According to my parts book, the 1970 Lightning was offered with two different gas (petrol) tank sizes: 2 and 3-1/4 (commonly called 4) gallons. As near as I can tell, the larger tank was typically supplied to home markets while the smaller tank was typically supplied to US markets. True?
I have the 2 gallon tank (on my yet-to-run-again A65) and I remember from my HD Sportster days that small tanks look good but are impractical unless you're fond of hanging around gas stations.
My question to those of you who also have the small tank is: Even though my stock 2 gallon tank is dent-free and the original paint still good, would it be worthwhile to convert to the larger tank? If so, are the 3-1/4 gallon tanks and all of their various trim pieces still available?
1970 A65L (Yep, it's one of the "Y" bikes) 1942 HD45 1942 Boeing N2S-3 1930 Ford A
The capacity ratings for these tanks is in imperial gallons. The "2 1/2" gallon tank on my 71 holds close to 3 US gallons. Likewise, the "3 1/2" gallon tank on my old T150 held 4 US gallons. At least with the Triumph one could use a TR6 tank on a Bonnie to get more capacity. Most of the people I've met who had Euro tanks on OIF BSAs said they got the tank from England. Is it worth it? I certainly would like to be able to go more than 100 miles between fill ups.
Harvey, My A65 tank is about 2 3/4gallons. I modified the reserve petcock so it holds about a half gallon in reserve. I can go a little over 100 miles before I hit reserve. By then it is time to give the butt a rest and stretch out those shoulders and hands.
Harvey, My personal view is I like the looks of the larger tanks, but rarely have I owned one. Also, I've never owned a '71 or '72...
I suppose for the racing crowd, the smaller tank allows less weight upon the boik...?
Trevor's point about the strap is a good one. I haven't had a large tank to understand Trevor's point about noise muffling, but I must wait to see if it is a true statement, and if true, enjoy the sensation, and quieter ride.
On my Super Rocket, I often got a little over 100 miles per tank full, before having to switch on the reserve petcock.
When I owned my first A65, it had the fiberglas "loaf of bread" tank, which I believe only had 2 gallon capacity, and I was always hunting the next station on any 'long' trip... Brett
The concentric carbs use smaller main jets almost a 5th smaller in size ( my dadis super rocket is using a 290 main on a concentric as opposed to a 390 on a mono block) so the economy should be much better over a good distance.
AMAL would have sold every Concentric carb they made in the late sixties if ever word of that got out. Who wouldn't be ditching the Monobloc if you could save all that gas. I am a convert..
Joined: Sep 2002 Posts: 7,811Alex
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Joined: Sep 2002
Sorry allan, but the main jet size difference between Monobloc and Concentric carbs has little to no direct bearing on the mileage. If the carb is jetted to give the correct running mixture at full throttle all else being the same, the specific fuel consumption will be the same regardless of the absolute jet size. i.e. a correctly jetted Monobloc and a correctly jetted Concentric will have the same full throttle fuel consumption.
The main reason that concentrics often, but not always, show a slight improvement in mileage is because the transition between idle and running is better managed on the Concentric. John Healy has explained this several times, mainly that at small throttle openings monoblocs suffer from a collapsing volume in the chamber formed under the slide. To compensate, the mixture usually has to be enriched through this range to give good running and prevent hesitation.
Now, to get back on the subject of the big tanks: I really like them and am looking for one to put on my Royal Star. I had the one off my '62 A65 on there for about one year and I really liked it. 200 miles of range and it just feels a little more substantial, great for longer trips. The can be a bit harder to find here in the US...and you have to pay particular attention that you get a twin carb tank if you have a lightning. The cutouts for the twin carbs are a requirement. Also, a correct one with the metal badges for a '69 or '70 will be even scarcer here in the US, though the earlier ones with the plastic badges will fit, too.
A smattering: '53 Gold Flash '67 Royal Star '71 Rickman Metisse '40 Silver Star '37 Rudge Special sixtyseventy Lightboltrocket road racer...and many more.
Agreed on the carbs discussion. An engine runs best as some predesigned fuel mixture. Carbs area at best devices that try to approximate this using different methods with different results. One only has to look at electronic fuel injection to find something that provides the "predesigned fuel mixture" much more effectively than a carb. Fuel injection engines start easier, run smoother, and are more fuel efficient than carbs. The good side of carbs is they are easy and inexpensive to fix and make our motors pretty simple.
On the tank discussion, I offer this Alex: When you are on the backside of the sixties try 200 miles on an A65 without a break. OTOH, a bigger tank means less trips to the pump and there is nothing wrong with that. Mr Mike
<snip> On the tank discussion, I offer this Alex: When you are on the backside of the sixties try 200 miles on an A65 without a break. OTOH, a bigger tank means less trips to the pump and there is nothing wrong with that. Mr Mike
Try 300 miles without a break! Of course I cheat. I have a BunSaver from BassPro to go with my aluminum 5 gallon aux fuel tank. It's the only way I have done two 1100 mile rides in 24 hours on my 1971 BSA Thunderbolt.
I've often wondered if when they say 2 gallon (imperial gallon) tank they actualy mean 2 gallons PLUS reserve...I have the US export 2 gall tank and a couple of times I've put 9 litres (almost exactly 2 imperial gallons) into it and havent been on reserve when ive done it?
Has anyone ever actualy measured how much these (and other) tanks hold or is it just some name given to them which isnt actualy an exact measuer?
BTW when concidering range on these tanks dont forget that when they were made you could get real petrol .....im convinced that the crap we pump now looses about 20% in terms of MPG and (as Trevor once described the "petrol" now) its realy just very very very light fuel oil with loads of addatives to make it burn!
"There's the way it ought to be and there's the way it is" (Sgt Barnes)
I actually filled my tank an drained the main and then the reserve measuring both That's when I confirmed that my reserve held about a miles worth of gas. I learned this for the first time on the road and pushed the bike to the next gas station. I modified my reserve so it held two quarts. And you can get a little more reserve by leaning the bike over and running the gas from the right side to the left side. Guess how I know that???? My A65 holds about regular 2 3/4 gallon (10.4 liters) and minimum 2 quarts (without leaning).