CARB OVERFLOW FROM BOWL TUBES

[watty51]

My first post at last no longer a lurker !
Live in Balsall Common (10 mins from NEC and Motorcycle museum)

Purchased CB350F 1972 about a year ago steadily restoring when time allows. Got lots of inspiration looking at Roy's cb350f build. So thanks for that Roy.

So far have stripped carbs cleaned and replaced as necessary, put on bike - then took off bike as carbs leaked from overflows - reset float height as Clymer manual - put back on - still leaked but not as bad, tapped all float bowls with soft mallet and bingo no more leaks. Left fuel tap on all over the weekend and no leaks.

Did all the timing etc all okay

Started bike up, ran a bit rough then after a few minutes fuel came out of the carb overflows.

So in summary..... No leaking carbs with engine not running,  but with engine running carbs overflowing.

Has anyone had this problem before, I searched forums last night but couldn't find any info.
Thanks
Mark

[gtmdriver]

Are the floats moving freely? It sounds like they may be sticking if you had to tap the carbs to make them seat.

If the floats are moving freely then it must be the needle valves which are not seating.

Did you replace the needles and seats and if so were they OEM or aftermarket?

Some of the aftermarket stuff is not OEM quality.

[ST1100]

And just for the fun of it: checked the overflow standpipes for cracks/leaks?

[Bryanj]

Polish the pivot pins with very fine wet and dry

[watty51]

Just got in from the garage and just for a change took off carbs. Checked all items replaced were put in correct, they were, so as suggested polished all the float pins with wet and dry and checked needle valves were seating correctly.
Checked height of floats made sure they were set to 21mm and put carbs back on bike.
Turned fuel to on and no leaks.
Started bike on choke still no leaks so things were starting to look good, but engine was really running rough and would not idle, Checked all spark plugs and the bike was running rich. Cleaned up spark plugs tried again same story.
The bike is running far to rich. Is there a good point to start to look for an answer. I was thinking the floats are still set to high and this may be the reason for the rich state
All the items purchased for the carbs were oem parts.
 

[wolfheze]

Hi. Nothing to do with bikes but  have you been in Balsall long? Went to Heart of England 40 years ago.

[watty51]

Good point Oddjob, it seems that ive been convincing myself the problems lies with the carbs ( seems to be more questions asked about them on this forum then anything else).
Will put the carbs back on and check the timing again during the week, maybe I've overlooked something quite simple



Answer to Wolheze have only been in Balsall for about 15 years so didn't go to Heart of England, my kids did though

[wolfheze]

Have a lot of memories of Balsall Common, some good some not so. My first girlfriend lived in Gypsy Lane. Had a big crash on my RD 250 in 1980 on the left hander in station road by the Brickmakers, the bike slid across the road and up onto the pavement narrowly missing a lad from school.I ended up in the gutter. Fortunately for me nothing was coming the other way or I probably wouldn't be here  boring you with this 

[wolfheze]

Just  remembered the guy my rider less bike nearly took out has now bought the rights to use the Francis Barnet name.Think they produce electric powered bicycles.

[royhall]

Thanks for that Watty, never been an inspiration before. Glad it helped though. Cheers Roy.

[Greg65]

Thanks for asking that question Watty, just come in from the garage with the same problem. Heading out to remove the carbs and recheck, by the way is there an easy way to remove 400 carbs and air manifold?

Greg

[watty51]

When you've took the carbs on and off as many times I have ( think I could do it with a blindfold on) you just get use to squeezing this bit in here 1st, then this bit in 2nd...so on.
I have got a 350f but always take out the air manifold the right hand side but watch out for the overflow point on the bottom of the manifold.
The carbs basically, undo 4 retaining clips and pull/wiggle back. TAKE YOUR TIME WITH THIS BIT they will come off eventually
Not much help i know but once off just make sure you take lots of photos of the insides of the carbs and keep everything in order.

[ST1100]

...is there an easy way to remove 400 carbs and air manifold?

On my 500/4 I found it helpful to gentle warm the isolators with a heat-gun...