So for anyone who saw my post in the newbie corner (pics will follow when the weather gets better) my problems have got worse.

Before I rode it back to London (week after I bought it), it was dark and I noticed when I started it there was a puff of smoke coming from the headstock area and a slight plastic burning smell. I chose to believe I didnt see it  and rode the 90 miles home with no issue (aside from the hesitation I described earlier in the newbies.)

Fast forward and I took it out last week. After about half a mile, I noticed the idle revs were dropping at traffic lights. I could rev it to 2k or so and keep it alive but it started become a real fight to keep it from stalling (as well as looking/sounding like a complete cnut). Pulling away from another set of lights the power just disappeared totally, 1st/2nd, throttle pinned, nothing but some pathetic lurches forward. It stalled again and wouldn't restart. Pushed it to a parking space and had a fag. I gave a it a few cranks and it was struggling to catch. After a couple more fags, I managed to get it started and blasted the mile home at over 6k rpm then proceeded to google...

A week passes and I get to look at the bike again (last saturday) First though/check was the battery. Got a multimeter and checked voltages across the battery. 12.7 at off, 14 odd when on. Switched all the lights on and it didnt drop below 14v. As it had fired first time, I decided to do a cautious lap or 2 of the block. Just like clockwork, same issue happens again. I got back and pulled up, the revs dropped steadily until stall within around 10 seconds. I did notice the burning smell was back again.

I don't know if I've got one problem here or two. Clearly something is burning up in the electrical system somewhere, i've read it may be the keyswitch.

And then theres the loss of revs issue. Does anyone have any ideas for a first check? I'm wondering whether when the bike is left, the carbs fill up of their own accord via gravity, which allows me to start and ride a little way, and then there is an issue with the fuel pump/filter/relay which isn't refilling them fast enough. Could this be a possibility? How would I go about checking the pump and relay? Fuel is fresh and full, (petcock on...) I rode 150 miles before these issues so i'm hesitant to think carbs straight off the bat. Any ideas? I wanna ride this bitch!

Going on what you have written there, I'd say it's a coil pack failing.

Could be a kinked breather or some other pipe under the tank too.  Although the burning smell is a bit of a giveaway.  I'd get the tank off and see if you can spot something.

Thanks for the quick replies. Small update after poking about a bit today after work. Started first time again. Smoke and burning smell again. I tried to trace the origin of the smoke no joy, I might try at night with a torch, its much more visible then. When it happened the first time, it was dark and there was clearly smoke floating around the front of the bike, now I think about it, it may have been more from under the tank than the ignition. Couldn't see anything obviously melted or smoking around the keyswitch today. I crouched next to the bike and listened to the fuel pump, it was ticking/clicking sharply on a fairly regular basis, which I believe is normal operation at idle. Pulled the pump relay and had a look, it looked brand new. There didn't appear to be any dodgy splicing/relay bypass from what I could see. Junction box clean inside. There is a datatool alarm which the previous owner told me he put it on a maintenance charger because of. I'm unable to physically connect a charger to the bike so its been sitting for 3 weeks now, but the battery is good and strong. Seems to have been wired in pretty professionally, and although I did find out how to bypass the alarm i'd rather keep it, it being parked on the street in London. So, actually a fairly big update, saying not very much.

The coil packs are a new one to me and I hadn't considered it before. Next job is tank off, check plugs and leads, tank breather, etc...Cheers again for the help so far.

Minor update - managed to lift/rotate the tank and get a bit more of a look underneath. One thing I did notice was that I couldn't see any pipes connecting to the tank other than the petcock. Should I have a breather/vent pipe somewhere? It was a bitch holding a 3/4 full tank steady on the back of the bike whilst poking about so I'll drain it and disconnect the line at the petcock so I can remove it properly. Still can't trace the burning. Still fired up first time and idled okay, battery good with 14.5v. I also don't believe any mods have been done to the airbox/emissions as all the shit was still in place, looked pretty standard from what I can see.

Could it be something stuck in or sticking to the downpipes....oil leaking over down pipes????

Quote from: Alzo on June 19, 2016, 06:35:36 PM
Could it be something stuck in or sticking to the downpipes....oil leaking over down pipes????

I guess it could be, but it was a total cold start the first time at night, and if I recall correctly the smoke was around almost instantly. I also let it idle today (which it did with no problems) and all of the headers were hot to the touch - perhaps not the most reliable way of checking spark but still. I really need to get a proper look at the plugs etc so the job for tomorrow is to siphon the fuel out and fully remove the tank/airbox. It just seems strange to me that the issue happens in such a regular way i.e after a mile. Never had issues starting it even after I left the lights on all night. Never needed the choke, and I checked the action of the choke - applying choke after its started stalls it. Idle is fine, initially. Can't help thinking its a fuelling issue but will check coils as suggested also. Sigh...

Update - I threw in half a bottle of redex, switched to the reserve tank, (test petcock) and turned the idle knob up a little. No issues, although the revs do drop slightly in traffic to maybe 900-1000 (currently idling at 1400-1600) it didn't stall. So I guess i'm in need of a carb clean/balance.

One thing I did notice was that it was running very hot and thats when the idle seemed to dip again. The fan is turning on and off correctly as far as I can tell. The temp gauge is just over the halfway mark. When I rode the 90 miles, it was obviously at motorway speeds so the temp hardly registered. When its around town, the needle rises and it acts up a bit, bogging slightly. I got back and opened the fuel cap, no sound.

I still want to check/change the plugs but is all of this (including full choke stalling it) indicative of a rich condition? I also know these bikes get hot, and when they do, they get pretty finicky...its only 20 degrees C here at the moment...am I in for a summer of pain? Ha.. Gonna change the filters, fluids and plugs and get the carbs set up I think, see how I go.

if the temp hardly registers at speed and it boils up in town then the thermostat could be goosed..  doesn't answer the smoke question unless it's coolant escaping somewhere.  do you know when the valve clearances were last checked ?   if the engine runs quietly then they probably need checking. I've had hot starting issues with Kawasaki bikes of this vintage that has been helped by having the correct valve clearances set. 

sounds like it just needs some TLC and obviously to find the cause of the smoke / steam.

HTH

Thanks for all the help on this guys. Since I turned up the idle a hair, i've had no issues. Temp gauge reads correctly as far as I can see, warms up nicely to just under half way and drops down to around 1/3 when it gets a bit of air over the rad. However its definitely running rich, or i'm thrashing the tits off it, i got 90 miles to reserve the other day. Although, that could be the litre of redex 

As one problem disappears, another appears - making new post now...

EDIT: The smoke is coming from something on, or leaking onto the no4 header. What, I don't know...