New 750f2 owner, member intro & few ?'s.... Carb issues for now

Posted by Matt Story on Aug 09, 2012; 3:28am
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/New-750f2-owner-member-intro-few-s-Carb-issues-for-now-tp4026717.html

Hi, my name is Matt.  I'm a brand new member here.  I'm in Flint Michigan.  Great site.  Already found some useful tips before joining up.  I just picked up a 77 CB750F with about 8000 miles on it.  $700 was the sale price.  Apparently it was stored indoors.  Its pretty clean with little rust, and couple tank dings.  Side covers are wasted.  The PO started to rebuilt the master cylinders and stopped half way.  I have owned a 350four and 550four, and know these are great bikes once sorted.  Was looking for a while waiting for a good or fair deal on a CB750 to come along when I found this one on CL.  It won't currently run well, but I'm making progress.  Carb problems are the primary issue.  The PO also claimed to have had the carbs rebuilt, but 'the shop' didn't do a sync job like they were supposed to.

On a side note, I am also currently neck deep in restoring a 75 Moto-Guzzi 850T.  I picked this bike up partly to have something to ride while I finish the Guzzi, knowing that it should be simple and quick to get the CB road ready, and not have to spend much money on it.

First things first.  I set the point gaps and did a static timing.  Getting spark on all four.  I will look into the valves once I make some headway with the carbs.

As received, the carbs were leaking out the overflow outlets and one thru the intake opening.  My brother and I took the carbs off and gave them a cleaning.  They were fairly clean, but not spotless.  We found that the #3 float was installed upside down.  The Accelerator pump diaphram is wasted and a new one will be ordered.  Thanks to Re-run, we learned that the apparently non-removable slow speed jets are removable.  We took them out and found 1 & 4 were partially blocked, with 2 & 3 fully blocked.  We got those cleaned up nicely with copper wire and cleaner.  We checked that the floats were equally buoyant, and their heights are in spec..

After all that we put the carbs back on, and now it will run with the choke off (would barely run with full choke before) but won't idle.  All four pipes are getting hot now.  Now that the slow speed jets are clean, three if not four of the carbs are overflowing thru the overflow tubes and/or the air intakes.

My first battle is to stop the overflow.  My needles have very slight detents in the rubber where they meet the seats.  They are quite pliable.  Since the seats aren't removable, (or can they be removed like the slow speed jets?) I didn't clean them as well as they should be.  My next task is to clean the needle seats and/or polish them.  I see some other sites recommend using a hardwood dowel to polish the sealing edge.  What does the membership here recommend for cleaning/polishing the seats.

Once I get the needle valves closing up, how high should the gas level be when checked with a clear hose?

I will be placing an order for needles, accel pump kit, if not rebuild kits.  With everything cleaned up, I think the kits are probably overkill.  What brands or distributors (carb parts) would be recommended or which ones should be avoided?  I ask because I saw somewhere there is at least one brand that should be avoided.  The web stores I have found so far don't specify the brand they are selling.

I am going to also buy rebuild kits for the MC's, new bake line sets, the factory tires need to be replaced.  Going to go down the periodic maintenance schedule and hit the whole list.  I'd like to order as many parts as possible at once to save n shipping.

Any comments or suggestions are greatly appreciated.

Thanks,

Matt