Think my bike is misfiring?

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Riding to work yesterday, not a problem, riding back from work (and coming in this morning) the bike sounds odd, when you get on the gas it sounds like it is driving over bumps, you get a pulsing effect from the engine waaaaaahhhhh-wa-wa-wa-wa-wa-wa-waahhhhhh like that, it doesnt seem to do it all the time, differs between gears too, had some at 4k rpm in 2nd and 8k rpm in 4th today, so im thinking dying coil, or a loose connection somewhere?

does sound fair bit like this:
http://www.youtube.com/watch?v=4LOOhe_ZF_g

so i think its a misfire, i know how to check the primary and secondary windings on the coil's...but is there anything else i should be looking for/checking whilst im down there? Isn't there

My engine is still rich on idle and there was a small amount of carbon buildup around the metal (not ceramic) edge of the sparkplug, plugs are CR9EIX and have done ~2500 miles so far.

when i checked the plugs before, all gave a spark, but it wasnt as bright as i would have imagined it to be, was definitely less blue and intense than what you get on a gas stove ignitor for example.

[R P Corse]

My first point would be to check those spark plugs - I hate iridiums with a passion! Burn out too quick IMO, even though they say they last longer, mine never did, especially on 2strokes. Check each plug is sparking!

Did you touch any of the timing recently?

Check you are getting fuel into the cylinder, I know you just cleaned your carbs out, but maybe something is blocking the carbs - it can happen if you've just stripped them, you think they are clean but sometimes get little bits of crap like dust etc...

[R P Corse]

Sorry just seen the bit where you checked the spark lol

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they are on the old carbs, the ones i cleaned out are from a dynojetted race bike, i will strip my current ones over the weekend, and as the coils will be exposed i thought i'd best check them then.

as far as i can see, it cant be battery as thats only a few weeks old, charging circuit seems ok, so it could be the CDI, coils, or HT leads, i think there is something inside each spark plug cap that you can test as well, a resistor maybe?

anything else for me to multimeter??

[R P Corse]

Could always do the coil stick mod lol

Ermmmm well maybe clean out your carbs mate, could well be an issue, is certainly look at the spark plugs being ONE of the problems, I think that's just me not liking the iridiums...

The tests are pretty much the ones you've listed... If all is ok then carbs need a clean out n see from there

[Tirpitz]

If I were you I'd change the HT leads. They don't last forever and they can cause hard to fathom faults when they start to go. You need a metre of HT lead for the swap. Obviously use the existing OEM leads to cut your new ones to the required length. On the old ones you will see like a rubber ring shrunk onto the lead at the coil end. This helps to form a waterproof seal. Make sure you pull these off the old leads and push them on to the new ones, don't chuck them away with the old leads. Then you will need to label up your new leads with cylinder numbers to help in future - a bit of gaffa tape wound round with the number biroed on seems to last.

It's a no-brainer really. A metre of lead will cost you about £2. It's not worth not doing for that money.

I've had a few bikes which have developed irritating misfires and every time it has been the HT leads. TBH I think the stuff the Japs use doesn't fare well in the British climate.

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checking the coil windings now

left hand coil, primary winding resistance = 3.8 Ohm, so slightly high
secondary winding = 24.3kOhm which is quite a bit more than it should be.

right hand coil, primary winding resistance = 3.8 Ohm, as above
secondary winding = cant get one at the moment...i have a connection between the top and bottom of the spark plug holder, gonna check the HT lead to see if there is a current flowing.

so i think i need new coils and HT lead, the spark plug holders seem ok.

i have posted a question in the electrics section about the IC ignitor if you wanna have a look please Tirpitz?

[R P Corse]

If you do need coils mate I may have a spare set laying around - that is if the H and L coils are interchangeable

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ok, turned pilot air screw another 0.5 turn out and swapped standard air filter for K&N as pilot was running way too rich.

pilot is now sorted.

shimmed up the standard N77S needle with 1 shim to try to richen up the mix a tad, bike now pulls from 2k like a trooper, even in 6th gear, up a slight hill...but now it starts to splutter at ~8k rpm so i think its now too lean, i take it that larger main jets (stock K95's are in at the moment) say 98's or 100's might help to richen up the mix now.

the misfire was caused by toad HT leads, one had no connection where it plug into the coil, and two had really bad connections at the spark plug holders.

still think the coils might be on the way out, will look at getting the jetting sorted first...