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

[ManicGTI]

Having faffed around with my carbs a few times in the last year, I've ended up rebuilding with all new O-Rings, Jets, needles, float valves etc and it appears I have eliminated the 'overflow' leaks...

However, I hooked up the tank to them yesterday and I'm still getting a leak.  It appears to be central, and mainly coming from the central fuel supply T-piece.

Is there any particular technique/trick to sealing these up?  As a first pass I'm going to separate the carbs and try a bit of Silicone Grease.

Thanks,

David

[hairygit]

If you're taking them apart anyway, renew the "O" rings on the T pieces (4 on each, so you'll need as that will almost certainly be a better and more reliable fix than grease or sealants. I'm sure Bryan J will be able to tell you what size they are.

Sent from my X5 using Tapatalk

[AshimotoK0]

Not listed separately in my 400/4 or 350 four parts lists only as part of a kit.

If they are the same size as the 750 the size is 7.8 x 1.9 mm pn 16173-044-004 . This was from the 750 4/69 sandcast parts list .. one of the only Honda ones to list all individual  'o' ring sizes

I got mine from Yamiya (sold out at the 'mo though)

http://www.yamiya750.com/index.php?main_page=product_info&cPath=246_21_181_143&products_id=1419

http://www.yamiya750.com/index.php?main_page=product_info&cPath=179_273_207_214&products_id=2865

[tom400f]

Hi Dave

You could try asking this guy: http://www.ebay.co.uk/usr/gerben1956

I think Trigger put me on to him.

[Chris400F]

I recall member andut on here had a T-piece and connecting pipes from me early last year from some parts I had.
I don't know whether he fitted new O rings or just used the ones that were fitted. Maybe he can remember.

[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]

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

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!

[Bodd]

I put a smear of Hylomar blue on mine when I rebuilt them as a precaution and they haven't leaked yet.

[ManicGTI]

Success!  Well partially...hooked the carbs up on the bench and no leakage now from any of the joints now, and all four bowls are now getting fuel.

Slapped them back on the bike and It's not starting, but i'll save that for another thread

As always, thanks for the input guys!

Dave