fishermantwo
Well-Known Member
Best to avoid ethanol in outboard fuel as it absorbs moisture.
Carburettor cleaning- what's best?
- Thread starter sparkie
- Start date
steve66
Well-Known Member
Yes I use one. Only really useful for setting carb jets correctly
JumbleDuck
Well-Known Member
I tried one years ago in my Herald, without much success. I suspect that it takes a lot of practice to identify the colours properly. With an even slightly over-rich mixture it also tended to soot up very quickly ... if your outboard is 2-stroke I suspect that would be an even bigger problem.
steve66
Well-Known Member
Cleaning a carb is really easy once you know how they correctly work, There are different jetting systems that work independently of each other. Once you work out what orifice leads to what it actually does its pretty straightforward. In a nutshell if your problem is within the first 1/5 approx. throttle the problem is in your slow/ pilot jet system ie tickover. If your problem is in mid / high range its associated with the main jet. There are a few exceptions to the rule but 99% of the time this is the case. I clean hundreds of small hp carbs and have an industrial ultrasonic cleaner but usually a good squirt with carburettor cleaner in appropriate places does the trick without the need for ultrasonic cleaning.
sparkie
Well-Known Member
All really interesting stuff chaps. Didn't realise ultrasonic was a DIY job. I'll look into that. I've got a Colortune from the 70s, but it's too big to use in the small plug hole on the Tohatsu.
steve66
Well-Known Member
Sparkie, what is the problem with the carb, tickover , rough running etc?
JumbleDuck
Well-Known Member
If only they were all like that! The DS carb has, as I recall, five jets (main, auxiliary, idle, power and accelerator pump) for its twin chokes and two or three air bleeds as well, There are passageways all over the place inside the body. Of course an outboard will have something a lot more tractable.
steve66
Well-Known Member
French complication. I bet it went well once set up correctly though. Lovely looking cars IMO.
sparkie
Well-Known Member
Yes all of that, the symptoms are those of a weak mixture, including racing at tickover occasionally. The frustrating part is I can get it running perfectly, all the usual tests, leave it 24 hours, come back to it and it runs like a pig again. Take it apart, clean it all again, all fine and dandy and then- yes it goes crook again. New fuel, filters everywhere, no difference. For the first 4 years or so it ran perfectly.
JumbleDuck
Well-Known Member
Lovely to drive and goes like stink, but when the second choke opens you can almost hear the air rushing into the petrol tank. I had mine converted to LPG - more complication - which keeps the running costs a bit more reasonable.
steve66
Well-Known Member
It sounds like needle valve and/or float problem.
Gordonmc
Well-Known Member
I have a colourtune, but its only of use if the cylinder is firing and, as someone has mentioned, you need to adjust the mixture.
An alternative to aerosol carb cleaner is brake cleaner which I use as a universal solvent for all sorts of jobs. Cheap enough to dunk a twin-choke webber in to soak off gum after an hour or two. I don't have a compressor any more so use the spare tyre to blow through the jets.
The carb, btw, is off a 3.0 V6 Essex in a Scimitar.
An alternative to aerosol carb cleaner is brake cleaner which I use as a universal solvent for all sorts of jobs. Cheap enough to dunk a twin-choke webber in to soak off gum after an hour or two. I don't have a compressor any more so use the spare tyre to blow through the jets.
The carb, btw, is off a 3.0 V6 Essex in a Scimitar.
steve66
Well-Known Member
Be careful soaking carbs in solvent. Neoprene needle valve tips melt with some solvents and also there are plastic jets in some outboard carbs that can become enlarged. I wish carbs were built the same as twin choke Webers .
propnut
Well-Known Member
Another one for sonic cleaner.I mend out boards for a living and have found that with the introduction of 4stroke engines the passage ways are so fine that it is the only easy way to clean.Fill the cleaner with degreaser for even better results.
sparkie
Well-Known Member
Both look ok, and I've cleaned the needle valve of gum etc, but it's spring loaded as you probably know. Is this likely to weaken over time so as to allow too much petrol in? If the float were cracked I think I would hear fuel sloshing inside, but maybe not. Would too high a fuel level give rise to these problems? I've always felt it to be too weak rather than too rich. Anyway thanks for all the advice so far.
sparkie
Well-Known Member
Yes sonic cleaning seems to be getting the thumbs up, which is helpful. Cheers.
steve66
Well-Known Member
Sparkie, is the needle valve holder on the float steel? If so may need a little adjustment. I do know Mercury are having small carburettor problems and actually have changed manufacturers . I was having a chat with a friend and he showed me a box half full of Mercury /Tohatsu carbs changed under warranty.
sparkie
Well-Known Member
From memory yes it is. Interestingly, one of my affected friends (Mariner 5) bent the "arm" a bit and it improved matters greatly. (After he mistakenly filled it with diesel(!) he swears it's going better still............) I've not altered mine at all as I imagined that it was factory set and couldn't see how it could change. I also wouldn't know which way to go with the level. Higher or lower? So I've left it alone. My carb is a Keihin, but there's no model no on it anywhere.
lenten
Well-Known Member
had problems starting my 15 hp yamaha 4 stroke----tried carb cleaner ---no sucess---had it ultrasonic cleaned at d +r engineering walton marina ---perfect---touch wood---i always disconnect the fuel line from the outboard and run the carb dry---then use the remaining fuel in the tank for my strimmer/chainsaw---however the mechanic advised me to disconnect the fuel line from the tank to avoid stale fuel left in the line and that honda said not to use fuel more than 6 weeks old------regards lenten
steve66
Well-Known Member
Bending the float down will mean the float will not rise as high so less fuel in the bowl. The revs rising on your engine could be it is running out of fuel out of the float bowl. Obviously bending up will be the reverse. An inspection of your spark plug will let you know what's happening mixture wise.