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Offline Biffern

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Misfiring
« on: 05 October, 2018, 02:53:00 PM »
Hi, strange goings on. Bike starts first time, but when I pull away (after the engine has warmed up) it misfires on #3. Once it's above 3000rpm runs perfectly, once it's been run the problem disappears. This only happens when the engine is cold. I thought it was damp and dried it off and sprayed WD40 on the leads and plug caps. The problem never appears again until the bike is left overnight. Any thoughts please as to where I should look next.
TIA Ernie
« Last Edit: 05 October, 2018, 02:57:12 PM by Biffern »
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Offline Scott_rider

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Re: Misfiring
« Reply #1 on: 05 October, 2018, 03:29:55 PM »
Is it a misfire or a stutter?

If it's a stutter, a lot of Biffers do that (apparently) mine included.

Offline Biffern

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Re: Misfiring
« Reply #2 on: 05 October, 2018, 03:35:26 PM »
Thanks for the reply, it's definitely a misfire. When it decides to kick in it sounds like detonation is occurring. But that could be because the chamber is full of unburnt fuel.
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Offline jm2

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Re: Misfiring
« Reply #3 on: 06 October, 2018, 01:50:53 PM »
#3  Isn't that the lead that is prone to damage ?

As in, the lead that gets abused as most difficult to remove when doing the plugs/removing tank etc.
In that case, HT #3 lead paritial failure (near the cap).
Only do it right - no bodging please.   Keeper of the failed stator list.   John.

Offline Biffern

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Re: Misfiring
« Reply #4 on: 06 October, 2018, 04:54:04 PM »
Hi jm2,I've had a pm from bifferman pointing me in the right direction. I'll have to take the tank off and have a look. What is really confusing me is I was out yesterday in the rain and the problem didn't happen. It reared its ugly head when I first set off, after that no problem from starting. But I'm now going to follow the advice on this site. Thanks guys.  :020:
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Offline Biffern

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Re: Misfiring
« Reply #5 on: 03 December, 2018, 12:01:43 PM »
Update:- tank off, thanks to those who suggested removing the banjo. Irridium plugs fitted. Coils checked with multimeter. Primary and secondary measurements correspond with Haynes manual, well near as . Mine are 2.7 ohms primary,  secondary 30k ohms (with plug  leads attached). Out of curiosity I tested each coil to the ferous core and get the following readings:- primary 19M ohms on coil unit for plugs 1 and 4, 7.7M ohms coil unit for 2 and 3. Considering my multimeter is a cheap one and it's output voltage is less than any voltage on the bike. It seems to me that one coil could be failing at the higher voltages applied.  The bike won't run,but tries to fire up on the starter button. I'm going to order a new coil and see if that cures it.
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Offline stergios

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Re: Misfiring
« Reply #6 on: 03 December, 2018, 09:32:55 PM »
the bike should start as it only misfired before.

please check

0 signal wires on coils are connected? breather hoses all in ? maybe you removed a injector plug (no start with one off)

1. the spark plugs caps are seated. it clicks when it is correctly pressed

2 location of spark plug wires on the coils and on plugs maybe you mixed something so firing order is wrong

3 fuel system check as per manual see attachment ,

the bike should run as bad as before at least so please check what is diffent after your actions.