A difficult diagnosis

[1340fxd]

Problem: Bike was running fine but recently has coughed and spluttered on starting, runs OK once warm but still not as responsive as she should. I fitted new spark plugs – problem goes away – for about 100 miles then repeats. Fit new spark plugs (iridium this time) – bike runs really well – 100 miles later after idling at traffic lights, starts to run all lumpy.

When I say lumpy, she appears to be running on all four cylinders but fluffs up when I open the throttle. The plugs are a very dark brown but not black soot.

Factors: I have fitted and fully charged a new battery and new plugs.

My diagnosis: I think the spark just isn’t hot enough to keep the plugs self-cleaning. I suspect it’s either a dead or on the way out coil or the Newtronic contactless ignition.

Has anyone had a similar experience please?

[Al]

http://www.z1ownersclub.co.uk/forum/vie ... php?t=9699

Might be worth a read through this before you condemn the ignition.

Are all four plugs the same colour?
If so its unlikely to be one coil or one pick-up.

My guess is that mixture is very rich in the pilot system / choke settings.
Are the chokes fully off?

The next hotter running plug may burn cleaner but it wont help with a cold engine which is when you experience you're problems.

A more free flowing filter may help (k&N) or weakening off the mixture in the pilot department.
Are you using regular or premium fuel?
Less choke to start the bike may help also.

Iridium plugs don't burn hotter. They have the heat range that is printed on the outside.
They may be slightly less inclined to foul but they were conceived to extend the period of servicing on modern engines (lean burn engines) and very high performance engines, which these are not.
The central electrode is of a more substantial material which resists wear however as far as i can tell the nose insulator is made of the same material as good old 'any other plug'.

I believe that this is where you're problem may at least, in part, be coming from; fouling of the porous nose insulator if you're' plugs only last 100 miles.

It would also be worth confirming that although you have a new battery that you're coils are receiving full battery voltage.

AL

Edit to correct misleading typo

[Pigford]

NEWTRONICS IS NOT A PARTICULARLY GOOD SYSTEM
As its an optically triggered unit, it must be set in dim light - NOT IN SUNLIGHT Or the timing may well be out

Is there a good 12 volt + feed to the coils

[gray]

when you say it was running fine , and then deteriorated you didn't say when that was .
It it was running fine last summer , got laid up for the winter and then started running rich this year when you broke it out of hibernation , could be the fuel. That would affect all cylinders equally . And as it's so dear , we're all guilty of trying to conserve the stuff , and don't like throwing it away. Unleaded goes off surprisingly quickly - 6 weeks my local garage says , and they race TVRs so I respect their knowhow
Just a thought - could be a quick fix.

[1340fxd]

thanks zorded - some interesting observations and link to the useful thread. I suspect that my pilot settings are too rich, fouling the plugs which then can't clear themselves.

Will follow-up and if it's the case, you have saved me a lot of time, money and frustration. Fingers crossed it is the solution.

[Al]

Brown is the new black.

Black nowadays means a probable misfire or more drastic; flooding carbs / desperately over-rich mix, for what ever reason.
If you look at the mixture strength for modern vehicles using modern plugs and contemporary fuel they are light tan at their darkest to mid grey with perfect combustion conditions.

I use the colour constant in the top of my disposable lighter as a guide.

Could try any of these;
lower the fuel level by a mm.
free flowing air filter
retard ignition by 2 degrees
higher octane pump fuel
octane booster
next heat range up of plugs
boosted ignition system
reduced (weaker) pilot settings
choke system overhaul
filling up fuel from a different location or company
change plugs more regularly
less choke to start
less idling on choke
fewer short journeys

which all plays neatly into the hands of thrash merchants like me; drive it as often as you can as hard as you can!!!!

An in-line fuel filter may slow down the recharge to float bowls if there's a suggestion that you're' pingel is flooding the carbs

From the list above; i doubt that any of these can be done in isolation without there being knock on effects. For myself it has been a balancing act to get the right combination of subtle changes that work with my present setup.
FYI i have done all of the above to a lesser or greater extent and some i have backtracked on but it seems to be fine for now.
If you do none of these at least you are aware of the potential and if it re-occurs there are at least some possibilities to try out.

Good luck
let us know what you find.

AL

[1340fxd]

Well - could it be this simple?

I checked the pilot screws and they were two turns out, so I re-set them to one turn. I cleaned the blackened iridium plugs. She starts up OK and appears to run well with a "splashy" (i.e. slightly lean) exhaust note on tickover.

If zorded is right (and I think he is) my old plugs could cope with the over rich pilot mixture but the new iridiums got killed by it.

Thanks mate