Hi guys,
since few days my bike (cb400sf) started acting funny:
the rear light is always on even iwhen the lights switch is off (i’m not sure though if it has always been like this),
the indicators work only if the headlight is on and the headlight has an intermittent power loss following the indicators signals
when cold the idle drop instantly and to restart i have to switch the lights off otherwise it won’t start…
when opening the trottle i notice a light power loss in the headlight, mostly when cold, almost visible when hot…
the battery seems fine as it starts at first touch every morning with no esitations
any suggestions where to look?
maybe some fuses? some wire that earth somewhere it shouldn’t?
Start checking wires at pinch points and places they move like up around the headstock . Check all your connections earth frame and plastic . behind the fuse box is often a good starting point .
What NumNum said, but I’d start by making sure all the earth contacts are clean and sound. It’s quite staggering what a lost earth connection can do to the rest of the electrical circuits.
mmmm, do you know where are those connection earths are usually in a bike?
how do i recognise them, are they basically like a wire that somehow touches the frame for ex.??
Well, thet all vary a bit but all modern bikes are “negative earth” so they are neutral conductors using the frame (and some other connected parts) as that side of the circuits.
Sort of logic:
The battery connection to the frame. (Doesn’t sound as if that’s an issue if the starting is good, but check the N connection at the battery and the frame in any case. Clean and apply Vaseline/reconnect. So you’ve wasted 5 minutes?)
Engine to frame. As above.
Fuse board to frame. As above
Then start hunting out other connections to the frame, they can be in stupid places. As above. Look in the handbook and count the connections. Wont tell you where they are, but at least you will know how many you are looking for!
So you have now eliminated the earths thing but no improvement? Not time wasted. You’ve done an often skipped maintenance job.
Then you are in to NumNum’s list.
It was the earth connection that often lives behind the fuse box was what I was pointing towards … I was on me phone and driving ( not on the public road ) so typing is awkward … Quick as I could was the key 
Two people with the same idea on an electrical problem. That don’t happen too often.
Whats the odds now on us both being wrong and it being a break on the negative side of some silly electrical sub-circuit?
I would not bet the underwear drawer on it that is for sure 
thanks a lot guys,
tomorrow morning i will have a proper look at those points you mentioned, if i find them :)…
the indicators and the clocks are after market so i’m wondering if the previous owner messed up something when fitting them…
let you know how it goes…
sounds like some1 has wired in the indicators with the headlight and this may be cause of power loss if the 1 feed is supplying headlight and indicators.
if you have no joy get it to steve hallam in croydon 07870280288
so indicators should have a separate wiring then, i’ll check…
to clean the connections will some wd40 do the job??
No, WD40 will not clean the connectors. It will drive out any water but will not clean.
Ignoring broken wires, the usual reason for a connection going down is corrosion. What usually works for "cleaning those is to take the joints (plugs, terminal connections and the like) apart and put them back together again several times so that you mechanically clean off the contact surfaces.
You can buy “switch cleaner” stuff but I’ve only found that to work when you can get in with a bit of cloth and rub the surface with the cleaner. On car/bike electrics you just can’t get at most of the surfaces.
Or you can buy a little brass brush from a tool shop . Looks like a toothbrush but with brass bristles .
And you can get one of those into the female side of a multi-pin plug?
When’s your next demonstration of walking on water?
You use your long nose pliers and pinch a tuft . Being brass it stays pinched then you jigly it in there . You get the first third clean and it makes a fine job of the male side which in turn makes a nice job of the female side as your not sliding gunk over gunk . Its much easier than papering the male pins individually too . Technique and style is everything 
Interesting subject. Hope you got your electrics sorted Pepiino.
I’m planning (hoping/fantasising) to do a complete frame upwards restoration of my 14 year old hornet.
I think the engine is good - but the bike has had a hard 46,000 mile life and has been ridden through every winter including the ones with the ice, salt and snow - and it shows.
I really want to rejuvenate the electrics as the system is showing signs of distress (battery possibly not charging like it should, headlight coming on 4 or 5 seconds after the switch is turned on etc).
I would love to just fit a brand new loom - but for practical/budgetary reasons I guess I am going to have to get to grips with cleaning the connectors myself (looking keenly at Oldguy/Numnums techniques here).
I really don’t know where to start - this will be my first total strip down and rebuild and I am already checking out two speed drills and heat guns in anticipation of the bolts and screws that are bound to be completely fused by now.
The bike has always been my winter hack and runaround - so part of me thinks sod it - i’ll just part ex it for a newer 600 (probably and sv650 or something) - but on the other hand restoring it is the tougher but ultimately more rewarding route (hopefully).
Yes … Rewarding … Thats what us idiots who attempt things like kreditkrunch and the rat tracker call it . In private we curse our addiction and spend much time between parts arriving and bolts snapping lying in bed unable to sleep and wandering into the garage at 3am to see if any fairys are stealing things and moving stuff when we not watching .
Hi guys,
sorry i couldn’t connect this weekend,
so i checked and cleaned all the connections and found the + pole at the battery a bit loose, that was probably causing a non sufficient power supply to the system, sorted!!
(the rear light still on all the time but i don’t mind it…)
while checking i noticed a wire earthed to a metal plate underneath the tank ending in a female spade connector actually not connected to anything, what that may be???
If at all possible see if you can get hold of a wiring schematic for your bike. I found one for my bike on the internet and just re-wired my entire bike thanks to that schematic and everything actually works! It should show where every wire goes and from that you can work out what that loose cable you found should be connected to.
Ha! 
yeah - I totally recognise that experience - based on past mistakes and experience I am trying to plan this one meticulously - by working out exactly what I am going to do and need beforehand - and having parts diagrams, notes on parts suppliers etc all ready for when I need them + I am going to take loads of photographs before dissassembly and put everything in bags with labels so I don’t forget what is what and where it goes.
Even so - I still know It’s going to be a bugger and I’m going to run into unexpected problems and have to learn new things and buy new tools. My biggest fear, the thing which actually creeps me out - is the inevitable seized and snapped bolts - which are gonna require heating/drilling etc - this is something I do not have much experience of and have c0cked up in the past - and I really do not want to have to learn how to use helicoil inserts if I can help it.
So when it comes to the drilling I am gonna read everything I can on proper technique and take loads of time over it. :unsure:
Yeah - it’s a form of masochism to be sure - I guess it’s like a bondage session when you know there is gonna be pain, frustration and tears but you do it for the warm glow you get afterwards (if it goes right) 
