Electrical woes on a Rebel - Honda Shadow Forums : Shadow Motorcycle Forum
 
LinkBack Thread Tools
post #1 of 9 (permalink) Old 09-02-2008, 10:44 AM Thread Starter
Member
 
highlandman's Avatar
 
Join Date: Sep 2006
Location: Simpsonville, SC USA
Posts: 902
Electrical woes on a Rebel

My son rides a 1999 Rebel 250. About 10 months ago it died -- no spark -- and after the usual fiddling around looking for the problem, I replaced the ICM and it ran fine.
Lately he's been complaining about the battery being weak. It wouldn't start on Saturday so I charged the battery for him and here's where things get interesting.
After 2 hrs on the charger (at about 1 amp) the voltage came up from about 10.5V no load to about 13 no load, but as I watched the voltmeter (charger disconnected) it was gradually running down. So I let it sit for a couple more hours, and it ran itself down to about 12. Another hour on the charger and it seemed to be holding steady at 12.5V.
So I took off the charger and cranked it and she started on the first rev, and was running sweet. Out of curiosity I put my meter on the battery terminals and I was reading about 13.5V at fast idle.
The obvious thing to do next was to rev it up a little and see if the charging circuit would kick in. At about 1500rpm (no tach, just by ear) I saw a voltage of 14.55 and then it died. Just went down like somebody hit the kill switch. And won't start at all.
I've checked the usual things, and I have no spark again on either cylinder. (Now that the battery is charged it cranks like crazy though.)
So did something happen to take out the ICM? Could a voltage of just a little over 14.5 kill it? (I would have thought it had a higher rating.) If so, is it a problem with the regulator? Could it even be -- strange as it sounds -- something I did with the DVM?
Ideas? Anybody know what I should be seeing at the battery terminals on this bike?
Thanks
-Glenn
highlandman is offline  
Sponsored Links
Advertisement
 
post #2 of 9 (permalink) Old 09-02-2008, 12:46 PM
Senior Member
 
Join Date: Aug 2005
Location: Elvis land
Posts: 2,030
My daughter has a 2006 Rebel. Battery must be a weak point as hers did not last a year and it was on a battery maintainer 24/7 when not in use. I put in an AGM. We'll see how long it lasts.

Any who, I'll measure my daughters battery tonight while running and get the results back to you. No I mean I'll stand still and have the bike running.

Three things that are not long hidden; the sun, the moon and the truth.

2005 Aero


1972 Honda XL250 Motorsport
2006 Rebel - daughter (Now gone)
1974 XL100
thunderglass is offline  
post #3 of 9 (permalink) Old 09-02-2008, 01:03 PM Thread Starter
Member
 
highlandman's Avatar
 
Join Date: Sep 2006
Location: Simpsonville, SC USA
Posts: 902
Thanks Thunderglass -
I found a wiring diagram and it looks like there is no connection between the battery/charge circuit and the CDI module. The module gets power off its own coil on the alternator. So very doubtful high batt voltage did any damage to the box.
I'd still like those numbers if you can get 'em though.
Anyone have any other ideas what might cause premature $120 CDI failures?
Thanks
-Glenn
highlandman is offline  
post #4 of 9 (permalink) Old 09-02-2008, 01:36 PM
Senior Member
 
tubes_rock's Avatar
 
Join Date: Jun 2006
Location: Northern NH
Posts: 5,233
The ICM must get power form the battery/charging circuit unless it has a magneto or something. I don't think they do. That coil on the schematic is probably the pulse generator. It uses that coil to make a pulse every revolution to tell the ICM the position of the crankshaft so it can time the spark.

--Justin

Currently Running Stable:
2010 Honda NT700V
1986 Shadow 700
1986 Honda Trail 110 (Postie Bike)
1987 Honda Rebel 450
1973 Honda Mini Trail 50
tubes_rock is offline  
post #5 of 9 (permalink) Old 09-02-2008, 01:55 PM Thread Starter
Member
 
highlandman's Avatar
 
Join Date: Sep 2006
Location: Simpsonville, SC USA
Posts: 902
Well, I was convinced of that too until I found this:
http://www.rebel250.com/rebelforum/viewtopic.php?t=3808
(I know it's not the right year but I don't think they changed before the early 2000s)
The two y/b wires are the coil primaries, the dg is ground, and the l/y is the pickup signal. The b/w is the kill circuit (and I think they have the on-off reversed on the kill switch). That just leaves the r/b wire, and it comes from a separate coil on the alternator. There's no connection I can find between the CDI and the main circuit except for the common ground.
When I get home I'll pull that and see if there's an ac voltage on that r/b wire, among other things.
I'm still irked at the thought that this might be a weak point in the system. It's supposed to be Honda reliable, right? (Which would mean that I caused it, and I won't be happy until I figure out how.)
Cheers
-Glenn
highlandman is offline  
post #6 of 9 (permalink) Old 09-02-2008, 03:40 PM
Senior Member
 
tubes_rock's Avatar
 
Join Date: Jun 2006
Location: Northern NH
Posts: 5,233
Wow, if I didn't know better, I'd say that was a magneto! The ignition switch grounds the CDI unit when it's "off" and leaves it open when it's on, just like the kill switch. That's how magneto systems go together. (It's a lawnmower ignition system!)

Also, most of the "powered" ignition system, like in the Shadows, use a TCI (transistor ignition system), not a CDI (Capacitor-discharge ignition.) CDI is what many magneto systems use. Craky, this is a magneto!

--Justin

Currently Running Stable:
2010 Honda NT700V
1986 Shadow 700
1986 Honda Trail 110 (Postie Bike)
1987 Honda Rebel 450
1973 Honda Mini Trail 50
tubes_rock is offline  
post #7 of 9 (permalink) Old 09-02-2008, 06:35 PM
Senior Member
 
Join Date: Aug 2005
Location: Elvis land
Posts: 2,030
Here's the info. measured at the battery.

Ignition off = 12.8 volts
Ignition on, engine not running = 12.23 volts
Engine running at idle = 12.50 volts
Engine running at about 1/3 to 1/2 throttle = 14.80 volts

Hope this helps.

Cheers.

Three things that are not long hidden; the sun, the moon and the truth.

2005 Aero


1972 Honda XL250 Motorsport
2006 Rebel - daughter (Now gone)
1974 XL100
thunderglass is offline  
post #8 of 9 (permalink) Old 09-03-2008, 08:58 AM Thread Starter
Member
 
highlandman's Avatar
 
Join Date: Sep 2006
Location: Simpsonville, SC USA
Posts: 902
Okaaaay....

Thanks, thunderglass, those numbers match mine pretty closely. The battery seems to be holding its charge well, too.

As for the spark:

I pulled the tank and seat last night so I could get at everything. Popped all the connections and measured resistances of the coils, the exciter, and the pickup. Measured voltage from the exciter and the pickup. All apparently functioning. Measured continuity on all the relevant points of the wiring harness and ruled out any shorts. Measured the function of the kill circuit (Justin, I was right about the kill switch - the contacts are reversed on that diagram). Everything was fine.

So I snapped it all back together and gave it a crank ... and ...
... it started on the first rev and ran fine.

I suppose there was a loose connection somewhere. Oh, by the way, I did try to crank it before doing any of this stuff, in order to try to rule out an intermittent problem inside the CDI. So this isn't 100% conclusive, but I did feel like one of the molex connectors on the CDI wasn't seated as well as the others.

All in all the battery/charging thing was a red herring; the problem was that he was running the battery down because the spark wasn't consistent.

Anyhoo, thanks for the help and the info.
-Glenn

PS I love cheap repairs.
Oh, and there is one small difference between what I have and the diagram I linked to (at least in this particular circut). Instead of two separate coil primary wires, both coils come from a single primary connection and the extra pin is connected to the side stand switch.
highlandman is offline  
post #9 of 9 (permalink) Old 09-03-2008, 09:21 AM
Senior Member
 
tubes_rock's Avatar
 
Join Date: Jun 2006
Location: Northern NH
Posts: 5,233
Well, that's great news! I love cheap fixes too!

Interesting system that the Rebel uses. it's simple as all get out, and that's probably why it's so reliable. (When the wires are all connected!)

--Justin

Currently Running Stable:
2010 Honda NT700V
1986 Shadow 700
1986 Honda Trail 110 (Postie Bike)
1987 Honda Rebel 450
1973 Honda Mini Trail 50
tubes_rock is offline  
Sponsored Links
Advertisement
 
Reply



Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Honda Shadow Forums : Shadow Motorcycle Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome