How do I clean a carburettor?

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chuzzlewit

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My old Yamaha 60 hp 3 cylinder ob seems to be firing on its middle cylinder and intermittently on the top cylinder. Taking the ht lead off the bottom plug has no noticeable effect. I think there may be sludge in the bottom carb.
I am taking each carb apart in turn , washing the bits in petrol and blowing vigorously through all the holes.
Is this the general idea or should I be using a special cleaner or poking fine wire through the holes?
Any advice gratefully received.
 
Don't use a wire as you may damage the airways or jets.You can buy carbuettor cleaner from car shops.You'll need a compressor to blow through.Lung pressure is not enough.Some people use ultrasound cleaners with good results.
 
I just had to fix a (smaller) O/B and used brass wire (suede brush) to clean the very blocked up jets. Petrol wasn't going to do it. Dentist friend (and sailor) used an ultrasonic cleaner for his finger nails, until he read that it bu++ers up the capileries. But for carb bits, very good.
Also asked to look at a Solex moped ( one of those with the engine on the front wheel) the cr+p in the tank from evaporated fuel mix after 12+ yrs of non use was not interested in dissolving in petrol at all. Thick toffee.
So carefull use of soft wire can help.
A
 
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Carb cleaner should be more effective than petrol although I have never used it.
Anything petrol will remove will have been removed in the normal course of events.

I am in favour of poking a soft copper wire through all the jets. That wont damage them although a steel wire might. I have had to do it!
Ultra sonic cleaning baths all very nice if you have access to one. Similarly an air compressor!

BUT are you sure there is not an ignition problem. No change when removing a plug lead normally indicates no fire on that plug.

Plugs good, preferably new ??? Leads good and not earthing ?

Checked for good sparks on all three cylinders ??

Checked compressions?

Wiring generally good? No shorts or bad connections?
 
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Thanks for advice. All 3 carbs cleaned and all 3 cylinders are now firing . It only took 5 hours! I'd taken it back to the professionals 3 times. Just shows: if you want something done properly, do it yourself.
 
for the future you might try this, its always worked for me

top shelf of the dishwasher, then rinse in white spirit

usual rules apply as when washing warps in the washing machine . . .
 
I've found that acetone will dissolve the varnish left behind after petrol evaporates. 10 mins soak in a jar of the stuff is usually enough - then run some petrol through to wash out any remaining acetone. Don't be tempted to soak carb bits in acetone overnight, as any rubber seals will swell and split. You may wonder how I came to know this ....
 
in the US were are coming across another problem in our 4 stroke outboards.

Ethanol - up to around 10% in gasoline from the gas stations.

I believe all the 4 stroke outboard manufacturers in the US are suffering from this one.
So, when I get home next week, it will be outboard stripping and trying to get to the carb. I tried running carb cleaner through it to no avail. Although the unit is 3 years old now, it has not seen a great deal of use, but is now running flat and not getting up to full rpm.

It seems that marina gasoline is exempt from this blight, so no more filling cans at the gas station.
 
I have always completely dismantled the carb including jets, emulsion tube, float etc and used compressed air and WD40 to clean. Make sure that you blow down the air passages too.

Also make sure that you check float height before reassembling.
 
There is another way if you don't mind stripping the whole thing and get all the plastic and rubber bits off, it's simply to boil it in water, no need for expensive stuff or compressor, just water.....and it will disolve some **** in corners that are not accessible at all...
 
I bought a second-hand Flymo which started easily and ran well………………for a while. I returned it to the shop and they cleaned the carb ultrasonically. Don't know if all such shops have them but it might be worth a try. No charge to me of course.
 
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