Honda-SOHC

SOHC.co.uk Forums => CB500/550 => Topic started by: simonster on November 27, 2014, 09:53:32 PM

Title: Advice on re seating a float valve and needle
Post by: simonster on November 27, 2014, 09:53:32 PM

I would prefer to re seat or lap what looks to be an original 1.8 float valve and needle opposed to replacement. It may seat perfectly well, I'm not sure as the bike hasn't even seen fuel before today (whilst in my ownership). So while the carb is split it could be a wasted opportunity esp if it drains fuel once hooked up. Has anyone got any thoughts or words of wisdom?


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Title: Re: Advice on re seating a float valve and needle
Post by: mickwinf on November 29, 2014, 09:39:08 AM

I did polish mine with solvol autosol and they don't leak.

Title: Re: Advice on re seating a float valve and needle
Post by: simonster on November 29, 2014, 12:38:50 PM

I've polished the seat and needle on carbs one and two with a cotton bud and autosol and now testing it on the bench with clear fuel line to measure fuel loss, but at the moment the level is dropping about 10 mm in the pipe per 30 mins. Fuel is obviously breaching the needle contact but minutely. Is this expected on these carbs or should I expect a 100% seal?


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Title: Re: Advice on re seating a float valve and needle
Post by: Bitsa (Ralph Wright - RIP) on November 29, 2014, 02:06:51 PM

If your test pipe is open to the air allow for evaporation
Cheers
Bitsa

Title: Re: Advice on re seating a float valve and needle
Post by: simonster on November 29, 2014, 02:49:15 PM

This is the set up, carbs 1 and 2 have had the seats polished and 3, 4 haven't. 1 and 2 are dropping fuel approx twice the amount per 30 mins to 3 and 4. Polishing had clearly reduced the loss but not fully sealed. I'm not sure of the evap rate but 10mm per 30 mins in a 6 mm inner diameter pipe seems excessive??


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Title: Re: Advice on re seating a float valve and needle
Post by: Bitsa (Ralph Wright - RIP) on November 29, 2014, 03:00:44 PM

Does sound a bit too much for that can you not get new ones?
Cheers
Bitsa

Title: Re: Advice on re seating a float valve and needle
Post by: simonster on November 29, 2014, 05:11:15 PM

Buying new obviously would solve the issue, but wherever possible I've refurbed on this build and brass fittings should in principle never wear out given normal usage? Plus I was unsure as to whether new would have the same issues, metal on metal opposed to rubber ended needle and what working pressures these valves are tested to, given the pressure created in the fuel tank in warmer weather? Or should the fuel cock always be closed at the end of each journey?


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Title: Re: Advice on re seating a float valve and needle
Post by: matthewmosse on November 29, 2014, 05:23:06 PM

My own experiences are faily limmited, I did put several hundred thousand miles on my 500/4 and only ever needed to soak the carbs in redex if they started sticking, and I generally always try to turn the fuel tap off if not in use.

Title: Re: Advice on re seating a float valve and needle
Post by: simonster on November 29, 2014, 06:41:18 PM

I'm not going to chance it so ordered a set on fleabay.


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