OK, here's one for the electrickery wizards.....

As some of you may remember, a while ago I fitted one of Rick's trick reg/rec units and a new stator to my NC35. All stock charging system wiring was eliminated, and the reg/rec is directly connected to the new stator and the battery. So, all new copper everywhere. All connections are clean and in good contact, looking brand new still (and so they should do!).

Yesterday, I went out for a slight ride. 90 miles from Sussex to Bournemouth. Then a few miles to Wimborne. After that, I went to Henstridge Airfield as part of a convoy to raise money for a local kidney unit (there was a Rothmans NC24 too). Nothing untoward showing on my voltmeter.

When I left the airfield, almost immediately I noticed the voltmeter was reading low. Even though it reads barely 13V when the true voltage at the battery is well over 14 (I've verified this several times), the reading was low enough to make me stop and check everything I could get to. Nothing obvious found, although in hindsight I made some fatal mistakes. I decided to blame the meter for being crap, largely because it is. I also did the old check the headlamps glow when revving, and they didn't seem to, but I get pretty much full output just off idle so I figured I was being paranoid. After a few more miles with the meter disconnected, the inevitable happened and I arrived back courtesy of recovery.....

I found the problem immediately after grinding to a halt. The fuse on the output from the reg/rec had blown. Well, actually it hadn't blown, it had been incinerated, almost being fused into the holder! I could find no damage that would have caused a short, and surely a massive short would have dragged the battery to nothing pretty much immediately and toasted the wiring as well as the fuse which clearly burned over an extended period.

The recovery guy looked at the remains of the fuse and declared that it had failed due to poor contact within the fuseholder, and that it had caused excess resistance leading to it burning, and then exacerbating the original issue. I an sceptical, but have no better explanation unless it got toasted by having done 30/40mph in convoy for an hour and a half. The bike did not run hot, the weather was cool, and there were light sprinkles of rain. I use the same type of fuseholder for the low beam, and it lives in the battery compartment with this one. It is mint inside.

As yet, I have not investigated. I will of course measure for shorts, but I am a bit puzzled unless somehow it shipped in some moisture and fried. Mr recovery said not to panic and that he's seen it dozens of times, and that just replacing the burned holder will fix the issue. I just worry it's sign of something more sinister. It's been on there at least two years before dying. It was running a 20A fuse. The battery is quite new, and I went for a YTX9 as opposed to a stock YTX7. Plenty of others here have done so without issue, I cannot imagine it would cause an issue?

Anyone got any theories other than an iffy fuseholder?

Quick update. I haven't been back to my friend's place yet to tinker with the bike, however he's replaced the fuseholder, checked for suspicious drains or any obvious wiring damage, with nothing obvious found. The new fuse hasn't blown with the bike running for a few mins, and it is charging on all the right numbers.

Plenty of miles of test running will be done before I dare venture the near 100 miles to deposit the bike back at the usual place of residence!

Given no other identified issues, I can accept the explanation offered by your recovery man. Poor connection will initiate a repeating process that eventually result in the exact situation you experienced.

Well, I pottered around town last night and covered about 15 miles without further issue. Not the slightest hint of any unhappiness from the fuse of the holder. I'm going to give it another dose of the same in few days, then back to Sussex on Sunday. If I make it back without issue I'll close the book on it.

I noticed last night that the hooks on the front of the battery box have become weakened, resulting in the strap being able to ping off. I wonder if the battery bouncing about a bit (the fuseholder lives right above it) might not have helped? I still have an old undertray, so I'll take the metal hook off and rivet it to the front of the battery box so there's something a bit more substantial to hold it in place. However, I presume it's rubber to give a little cushioning upon impact rather than hold it absolutely in place like most car batteries? Or is it just to allow slightly different sized batteries to fit?