SOHC.co.uk Forums > CB350/400

CARB OVERFLOW FROM BOWL TUBES

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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.
 

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