Multimeter is going crazy (strange readings)

Hey there DTT!
I'm not too good with bikes yet and have been working on my first bike for about a year now, but hopefully getting better.

I've finished everything on my 74 CB200 accept an electrical problem I've run into.

The bike dies after riding less than 20miles. The spark cuts off and engine braking slows it to a stop. Let it sit for a few minutes and it'll start back up then ride a little longer till it dies again. I'm able to limp home this way.

Friends believe it's a bad charging system or maybe an old coil that get's hot and stops working till it cools back down. I don't know.

When the bike is not running I take my multimeter to check my battery voltage when the bike is off and it reads close to 12v. Cool. But if it's running my multimeter goes crazy. 18v then 5v then 20v and so on. Moving so fast I can barely see it. The meter doesn't even have to be touching the bike. It freaks out anywhere within 3 feet of the bike on every setting on the meter, almost as if there's an electrical field or something.

What does this mean? Has anyone heard of anything like this?

I can't figure out what's wrong with my bike without being able to use my multimeter. And it's a good brand name multimeter, but I've also used other meters too, so I don't think it's the meter's fault.

Any help is appreciated! Thanks guys.

I'm not the expert that is going to reply to this with the best answer but I can give you a starting point... Are the regulator and rectifier original? If so look up the checks you can do to verify rectifier and regulator operation and do those. It could be that one leg of your stator is sneaking some ac current into your electrical system...

Yup. Replace your regulator. The fluctuations probobly ruined your battery also.

What type of meter are you using and are you setting it to the correct settings? NOT AC voltage for instance? Picture or link helps here.

A battery that is good will read above 12.5 volts at rest. BEST to charge yours fully then test.

What has been done to the bike? Is it stock charging parts or aftermarket? How much has it been messed with.

Honestly sounds like you are not charging at all, the battery will regain a small amount of charge and allow you to run for short periods.

Have had the exact same problem with the same bike (sans the freaking out @ 3feet).
Replace the rec en reg with the kohler one. http://www.hondatwins.net/forum/viewtopic.php?t=14530

Works like a charm!

A battery should not read near 12v, it should read above 12v. If fully charged its still below 12, replace it.It will drown itself.

Gonna try and renew this thread. I'm currently having the same issues. I have a pair of SL100's and one of them is having a charging problem. Its kinda hard to diagnose because the multimeter goes nuts when around the running bike. Even when the leads aren't attached.

Also, the rectifier seems good, after doing the continuity test described in the manual.

I get normal multimeter readings from my other SL100.

Going to recheck the entire loom and make sure the stator is attached nice and tight.

Any ideas from anyone?