Topic: 1981 CB750 Fuel Pump

[steve]

The automatic fuel petcock on the carbs that is vacuum driven needs replaced or rebuilt?  Does anyone know where I can get a rebuild kit?

Can I just bypass it and direct feed the carbs?

Thanks

[ekpent]

 I am working on my 1982 CB900F right now. I noticed that the previous owner had already bypassed the auto fuel shut off valve that sits on top of the carb bank on this bike. So yes you can go without it but you have to make sure you do not have a leaky petcock. My petcock leaks and it is riveted together. I have already drilled the rivets out and have it taken apart on the bench and will probably go with this kit to rebuild rather then chase all the parts though I believe the rubber disc with the 4 holes is the same as used on 1973-77 Yamaha XS650.
  Your 1981 may be a different size though not sure,just make sure your petcock is not a leaker    http://www.ebay.com/itm/HONDA-FUEL-PETCOCK-REBUILD-GASKET-KIT-CB650-CB650SC-CB750SC-CB900-CB1000-CB1100/121240091093?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

[steve]

Thanks for your reply.  So it is a furl shut off?  I thought it might be needed to pump.  I could not find any info on it.

Thanks

[ekpent]

 Yes it is a vacuum operated remote mounted fuel shut off. There should be a hose running to it from one of your carbs that operates the vacuum and will need to be plugged if you bypass it. Other makes like Suzuki and such have that vacuum operated shut off connected to the petcock,not these Honda's.
 Just out of curiosity what have you determined is wrong with it, is your bike not getting gas when running or is it getting to much and is flooding/overflowing when parked ?  If it is the latter then check your oil for gas getting in the crankcase.

[Jerry Rxman Griffin aka MuthaF'er]

I am working on my 1982 CB900F right now. I noticed that the previous owner had already bypassed the auto fuel shut off valve that sits on top of the carb bank on this bike. So yes you can go without it but you have to make sure you do not have a leaky petcock. My petcock leaks and it is riveted together. I have already drilled the rivets out and have it taken apart on the bench and will probably go with this kit to rebuild rather then chase all the parts though I believe the rubber disc with the 4 holes is the same as used on 1973-77 Yamaha XS650.
  Your 1981 may be a different size though not sure,just make sure your petcock is not a leaker    http://www.ebay.com/itm/HONDA-FUEL-PETCOCK-REBUILD-GASKET-KIT-CB650-CB650SC-CB750SC-CB900-CB1000-CB1100/121240091093?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

Can't say for sure but I came across this 'rubber disc' as being correct for the CBX and the CB1100F - 16955-268-020  - It is for, among others, the early K's. Just $2.58 to try (Motogrid price). Bolt Depot has 3mm X 0.5mm X 8mm stainless button head allens #7219. Amazon has a tap/handle/drill kit for $12.37 Du-Bro 372 or just the drill and tap for $6.37 https://www.amazon.com/Du-Bro-372-Tap-Drill-Set/dp/B0006O4H1I/ref=sr_1_1?ie=UTF8&qid=1503942713&sr=8-1&keywords=du+bro+372

[ekpent]

  Thanks for posting that Jerry. That part number does reference the early CB750's and other bikes but unfortunately the petcock on a 1982 CB900F is an odd duck. As seen in the pictures the 4 holed rubber disc is a whopper, its bigger then a quarter at around 27mm,larger then the part you referenced.I went ahead and just bit the bullet and bought the kit that I showed on E-bay. Has 3 other o-rings that will be good to replace also and not much info I could find on size etc. on the web other then the disc may be an xs650 at around $7.00 from my local dealer. Guess the seller gets a financial reward for putting all this 'top secret' stuff together and saves me a hassle  and hopefully its been confirmed to work. He has sold a lot of them.