main fuse blowing on mz 125 sx....

[jayded1]

Any ideas what might be causing this? I'd start the bike ride about 300 yards and then nothing the main fuse is shot, that happened 3 times now it blows as soon as I hit the starter. can't find an intermittent short anywhere, i'm loosing my mind here please help.

[phlat65]

I would pull the timing cover so you can turn over the engine by hand, replace the fuse, and turn the engine over w/o the starter. if it blows then, suspect wiring at the magneto, or ignition system. if it does not blow, then unplug the starter relay, and hit the botton. do you have a multi meter?

[DAVID THOMPSON]

sounds like a short to ground some where inspect the wireing harness
for any cuts or breaks

the instalation of the harness was poor on my rt125
wires were chinched up to tight with the cable ties the wires to the
rear turn signals were streached so tight they were a tuned music insterment

take the gas tank off and inspect the whole system
as the bike has no kick start get some one to help you bump
start it with a new fuse if it blows there is a short some where

every electrical problem i have had with the rt 125 was traced
back to a poor quality wire harness and a bad starter relay
and the oem battery was junk

if it is a sx has it been dropped some thing may be shorted in the handlebar switchs

as 1 of your checks disconnect the front and rear brake lamp switches
the rear one has gone bad on me 2 times and may have
shorted to ground on yours

[jayded1]

Thanks guys, I'll try both suggestions. Yes, I have meter what volts & amps should I be seeing on the starter relay if it is not the mag wiring or ignition system?
My bike did take a fall about 3 weeks ago so I'll check the switches too. You are right about the wiring being tight! I've replaced the OEM indicators and added a little slack.

Thanks yet again, as soon as I can I'll give you an update as to what I've found.

Regards,

David

[DAVID THOMPSON]

if you have an amp meter use one of the old fuse pieces
to make a jumper to install a amp meter in line with the fuse
in an out board test rig
the headlamp is 12 v at 60watts with tail and ingtion system
about 7 to 8 amps
see my blog at
http://spaces.msn.com/members/wd8cyv/

for a drawing of test rig
THE DRAWING HAS BEEN POSTED
RIGHT CLICK AND OPEN LINK TO VIEW
OR
RIGHT CLICK AND SAVE TARGET AS
FOR A COPY ON YOUR COMPUTER
i am out of space here for pictures
WARNING AMP METER SHOULD BE ABLE TO HANDLE AT LEAST
20AMPS AND IF IT PEGS FULL SCALE GET IT DISCONNECTED FAST
ALWAYS USE A FUSE WITH IT

[Islander]

Also, if you disconnected your battery at all. Remember black is positive and brown wire is negative in the german wiring. I blew four fuses before I figured that one out.

[DAVID THOMPSON]

yes the germans use brown for ground

and in recent times some idiot started using black as a plus wire

when red , yellow or white were the hot ones blue = turn signals

and brown , black and green were the grounds
.....green = wire to netural sw from idiot lamps

now it is all screwed up
SO BE CAREFUL

[jayded1]

the key switch!

[DAVID THOMPSON]

?? was the key switch going bad or was it crap on the back of it where
the wires go in ??