Morning All.  New to the forum so apologies if this has already been covered.  I resurrected my '77 DT400 during lockdown (I've had it 25 years but it's been mothballed for the last 10 years....kids!). In true 'stroker style it started in the second kick.....awesome.  The electrics always used to be poor, I just put it down to 6v.  Now I'm old and sensible I thought I'd better get to the bottom of it.  Basically everything works off the alternator (ie engine running, lights good etc....but the horn is barely audible), but nothing works with just the ignition on (it's the original 4 position switch). I'm getting volts as far as the rectifier but I think it splits prior to that and goes to the switch.  Any ideas or previous experience would be greatly appreciated.  On a similar note, can anyone recommend a 6v battery available in the UK, the eBay special is rubbish (won't charge above 4.6v......but the lights should still work, just dim, right?).  Thanks in advance.

 from Salisbury, Biggles!

Re the horn, if there is a small adjusting screw/bolt on it, then screw this into different positions (in and out) to see if it makes any difference. You can remove it from the bike and do this on the bench, wired direct to the battery.

Talking of which, is the original (Yuasa?) still available through your local dealer? Some folks have used gel batteries with success, although sometimes you have to adjust the connections and battery orientation.

You'll need to look at a UK ignition switch "legend" to determine which functions work in which key position (US will be different). A European market Service Manual would be a useful thing to have for this.

Over time, of course, some of the electrical connections deteriorate and so benefit from a good clean, particularly the earths.

There are 12v conversion kits available, but fitment of those is out of my comfort zone!      

Thanks for the info. The horn works fine off the bike with a 6v supply so need to do some more digging and yuasa batt ordered. Cheers.
 

What handlebars are fitted - chrome, painted? Some of the switches might take their earth through the handlebars, and it's not unknown for paint, plastic, rust etc to interfere with this.

It's a '75 so chrome.  Funnily I always thought it was a later bike as it's a '78 reg but according to the chassis number it's a US '75. Wierd that it should be imported after a couple of years....but what do I know? So on the way back from picking up my new battery I discover that the head gasket has a slight leak.  So I'm going to take the head off as a priority over the electrics.  It's probably about time as I've had the bike 20 of years and never had a look inside (if it ain't broke, don't fix it being my motto, though sadly it now is!).  I'm going to trawl the forum, but any top tips appreciated.  Also, decompression valve; can't get the little o-ring for love nor money. Is it something Gucci or just a heat proof standard 5mm x 1mm?  Thanks again.