Despair Shop 37 – Teaching an old dog new tricks.
Picked up a pretty grubby ZX6R A1P the other day – one of the 636’s. Scruffy but I could see potential and it wasn’t dear. All I had been told was that the previous owner couldn’t get it to run and it was suspected that the Datatool alarm was playing up. Well he was right on the second point – couldn’t turn it off so it had to come out. Whoever installed it had done a superb job and it took ages to take the loom right back to find all the cut wires. Pretty routine stuff – just a bit time consuming. With that job done I set about seeing if the engine would turn over, which it did. The fuel pump worked, which was nice, the carbs clearly needed a good clean. Standard stuff again so I won’t bore you with details and photos. With the carbs back on the bike and full of fuel I went for the start. The bike burst in to life for a couple of seconds and then stopped. Strange as when it did start it sounded like it was running on all four and when it cut it cut suddenly – not like fuel starvation more like somebody had cut the ignition.
I checked and double checked everything but spent an hour or more trying to get it to stay running. Sometimes it would stay running for a few seconds, cut but then start again and sometimes it would run for 30 seconds, stop and then not want to restart. Clearly an intermittent fault – deep sodding joy, I hate them. Then I had a bit of a breakthrough, I noticed every time it would die the neutral light would flicker, definitely looks like an interruption in DC power somewhere along the line but where? I started tracing live feeds back to source and hot wiring them direct to the battery to see if supplying a reliable live somewhere would solve my problem, it did I found an issue with a large white connector under the seat. I didn’t know what it was at the time, but I now know it is the connector to the voltage regulator. I disconnected it to see what would happen and the bike ran and kept running – there was my issue. I thought at first the connector was some sort of module, I was losing light by now so I gave up for the evening and came in.
You can see in the photo how much of the loom I had to peel back to get the Datatool alarm out of the system. Anyway quick post on a couple of forums and I soon had the answer that it wasn’t some sort of module – it was just the connector for the voltage regulator – Bingo!!
What I now believe to be happening is that there is a faulty regulator that is using what we electronics geeks call a crowbar. It’s a safety thing that essentially shorts out the output if the device goes faulty. This was causing a lack of power albeit usually only for ½ a second or less, but enough to kill the engine or at least cause it to falter. Never seen this before, normally when regulators fail you either get a flat battery or the battery gets dried out from over charging and bulbs start blowing.
All is now well, a new regulator is on order as I don’t have one. Carb number one has decided to overfill though so I need to look at that next. I had already cleaned the carbs once but I suspect there may have been some grot in the fuel lines. No big deal, I’ll soon sort that.
Update on the carbs – I inspected the needles under a powerful magnifying glass and didn’t like the look of a couple of them so I changed them for new ones. I cleaned all the seats again, put them back together and tried them on the bike. Oh bugger, one of the cylinders has got fuel in and now it won’t turn over!! I knew it had to be cylinder 1 or 2 so after much swearing, I got number 1 plug out which was dry, so it’s not that one. Number 2 turned out to be the culprit. Yes number 2 in name and in nature!! The plugs are a complete pain to get out in these bikes, 2 and 3 are ok, but 1 and 4 are a nightmare unless you have a tool of exactly the right length. Too short and you can’t reach the plug, too long and the air intake ducts get in the way. I got there in the end, but it just shouldn’t be like that, it would have taken a simple design change to make it really easy – oh well, I shan’t be keeping it long.
While I was in there I got the regulator off the bike ready for a new one to turn up, removal and fitting are straightforward enough – just 2 bolts hold it in place.
Next job – panels. This could be a lot harder than I thought as there don’t seem to be many for sale. A repair is probably doable but very time consuming. I think these are Chinese replacements as the material they are made out of seems far too brittle for something a Japanese manufacturer would turn out.
Article provided by David Powell of Boston Bike Bits.
