopper wiring diagram. Which gave me the result of not being able to use the off switch on my key...hahaha duh

I did readjust my valve tappets, carbs, and timing again. Took it for a short jont and still cant help but love this bike to death! Sounds good, runs good, pulls hard, did my first garage burn out hahahaha.. Cant help It.

Even with the small issues I have no chioce but to invest my time and money because I definately feel it will reward me.

scottly · « **Reply #15 on:** June 09, 2011, 08:35:42 PM »

Quote from: 750four on June 09, 2011, 06:56:45 PM

Check the pic above. I have the red going to the field + and the green to the ground in the field. The white is ran to the battery terminal and the black goes to the key switch ignition. We all know where the yellas go. The other green ground is not tied down at the moment.

Yeah, I looked at your pic, as well as one on Rick's site. Wire it the way I said in my last post....

750four · « **Reply #16 on:** June 10, 2011, 05:03:45 AM »

OK, it's worth a shot. I've had the harness cut off awhile ago so I really can't remember how the thing was routed...LOL. Guess that will teach me.
Thanks

750four · « **Reply #17 on:** June 10, 2011, 03:10:07 PM »

Scottly. You're the got darn man! You were right on. I checked the battery before the start and it was at 11.5 . After thestart and about 90 seconds of higher idle off and on. Turned off and sitting and 12.3 ish. For now I know it is at least sending the charge. Now to see if the stator and all that mess is working hard enough to keep me rolling.
Thanks a ton!

scottly · « **Reply #18 on:** June 10, 2011, 07:07:14 PM »

You're welcome!

I wouldn't worry about the stator, but I would relocate the reg/rect to a cooler location, like under the seat.

Syscrush · « **Reply #19 on:** June 10, 2011, 10:51:52 PM »

Do a bit of research and find out if your R/R is a MOSFET type (good) or SCR type (bad). Consider changing it to the good type if it's the bad type.

750four · « **Reply #20 on:** July 19, 2011, 10:04:45 AM »

Quote from: Syscrush on June 09, 2011, 11:10:56 AM

Quote from: 750four on June 08, 2011, 04:06:11 PM
So the reg/rec is a rick's unit 10-100. It does mention not grounding. So if I run the ground from it to the battery than I can't ground my battery to the frame? I need to redo some wiring now.
No R/R will require you to not run a ground strap.

Maybe I'm not not reading this correctly....but it seems that my bike was charging when I had the reg/rec ground connected to the stator. That's after I moved the black to the ignition, the white to the stator, and the red to the battery.
I tried grounding all grounds to the chassis and now it's not been charging. I'm thinking that the reg/ rec should be grounded to the stator and the other to the frame? battery to the frame too? But which one to where?? reg/ rec has 2 grounds, I guess I have a 50/50 shot...

Syscrush · « **Reply #21 on:** July 19, 2011, 10:14:13 AM »

I like to run a R/R straight to the battery, and then a ground strap from the batt to the frame and/or engine. Everything else that needs ground can get it from the frame or engine.

750four · « **Reply #22 on:** July 19, 2011, 02:23:05 PM »

How about the stator ground wire? Grounded by frame or connected to a ground from the reg/ rec?

States on my Rick's combo to make sure that the stator is not grounded...
Also, I've read that some charging systems use the ground to dump extra voltage.

Syscrush · « **Reply #23 on:** July 19, 2011, 02:51:37 PM »

Quote from: 750four on July 19, 2011, 02:23:05 PM

How about the stator ground wire? Grounded by frame or connected to a ground from the reg/ rec?

States on my Rick's combo to make sure that the stator is not grounded...

I don't know enough about these bikes to give specific advice on that.

Quote

Also, I've read that some charging systems use the ground to dump extra voltage.

That's how an SCR or FET type voltage regulator works, by shunting current to ground.

750four · « **Reply #24 on:** July 20, 2011, 04:15:41 AM »

yes, I was wondering if the shunt was returned into the field coil for some reason? Is there an option to switch over to the permanent magnet, single phase charging system?

I put together pma for my xs 650 with a banshee flywheel, older ninja coil, and a reg/rec combo deal. It even runs off of a mini 12v battery. Runs like a champ. I wish we could figure out a swap for the sohc.

My CB has given me so much trouble, I'm thinking of parting it out and finishing my Yamaha. $:-\$

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Author Topic: 71' CB750 ..I'm hooked! but trouble in paridise? (Read 4553 times)