Rectifier earth. Lm

On my newly running rebuild, the charging system was not working, and so after much head scratching, checking correct connections and continuity checks etc I have eventually got my charging system to charge on my rebuild. The cure was to put a dedicated earth on the rectifier, and out went the ignition light and charge into the battrey. When I dismantled this bike I do not recall seeing an earth to the rectifier and so presumed it earthed itself through its mountings (as I saw an earth on the wiring diagram). So my question is…is one earth suficient and is there a preferred way to earth the rectifier?

what bike is it? if its a T3 type the rectifier earth wire must be routed from one of the two bolt holes on the bottom of the unit, the top of the unit (where the heavy red ‘live’ wires fits) is the ‘live’ side and the bottom is the earth side. on my T3 I have run a wire from the earth point under the tank where the H/light earths etc are run to, you can really earth it at any suitable point on the bike and yes one wire is enough.

northwest2013-04-09 19:31:26

Thanks for that info. northwest wrote; what bike is it? It’s a LM.I have earthed it on the bottom hole as I wasn’t getting continuity from the top holes on my multimeter, so worked out that I had to use the bottom hole, but didn’t think of one side being negative and one side being positive but now you mention it it all makes sense. I have just been looking at the parts list for my bike on the Steine Dinse site and now notice that there is an earthing wire “17748500” for the rectifier. Doh!

I tend to run any extra earths back to one of the mudguard bolts behind the battery and then link that to the -ve of the battery for good measure.

Good advice Don. Thank you.

Best earth is to keep it short to the frame, make very very sure the main battery earth IS a BIG cable and is clean and tight, then add earths at every point I just added an extra earth at the headlamp and the tail lamp, the difference in light brightness is very noticable…On Tonti bikes there is an earth "cluster under the front of the tank on the right hand side you really have to look for it to see it tho, about 3-4 earth wires there

Think that uses one of the bolts that secures the multi-plug mounting plate to the frame, make sure all that metal is clean and shiny underneath the bolt, including the tag-washers, no paint no rust, had to do it a couple of times I think

One other tip is to use one of those sprag washers with the sharp bevels on it to ensure it bites into the metal I always cover with a smear of good old vaseline as well as it keeps a good contact and stops corrosion, I have it on my Spring and Autumn check list to recheck too

Well worth writing your own service schedule and check list I tend to have mine spread out and it is in a ring binder with the pages in plastic folders so they don’t get grubbyit does mean there is almost always something t do BUT rarely hours and hours of somethings as it IS split between 3 bikes and 2 cars…but the play off is rarely a vehice ever failing an MOT and rarely one breaking down “on road”

If you work it out for your self it does become a good way to keep on top of even basic checks and mtce, one other thing I do is leave a marker if anything is left undone over night, …better that than forgetting to tighten something.