So I've been riding her all week after the charge mentioned above. The commute is a gentle 8 miler with only a couple of open roads where I can open her up, mostly below 5000rpm. Bearing in mind that I have not been using my headlight dues to driving in quite bright conditions, I have not tested the voltages across the terminals yet, but the battery seems to be holding its charge.

I will give the voltages a quick once over tonight, and see how the battery tender reports on the health of the battery, but could this in fact be an electrical issue not rooted with the usual candidates? Of course if the battery tender does actually report the battery is very low again, its obviously the reg/rect, but I want to be 100% sure.

So my issue seems to have returned with a vengeance. I had new chain and sprockets fitted around 2 weeks back, shortly after which the bike refused to start in the mornings. Probably unrelated but I'm not an expert

So the problem is, the ignition makes a single, loud clicking noise and then sounds as though the battery is too flat to start the bike - but I don't recall hearing the click whenever I started the bike when the battery seemed healthy. This happens after charging using a Halfords battery charger, once the charger itself reports the battery as fully charged.

The bike bump starts fine, and the lights are fully working right off the bat, as is the dash and neutral light. I get the feeling there is something far worse wrong with her than just a dud battery ;(

I have not tested the voltage of the battery at full charge yet, but I thought I'd get this out there to see if anyone has any ideas. Will report back later tonight hopefully, once I dig out my multimeter.

EDIT:
Just took a reading after the bike refused to start - 12.45V across the battery terminals.

12.45 is very low and indicates the battery is quite heavily discharged. However, frustratingly it's enough that everything seems to work fine except the starter.

Has the bike been left a long time since you last rode it?
Did you do anything after taking the reading of 17-18V at fast idle?

I haven't done much with the bike or my riding style since the last readings, other than run the lights more because of the weather. Other than the blokes at the garage fitting the new chain/sprockets, it's been left well alone. It has been very wet between then and now, and maybe some corrosion has set in or something similar.

I can't get a running/idle reading across the terminals as I can't start her without bumping, and she's almost empty right now which makes things even more of a pain.

Last time I fully charged the battery, it was left for around 4-5 hours plugged in, and then left standing overnight. This time round I think I only left it plugged in for a couple of hours, but the charger reported it as being fully charged.

I will give the battery a good overnight charge and see how the readings are in the morning.

Just put the battery back on charge and the charger is reporting <20% charge. Looks like it is playing silly buggers.

You could try a load test on the battery. Engine not running, headlights on while measuring the battery voltage. A good condition fully charged battery should remain above 12 volts for 15-20 minutes. Better indication of battery capacity.

magg wrote:You could try a load test on the battery. Engine not running, headlights on while measuring the battery voltage. A good condition fully charged battery should remain above 12 volts for 15-20 minutes. Better indication of battery capacity.

I'll give that one a go tonight. Just had the battery back in the bike, with 13V across the terminals after an 8hr charge. Starter didn't even turn over twice before it gave up. With the issues I had when I first received the bike, I'm half tempted to just get a replacement battery and reg/react ordered.

If I am to buy a new reg/rect, what is the thermal adhesive I need to use to secure the unit to the frame?

I will most likely be buying from David Silver Spares, but I don't see any kind of thermal adhesive on there.

If a fully charged (allegedly) battery won't start the bike at all, then it's pretty certain that it's knackered, and it's almost certainly going to be the 17-18V from the reg/rec that did it. Before spending £59+ VAT at DSS for one, it's worth taking a look on eBay. DSS don't seem to carry the Honda OEM one, but are virtually charging Honda prices for an aftermarket part.

Don't buy a secondhand genuine one as they usually lack fins which helps them on the way to destruction as they overheat, but consider some of the offerings on eBay. Dirt cheap is almost certainly going to be trouble, but middle of the road should be fine. I got one of these from this seller http://www.ebay.co.uk/itm/HONDA-HORNET- ... 460787edf6 the best part of two years ago, and it's behaved impeccably. You can also fit one from certain models of Yamaha R6 with a little work. I think you have to break the connections out of the connector and fit each pin individually, but if you do a search on the forum you'll find several threads on fitting one, plus other make/models. There are lots of threads on here with people's experiences of using aftermarket reg/rects like the one above, R6 ones and others, so I'd have a little search about and decide what you want to do before firing almost £80 at DSS for one if you include postage.

As regards the thermal stuff. Due to the way the things work, the reg/rec gets very hot in normal use as heat is a by-product of the manner in which it converts AC from the alternator into DC for the charging circuit and regulates the output to the correct level. Excess output is effectively turned into heat. This means that keeping it cool is vital to keeping it happy. Excessive heat can cause electrical components to run out of spec, and eventually lead to them breaking down and not functioning correctly even when at the right temperature. Think about why you have aircon units in server rooms, a big heatsink and fan on the processor in your PC, etc. Hence why even on a cool day, a knackered reg/rec will still not work properly, in your case giving too many volts to the charging circuit and damaging the battery. In extreme cases, they have been known to catch fire!

So, you need to help keep it cool. The unit is mounted against a flat plate on the subframe, which effectively acts as a heatsink and helps conduct the heat away. In computers, and on other things with microchips and other components that get hot and need a heatsink, it is common to spread a conductive paste on them to ensure the maximum thermal conductivity between the component and it's heatsink. On my NC35, the plate on the subframe appears to have a very slight shape it it, so in theory there's a bit of a gap between the reg/rec and the plate in places, which means that it isn't transferring quite as much heat as it could. A coating of thermal paste could be used to help reduce or eliminate the gap or gaps, and increase the heatsink effect of the subframe. These days, you can also get sticky pads that do the same sort of job. Personally, I don't use the stuff, however the previous owner acquired a chunky aluminium plate to go between the reg/rec and the subframe, so the extra material will help. I've also seem people fit computer fans to the reg/rec.

You can get thermal pastes, adhesives and pads from somewhere like Maplin. Depending on the grade, it will cost up to a tenner for a syringe of the stuff, and you get very little for your money. However, there will be enough for what you want to do. The pads come in varying sizes and thicknesses. I've not used pads, so I don't know how much give they have, so if they aren't very squishy, they won't be much good for smoothing out any contours in the plate on the subframe.

http://www.maplin.co.uk/thermal-compound-351526

http://www.maplin.co.uk/thermal-adhesive-tape-346530

The above are simply suggestions, there are dozens and dozens of sources and choices for thermal pads, adhesives and compounds, so have a search on eBay, Maplin etc....

speedy231278 wrote:If a fully charged (allegedly) battery won't start the bike at all, then it's pretty certain that it's knackered, and it's almost certainly going to be the 17-18V from the reg/rec that did it. Before spending £59+ VAT at DSS for one, it's worth taking a look on eBay. DSS don't seem to carry the Honda OEM one, but are virtually charging Honda prices for an aftermarket part.

Don't buy a secondhand genuine one as they usually lack fins which helps them on the way to destruction as they overheat, but consider some of the offerings on eBay. Dirt cheap is almost certainly going to be trouble, but middle of the road should be fine. I got one of these from this seller http://www.ebay.co.uk/itm/HONDA-HORNET- ... 460787edf6 the best part of two years ago, and it's behaved impeccably. You can also fit one from certain models of Yamaha R6 with a little work. I think you have to break the connections out of the connector and fit each pin individually, but if you do a search on the forum you'll find several threads on fitting one, plus other make/models. There are lots of threads on here with people's experiences of using aftermarket reg/rects like the one above, R6 ones and others, so I'd have a little search about and decide what you want to do before firing almost £80 at DSS for one if you include postage.

As regards the thermal stuff. Due to the way the things work, the reg/rec gets very hot in normal use as heat is a by-product of the manner in which it converts AC from the alternator into DC for the charging circuit and regulates the output to the correct level. Excess output is effectively turned into heat. This means that keeping it cool is vital to keeping it happy. Excessive heat can cause electrical components to run out of spec, and eventually lead to them breaking down and not functioning correctly even when at the right temperature. Think about why you have aircon units in server rooms, a big heatsink and fan on the processor in your PC, etc. Hence why even on a cool day, a knackered reg/rec will still not work properly, in your case giving too many volts to the charging circuit and damaging the battery. In extreme cases, they have been known to catch fire!

So, you need to help keep it cool. The unit is mounted against a flat plate on the subframe, which effectively acts as a heatsink and helps conduct the heat away. In computers, and on other things with microchips and other components that get hot and need a heatsink, it is common to spread a conductive paste on them to ensure the maximum thermal conductivity between the component and it's heatsink. On my NC35, the plate on the subframe appears to have a very slight shape it it, so in theory there's a bit of a gap between the reg/rec and the plate in places, which means that it isn't transferring quite as much heat as it could. A coating of thermal paste could be used to help reduce or eliminate the gap or gaps, and increase the heatsink effect of the subframe. These days, you can also get sticky pads that do the same sort of job. Personally, I don't use the stuff, however the previous owner acquired a chunky aluminium plate to go between the reg/rec and the subframe, so the extra material will help. I've also seem people fit computer fans to the reg/rec.

You can get thermal pastes, adhesives and pads from somewhere like Maplin. Depending on the grade, it will cost up to a tenner for a syringe of the stuff, and you get very little for your money. However, there will be enough for what you want to do. The pads come in varying sizes and thicknesses. I've not used pads, so I don't know how much give they have, so if they aren't very squishy, they won't be much good for smoothing out any contours in the plate on the subframe.

http://www.maplin.co.uk/thermal-compound-351526

http://www.maplin.co.uk/thermal-adhesive-tape-346530

The above are simply suggestions, there are dozens and dozens of sources and choices for thermal pads, adhesives and compounds, so have a search on eBay, Maplin etc....

Thanks for the buying advice, I will do a little research for now. The walk to work can't do me any harm for the time being

I do know the thermodynamics involved in AC/DC conversion and the behaviour of the interface between the reg/rect and frame, I just assumed there would be a widely-adopted standard of paste/pad to use especially as these things are guaranteed to fail at one point or another

I do like the CPU/heatsink analogy though, very useful for those of us geeks not in the know!

EDIT:

I was being a total nugget - I was expecting the pad/compound to be the gluing mechanism. If I'd realised the thing was bolted on I could've used some of the Arctic Silver 5 sat on my desk!