Topic: Carby balance tube???? on 750 K2

[k2 sohc]

what does this balance tube do, that connects carby 1 & 2 together and carby 3 & 4 together. A month ago I replaced the tube between carby 3 & 4 because the tube had perished away over the years unknown to me and the bike has been running well. I only spotted this when I was replacing new carby fuel lines. On the first ride I did since all the replacements I had travelled no more than 30 miles when I lost all power in #4 cylinder. All other 3 header pipes were hot as, #4 header pipe was warm. Road side inspection showed good spark on #4 plug and was very wet. On several attempts #4 cylinder did not come to life. On pulling down the motor #4 piston had a hole in it. As the bike has been running very well over all these years, could the replacement balance tube cause #4 carby to run very lean? causing piston to melt a hole in it.

thanks Alex
Australia

[HotCarl73]

I think the long tubes between 2 and 3 are just the vent to atmosphere and the small tubes between are to connect the vent to the 1 and 4 carbs. I'm no carb expert but I think if those tubes weren't even there, all the carbs would be vented and work fine. If that vent was plugged up on any carb, that would cause problems because air couldn't get into the bowl to replace the falling fuel level and there would be a vacuum making the carb not deliver fuel. It's like when you get no fuel through the petcock if your gas tank vent is plugged or not working. I'm just guessing, wait for somebody smarter than me to chime in.

[k2 sohc]

thanks hotcarl.
I will see what other reply's come back with

alex

[dusterdude]

Im guessing its a vacuum balance tube of some sort

[k2 sohc]

thanks fellows there was nothing in the oil pan to show anything, just fine aluminium chards.
the barrel will get away with a hone. so it back to rebuilding the beast
thanks for the replies

[evanphi]

Those tubes are the bowl vents. The short ones that connect 1-2 and 3-4 make the air vents on 2 and 3 connect to the 1 and 4 carbs respectively.

If they were plugged, the bowls wouldn't fill with gas as quickly as needed.