Fuel System: Gas (Petrol) tanks, Carburators
I’m in the process of rebuilding the petcock of a recently acquired ’67 CL77. The tank was pretty much yukked up from having ethanol gas sitting in it, and the petcock was completely clogged up with the MAIN standpipe being split and in terrible shape. The prudent thing to do was just remove it from the petcock body ‘cause there was no point in trying to save it. Fortunately, I was able to get it all out.
After clearing out the clogged ports, I soda blasted the body and am replacing the MAIN standpipe with a piece of 7/32” brass tubing that I’ve turned down one end slightly for an interference fit in its port. Since mine was in such bad shape, I kinda guestimated that the end sat about 5 cm above the mounting surface….. and that’s my question. Does anyone know what the correct height is for the petcock’s MAIN standpipe??
Thanks in advance.
Measured today the standpipe on a spare 1967 CL77 petcock I’ve had for some time. Vertical rise is 49mm, on the slope length it’s 50mm / 5cm. I have no reason to believe the standpipe was ever altered or replaced. So, you probably have it just about right.
Don't suspect it's very critical.... mainly just how soon you're required to switch to RESERVE, and just how much RESERVE you do have to make it the next station.
Best in the new year,
Another petcock question……
A local friend of mine also has a ’67 CL77 scrambler, and brought his petcock over for me to redo the standpipe. His was split all the way to the base (like mine was originally), but he wasn’t aware of it. He was riding along fat, dumb, and happy when the bike began sputtering and quit. His petcock was in the MAIN position when it happened, but when he switched over to the RES position, still nothing. He managed to get the bike home and found the problem once he pulled it out of the tank. Because of the split, he was technically running on “reserve” all along.
Anyway, his petcock was a little different than mine. His has an additional port in the back with a fuel barb inserted, but closed off with a rubber cap. He asked that I plug it up, which I did.
Mine has a place for that barb, but it was blocked off at the factory with a permanent brass plug. On his, I simply closed it off with some solder.
The question is, does anyone know the purpose of that additional port in the back??
That extra barb is a connection for a crossover tube that connected both sides of the tank together. It was thought that you had to connect both sides of the tank to get all of the fuel out but, in practice, it sloshes aboout enough to make the crossover unnecessary.
Honda removed the connection on later tanks and petcocks.
'60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160
'66 Matchless 350 '67 CL77
'67 S90 '77 CB400F
It's funny, kinda, but I have forgotten all of the nuances of the CL I had back in the late 60's and early 70's. Don't believe that one had a crossover connection. Had the tank off enough you'd think I'd remember something like that.
Getting old sucks - plain and simple.
If your bike had a crossover tube you wouldn't have forgotten it!
To remove the tank you had to remove the crossover tube by pulllng it off and then trying to plug the tap and the tube quickly and at the same time, otherwise you ended up with a petrol spillage!
Even if you drained the tank there was usually enough left to spill out over the engine.
If you don't remember this I'm sure you had a later bike without the crossover tube!
Incidentally, I'm not sure the fuel does slosh about that much, a while back I came to a stop at the roadside with my CB77 'out of gas' when there was definitely some left in the 'other side' of the tank. I think the crossover tube was deleted to save a few Yen per bike, the tube was deleted from the CB models round about the same time.
The crossovers are removed and plugged on both of my bikes just to make removing the tank for servicing easier.
I've a plan to reinstate the tubes on my bikes with a quick disconnector fitted to them, problem is that there's not much room to fit it in so I haven't done it, yet.
Worth doing though as getting at all the fuel will give me a slightly better range and or increased peace of mind when /if I and to switch to reserve.
I reckon on around 100 miles from a full (main) tank on my CL77 with a max. reserve range of another 20 miles, exceed this at your own risk!
CB77 with a larger tank is more, about 160 miles on main tank, again with a reserve of about 20 miles.