How not to change a float bowl gasket!

[GrahamH]

My bike, a 1966 CA77 was running well but smelled of petrol, and then I noticed it actually leaking out of the carburettor when the bike was on the side stand. I had read about a home made float bowl cork gasket working well and stopping any leaks so decided to try it. I used a rubber/cork material that was advertised as suitable for use with petrol, carefully cut to shape and glued to the float bowl rim with double sided tape...and it worked a treat! Well it worked OK for about 10 days and was leaking again. On inspection the rubber/cork material had become spongy with the fuel and the glue was a mess.

I took off the carb’ removed the jets and ensured they were clean. I had previously fitted a size 2mm float needle valve but found the bike could run out of fuel on a long run at full throttle so decided to replace the original 2.5mm valve. Also the float height was adjusted to 26.5 mm measured from the gasket seating face,(it was closer to 30mm before). Then it was put back together with a new genuine Honda float bowl gasket.

The results of this are:

Starts and idles OK, responds well to large throttle opening, but on light low throttle running there is an intermittent misfire reminiscent of running out of fuel, not all the time but enough to be irritating and obviously not correct.

Surely it must be my doing in messing with the carb’ but could the float height adjustment cause this? Or should I zero in on the slow jet (#35)? I didn’t do anything else to clean the carb other than removing and checking the jets; should I give it a session in the ultrasonic bath?

What would you do next?

GrahamH

[deuce_7]

My bike, a 1966 CA77 was running well but smelled of petrol, and then I noticed it actually leaking out of the carburettor when the bike was on the side stand...

...What would you do next?

GrahamH

Is the fuel leak stopped? Another source of a fuel leak running down, over and around the carburetors is the petcock-to-tank joint, sealed by 5mm screws and red fiber gasket packing washers.

[sky.fred]

The float should be checked for leaks, as the welds can become porous and it can fill up with gasoline.
A Honda 125 Cbs or SL float replaces it perfectly.

[GrahamH]

I think it is important to report back on any issues and the issue this time was caused by fitting a non standard gasket which sort of melted and screwed up the carb’. I had previously removed the carb’ and cleaned just the jets to no avail so this time it was removed and spent 30 minutes in an ultrasonic cleaner dunked in carburettor cleaning solution followed by a blow though of all the holes with a jet of carb cleaner.

Working on the carb’ is getting easier with practise; I have found it easiest to remove the air cleaner to gain access although that in itself is a bit of a pain. After a struggle I hit on securing it with cable ties as hose clamps were just too difficult to fit. Also just fitting the carb’ flange nuts requires fingers much smaller than mine so the solution there is to use some electrical tape to hold the nut in an open ended spanner to get it started on the stud.
But the biggest and most important tip I can offer when working on the carb’ is to put a piece of rag in the drain hole under the carb on the drive side. It is easily big enough to swallow a M6 nut or washer which is not so convenient.

Back to the plot. The deep cleaning has worked and the bike is again running very well again, possibly even better than before. Maybe a cork float bowl gasket would be OK but don’t be tempted by the rubber/cork stuff, (although it is working well for a fuel tap gasket), use the genuine Honda.

For reference the bike is a 1966 CA77, carb’ is a PW22 with 120 main jet and 35 pilot and 2.5 float seat. The PW22 is fitted to the CA77 and C77 whilst the CB77 twin carb use two PW26. The float height of the PW22 is 26.5 and for the PW26 is 22.5.