SOHC.co.uk Forums > CB350/400

Leaking Carbs after rebuild - T-Piece O-Rings? (Resolved)

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Bryanj:
500 is 7.8 x 1.9 same as 750 so it is distinctly possible that 400 is as well

ManicGTI:
Thanks guys,

I have already changed the O-Rings themselves.  I've gone back into my Ebay history and it's Gerben1956 that that I bought my replacement O-Rings from.  It was listed as a CB350 / CB400 set at the time.

The rest of the rebuild parts (Jets, Needles, float valve etc) I've used are from Cruzinimage.

Maybe the O-Rings I received were incorrectly sized...the other plastic carb spacers don't seem to leak.  I do have the O-Rings for the cruzinimage kit still so will take a look at them again.

How long should it take for the carb bowls to fill once connected to the tank?  Three seem to fill fine (and drain as intended), one of them doesn't seem to fill at all.

JamesH:
Sounds like a stuck (closed) float on the carb that isn't filling. Try tapping with a spanner and see if it fills (releasing the float). Sometimes the floats hang on the rough cast edge of the pivot posts. I always lightly file the posts with 800 grit wet & dry when rebuilding which seems to do the trick.

J

ManicGTI:

--- Quote from: Jamesh_sussex on January 13, 2016, 01:45:57 PM ---Sounds like a stuck (closed) float on the carb that isn't filling. Try tapping with a spanner and see if it fills (releasing the float). Sometimes the floats hang on the rough cast edge of the pivot posts. I always lightly file the posts with 800 grit wet & dry when rebuilding which seems to do the trick.

J

--- End quote ---

Thanks for the tip, I'll take a look once they're apart again.

ManicGTI:
Thanks for the pointer on the posts, I've filed them all lightly to try and minimise sticking, all floats seem to move freely in air.

I took a look at the new O-Rings on the T-Piece and they feel very slightly loose, as if the ID is minutely too large.  I maybe over analysing it though.  I have the old O-Rings still so as an experiment I have fitted 1 old and 1 new O-ring on each side of the T.  It 'feels' like it's a firmer fit now.  A small amount of Silicone grease on all the O-Rings at the same time.

The new O-rings on the plastic joiners feel firmer, they weren't leaking anyway so i've left them as is.

Heading up to the bike again on Sunday so I'll hook it up and see if it has made the difference.  This is getting really frustrating now!

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