Lead free fuel

[lawnmowerman]

I have recently purchased an A10 SR and I am not sure about the suitability of lead free fuel. Would the original valve seats be ok or do I need to use addative. I am using the higher octane fuel at the pumps as it is a high compression engine. I will not be doing many miles so is it probably not worth having new seats fitted if the existing ones are unsuitable.
The engine has been rebuilt so I have no idea if the seats have been changed and there is probably no way to tell without tracking the previous owners.

[MG]

There's serious discussion going on between engine experts on this topic. Some claim that the valve seats have accumulated enough lead over the years, so that they can be run with lead free fuel without any problems. Others disagree. Experience in operation shows different results.
There is no way of checking, whether your head has been converted to lead free, even if diasassembled, only a hardness check on the seat rings can show if they are suitable for lead free operation.

I personally use valve protection additive and I would suggest that you do so, too. If it doesn't help (because your head has been converted), at least it doesn't do harm.

One thing the modern additives can't actually do, is to reduce the tendency of the fuel for pinging, like the old tetra ethyl lead did. Therefore your approach to use high octane fuel is definitely correct.

[muskrat]

G'day lawnmowerman, If using std valves I would use an additive just to be on the safe side. The odd tankfull without it won't hurt. The main problem with unleaded  is pinging, which can be overcome by richer carb settings or retarding the timing a few degrees. Stick with the highest grade petrol available. Over here it's 98.
Cheers

[groily]

The debate's been rumbling around for ever. I used to think additives were necessary having read all the scary stuff that came along when leaded fuel was broadly withdrawn, but I'm not so sure some ten or more years and loads of road miles later.
I've been running all sorts for many thousands of miles without additives now, and the last time I looked at the A's valve clearances (the other day), the exhausts had closed a thou in 5000 miles - maybe. No trouble in 20,000 miles with it, anyway. That's an iron engine and cooking spec, a cruiser not a thrasher so stays mainly under 4000 rpm at a guess. Same story on my B.
On other alloy head but non-BSA vertical twins, I never seem to have to adjust valve clearances. One of them hand-on-heart has the same inlet valves and seats, and the same exhaust seats, it had in 1976 when I bought it, and has done zillions of miles and not been cossetted. On its third set of pistons and third bottom-end job in that period. Not a hc engine either, 7.somethings in there. On a couple of others, one with over 9:1, t'other at 8.25, no signs of trouble either yet, but I haven't done enough thousands on them yet to know for sure.
 
Guess it all depends how good the original seats were - and still are. Some people say that if an engine is generally run at under 3000 rpm, seat recession won't happen anyway, but haven't tested that theory.
 
Agree it can't hurt to put additives in - although there's a school of thought you should always use the same one, whether it be potassium-based or manganese or whatever. Another school of thought says additives should be used with 98 anyway - that was the advice here in France when leaded was withdrawn some years ago.
Agree also 98's obviously good on the higher comp engines but I find 95's fine on my lc ones, which run standard ignition timing. My highest compression engine I set a tad retarded as per common folklore just to be safe, and no pinging as far as I can tell over the disembowelled megaphone that passes for an exhaust and the greedy hiss of the twin concentrics.
I suspect the quicker As are maybe more sensitive than some other engines, judging from the recent thread here about pinging that couldn't be eliminated.
The only engine I ever had that consistently pinged despite best efforts was a 4-valve Krauser-headed BMW 1000 twin running 10 to 1s - that needed octane boost, best leaded gas, infinite care with the Dell'Ortos and the ignition timing and was frankly impossible. It also destroyed transmissions, camshafts - and eventually my wallet.

[a101960]

A subject close to my heart this is! I have long suffered the problem of pinging and I just can't seem to eradicate it. I use 99 octane and I have played extensively with both timing and the carburettor settings all to no avail (RGS fitted with 8.5:1 pistons). The best I have so far achieved was running with the ignition well retarded, but the engine ran flat and lacked go. I can get it to go like S**t off of a chrome shovel but then it will pink audibly under load. Even Eddie Dow reckoned that 35 degrees 3/8" BTDC was to much. He recommended 5/16" (See Beeza Bills website - Eddie Dow Twin Tips) http://bsa-a10.hailwood.com/tt11.html It is also worth noting that the Motor Cycle magazine road test of November 22nd 1962 said this of the RGS: "Although 100 octane petrol was used, pinking was audible if the throttle was opened hard on full advance at any engine speed" and this has been my experience, that said it would seem that pinging has been an issue with the Rocket motor way before leaded petrol was withdrawn from general sale. With regard to richening the mixture all I achieved by doing that was sooty plugs. I am inclined to think that unless the timing is spot on on both cylinders this could also be part of the problem. The late Bob Currie once wrote that he experienced pinging and running on with an early A7 just after WW2 using "pool petrol". Modern petrol is a bit better than pool petrol, but it does seem to me that the basic head design might be less than optimal for high performance. I am not into thrashing my bike I have to pay due regard to its age, but it would be nice to get it running as near perfect as possible.

[groily]

There could to be something about these engines in their better configurations, I agree, as your earlier thread and note above seem to suggest. Can't remember whether anyone else with a hairy A came back with reports of the same thing?
Thinking about it again, I really don't think it is the petrol, or not just the petrol anyway. There are too many period machines running well over 8.5 to 1 which don't have these problems, so why an RGS with a bit less than maker's full advance and the right plugs and carb set-up and decent valves etc etc should cause you all this grief is baffling.
 
I notice on my one and only and very unloved modern there's a gizmo around the induction manifold that is (I presume without wanting to know) some sort of ignition retard device for heavy load low rev situations . . . maybe we need someone to do some experimenting with a vacuum device attached to a movable Boyer-type ignition backplate! For that's the only way I can think of of getting the right advance for high revs and enough instant retard for high loads, like on hills, when winding her on at mid rpm, etc.
The basic Boyer-type electronic ignition set-ups, of which I have only one, doesn't have the necessary, but maybe they or someone else makes something? Drill and tap the inlet stub(s), vacuum pipe to backplate, springs to control it - just like a car distributor. Certainly could be done. I forget how many degrees of instant retard a typical auto distributor gives on the vacuum, but a good few . . . Anyway, enough to make a purist cringe . . . and, in my 'I Love Mags' mode, me too.

[muskrat]

G'day Groily, I was under the impresion that those vacume things advanced the timing. But your on the right track if we could get one that retards instead.On Boyer type ignitions it could be built into the black box. I recently tuned a mates '99 Buel that has a vac advance linked to the ign moduel and found the pinging was less with it disconnected but snap acceleration suffered. So re-connected and retarded the ign 3 dag, fixed. My high comp (10.5) A10 pings like mad at anything more than 31 deg, and thats running 98 boosted to 105. I have found that indexing the plugs helps. The same for my Rhonda Whore.
Cheers

[a101960]

I have found that indexing the plugs helps.

Indexing the plugs, a term that I am not familiar with. Could you please explain this for me?

[muskrat]

Means to shim the plug so that the gap is towards the center of the combustion chamber. mark the porcelin adjacent to the gap an d re-place the plug. Note where the mark is then place shim (washer) under plug to bring mark towards center of head. Clear as mud.
Cheers

[a101960]

Muskrat, thank you for the explanation. I will will try that out. Every little bit helps, as the Tesco Super Market chain is so fond of telling us. Is there any science behind this? I am contemplating fitting  lower compression pistons and or converting the mag to manual operation. Currently I am running 33 degrees BTDC but with a manual set up it would afford a bit more control, in fact on the A10 performance models I think that they were originally fitted with manual advance for that very reason. I spent the whole of this summer playing with settings and achieved nothing. Its all very frustrating.

[groily]

You're right, muskrat, they call 'em vac advance devices - but when you wind open the throttle at low/mid revs the old car-type gizmo retards it from wherever it's at until the load reduces when the diaphragm spring hauls the cb backplate back to where it needs to be on the simple weights and springs advance. In principle . . . Just as we might retard the spark at the lever on a manual mag on a hill 2-up etc. (No idea what the more modern thing on my unloved modern does exactly - maybe it's cleverer.)
Guess all these things are compromises - but the main advantage, I always believed, was for that snap acceleration that might otherwise induce pinging, and for slogging up hills. Anyone remember those Ford windscreen wipers that worked (or likely didn't!) off the inlet manifold vacuum?
When I had a fairly hairy car with triple webers etc and no vac advance fitted, it was a bit like the Buell you talk about and took a bit of fettling to get it right. But we get there in the end. That needed a 'book' 36 degrees at full mechanical advance, starting from 10-12 degrees static, but worked best overall at 34 fully advanced - which is probably back to the fuel thing where this started. Maybe Boyer make a system which compensates for throttle/revs already, don't know, as mine is a basic Norton kit fitted to something else (with an alternator!). Not much use to us though if we've got a mag and intend to keep it.
My highest compression bike runs a couple of degrees retarded at full advance compared to 'book', with a manual mag, twin concentrics and B8ES plugs, no probs. Don't know what it's like at slogging though as it's a revver and a thrasher (until I bust it and have to start again).
Thanks for explanation on plug indexing - never heard of  it before - a neat trick.

[muskrat]

G'day all, if you shine a torch at the wall and put your finger in front of it you get a shadow. Thats what the earth electrode on the plug does to the flash, so indexing helps for better combustion.
Groily, what size carbs, cam and comp are you running ? I have a pair of those Kehin PWK 30's flat slides (140 mains), 357 cam and 10.5:1 comp. I am also running a Boyer for a sNorton Commie as it has a shorter advance curve (commies use 28 deg full adv) and set it at 31 deg full adv which gives me 10 deg at idle. Pulls like a train up to 3500 then flattens out till the cam comes in at 5000. Still running in (300 miles so far) so haven't explored top revs yet.
You can take the boy off the race track, but you can't take the race track outta the boy.
Cheers

[groily]

That's an almost embarrassing question Muskrat in connection with the particular beast in question, which ain't a BSA . . .
However, since you ask and I'm not shy . . .That engine started as a stock '53 G9 Matchless; it has later SS cams, a pair of 626s, it's bored to 70mm from the standard 66mm (which is scary if I look at the cylinder wall thickness down below - thank gawd the protruding spigot on the sleeves goes against a deep throat on the cases) and the pistons are  lumpy +20s from (I think) what was known as the Matchless G9B, a 550cc variant of the mid '50s. The engine's near-enough square, with a 72mm stroke, and volume is actually about 560cc. The barrel base flanges have been milled down and compression is over 9 to 1 but haven't measured it precisely. The ports have been opened up a bit, the valve guides have been cut right down (too far - it smokes on the overrun as a result). Will put new proper guides in sometime - but not yet, too much fun. It has an oversize breather off the timing cover, some non-standard mains that are lighter than the normal bulky items (will probably not last but who cares?), and pulls an easy 50, 70 and never-tried-over-90 in the upper gears if you wind it on a bit. With an amplifier where convention suggests there should be a silencer it's a bit noisy. No pinging anyway - and no oil leaks! Reckon the last owner was trying to make a poor G45 copy but got into a tangle. Overall though, not bad for a '53 '500'.

My Boyer set-up is the standard basic Norton Dommie/Atlas type, but not sure what its detailed spec is. It's fitted to an Oilfield Constellation cafe racer. I set it up by ear really, using the little arcs in the sensor backplate to adjust things a tad at a time till it pulled cleanly through the range without flat spots or pinging. 8.25 to 1 I think.  Probably about 33 degrees full advance at a guess but have no idea what full retard is - will know when I strobe it for reference before pulling it apart next time. A bit new-fangled for me and hard to mend at the side of the road. Plus losing a whole toolbox for the twin 6v coils etc. Might put a spare K2F on it yet!

[BSA500]

I am using 8.5:1 on an a7 with alloy head and an auto advance on the mag.The only time I have had pinging is when one plug was going a bit duff, other than that no issues?.Not much help I'll shut up now.

[beezalex]

I've run vintage motorcycles and cars on lead free gas (some over 100,000 miles) for over 20 years and have never had any indication of valve seat recession.  It's a myth and that's all.  Now, tetraethyl lead is a knock inhibitor and works well for that.  However, the cause of knocking, pinging or pinking (really detonation) is caused by the air/fuel mixture being ignited by hot spots in the combustion chamber.  There are three things you can do to prevent this short of crutches like retarding the ignition or running too rich: Run higher octane/leaded fuel, reduce compression ratio or modify the combustion chamber to remove hot spots.  Any and all of these will work, but I have had great success removing sharp corners from piston crowns (particularly around the valve recesses) and polishing the combustion chambers.  Also very effective are pistons that produce a proper squish area which tends to quench hot spots, but this is, of course much harder to do since it requires new pistons.  I have turned several BSA's that pinged horribly into ones that NEVER ping just by careful massaging of the combustion chambers.

BTW, running richer will eventually only make it worse since built-up carbon in the combustion chambers makes a great hot spot.