misfire that won't go away..

[Muddi Camel]

help...... please
I've got a low mileage foxeye that's not been used over the winter. Battery's been trickled all the time, so it starts on the button, but runs rough. It was all serviced & balanced at the end of the summer and ran beautifully. 
The plugs seem clean still, but pulling #4 lead off and there's little change in engine note - significantly less than the others. The leads are doing their thing, and I can't see how a dormant plug could die over the winter....
As there seems to be a spark getting to each plug, I suspect fuel.
I've just put a load of fresh fuel in...  no change.
Is there anything else I'm missing?
Thanks

[ade the blade]

you have answered your own question mate...renew plug #4 and all should be well. if engine note shows no change in running then obviously that lead or plug aint doing its thing. switch plug 4 with plug 3 and see if `no change` follows it. good luck.

[Muddi Camel]

I tried a complete new set - no change.
I'm wondering if the fuel may have "gone off" and/or gummed something up - hence putting a load of fresh stuff in.
 

[Dead Eye]

If its specific to one cylinder then I doubt its a fuel issues, sounds more like a spark issue to me.

What did you replace? All the plugs, all the leads, both?

If you replaced only the plugs then I'd suggest its probably the lead to cylinder 4 - the coil pack should be fine if no other cylinder is having issues (there are 2 packs which control 2 cylinders each). Best thing to try is to take the cap off the plug and the lead, trim a few mm off the end and replace the cap and see if it helps.

[ade the blade]

my money is still on electrical. if it was fuel then you`d possibly have terrible probs just starting it ! are you getting a nice meaty spark from lead for that plug as strong as the others, if so, is it constant? try trimming back the lead end a little bit. seems strange how it can fire up on the button and then run rough.  perhaps that coil pack is breaking up ( think it `sparks` #1 lead too ) play about with the leccy side mate only other possibility is water / condense in #4 float bowl. how much new fuel have you run through the carbs?

[ade the blade]

sorry Dead Eye...........bit of an overlap there, but hey, great minds and all that

[bigsteve]

Her in doors has low mileage 600 boxeye same story not used for few months and ran really rough
 
  I sprayed WD on to headers and noticed number 3 not getting hot like others
 
  checked and swapped plugs 10mm off leads then new NGK plug caps still the same
 
  ended up being one blocked idle jet in the carb

[Muddi Camel]

It seems rough throughout the rev range - I suppose that sounds more like electrical because different jets come into play when it's at speed?

[ade the blade]

have you tried Big Steves suggestion (spraying wd40 or plain water onto headers to see if #4 is `cold`? coming back to my suggestion of water / condense in carb bowl, this obviously will affect performance / fuel flow across the rev range too. still betting on sparky things

[Muddi Camel]

You should've heard the expletives from the cantakerous codger next door earlier 
Anyway, no I've not tried the wd trick yet, but I'll have a go tomorrow most likely.

[bigsteve]

You should've heard the expletives from the cantakerous codger next door earlier 
Anyway, no I've not tried the wd trick yet, but I'll have a go tomorrow most likely.

  good job people next door were out when I fired Suzuki up with no headers fitted     
 
 

[Gnasher]

ended up being one blocked idle jet in the carb

    


This has to be the most likely cause if as you say the lead to No4 is providing a spark.

[Muddi Camel]

  good job people next door were out when I fired Suzuki up with no headers fitted   

The freaky thing is - between him & his son, they've got more machines than I have.  they play "musical cars" outside so that they always have their favoured parking spots....

Anyway, I'll have another go at it shortly. Doesn't the normal running jet take over from the idle?  Would both be blocked?

[bigsteve]

When I stripped carbs down and checked jets it was one jet blocked  but I cleaned everything 
So yes you could have both blocked  only real way to find out is stripping them
I tried running cleaner in fuel but that didn't work

Sent from my Orange Monte Carlo

[Muddi Camel]

ok thanks. What gaskets etc. will I need to get hold of?
Thanks

[bigsteve]

none just carb cleaner and thin wire