NC35 cutting out

[speedy231278]

Just when I was hoping everything would be sorted, I've now got yet another thing to try and fix!

Earlier today, I got the bike back together after fitting a new stator and one of RO's trick MOSFET reg/recs. Went out for a ride to see how it performed and ran into a terminal issue. The output seemed a little low, but that's not the issue as last weekend the bike was running fine with lower readings on the voltmeter I wired in.

The bike was running fine, no odd noises, no hesitation, nothing unusual, then all of a sudden it just died. From 9000rpm to zero just like the kill switch had been pressed. The bike fired up again after a few moments, but only ran for a couple of hundred yards before exactly the same happened again. That was the end of play, and eventually I got the bike back on a flatbed recovery truck.

Given that I wired the voltmeter in using the feed to the kill switch, I was hoping that maybe something had gone amiss after I'd had the connector for the switchgear apart, but seemingly not. I'm sure it's not battery or fuel related. The voltmeter was not suggesting the battery was excessively low (and later on, while a bloke from the RAC was attempting to help sort it, being connected to a jump pack started the bike for literally a second before it cut out again), and last time I had a charging system failure that depleted the battery the bike spluttered for a while before stopping. The bike did not run short of power or misfire before stopping, and the fuel tap has been tested and working since I got back. I'm sure it's electrical, but I'll be damned if I can find anything wrong yet.

I've tested the kill switch, and it has connectivity in the run position.
The fuse for the ignition had not blown.
The feed from the fusebox to the switch is OK.
The feed from the switch to the ignition is OK.
The feed from the switch to the coil packs is OK.
The feed from the ignition to both coil packs is OK.
The neutral and sidestand dash indicators seem to function normally, so I am assuming the switches are OK.

Several of the pins on the plugs for the switchgear were very blued up from corrosion when I had it apart, and I cleaned the worst ones on the switchgear side. Once before after having this one apart, I had an issue with the bike not starting, but after taking it apart again and spraying with some cleaner, the issue was resolved. I would be very surprised if it was the same thing as I don't understand why it would start working again, albeit only intermittently?

I'll see what happens in the morning when I've put everything back together again, but what else should I be checking if it's not as simple as a few scabby pins having a sulk?

[Icemaestro]

Did lights/dash go dead when the bike died? What happened when you tried to start it straight after? Clicking, turning over, or nothing?

[bikemonkey]

Electrical gremlins love you.

I know it's radical, but maybe replacing all the electrical items on your bike for low mileage ones might do the trick?

I seem to remember your bike has a high mileage, maybe things have just had enough?

[speedy231278]

Did lights/dash go dead when the bike died? What happened when you tried to start it straight after? Clicking, turning over, or nothing?

Everything else was fine. Power to everything, starter turned happily. I'm convinced that the only logical explanation is the ignition circuit, but other than it being something that only occurs under a specific set of circumstances, I'm currently clueless. It cannot be coincidental that I've disconnected the kill switch so I could attach the voltmeter to the spur that feeds it, and now I have a fault that mimicks the kill switch being in the stop position. The RAC bloke sugested the voltmeter might have overloaded it, however I explained the feed for that was taked before the switch not after it!

First part of today's work will be to try and clean up the loom side of the connector for the switchgear, and that's not going to be fun...

[speedy231278]

Some progress, but nothing like a solution yet. The bike will now run, but it's utterly gutless and barely accelerates at full throttle in first gear! I'm also ending up with more questions than answers. One thing I have found is that even with Rick's trick reg/rec and a new stator, you still barely get any charge in the system if you are running UK spec 60/55W headlamps. The max I was getting was 12.8V at 5K, with a pair of 60/35 I was getting a healthy 14.5V at anything more than idle.

Now, when I went out last night, the lower fairing wasn't on the bike. The while I was working on it, the wire clamp on the fairing bracket for the idle adjuster gave up the ghost and snapped, leaving the adjuster a little less secure than it might otherwise have been. When starting the bike this morning, it didn't rev very high on full choke, and when the choke was put in, it stalled. It stalled again when I stopped blipping the throttle after I started it a second time, so I theorised the idle setting had been disturbed, and whether or not that was the case, it got the engine running without stalling. The odd thing is that the idle started creeping up again a little afterward, and even when it had been running long enough to be warm, it was still a little tetchy and would settle at slightly different rpm after a few blips. I fail to see how having the idle adjuster miles too low would cause the bike to instantly cut out with the throttle open pulling 9K like last night....

I did have the top and bottom halves of the airbox off in order to get at the switchgear, both last weekend and this morning. If, and I say if very nervously, the cut out issue was indeed the kill switch circuit having a funny five mins, could I have upset something in the fuel system by having the tank and airbox off? People often suggest air leaks for funny idling and revving issues, although I haven't had the carbs off in over a year. The air filter is due a visit to the bin, but it doesn't look excessively dirty. I checked the fuel tap yesterday and it seemed to flow fine in both main and reserve positions. I could be just imagining things, but I could swear the bike seems to rev just a little slower when blipping the throttle, however there's no hint of a misfire.

The new stator is wired directly to the reg/reg, and the output from it does pass very close to the rear coil pack. Is there any chance it could be inducing interference in the charging circuit that's done soething nasty to the ignition (bearing in mind it would have to pass through the reg/rec first!)? Also, something else that bothers me is that the stator I have is 102mm and the old one was 107mm. Is there any chance it could have a knock-on effect.

Next plan is to take everything off right down to the carbs to make sure everything is sat down correctly, but I'm running out of ideas!

[speedy231278]

Anyone? OK, condensed version without too much info as above.

Engine starts first time and runs, but is utterly gutless.
Full throttle at 2K gives barely any acceleration, no misfire, no stumbling, it just doesn't want to rev out.
No odd noises, but seems to respond a little slowly to blipping the throttle, revs also seem to drop a little slowly.
Idle is slightly erratic, often settling at different levels.

While the RAC bloke was attempting to 'fix' the bike, it was turned over from his power pack a considerable amount of time despite me suggesting it would foul the plugs even though they are Denso Iridiums which seem fairly immune to it. Could they now just be producing a crap or delayed spark? Is it possible the switchgear connector is still the issue, and limited power is getting to the coils?

If I don't get it sorted this weekend, it's off to a bike shop, and gawd knows how much time and money it will take them to find the fault...

[arsey30]

Initial fault sounds different from the current one.
First one sounds like ignition, [ loose/ touching LT wire] but not flat battery as the starter would not have turned over the engine.
Now it won't rev, check that all cylinders are firing [ex pipe temperature at tick over with choke off]
It does sound like a fuel/carb problem now.

The charging voltages make no sense. The generator should maintain a charge [13.5 to 14v] with the original 60w main beam head lamps, so why not now with new 60/55w lamps?
Suggests like poor regulator, can you try another, but if battery is now fully charged, regulator will not affect engine performance.

[speedy231278]

Agree the battery was not the breakdown issue, and that the current one is probably something induction related. I don't believe I am missing any cylinders, the bike sounds like it's running on all four, although it may be just a fraction muted. However, it's hard not to think everything sounds and feels wrong when you have a serious issue!

I did check the fuel tap to make sure it was flowing freely, however quite how you judge what the flow rate should be is anyone's guess. I wondered if maybe there was a partial blockage in the breather, but leaving the cap open didn't seem to make any difference to the behaviour. Fuel pipe wasn't kinked, I have had that issue before and it caused the bike to give symptoms like running onto reserve.

Could a single dodgy cylinder really cause the bike to lose what must be 95% of it's power yet still sound almost entirely, if not completely fine?

With ref to the charging output, it was not stunning on the old reg/rec, which is why I got one of Rick's MOSFET ones. With the standard low beam lamps fitted it is bang on the numbers, but the Nightbreakers are dragging it down to pretty much battery level even at 5K revs. I do have a few queries related to this, but as it's working fine with the OE spec stuff it's not my main concern right now. I will stick the old reg/rec back on just for argument's sake, but I'm sure it won't do any better.

[bikemonkey]

I don't think Nightbreakers are your issue.

I have them in my bike and at idle my voltmeter is still showing 14 volts with them on low beam.

Get your plugs out and have a gander at them. While your at it you may aswell check the coil packs.

The when you put it all back together, double check everythings seated properly. I remember my bike ran like a pig when I hadn't got the carbs back on properly.

[richyrd5]

Sounds like carb/ignition problem.check EVERYTHING when u put it back together.good luck