nc29 spluttery... loosing spark : Still broken

[gravis]

Hi all,

since finishing my rebuild my nc29 has been a bit spluttery all over the rev range however not all the time. Its always been a bit tricky to start but this morning it just didnt want to know at all, almost run the battery down trying. I dont know if the fuel pump on a nc29 should prime or not? But i dont hear any noises when turning the ignition on. Although the only way i did get it started was by turning the key on and off 3 or 4 times and then it started up but was very spluttery. Theres plenty of fuel in the tank by the way. One of my friends said it could be the carbs but I have a hunch its the fuel pump, anyone else had the same symptoms as me just want to be sure before i go and by any more parts for it.

Thanks!

[dunkenb]

How's your battery? When my battery was on the way out it started to do that.

[gravis]

How's your battery? When my battery was on the way out it started to do that.

Battery should be ok, I replaced it with a new bosch one in January this year

[gravis]

I tried a few things last night and it seems it was just a loose connection, the brown connector that is under the fuel tank... not sure what that is exactly though. I also disconnected the fuel pump and had a look at the points (seemed to be ok) and reseated the electrical connection for the fuel pump. Im not sure which action was the fix but low and behold its running spot on now so im not complaining

[gravis]

OK spoke to soon, was running like a dream for a while and then died on me again, this has happened a few times now. I seem to loose 1 or 2 cylinders and then just cuts out completely and rolls to a stop and then wont start again. Cant bumb start either. This must be an ignition problem? Either HT leads or coil packs? It seems that if i take the tank off and jiggle some wires connected to the coil packs it does come back again (at least thats what work this morning whilst I was sat by the side of the road), so im hoping and praying that its just a simple dodgy connection... Does this sound symptomatic of something else though? Should I be thinking of replacing the coil packs and ht leads anyway as it is a 21 year old bike.

Cheers

[dunkenb]

Think it sounds like a loose wire like you say.

[greggo]

Which cylinders go down, is it the same every time? When it dies are all other electrics running. And yes from memory you should hear the full pump prime when switching on. Your symptoms are a bit odd at first it sounded like fuel pump or pump relay, then more ignition...so....

I'll assume your plugs are gapped, carbs cleaned and valve clearances good.

Swap coils see if the problem moves with the coil.

Check the ignition pickups aren't loose or filthy under the alternator cover. If they move all of about a mm they wont trigger.

If you can get another fuel pump relay to check try that. Or next time it won't start put something solid (like a quality screwdriver) against the fuel pump. You should feel it oscillating.

Either of those could cause your symptoms.

[gullarm]

Try the pickup coil, its fitted on the left hand side of the engine, it connects to the connector under the fuel tank and its a brown wire and other wire.

Mine was going open circuit, the way I found out was to run a set of wires from the connector block to a DVM under the rear seat, when the bike wouldn't start I checked the DVM on the OHMS setting and it was open circuit - after 10 mins it returned to its normal resistance as per the manual.

If you tried to remove the seat and tank to check it would be back to normal by the time you removed your parts.

Another option is to bypass the fuel pump. Remove the fuse so it doesn't run on dry.

[Davez29]

Yes, I would go with wiring, coils, ht and maybe plugs as mentioned.

One tip, if you can't decide which cylinder is causing problems is to buy one of those cheap infrared temp guns off ebay and allow the bike to warm up, now point the gun at each downpipe and take a reading its surprising how quickly you can pinpoint something is amiss even by a small amount such as an irregular problem. Now you can swap leads, coils and plugs with a better understanding what's causing the problem. Better than trying to touch each pipe to see if its getting hot.

To give an example I had a problem with a blocked jet but could not work out which cylinder as all pipes seemed as hot. But within seconds of using the infrared gun I could see cylinder four was a good 50° under compared to the other pipes, problem narrowed down quickly.

[maximusgnarl]

Mine went similar for a while and turned out it was the stator on its way out. Just a thought.