<-=- Club Bevel Heaven -=->

this is a question for my oz readers in particular. a recent discussion with a few well known bevel specialists in oz have all told me to not use a well known premium unleaded petrol in my mhr, my reason for contacting them was that i keep fouling plugs, at a recent hot rod function with my father, discussions with owners of chevy block motors who were running premium unleaded with a valve additive, i also run a valve additive with the petrol, were also fouling plugs, one bloke said when he stopped the additive things were good. Is anyone out there finding the same problem with their plugs if they are running a valve additive to the fuel of their bevel, the carbies are off for a rebuild at the moment so i cant test this theory right now, but it does not always foul the plug on the same cylinder, a plug lasts about 50 km and i always change both plugs not just one, if it continues once the rebuilt carbs are on and balanced, whats the next step in the process of elimination, regards darren

If your talking about Shell Optimax,yes I get fowled plugs on it,and it will not burn off,have to hit the plugs with a wire brush,I just dont use it.I also
dont bother with the addative and so far OK.This is in Sydney.

Hi,

Just a UK perspective ...

My SSD doesn't like Shell Optimax or BP Ultimate or Castrol Valvemaster Plus. Bogs and fouls plugs, worst on Optimax, least on Valvemaster.

Strange, 'cos my RGS Corsa is better on Shell Optimax ... but also doesn't like the Castrol or BP Ultimate.

Craig in UK

A vieuw from Holland:
One of the last bevel specialists overhere told me to use ONLY Shell V-Power, because of it's cleaning additives.
I use it with Millers VSP additive (valve seat protection) in my Mille, no problems so far.

Hi Darren,

I'm in Western Australia and have had a similar problem when running my Darmah in city riding. I use a slightly hotter "6" plug which seems to help. My bevel mechanic guru advises me that you should never use a BP Ultimate type fuel, just plain Premium plus a valve saver. His logic for this is that the 98 octane type fuels have a much higher "octane density" (ie power per volume) than what PHF carbs were designed for. Using this fuel means that the carbs have no choice but to supply a rich mixture, as PHF carbs supply fuel "by volume". You can adjust this at idle with a mixture screw, but the pumpers supply a set volume of fuel (unless you want to mess with them) as do the jets, and the air (past idle) is limited by many other carb parameters. So unless you want to fool with jets, needles etc to experiment, he recommends not going past premium fuel. The 98 octane is apparently best left to computer controlled injection systems that manage the mixure automatically.

I use FlashLube valve saver and had my valves checked a month ago, and it seems to be doing the job well, but I do have to clean/replace my plugs around every 800km. Next major head service, guess what I'm gonna do!!!

Regards,

Kevin

Im sorry, but I don't agree, "higher octane density" is just BS, the so called premium fuels have the same ingredients as plain 98 fuel, but they have more cleaning additives, no Dellorto or other carburetor will "notice" this, but the entire engine, including plugs, will stay cleaner.
When fouling plugs, there's something else wrong, like weak ignition, bad leads, or just worn or wrong heatrange(!) plugs.
The premium fuels are the best option for any engine, including bevels!
As for computer controlled engines, they will run on almost anything, even when using bad fuel, the computer will notice this and retard the ignition for example, to prevent problems like(high speed) pinging/ nocking!

One more thing:
As the ignition on my bevel is (German) Bosch, and Ducati advices Bosch plugs in the owners manual, I use only Bosch plugs.
I have good results with the W5AS silver electrode (racing) Bosch spark plug with 0,6 gap.
Standart plug for most bevels is Bosch W6BC copper core with 0,6 gap.

thanks to everyone so far to your replies. After speaking to several highly regarded mechanics of ducati genetics they all warned me away from that brand of fuel that craig and vince mentioned but i didn,t want to use brand names because some companies might get upset, so in oz that sort of goes against what peter has to say about his dealing with his type of fuel he is able to get over where he is,in regards to machten and his reply i was running a hotter plug but i would still only get about 40km out of a plug and it would alternate between front and rear plugs fouling . So this is where i am at, firstly i had the carbs cleaned and tuned properly by someone who knows what they are doing, same result, then we checked the electrics and all ok there so now the heads are off and they are going to get new valves and seats, harder seats so i can run it on just straight unleaded to take away the need for a valve additive with the fuel although the other stories i did hear about plug fouling was to do with the valvemaster brand of additive so i haven,t tried any other brand to see if i would get the same result or should i say lack of result, so when the heads are back together we will see if there is a different result. Now another result, i just picked up a 76 900 ss rode it with 2 year old fuel in it with stp high octane additive added to the premium unleaded caltex fuel and the thing reved through the range crisply and purred like a lion figure that one out.

Darren, what brand and heatrange plug are you using?
If you are using the japanese NGK, try the Ducati original Bosch plugs I mentioned in my other post, but check the right heatrange at your Bosch supplier.
I don't think japanese parts go allong well with a classic European engine.....!!!
Just imagine Dr. Taglioni testing his first bevels with japanese parts....????
No way...!!!
Ad for the lead additive, I know lots of beavel owners with original Ducati bevels ( 750 yellow Sport 1973, Mille S2 1986, 900MHR 1981) who don't use any additive at all, just plain leadfree fuel, and they are all running fine for many years now.....!
As I said before, in my 1985 Mille MHR, I use Shell V-Power premium fuel with 97 octane and the right amount of Millers VSP additive, I also run K&N airfilters, and I change carb. settings often to get better results,( the Mille is very sensitive for carburator settings) but I NEVER had a (Bosch) plug fouling....!!

peter, i have ngk plugs in there at the moment because i thought while im chopping and changing everything to try and sort out the problem ,because i was fouling the bosch as well, and when i bought the bike it had the ngk in there, ive got the k and n filters on and in regards to the leaded fuel like everything else thats good for us the government took that away from us as well so we are a little bit limited on our choices of fuel over here.I am hoping that when the heads go back on i can run straight unleaded with a octane boost additive to give me that leaded feel anyway that will teach me to buy a bike that was sold as running when i stored it mate, maybe like everything else that seems to come into the country at the moment you have to check if the product actually is made in its country of origin and not a imitation copy. good on ya peter for your thoughts and reply

Hi,

A further comment on the "octane density"...

I should probably have written this as "octane/density". The octane part is largely irrelevant. The octane rating is merely a measurement of the ability not to preignite under compression pressure. Given stock bevel compression ratios, this probably doesn't matter. Density, on the other hand is important. Here is what Elf says about their low density, high octane racing fuel...

[i]Can I expect more power by tuning Elf BFK-07 in bikes or karts?
Yes. Given the specifications of Elf BFK-07 you can expect better engine performance providing the engine is tuned to meet the demands of the fuel. Elf BFK-07 has a very low density of .700. It is also a very fast burning fuel in comparison to PULP. Given this, we would recommend that for both 2 stroke and 4 stroke engines, they be enriched by 12% to 15% depending on engine condition tune etc. By resetting the carburetor and correcting the ignition timing and you can expect better engine performance and power throughout the race duration. [/i]

ie. -- an example of lower density running lean. The corollary is that higher density runs richer. PULP has a density of mid 700s. UPLUP has a higher density in the higher 700's. In effect, the density relates directly to Mega Joules / litre. (that's why LPG has less power without turbo/super charge/ pre injection compression) The effect of this in a volume regulated carb is that with denser fuel a greater amount of volatile compounds are vapourised into the combustion chamber because the fuel mixture is regulated by the combination of fixed size jets and the carb throat widths. Have a look at the fuel standards, if you inject the same volume of a higher density mix, is it richer? In summary, I'm not convinced this is BS, I think there might be some science in this. (but I'm happy to be convinced otherwise!!!)



Regards,

Kev

As an aside...

My experience is based on using stock darmah airboxes and filters. Changing the air/fuel mixture by allowing more air would be differnt.

Kev

Kev,
We are talking about premium fuels, not (Elf) racing fuels!
At least overhere in Europe, the premium fuels are suitable for every kind of engine designed to run on unleaded fuel, no matter what the octane demand.
Again, my '85 Mille runs great on Shell V-Power with the addition of Millers VSP ( www.millersoils.com) also my '73 Kawasaki two stroke runs great on it ( with synthetic Castrol two stroke oil injection), as does my '85 Alfa GTV-6 (with Millers VSP) and my '88 Pontiac Firebird runs ok with Shell V-Power 97 octane as well.
In fact, I use it in every kind of engine I have, even the Vespa moped of my wife, and my Briggs and Stratton 4 stroke lawn mower, never ever fuel related problems.
The quality of the new, modern premium fuels is so good, every engine will run good (or better) on it, without any adjustment whatsoever.
Again, your problems maybe something completely different, do you think the big oil compagnies will sell fuel that's not compatible with any kind of engine?

Hi Peter,

The purpose of the elf example was to demonstrate that fuel density has an effect on mixture. As I said earlier, octane is irrelevant for bevels,

I work in the petroleum industry and have some understanding of the construct of motor spirits. In Europe, I believe (if I recall correctly) the standard requires a change in components on quarterly basis, reflecting the needs of climate changes over the year. In Australia, the components change on a monthly basis and it depends on the region in Australia. So, wherever you are, your fuel changes all the time, so it is hard to make a sure assessment on components.

You said "The quality of the new, modern premium fuels is so good, every engine will run good (or better) on it, without any adjustment whatsoever. " I think it is more accurate to say that they probably won't run worse on it - for a while. I do think fuel density matters for a volume delivery carb system. It is an opinion that I have been convinced of for fuel in Oz.

Lastly, you raised "do you think the big oil compagnies will sell fuel that's not compatible with any kind of engine?". I refer you to LRP!!!!.

Kev

Kev, what about LRP?
Look at www.shell.co.uk than "Shell for motorists" than "Shell V-Power" than "Classic cars and Shell fuels"
Btw, see the connection between Shell and Ducati (and Ferrari as well)....!!!!