1983 DUCATI PANTAH 500SL
Q:
I have a Ducati Pantah 500SL 1983, which has been off the road for 20 years. Intermittently I have tackled various tasks and the bike is now ready to run. My question is, the fuel specified for use is 4-Star leaded and unleaded is not suitable. I have done some research regarding fuel additives and ‘lead pellets’ for the tank. I did approach a specialist to see if the valve seats and valves could be replaced, who declined the task. Can you suggest or recommend an option or solution, as at present I’m not sure which to trust?
A:
I know what you mean. I say that because if you look closely into this whole question of the banning of added lead in petrol, you will find a range of statements and answers. The trouble is, as always, that some information is based on scientific research, some on actual practical experience, but the rest is just opinion based on… well, what? Disregarding the question of lead for a moment, 4-Star petrol had a Research Octane Number (RON) of 98 so if you were to use a modern unleaded fuel, it would need to be at least as high as that. There are a number of Super-grade unleaded fuels that have this RON or very nearly (97), and one (Shell V-power) which is 99 RON. There is also the question of ethanol in modern fuel which changes its combustion characteristics, so you would need to experiment and possibly alter carburettor settings towards the rich side.
As you are probably aware, the lead in the old stuff had the effect of protecting the exhaust valve seats and this is also an issue. It is still possible to buy old-fashioned leaded fuel but the supply is extremely limited, so a more practical approach would be to use an additive which would, more-or-less, convert your unleaded into leaded.
Personally, I would have more faith in a solution which is carefully measured and put in with the fuel rather than relying on magic pills.
The thing is though: is the lead actually necessary? The way to tell if there is a problem is to assiduously check the valve clearances frequently as this will show if recession is taking place by the clearances closing up. That said, you might be best advised to use the additive anyway with the super unleaded, especially bearing in mind that your desmodromic valve gear does add an extra level of complication.
To be completely safe it would be best to also have the valves and sets replaced, and I think the refusal you were met with was because Ducati heads can be hard to fix in the machines which do the job. Matt Neal of Matt’s Machine Shop is very experienced in this field and if you give him a call on 01443 742791 he can give you some advice on what can be done.