RS125 eating spark plugs!

[stirlinggaz]

hi all,
after numerous problems trying to install a bigger carb, i gave up & decided to put bike back to standard, & take it from there.
so put 28mm carb back on,
airbox back on,
new spark plug in,
& voila! bike started first time!
so i now know my bigger carb is knackered.
no problem....
so i goes to start bike today,
started ok, idled for a few minutes then died!
wouldnt start back up.
checked all the obvious things,
then whipped plug out, checked for a spark,
smallest weakest orange spark ever!
this is a brand new plug!
& i cant understand what has happened since it ran last week?
as when i had it running, i only took it out for a short run then back home,
where it has sat since?
this is the third time i have changed the plug only for it to die in exactly the same way,
so its obviously the bike/carb/fueling.
as when i remove plug, its wet & black.
anyone any ideas?
as at this rate i would need a new spark plug for every journey i make!
something wrong somewhere!
cheers,
GAZ

[Kickstart]

Hi

How long did you leave it idling and why did you?

Doing short journies and leaving it idling will make it more prone to fouling plugs.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[stirlinggaz]

hi,
only left it idling for about 2 minutes max,
just time to tighten up tank bolt & by the time i put my helmet on,
bike had cut out!
was just gonna let it idle till screen had changed from "COLD".
as i thought that was the correct thing to do?
ie - not set off straight away from cold, is this right?
or do i need to buy ANOTHER plug, lol,
cheers,
GAZ

[Kickstart]

Hi

Add that to your short journey before. And probably idling with the choke on (knock the choke off as soon as possible).

Personally I would say ride off immediatly. Don't warm it up idling (takes ages, and dumps loads of petrol into the engine which will do a good job of washing oil from the bearings, etc). Just keep the revs rght down until it is up to temperature.

That said if should cope better than your seems to. Ensure the mixture screw is adjusted correctly (that is what will determine the mixture when idling). Same for the oil pump.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[stirlinggaz]

Hi & thanks Keith,
i did let it idle for a while last week, before & after run,
as i was adjusting idle screw.
perhaps thats why im fouling plugs then?
as i have always let it idle till almost up to running temp!
got bad advice in past then!
i will heed your advice & set off straight away & just take it easy till it gets warm.
so off to buy a new plug!
cheers,
GAZ

[alains]

try an irridium model depense on your heath rate
i think your standard is BR10EG try BR10EIX or denso IW30
____________________
the worst day fishing is better than the best day working

[Kickstart]

[stirlinggaz]

[Phil_P]

How about leaning off the mixture screw?
____________________
It is not enough to win, others must fail.
Moto Guzzi 1100 Sport Injection '96

[stirlinggaz]

[Phil_P]

I'm not sure if it is a fuel screw, if it is, turning it in would lean the mixture. I'm not 100% sure so hopefully someone else will put me right.

You have a 50:50 chance of getting it right by guesswork, and you won't do any damage by trying it both ways so nothing to lose by trying
____________________
It is not enough to win, others must fail.
Moto Guzzi 1100 Sport Injection '96

[alains]

gaz , i never had problem with irridium plug but i know problem can occur with oil fouling and top-engine & exhaust carbonized
clean it , avoid to scrap the center and if it work again here is your problem
____________________
the worst day fishing is better than the best day working

[stirlinggaz]

[Kickstart]

Hi

Depending on the exact model of carb it will either be an air adjustment screw or a mixture adjustment screw. An air adjustment screw works by changing the amount of air able to flow through the idle circuit. A mixture adjustment screw works by changing the amount of fuel entering the idle circuit. On the PHBH it is obvious which kind of idle adjustment the carb has. If the adjustment screw is on the engine side of the carb slide then it is a mixture screw, but if it is on the airbox side of the carb then it is an airscrew.

In either case turning it anticlockwise will allow more through ; more air with the air screw (so leaner) or more fuel with a mixture screw (so richer).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[alains]

2 strokes leave a deposit (oil excess burning) and when it begins to be important the performances get lower , the engine heat too much . to decarbonize , you need at least a rings change (or piston-rings,or top-end depense of their status) . i was talking about cleaning the plug avoiding to touch the little center , generaly it goes again and this is the sign of a clogged exhaust and carbon in the top-end (plug overheat)
____________________
the worst day fishing is better than the best day working

[stirlinggaz]

[Kickstart]

[stirlinggaz]

hi Keith,
sorry, i should have looked at the dellorto guide first!
ok, so my 28mm PHBH has little adjustment scew on side of carb, closest to front of bike, not at airbox end.(presume this is what you meant by engine end?)
so can i presume its a mxture adjustment screw?
& if i turn it anti-clockwise it will richen it up?
right - one more stupid question - im getting tired & my head hurts,
does richen it up mean leaning it off or the oposite, sorry lol.
but ideally, im told i want to lean it off"
am i getting it or not, lol
cheers,
GAZ

[Ariel Badger]

Anti clock =richer
Clock =weaker
Delorto are pants for this IMHO, very confusing
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Bikers make great organ donors, get 115 on your licence today.

[Kickstart]

Hi

Anticlockwise on that carb means richer. That means more fuel for the air.

Leaner means less fuel for the amount of air.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing