South West Bikers | Motorcycle Forum

I'd put new plugs in the remaining two, that's 1 & 4.
Make sure all are firing by checking the down pipes, it won't hurt you if you just quickly dab each one with your fingers, you don't have to hold them there to feel the heat!!!
If all are getting hot, then it's probably not the plugs/coils. Then start looking at fueling, check/replace fuel filter, drain carbs & tank & replace with fresh fuel. Also try balancing the carbs, if they're out by a fair amount it could possibly give similar symptoms to a misfire.

VTR - You might be right on the fuelling thing. How do the carbs get out of balance? I haven't really touched them since it was running fine. And how do I go about balancing them again??

ditto what vtr said about 2 more new plugs. even plugs that dont look too badly fouled can earth out elsewhere and not spark properly under compression in a head. Take it the plugs are all correctly gapped too? if swapping plugs around has helped then a complete fresh set would be the first thing I think I'd try.

if with new plugs it's still struggling to run properly, and is still fouling plugs (ie getting them wet with fuel) I'd perhaps start to think its running too rich (ie fuel height, pilot screws etc) or something

have you stripped and cleaned the carbs since you got it? if not and its not too much trouble to get them off again it might be worth tearing them to bits and setting them up as per the haynes book of lies

Yeah, stripped and cleaned and ran fine a couple fo weeks ago. Will check out HT leads and coils (thanks Age!) and need to find out which cylinders aren't firing.

Little Loris wrote:VTR - You might be right on the fuelling thing. How do the carbs get out of balance? I haven't really touched them since it was running fine. And how do I go about balancing them again??

Carb balancing is quite easy, if a bit fiddly.
You'll need a set of vacuum gauges & small pair of hands
The procedure is usually in the Haynes manual, but basically you'll need to lift/remove the tank. On each carb there'll be a small port that will either be blanked off by a screw or a rubber blank, tip;- the vacuum hose coming from the tank will be attached to one of the carbs, this is the port & all the other carbs will have a blank in the same place. Remove the blanks from each carb & attach the hose from each gauge. Start the engine & allow it to reach operating temp....now the fun starts!!!
Basically what you are doing is adjusting the throttle positions of each individual carb so they all have the same opening/delivering the same amount of fuel air mixture. So you'll have one carb (usually number 1 cyl) that will be the master which can't be adjusted & will be the one that you will use to adjust the rest to. The rest of the carbs (2, 3 & 4) will have a screw to allow adjustment of the throttle position, this is usually on the underside of the carbs which is why it can be fiddly....especially on V motors....& can result in rather warm hands
Once you've got them all reading the same, snap throttle open & allow the revs to settle, check the gauges. If the readings are still identical, you're done, if not re-adjust the carbs & give the throttle another snap. Keep doing this until the readings are all the same. When you make adjustments the idle speed will probably change, so you'll have to keep adjust that too.

Little Loris wrote:Yeah, stripped and cleaned and ran fine a couple fo weeks ago. Will check out HT leads and coils (thanks Age!) and need to find out which cylinders aren't firing.

If it ran ok a few weeks back, it's probably down to the plugs or leads/coils. As has been said already, change all/remaining plugs.
Just a thought, did you get the fuel from a supermaket filling station? You might have got a bad fill from when there was that problem recently.

I never thought of that Maybe I should drain the fuel system completely and fill it with fresh juice, just in case. Surely it wouldn't work at all if the fuel was contaminated?

Chuck in some silcoleane pro FST. That should help with any water or gone off fuel in the system. It's about a tenner a litre but you don't need much so should last for ages.

Oh and as for seeing which ones are working cup your hands around the headers without touching if there's room, or squirt some water at them. Saves burnt fingers

Fired her up last night and checked the headers. I wasn't expecting them to get so hot so soon so yes, I did burn myself

It seems that cylinders 1 & 4 weren't firing so I swapped the coils over to eliminate any other problem and narrow it down to a faulty coil. After swapping them over it fired on all 4 Weird or what?! Well, I was chuffed to say the least. Gave it a few revs and it popped a bit, which I guess is some unburnt fuel in the system right?

The idea was to swap them back over and I expected to be back on 2 again but it fired on all 4! It popped a few more times when I let off the throttle but after a few more revs it was running smooth again. I guess it needs to go through the gears a few times as it has only gone into 2nd down the garden path in the last 6 months.

Anyway, thanks to all that offered their help and especially Age, who was patient while I asked dumb questions on MSN Seems it was a loose connection or something. I'll try and post up a vid tomorrow.

Little Loris wrote:It seems that cylinders 1 & 4 weren't firing so I swapped the coils over to eliminate any other problem and narrow it down to a faulty coil. After swapping them over it fired on all 4 Weird or what?! Well, I was chuffed to say the least. Gave it a few revs and it popped a bit, which I guess is some unburnt fuel in the system right?
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excellent news. just a thought but you didnt by any chance have the lt leads the wrong way around on the non working coil at one point did you? some coils it seems to matter with, others not

Not that I know of. I connected it up exactly as I took it off. I labelled everything in fear of not being able to put it back right! I hadn't touched them before yesterday but will fire it up this weekend again to make sure everything has not gone back to square one.

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