Fuel...

[Padsta33]

Would I need to add lead replacement too unleaded petrol for a 57 flash? Or would it be okay to run her on unleaded?
Thanks all.

[Greybeard]

I use this stuff http://www.millersoils.co.uk/automotive/tds-automotive.asp?prodsegmentID=911&sector=Classics
Other additives are available

[Padsta33]

Excellent, thanks.

[Topdad]

Depends on compression ratio ,I would have thought . Mines on 8.25 and I've never used an additive nor have I had any pinking. I try to use the "best" rubbish available , but other than that get by on anything without any problems .

[BSA_54A10]

No BSA's require any addative to run on unleadded.

[Padsta33]

Interesting in mixed opinions.
I'm not sure on comp ratio, as untested.
Pretty sure tho she's low compression. (Was told so,)and its pretty easy too boot over.
So is additive snake oil or not?

[duTch]

 I have flat top pistons (7.25 I guess), and run on Premium with no additives, and no (fuel related) dramas. Usually use BeePee, because some guys reckon it's cleaner, but peridically get caught out and sHell or CalTex are all available, and sometimes I have better results, but still on straight fuel.

[terryg]

"So is additive snake oil or not?"

I don't think so. It depends on your exhaust valve seat material and the compression ratio.

I had the exhaust valve seats replaced in one ally head before I found out that BSA used material that is resistant to seat recession. Money wasted but lesson learned!

My bikes are running lowish compression ratio pistons but the over boring pushes up the ratio.

Empirically I have found that using super unleaded works well for me. No pinking and, if I choose carefully, no ethanol either.

[BSA_54A10]

"So is additive snake oil or not?"

I don't think so. It depends on your exhaust valve seat material and the compression ratio.

I had the exhaust valve seats replaced in one ally head before I found out that BSA used material that is resistant to seat recession. Money wasted but lesson learned!

My bikes are running lowish compression ratio pistons but the over boring pushes up the ratio.

Empirically I have found that using super unleaded works well for me. No pinking and, if I choose carefully, no ethanol either.

Like most things you read in the popular press, valve seat recession was over reported, miss represented and plain lied about.

All of the valve seat recession testing data came from the aerospace industry and happens at 30,000 feet running in lean burn mode at revs no BSA will attain.
It was all hype done by the media to scare the pants off everyone and sell lots of magazines with lots of aricles about how to fix a problem that never existed in teh first place.

[Topdad]

When I rebuilt my motor some 10 yrs ago I had all the machine work done by SRM basically because they were one of the few companies who told me that valve recession was mostly a myth. Mine certainly seems fine after 10 yrs and ,touch wood, I see no need to worry about it. The super unleaded seems to do the trick.

[Triton Thrasher]

Worst seat recession I've seen was on another well-known twin cast iron head with seats cut into the casting.

But it was on the inlet valve seats.

And I was using leaded 4 star.

[chaterlea25]

Hi All,
I have just had both a B31 and B33 cylinder heads fitted with inserts, the heads were really recessed on the inlets,
The B31 exhaust side of the head was very pitted, I suspect it sat for years with the exhaust valve open and moisture did the damage?? B33 exh was suffering from excess grinding ????
I have bult a few japanese 250 engines from the 30's for some reason  or other thay all needed seat inserts???

John

[morris]

peridically get caught out and sHell or CalTex are all available

Well... what the... Caltex...!? You guys still got that stuff? 
Must be at least 40 years since they closed the last Caltex over here... 

[BSA_54A10]

I would hazard a guess that a lot more "valve recession" is due to over ehthusiastic use of valve seat cuters than fuel causing valves to monentarily weld to the seat then ripping a lump out of it when opened which is the mechanism of recession.

[duTch]

Well... what the... Caltex...!? You guys still got that stuff? 

 They must've moved here, They took over the I think Ampol factory, but not 40 years ago (I even remember it as I think Ampol)

 If BeePee shut down production as they said they intended a year or two ago, they'll be the only local 'fuel' brewers.

 BeePee spent a LOT of $$ on infrastructure and upgrades a few years ago, so is a surprising move.