California eating spark plugs

Get down the pub. NOW!!!

It’ll look the same, but you won’t care

According to Dellorto, and IIRC Amal, the main jet only affects the mixture above 3/4 throttle. So unless the OP has been wringing the nuts off the bike, I doubt that would be the sole cause.Easier way to make it richer over most of the range is to raise the needle one notch.

I was advised BY the Dell’Orto importers, that the needle jet also needs upping. After all, none of us spend all of EVERY trip, flat-out, on main-jet. Hence my advice on increasing the needle-jet size.

No only main jet, the rest is easily compensated if necessary by idle screws. Bear in mind at lower throttle most of the air restriction is the throttle slide, and super free-breathing K&N’s won’t make any difference to that. They will to wide open though. EDIT: Qualification ~ my Spada ‘conversion kit’ included one step up larger mains, and the instructions said that’s all you need, apart from the basic setting up.
Mike H2013-10-12 21:56:58

So what you are saying Mike, is that at smaller throttle openings the different filters will have no effect. I would agree with that. They will only have a progressive effect at higher throttle openings.At very small throttle openings even a clogged filter will work perfectly. So basically we all agree that this will have no bearing on the plug issue, unless the OP has been running at or near full throttle for some time.

Sorry, no…idle jet only covers a bit of it…there’s a big area in the mid-range that needs richening-up, too.

Yeah but no but, which will be covered by the main jet, as there is always a large amount of overlap between stages. At least that’s what DellOrto tuning manual says. @ Brian: exactement monsieur

It works, believe me…up the needle jet by +2. Main jet + 10 to + 12%.

Well Spada K&N kit didn’t say nothing about needle jets, just main jets, which were included. I wouldn’t mess with the needle jet or needle at all.

Have to say on the PHF 30 mms in the T5 engine I contacted Eurocarbs and from 125 main they suggested 138-140 and did say that the needle jet would not need altering I tried the 138’s then the 140’s it is running 140’s now

I would. I have done. Works well. Ask my Mate, whose V-50 I upjetted for K&N’s. Needle-Jet & Main Jet changed. I rode it. Superb now. Flat, before the change.