Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board Proper fuel for 67 BSA Lightning

Just got my Lightning on the road again after nearly 50 years of dormancy. Engine rebuild was part of restoration. Question: What type of fuel should I be using? Searched the Forum but can't find a definitive answer. Currently burning 93 octane unleaded, ethanol-infused gas from local gas station. Is that OK or is non-ethanol preferred? Leaded?

Runs well. Starts easily and idles smoothly. Acceleration seems good. No knocking as far as I can tell. Not a racer. No long hauls planned. Just around the town and local countryside use.

Leaded vs non-leaded is not an issue. We were all afraid of valve recession problems back in the 80s when the lead first disappeared out of regular pump gas, but it didn't happen.

Ethanol in fuel is just a waste of money in the name of Feeling Green. It knocks down your gas mileage, it gunks up your fuel system if it sits a while, so if you keep it in your bike, you have to look out for the inside of your carburetor ... pilot passages and float bowls. It also eats up fiberglass, but that's not an issue on yours. But it's all you can get in many places.

The higher the octane fuel, the farther you can advance your timing to gain a tad more power without pinging. If you (as a test only, BSA engines don't like being "lugged") idle along at 2500 RPM in third gear, and then open the throttle fairly quickly for just a second or two, and it doesn't "ping", then your timing is fine for the fuel you are running. I just advance my timing so that it barely "pings" under the conditions above on 89 octane.

Of course, it'll run best on 110 octane leaded avgas, but (A) if the airport sells it to you in a can, THEY will be liable along with you if you burn untaxed fuel on the road (which may or may not bother you) and (B) the stuff is like $12 a gallon. I prefer to set the bike up to burn what I can get!

Lannis

If you can and do use your bike year round, the ethanol should not be a problem. Otherwise clean it all out before periods of un-use. We can get 100 octane here in Sacramento, which my Victor likes.

Your bike was designed to run on leaded petrol
Now lead is no longer in fuel
And fuel is not petrol
Now what of the modern slops will work best in your engine is going to depend firtly on what compression you are running
9:! or over will require the highest octane rating you can get your hands on
If you are running flat tops then you caan go down qite a long way
Running too high a grade of fuel ( which is not petrol ) will cause no problems other than lightening your wallet
Running too low a grade will cause the engine to ping which is not good to say the least .

As life is expense I use the cheapest stuff available
the only precaution I make is draining the fueltank when not in use for a couple of days
but then I've an original '60 polyester tank

Lannis said it all. I bought some 110 octane at a performance shop that serves a local race track. These old bikes love it and it even smells good. I mixed it two parts pump gas to one part high octane till it was gone, 93 octane is fine. Time your bike to suit it.
Mr Mike

a little anecdote about this *rap unleaded

Brought a bike a while back and the guy had filled it up with avgas , probably to perk it up a bit for sale. Anyhow i got it home and realised what was in the tank. Im going to put that PETROL in the A65 ,,, so i did.

without a word of a lie when i started it ( sill had unleaded in carbs and lines) as the real PETROL filtered trough you could hear the whole engine note change. So as any thinking man would i took it for a blast immediately .

MAN did that make me realise how much power this *rap fuel has cost us!

I use 100LL Avgas as it is readily available to me. Right now, with gas/fuel prices sky high, it is $6.50 here. I filled up several cans for the riding season before the prices took a sudden jump.

How I see it...
If wiki is to be believed:
From the 1970s many countries began phasing out and eventually banning TEL in automotive fuel.
For the most part in the US, leaded has been gone for over 20...if not 30 yearswhen

Innospec has claimed to be the last firm legally making TEL, and as of 2013, TEL was being produced illegally by several companies in China.[8] In July 2021, the sale of leaded gasoline for cars was completely phased out worldwide, prompting the United Nations Environment Programme (UNEP) to declare an "official end" of its use in cars on August 30 (although it is still available in aviation fuel for light aircraft.
over the road motor vehicles???

LL Avgas therefore being illegal (for road vehicles) and airports selling leaded are afoul of the law.
High test racing gasoline is OK except it is not road taxed? Again illegal for registered motorcycles.
In the US, What you are now legally buying is not gasoline but IIRC "spark ignition fuel". Usually called by grade E10 or E85 flex fuel.

MBTE replaced lead and was also stopped agound 2004.
No leaded
No MBTE
No legal choice
Now Ethanol....better off drinking than burning in your E10 powered engine

Won’t argue with the Hi Compression guys, or the racers. No experience with that here. IMHO, not worth the trouble for a daily rider.
AvGas is fun for the smell, and may in fact run OK (better?), but was intended for a set RPM, and in MY experience (as I have been contradicted) will gum up the carb if allowed to set a long time. This especially so if the bike/carb are the “normal” Brit slow leakers. Not running 10:1 compression or racing. AvGas has a dye in it to help ID it from others, and that is also a means of locating any leaks in the aircraft fuel system,….. look for the gummy blue residue. Look for the gummy slide…. I used it while I was getting back into it, in the learning phase, along with trying store bought octane boosters and was over thinking the whole thing. Quit using, and didn’t notice missing much except that neat smell!

If you want the great smell just put a drop of R in the tank.

Been running it for decades in multiple machines, BSA's, HD's. Have never experienced gummy slides in any of them. Spark plugs experience less fouling and show less soot, darkness, and deposits.

And yes, Avgas is different. Pump gas goes boom, whereas Avgas goes booooooom.

I use it in my shop in place of genral purpose cleaning solvent, since it is cheaper to buy. It evaporates quicker than pump gas, doesn't leave that lingering terrible pump gas smell, and lasts months compared to pump gas life of barely 2 months. No water sitting at the bottom of fuel tanks either like ethanol gas (spark ignition fuel).

My '68 Royal Star does not like ethanol gas. As well as some of my lawn and garden equipment. The ethanol attracts moisture will cause a clog in the idle circuit of the carburetor if the bike/snowblower sits for a while. The result is that it won't start, period. I'm well experienced disassembling my AMAL carb as well as the snowblower carb to clean the tiny orifice with a wire from a wire brush. I learned that from John Schumacher at Mobile Cycle Works in Ashley, Ohio. I use only non-ethanol fuel. Rec 90 is non-ethanol and is is sold in areas where there are marinas. In my neighborhood a Circle K station sells non-ethanol and recently Sheetz has come to the area that they also sell non-ethanol fuel. I recommend that you avoid ethanol laced fuel in your bike.

I have heard all the reasons to not use avgas. I have used it in my 650 Triumph race bike and never experienced a problem that I could relate directly to fuel choice. It works well for my purposes. Bought some yesterday. It's up- like everything- $6.10/ gal.

I had a 68 BSA Lightning that I purchased new. From new I never put anything in it except premium. I never had any problems, and it was an outstanding motorcycle. It was actually the most reliable motorcycle I've owned. Today, I refuse to put ethanol fuel in any of my motorcycles.

I only ride on the road these days so premium 98 is the fuel of choice.
When in more remote areas, i have bought 95 which is 10% ethanol
as i seldom do more than 90mph nowadays it really doesn't make much
difference. My bike has a 9.2-1 compression and an ignition advance
that copes very well, so it doesn't ping. As i may sometimes use the
lesser of the fuels and lots of stations may have had the fuel in the tanks
a while, i tend to jet the bike a little richer than optimum to be safe. I like
to ride my bike and have to just go with whats available. When i raced
i used avgas and blends thereof but now i just set the bike i prepare up
to run on 98 and it's fine. Most here race on methanol, i can't be bothered
to start the learning curve all over again and we beat most/all of them anyway
so i doubt it is down to fuel.