Org advice required again please - backfire & stalling

[kbh]

I know this seems to have been covered before but i seem to have tried everything......but i'll start from the top

Bike is curvy. I do appx 250miles a week so i average a new tank of fuel every three days. Bike has been running absolutely fine far the past few months and never skipped a beat. The other day driving home from work (whether was dry and had not been raining for a few days before hand) i was overtaking a car then all of a sudden the bike starting kangarooing and then backfired, it was then fine again for the next mile or so, then it did it again - kangarood and backfired - the engine still stayed running. btw i hadn't done anything to the bike, taking anything off or moved something around or replaced a part.
I was still a long way from home but over the next 20 miles it started getting worse and the bike would then cut out, a quick thumb on the starter and a few revs and it would start again albeit with a couple of backfires and i carried on kangarooing and backfiring down the road doing no more than about 25mph. Got to a straight bit of road and it seemed to stop so gave it a bit of throttle and managed to get up to about 60mph and it was ok, it backfired again a couple of time then was ok again....until i got nearer home and i started going up all the hills and it ran like a dog i was back to kangarooing down the road at about 15mph and constant bang, bang out of the exhaust and limped the rest of the way home like it. It seemed to get worse the more load that was put on the bike.
Anyhow got home, whipped out the plugs to check for spark, front one fine, back one not sparking. Tried the front plug in the back lead and got a spark, then tried the back plug in the front lead - got a spark albeit it seemed a bit weaker....Plugs were the right colour, no signs of either running lean or rich. Off i went to order new plugs....i thought that was problem solved.
While i was waiting for postie i thought i would drain the carbs - no water in them. checked the drain on the tank for water to escape, wasn't blocked.
Removed carbs, stripped them and they were as clean as a whistle - no build up, no varnish nothing all the jets were clear so sprayed everything with carb cleaner to make sure and put the carbs back - didn't think there would be water or blocked carbs due to me putting a new tank of fuel in every three days and it always gets a good blast. Checked the vacum & fuel hoses and there OK and fuel runs fine out of the tank into a jar with the engine running and stops running when the engine stops. Checked the fuel filter in the tank - clean as a whistle.
Also checked and lubed the choke cable and plungers while carbs were off - not sticking, no build - they both move nice and freely and open and close fine.
New plugs arrive. Check them both for spark in both leads - there fine. Fit them, put the bike back together......and.......ride it off the drive...and it starts kangarooing and backifiring again and stalls.....same as before.
Now i was thinking it must be leads/coils as any load seems to be a problem although it idles fine (i did tweek it up to about 1300 as other people have suggested, but it has always been on 1k and never been a problem) and will rev without a problem until about 7k and couple of small pops from the exhaust but no shoutgun bangs.
I Borrow both coils from someone and fit them..start the bike, idles fine, still a small pop at about 7k revs, put the bike back together again and go to take it out the drive and you guessed it, starts kangarooing and backfiring again. leads are on the plugs tight, tried sparying some wd40 as well but has not made any difference.
I've also made sure that the carbs and airbox are seated tightly, all breather pipes attached. Oil level on bike is OK. small film of oil on the inside of the airbox but that seems to be expected reading other threads.
Can't be chaffing on the loom with front seat bolts as i don't have any bolts and i've looked at the back subframe and all the wires look ok albeit i don't own or know how to use a multimeter to physically check.
As i said it was running absultely fine and for no reason just started out of the blue.

Has anyone got any more ideas please??

[Biker Biggles]

Crankcase breather pipes firmly attached to the airbox?
You seem to have covered most things,so closer inspection of the wiring looks favourite.

[Bibio]

needles/emulsion tubes are worn or rectifier/battery on its way out.

[kbh]

Breather pipes are all firmly attached...i was hoping it wasn't looking to be electrical as i know bugger all about that....
How can you tell if the needles/emulsion tubes or worn (i know what the needles look like but what do the emulsion tubes look like, where are they attached? don't someone say just by looking at them-i've suffered a sense of humor failure over this) have u got a pic of how any of these should look?
Bat's never gone flat on me and i've never had trouble starting it and the lights don't dim whilst running. Given my severe lack of electrcial knowledge is there any other simple tel-tale signs to look out for that it might be this or will it be a case of biting the bullet and paying the garage money i don't have to look at it?

[yorkie_chris]

Doesn't sound like emulsion tubes to me, they'd make it feel soggy and rich rather than kangarooing.

Doing it under load would suggest coils, but you've covered that.

Try run another lead from the earth on the battery to the frame.

can i ask a question which maybe on topic?


To test down to earth, is it okay to use a Megger (Insulation tester) or will it the same in industrial purposes with new equipment fry any drives/ control units?

(I.E in a similar way a jump start from another car can fry ecu's)

Oh and BTW electrical testing is easy. Ask for a multimeter off a friend (or buy one for £15 draper from Amazon or local DIY place or halfords). Seat off, headlights on and rev to 5k and voltage shouldn't be more than 14.5vdc. Will rule whether Reg/Rec has goosed. Half hour tops.

[Spanner Man]

Good afternoon all.

Sounds like you've covered most of the obvious.

Have you tried bypassing everything ignition related that isn't necessary for the engine to run? i.e. Sidestand switch & clutch switch. I have known these to play up when the voltage in the charging system rises with the engine revs.
A dirty or loose fuse contact could give you the symptoms you're having, as could corroded contacts on the ECU. Or indeed corroded contacts on anything ignition related i.e. the right handlebar switch.

At least you can carry out the above without spending more than time. If it's still playing up after the above, then it's most likely a fault in the loom, or a dodgy ECU.


Cheers.

I had a similar problem with a car once, it turns out a wire from the engine management box was rubbing on the frame under the dashboard, bit of tape and bobs your uncle. Only found this by accident after noticing a flash under the dashboard one night when the fault was starting garage wanted £150 for a new box said it was knackard.

[embee]

Don't put a Megger anywhere near any vehicle.

Check for the known wiring chafing points on the curvey, especially behind both the riders seat bolts (they're too long and can hit the wiring harness behind), also under the pillion seat where the wiring loops round a frame bracket towards the rear on the left side, then generally round the steering head where the wiring flexes as you turn the bars.

Also take apart as many electrical connector blocks as you can get to and clean/lube the pins (ideally some aerosol contact cleaner, but WD40 will do at a push), then do the same with all the fuses.

[kbh]

OK I'll try first responses first.......
YC - does it matter what gauge wire to use from batt to earth? Is the idea behind this to test for a bad earth?
Fallen Angel - Thanks....sounds easy...I'll get myself a multimeter ordered and post response when it arrives
Spanner man - I havn't tried bypassing the sidestand or clutch switch as i thought these would make the electrics die completely from the other threads i read rather than than just stall the bike, but it's worth a try...i'll search the other threads for the bypass destructions and give it a go.
Embee & Spanner man - Main chaffing points have already been checked apart from round the headlight. I did clean and check all contacts a few months ago throughout the bike when i had another intermittent electrical fault that seemed a real bugger to find but was eventually found to be starter relay, which i came across by accident and wasn't one of the symptons suggested, but as you say it is probably worth pulling them all again and checking them over just to make sure.