Re: Mysterious "t-piece" between carbs on '81 CB750K...

Posted by PunkAndRun on Feb 02, 2012; 12:45am
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Mysterious-t-piece-between-carbs-on-81-CB750K-tp3691494p3708598.html

Thanks to everyone for the responses, sorry I haven't kept up...the last few days have been hectic. I've finally got the old girl running more or less smoothly, so I'm taking her to work tomorrow to perform an experiment. I have attached a hose to the tee and jammed a bolt in the end of it...I'm going to ride to work with it in and home with it removed. I dismantled the carbs again and realized I never cleaned the fuel supply lines, so there was plenty of sludge inside the bowls and jets again. When I put the rack back on the bike the vacuum was gone...I'm hoping it was a matter of disrupted air flow that has now been fixed.

I'm really starting to think that it is just a dead-end hose, because I've seen several diagrams and all of them show it as just that...a hose that leads to nowhere important. I'll be sure to let everyone know how the trip goes, I'm very excited to get her out and on the road!

Also, I'm sure it's not part of the fuel diaphragm because that hose is still connected and in place. It's part #4 in this diagram and comes from the front of carb #2: http://www.bikebandit.com/houseofmotorcycles/1981-honda-cb750k/o/m2003#sch45654

Speaking of the diaphragm unit, does anyone know if leaving it on but re-routing the fuel lines to bypass it will cause a loss of vacuum pressure? It seems to be a dead-end and I don't feel any suction from the barbs for the fuel lines but I'm still having some odd idling behavior that seems like loss of vacuum. I've checked all the boots and haven't found any that seem to be leaking.

Thanks again for the help everyone, I'm not as well-versed in small motors as large so this has been a nice learning experience for me.