revtothelimit - motorbike forum

I took a break from the head melt.

Latest and most up to datest.

I replaced the coil for middle cylinder.

The bike fired quite readily,but kept dying as if starved for fuel,the right cylinder header remained cold.

Eventually it fired and held a steady idle,but the indicator fault remains. Blinkers are virtually unusable unless the revs are over 4k.

I took the bike for a run,just less than 10 miles. It'll hold sub 60mph speeds ok,but more than that it starts to hesitate like running out of fuel,so I have to back off the throttle.

I had fresh plugs in and I pulled them for a look when I returned. The middle cylinder is a nice coffee colour,but the right and left are as snowy white as they were unused. That's a worry.
Maybe there is more than one issue. Is there a fuel starvation issue which is separate from the indicator misfire?

Perhaps the Accent is at the root of it all? I don't know where I'd start with testing the Accent. I can't actually see any timing marks to check that!

I'll see if I can blag a set up instruction leaflet from somewhere.

Stumped for now anyway.

Did this fault just develop out of nowhere, or has it slowly snuck up on you? And what was the last thing you changed on the bike prior to this issue?

mangocrazy wrote: Sat Jul 12, 2025 1:15 pm Did this fault just develop out of nowhere, or has it slowly snuck up on you? And what was the last thing you changed on the bike prior to this issue?

A quick summary.

After a good ride (100+miles) 3 weeks ago,I filled with fuel and headed home. Just before I turned off the bike I notice the idle speed drop to where it wanted to stall. Investigation showed A bad float,this was replaced and normal service resumed. I also dumped all the fuel and I thought that was it.

The faltering idle returned along with the engine misfiring when the indicators were turned on. The bike is barely capable of a couple of miles before it's unridable due to misfiring badly. It's also difficult to start now too. A strobe showed no spark at idle on the middle pot. Replaced coil. No difference.

In that case I can only assume that it's the flux capacitor gone shonky...

Maybe there's a fault with the indicator circuit? I'd still be chasing a bad earth. I know that you've checked all the earth points are clean - but have you checked out the wiring itself? Wires can be connected at either end but have a break in the middle.

What’s the voltage on the battery when it’s running?

wheelnut wrote: Sat Jul 12, 2025 9:44 pm What’s the voltage on the battery when it’s running?

14 to 14.5v

Skub wrote: Sat Jul 12, 2025 10:22 pm
14 to 14.5v

As it should be. I just wondered if there was some correlation between the indicator issue and not getting a consistent spark to all cylinders.

wheelnut wrote: Sat Jul 12, 2025 10:59 pm

Skub wrote: Sat Jul 12, 2025 10:22 pm
14 to 14.5v

As it should be. I just wondered if there was some correlation between the indicator issue and not getting a consistent spark to all cylinders.

Yeah,it's a proper puzzle this one.

What happens if you ride with the indicators on?

Pirahna wrote: Sun Jul 13, 2025 6:32 pm What happens if you ride with the indicators on?

Is this like rubbing your tummy and patting your head?

Pirahna wrote: Sun Jul 13, 2025 6:32 pm What happens if you ride with the indicators on?

It misfires every pulse of the relay,the lower the revs,the worse the misfire.

I'm gonna strap the multimeter to the tank and see if I'm getting 14volts when the engine is under load,as low voltage would cause the problem.

The Accent ignition is another possible suspect,though it usually either works or doesn't work.

In assuming the Accent is an aftermarket solid state box of ignition tricks, like a Boyer Bransden?

I'd definitely be looking in its direction. Solid state lectrickery doesn't like funny voltages and does weird shit when said voltage is off. The indicator involvement, which causes fluctuations in voltage by design (i.e. you're switching lights on and off automatically) is another bit of evidence.

Seems like the indicators shouldn't matter of course, but the lights and the ignition probably share a common earth for example. There might not be anything wrong with the Accent per se but rather in the 'quality' of power it receives. Also gotta remember that all Solid State electronics typically work by comparing "high" and "low" voltages and if something is fucking with either then things get confused.

Could be as simple as an iffy relay in the indicator circuit introducing a sort of fuzziness to the whole set up. Mechanical things have a tendency to do that.

Had exactly the same sort of nonsense on the Bonnie with it's Boyer, redoing the power to the ignition with it's own, fatter, lines for both +ve and -ve made a huge difference.

If the indicators are 21 watt bulbs, that’s an intermittent 42 watt load. That’s substantial and can cause enough of a voltage drop to affect some electronic ignitions if there’s anything dodgy in supply or return current paths.

If the bike relies a lot on frame (“earth”) return, the scope for bad connections is huge. Relying on frame return for direction indicators or ignition is just bad practice and almost bound to cause trouble.

The sort of losers who persist with British bikes often install return wires from components, to the battery, tied into firm connections to frame, engine and fork yokes.

Mr. Dazzle wrote: Mon Jul 14, 2025 6:36 am redoing the power to the ignition with it's own, fatter, lines for both +ve and -ve made a huge difference..

It’s not impossible that the answer is there.

Also seen some dodgy kill switch systems.

I'm still with the dodgy earth and as I said before I'd be making up earth leads and running a direct earth to the coils.

On four wheelers with leccy problems I always run a jump lead from the engine block to the chassis, so I know i've got a direct earth. I wonder if anything would happen if you put a jump lead on say an exhaust stud to a clean earth point on the frame?

Again, not sure if this is applicable here, but can you remove fuses to see if anything changes when you isolate whatever fused circuits there are?

I remembered what it was that caused the indicator/diming lights problem i had on an older bike, it was an earth in the headlight bucket. There were loads of earths on the mounting bolt and one was broken and just touching. Again not sure if your bike even has earth points in there?

@Skub please feel free to tell me to FO.

I used to teach fault finding and investigation skills to engineers etc. Pietins comment struck a chord. Isolate individual circuits or systems splits the task down and should get close to the offending item. Or use comparative analysis. Same thing but it uses known symptoms or previously identified faults to rule out areas of the bike where it cannot be a contributing factor. This approach looks for changes that occurred prior to the fault and rules out anything after. Although subsequent changes, such as attempts to resolve the problem, can mask the original offending change(s) If you are interested, I can share first method or just look up Kepner Tregoe.

Lots of great info there folks,many thanks. @Buckaroo sounds above my pay grade,but interesting. I do tend to have a bit of a scattergun approach to life in general.

As all the cylinders show a good spark when the plug is laid on the head,I did a spark gap test today to give a better idea of how the spark may behave under compression. I stuck a screw in the plug cap and suspended it about 10mm above the head. Both left and right arced like a lightning strike,but barely a flicker from the middle one.

Since this is the coil I replaced and made no difference to the issue,then at least I know it not the coil/HT lead or plug.

I need a couple of croc clips to test the voltage when riding,but that'll not be today.

Did you connect everything back up properly on the LT side of the coil when you replaced it? Or maybe disturbed something else in the process.

Could you also try switching the LT supply between different coils so the "wrong" plugs fire? I'm just scratching my head trying to picture the sparking sequence of a 2T triple On the Bonnie it's dead simple, both plugs fire every time it's at TDC (give or take some advance).

Obviously don't do this when trying to actually start it.

Just thinking that if you move the LT connections and move your problem, there's your issue.

Mr. Dazzle wrote: Mon Jul 14, 2025 1:31 pm Did you connect everything back up properly on the LT side of the coil when you replaced it? Or maybe disturbed something else in the process.

Could you also try switching the LT supply between different coils so the "wrong" plugs fire? I'm just scratching my head trying to picture the sparking sequence of a 2T triple On the Bonnie it's dead simple, both plugs fire every time it's at TDC (give or take some advance).

Obviously don't do this when trying to actually start it.

Just thinking that if you move the LT connections and move your problem, there's your issue.

I was pretty careful with the connectors and I'd be happy they are all sound. There's only two wires for each coil. Switching the feed to see if the problem moves I should have done,but haven't yet. Convinced by the strobe,probably.
Firing order is 1 2 3 as you sit on the bike.