is valve additive fouling my plugs

[wdietz186]

I would try running without any additives at all. The lead replacement stuff is there to protect old cast iron valve seats and fairly soft steel valves. Our Ducatis use a silicon/bronze valve seat and pretty good quality steel in the valves. What the lead in the fuel did other than raise the octane of the fuel was provide an expendable coating/lubricant to the valve seating faces. This was mostly to prevent the valve face and seat forming micro welds when they were very,very hot. These microscopic welds would be broken when the valve opened again leaving a rough surface that burned away,slowly letting the valve sink further into the head. This doesn't happen on our bikes and as lead is pretty much banned in available fuels who knows what compounds are being used in these additives? I've run unleaded in my 750 GT for years and haven't had any problems with my clearances closing up or any evidence of detonation visible on the plugs or piston.

[radecal]

Have had similar issues with my 82SS (warmed engine). Chased plug fouling issues for ages and found that the fine print on Shell 98 octane is right. Very rich running on the 40s. I changed to another brand and got a better response but have dropped the idle jets back a bit and she seems to have settled down. Never an issue when the throttle is wide open, only just around town/idling. I suspect the electrical system may play a big part as well as the weaker systems in the older bevels don't handle the new fuels (or what they sell us here in Queensland) as well as my later ones. Had to go hotter on the plugs depending on the time of year.
I notice the Shell 98 doesn't run well in any of my bevels or belts (plugs seem to have a black scum on them) but the injected are no problem.
It is my understanding that due to government restrictions on hydrocarbon emissions being released into the environment, modern fuels are less "volatile" than the older leaded fuels. Kev may be able to confirm that with the techs.
Never used an additive but I have hardened valve seats in my runners so can't comment on their effect on plugs. Only thing I use is StaBil to keep the fuel fresh for extended periods if I can't use it in time.
I do know the fuel goes off bloody quick if left for more than a couple of months due to the way it is made now. 5 year old tin of unleaded looks and smells like paint varnish while another drum of old Super I still have looks like the day it was made and still runs in my AJS.
Even in my cars, I notice a big difference in mileages depending on when we get fuel delivered to town.
Often hear people complain about the swill we sometimes get.
Regards,
RAD

[abmartin]

I'll second what Rad says about fuel going off quickly. I use StaBil for all gasoline-powered motors that need to be laid up for more than a couple of months, which happens pretty frequently here in Canada. No more problems with gummed up carbs and difficult spring starting. My car, a Ford Probe GT, would turn on the check engine light if it sat for any length of time. It would extinguish after running a tank of fuel through it.

Bruce

[JasonBav]

Hi, I have just come across this forum post, I know its a bit old.
I live in Sydney, and have been having allot of trouble with fouling plugs, I have recently purchased a 1974 GT with 32mm dellorto's. The previous owner had a bevel mechanic replace the valves and guides and as well as new rings and a hone (so I have good as can get compression). I have a Dyna s ignition, a rely to power the dyna coils, a st2 rotor to up my charging.
My question is, with todays modern fuels and me playing around with the jets and setup of the carb I can't seem to get a good looking plug, if I go for a good hard run (run off the main jets and needle etc) and take a plug out they look o.k but the running around in the city, my plugs look sooty black and fluffy, is this is as good as I can expect. I mainly use 91 and sometimes 95, I read somewhere that they were going to bring a colour dye to identify what ron was what, but all the fuel I have seen looks like a yellowish to almost clear.
I was told by a bevel mechanic to go up to a het range ( NGK refrence a BP5HS) as he reckons todays plugs and what they use to be I am thinking heat ranges.

[Vince]

Bit of a waste of time reading plugs these days.Other than the seat of your pants there is only one good way and thats a Dino.
Give Mick a ring at Motocycle Weaponery at Mona Vale.He is there Dino bloke,very helpful and the best bit is he owns a Bevel.

[machten]

Dunno about that Vince. I've tuned Dellortos more than good enough for street use for 30 years without access to a dyno. Reading plugs is still relevant too. The fuel has changed but the combustion engine and the signals it leaves hasn't.

Kev

[Vince]

Maybe if you are are doing the strong light and magnifying glass stuff up the plug inner but thats beyond me.The black sooty or white or tan thing seems not so easy for me these days,they usually come out black and yes I am going to say it MODERN FUELS.Just fitted a set of brand new Mikunis to my Leverda and the plugs came out after 200ks looking like they should or did back in the day eg not black at all,nice and honeyed so maybe new tight non leaking carbs are whats needed.

[machten]

[quote]....so maybe new tight non leaking carbs are whats needed.[/quote]

Yeah Vince, I suspect you're right that that helps...certainly for trying to get the old damn things to idle and synch evenly. Over the years I've accumulated about 6 sets of PHF 32's and a mate of mine used to work in an engine development company. He had them all laser measured down the slide paths for me. The printouts made for interesting reading!

Kev

[machten]

All that being said, you can tune Dellorto's pretty well and you can read the plugs. This one of my mine from my 900 is a little lean for my liking, but close to right...

It's actually a little darker than you see in this photo...



Kev