Testing Voltage

andyw · Post by **andyw** » 23 Nov 2004, 14:45

I have a mark III with a faulty cdi unit (i assume) as the powervalve is not working. Now I know this can be down to the reg/rec giving out too high a voltage (more than 13.5v).
My problem is what happens if the voltage reading is only around the 8.5v this has been measured at the capacitor behind the headlights and also at the headlight bulb itself. the reading doesnt change regardless of the lights being on or off.
Question is if I replace the cdi will it blow or do I need to replace the reg/rec?
Your advise/views would be appreciated.

ps
I am based in Leic (anstey/cropston area) does anybody know of any legit places to ride?

chrizm · Post by **chrizm** » 23 Nov 2004, 17:46

I dont know alot about bike electrics but would check the input & output to the regulator, assuming it has one?

I will have a look at the wiring diagram later when I get in and re post.

I`m from Mansfield in Notts and all I seem to do is keep going up the desert! There is a meet there next weekend on the 5th & 6th if ur interested. See rideouts.

chris.

phil1 · Post by **phil1** » 23 Nov 2004, 20:42

i replaced the reg/rec at the same time, as having just spent £300 on a CDI and being told it can be damaged by a bad reg thought it better to change it, i am not loaded just couldn`t afford 2 cdi`s.
if you have 2 buy new, go to dave silver spares, the 3-4 week wait is rewarded by 25% discount worth around £130.

Chris · Post by **Chris** » 30 Nov 2004, 12:27

Hi mate,

Think i have the same problem, with my MK 111. The power valve \"flickers\" when you rev the engine, but does not seem to open up. When riding the bike, its OK at 25% throttle, but as soon as you open it up any further, it just feels like the choke is on.....and sounds like wauuuuurrrbbbbbbp !!.
I have done all the usual checks: sidestand/killswitch/thoroughly cleaned the carb/new plug/new fuel/airfilter/checked the reed vale/changed pipes & silencers.

Anything i have missed out....anyone ??.

If not looks like a new CDi & Rec.

Chris

pearse15 · Post by **pearse15** » 10 Jan 2005, 23:39

A recitfier can dammage the CDI as it converts the AC voltage produced by the engine into a DC voltage which operates the CDI. If the rectifier packs up, then it puts an AC voltage across the CDI which isn't nice. I'm not sure how one can be checked, as you'd still measure an output with a multi meter on the DC/AC range due to back readings etc. An electronics shop might have means to test it. M and P do a universal rectifier for £45

If i'm talking bollox then ignore me, it's late, lol

regards, adam

CRMR · Post by **CRMR** » 11 Jan 2005, 16:44

I think its a combined rectifier and regulator..one circuit rectifies the voltage into dc volts and the other regulates it to a constant output , which should be around 13 to 14 volts . the norm is \"\"If you get a high voltage reading then you could assume you have fried your cdi.

But as you have only 8.5 volts outputting then i think your lucks in ,,I would first check my loom for dirty or loose joints specialy round the rectifier unit, if that dosnt do it ,i would then disconnect everything that isnt needed to test the bike ,, ie all lights , switches horn exct ,If somethings slightly grounding itself to frame earth then this should help to find it..every time you disconnect a section , (like the tail end ) retest the voltage to the front light wires,, Remember , your looking for 13.14 volts dc on a meter

see how you get on , im only around the corner from you in glenfield ,, Matbee ill ave a look for you ,at weekend

edarter · Post by **edarter** » 11 Jan 2005, 17:24

hmmm....8.5 volts could also mean the rectifier has gone and what you are getting is your DVMgiving an average of an AC voltage, just a thought....

CRMR · Post by **CRMR** » 11 Jan 2005, 21:51

if his dvm's set on dc then itll ignore any ac anyway..Easyest way to check it is to change the leads around on the meter ,, if it says \"- 8.4 \"volts then its looking at dc cos its spotted the polarity wrong on the leads and giving it a minus figure , ac will give it a figure either way??

pearse15 · Post by **pearse15** » 12 Jan 2005, 18:25

Like CRMR said. sounds like a bad joint. Check the main grounding earth to the frame, moisture etc can cause them to rust up. Bit of copper grease on joints helps