Standard carb lines versus Special??

[s clarke]

Hi, I have been pondering this for awhile, and why do the std carbs have 4 lines to carb banks, and specials only 2? Is it for "balancing" the airflow? The jets on STDs are so much bigger! Any help would be appreciated.
SQUID

[John]

The carbs from the 78-79 have four hoses and the 80-81 vintage only have two. The extra ones on the older carbs are the bowl vents. The newer carbs have the vents cast into the intake bell. The carbs are the same for the Standard and Specials. The only difference may be the jetting. The mains on the older carbs are larger because the pilot circuit is fed through the mains on the older carbs, and in the newer ones, the pilots have there own fuel supply from the bowl, so they don't require the larger mains.

[s clarke]

Std Carbs

So if I wanted to, could I not hook up the bowl vent line, and leave it free to the atmosphere, and the bike would still run well? or must the "whole circuit" be contained, as far as "second" fuel bowl vent line, and air box nozzles, which enter into intake plenum? On Specials, you can run "pod" filters, but with the extra STD fuel bowl line....not, due to the extra line?
SQUID

[John]

There is no extra line on the Standard. Two fuel lines to the lower set of T fittings, and two bowl vent lines to the upper set of T's. That's all. You can vent the bowl vent lines to atmosphere if you want, but do not block them off. The carbs will flood. You can run pod filters on both the Standard and Special. This extra line on the Standard you refer to...is it connected to the nipple on the rear of the fuel tank? That is just an overflow drain for the recessed filler cap on the tank, and the hose should be routed to the area behind the swing arm pivot, where the battery vent tube terminates.

[s clarke]

Thank you, that "muchlly" helps!
Sid

[oldnortonrider]

Those bowl vent lines on mine, I've got running "out to atmosphere", like John says; on the ends of mine, I've got a small gas cone filter stuck on. Might keep out a dirt dauber nest or miscellaneous particles that don't need down into my carburetion.
They've been working fine for more than 10 years since I did it.