125 SM Won't Start

[125supermoto]

Was leaving to work, hit the start button and it wouldn't do anything just the tick-tick.
Has a fully charged battery, 12.8 volts, replaced the starter selenoid, replaced relay #19,
bypassed kickstand safety switch, cleaned and double checked all connectors,
moved them around hitting the start button, nothing.
Here's the funny thing: when I bridge the selenoid, it cranks right up.

I am running out of options if anybody could help me out I would really appreciate it.
BTW, the bike is stored inside a garage and is well kept.
Thank you and hope to hear from you guys.

[125supermoto]

forgot to mention that this bike has never blown a fuse nor has it had any electrical
problems before. could it be the diode inside loom?

[DAVID THOMPSON]

under seat unplug the 2small wires to the start relay and check the wires with a volt meter
is there power on the 2 wires from harness when button pushed
handle bar switch not sending power to relay maybe

if there is then check coil in relay with ohm meter to see if coil is good
mine went at 1500 miles
if start relay replaced then handle bar switch or its power supply is out
dave

yamaha relay part number 4KD-81940-00
dave

[125supermoto]

checked the purple wire that goes to the start relay when pushing the starter switch and have 11.5 volts.
can you tell me the ohms readings for the coil. the bike starts and runs fine once I jump the solenoid.
Thank you Dave

[DAVID THOMPSON]

check the brown wire it should be a good ground ..it grounds other side of relay

i need to get a battery for my meter to read the coil ohms
and its dark here now so tue afternoon answer on coil ohms
dave

[125supermoto]

found problem, shut-off relay attached to the rear wheel mud guard ( not the one in the front known as relay 19 )
Thank you for the help Dave.

[DAVID THOMPSON]

what is it's number on the wiring drawing if you know
dave

[125supermoto]

Dave, don't see it on the wiring diagram but here are some pictures of the shut-off relay on the rear of the bike on the
SM/SX model. I believe the RT does not have one in the back. don't know if it has it somewhere else. also found the diode 31 but that was not the problem. It has the same part number as relay 19

[DAVID THOMPSON]

it appears to be the same relay wires all same color its just located in a different place
on the sm
on the rt its on the front side of the battery mounted to the frame

it controls most of the bike
red/black and red/white

make a spade lug that fits to the lug on relay where the green wire connects and hook to battery minus or ground
this is a good check if bike still runs bad its the relay if it runs ok then problem is in the kill button/side switch neutral lamp circuit

this is where i thought the problem was in the relay ... it is just located in a different
place on the bike...
i have never seen an sx or sm in person the dealer was out of stock when i got my RT125
now i know where to tell an sx/sm rider to look
dave

NOTE there may be more wrong than this as what info i am thinking about from emails and posts
for this malfunction is not totally making sense sort of like 2plus2 equals 3.75

[125supermoto]

Dave, the SM/SX model have two identical relays one under the front top tube and the one in the back. I had one spare that I bought from grahams and replaced the one in the rear and problems solved. here are some pictures of the front one.
I was getting 12v readings in the front one when pressing start switch.

[125supermoto]

Dave, finally found a wiring diagram that shows both of them. Thank you for your help. Gus

[DAVID THOMPSON]

after some deep thinking i do think we are looking at the relay that turns off the head lamp when starting...

at least its a relay
BMW let the lamp ground Return go back through the starter armature on one of there bikes
when you crank the head lamp goes out neat idea no relay ....except
this causes blinking headlamp when the brushes get bad and dirty ....
so you bump start bike but can not go at night because of no headlamp
sucks big time i hate bad "good ideas"

i need to do some more looking this winter as i had a funny buzzing
noise when i went to start the other day

i have that one on mine
it must be under the tank
and i have not found it

i like to know the electrical system on my bikes well
as i some times on a Saturday wind up many miles from home on the 125
its not fun to call home for the truck
dave
wrote this while falling asleep so it may read funny

[DAVID THOMPSON]

after some more looking
it appears the rt has 2 relays also one by the battery and one on the right side under the gas tank
dave