stalls when i turn lights on

[alanjw]

hi all ,got a 1990 906 paso and if i turn anything electrical on when the bike is ticking over the engine cuts out ,lights ,indicators ,brakes or horn etc . The reg/rec seems to be ok ,battery been on an optimate and says ok (12.8v and 12.4 v on tickover ) any help much appreciated as not confident on getting bike out .many thanks

[englishstiv]

I can't be 100% sure on this but I had an old 860 GTS that did this and it turned out to be an earthing problem on the brake light, never blew a fuse but would stop. It sounds like it could be something similiar, the other way to look is to run with a meter attached and see if power is being drawn away or insufficient.
As with anything like this it may be a case of disconnecting all the the light wires from the loom and then reattaching and waiting for the rogue wire to appear.

As an aside were you in North Wales two week ago on the weekend as a nice 906 passed me going the other way sadly I was stuck in my van?

[ducapaso]

maybe leak/rusty contacts in main switch or wiring connections.
TRy to bypass the electical plant with a shortcut from battery to ignition fuse or to orange wire on ignition coils (is the +12v on coils "orange" )

[JWilliam]

I had this sort of problem when mine was new. A number of reasons for it, low primary coil impedance (replace with coils from a GPZ 500s), low voltge at Digiplex ignition unit (create relay bypass circuit). Those two helped a great deal so now the ignition is 100%.

[alanjw]

thanks for the tips gents ,cleaned as many earth points as i can see tried it and seems alot better ....will keep going !! not been on bike as yet since falling off last october on way to mot slow speed not too much damage .... had nos tyres fitted and fell off on first junction at 10 mph !!!
since cleaned tyres with sand paper to roughen them up .........will that be enough? or are the tyres too hard too grip (dot no 0405 ) ... obviously somewhat wary of going out again ....... do they need a long time to heat up ??? etc etc
great site and good advice ....keep iyt shiny side up !!! ...obviously i cant !!
cheers alan

[jcslocum]

There are a few grounds on the bike. Strip the body off and look and clean. Particularly the one on the back of the engine behind the right peg area. There are some under the seat as well and maybe one up under the front of the tank.