What parts typically fail/deteriote on small engine carbs?

stuck

LawnSite Member
Location
albany, ga
I'm not a carb guy by any means. I've probably rebuilt less than 20 carbs but anytime mine or my friends handheld 2 cycle equipment act up, I immediately go for the carb. I usually get a rebuild kit, clean, reassemble and like 80% of the time, that fixes it. The needles always look good, spring seems buoyant with no binding, the screen has very little debris, all metal moving parts usually look fine. So I'm just curious to anyone thats rebuilt these carbs 1000s of times, what is that usually causes the problem? Is it the diaphragm, flappers, or debris making it past the screen to some orifice in the carb body?

Thanks for the input.
 

Patriot Services

LawnSite Fanatic
Location
Tampa FL
Debris and corrosion in the tiniest passages. Since getting more emissions compliant those passages have only gotten smaller. The lack of adjustability on most carbs means they to be factory perfect to restore proper fuel air ratio. The newest option that seems to work well is the ultrasonic baths. Many new carbs are now considered non rebuildable and have to be replaced.
Posted via Mobile Device
 

tigerepairdotcom

LawnSite Senior Member
Location
duluth, ga
Improper storage lack of weatherization ethanol ect.! The fuel evaporates leaving behind troublesome particles in narrow passageways. Also it is harder and harder to make chemicals that cut through that sludge since the tightening down of the epa. A use 4 ultrasonic cleaners, Purple dragon full strength and heat my ultrasonic makes.
 

dboyd351

LawnSite Bronze Member
Location
Cape Charles, VA
Diaphragms seem the part that goes bad the most - they have to be replaced when they get stiff or wrinkled. Screens sometimes get clogged, debris clogs metering needles and small holes, and just general accumulation of gunk from old mix evaporating.
Like the others said, ultrasonic cleaners are really important for cleaning out all those tiny passages you can't get to. Shooting carb cleaner in all the holes will sometimes clean them OK, but I've had times where a carb I had rebuilt with new parts and shot cleaner thru all the passages would not work until put thru
the ultrasonic cleaner.
The combination of vibration, heated water and use of solvents or liquid dish soap just seems to throughly clean things you can't get to otherwise. Also, some check valves can be damaged by high pressure from the carb cleaner or even compressed air. Ultrasonic cleaners won't hurt them.
 
OP
S

stuck

LawnSite Member
Location
albany, ga
My brother has the cheap harbor freight ultrasonic that can only use water and soap but not solvent. Is that good enough? Thanks for the tip.
 

tigerepairdotcom

LawnSite Senior Member
Location
duluth, ga
Sometimes in a pinch I use water and a strong dishwashing soap like dawn or dawn power clean and the water is REALLY got 90% of the time that does the trick 1/2 cup mixed into water in the harborfriehgt one does it pretty well. BUT IT HAS TO BE HOT HOT HOT careful fishing the needle pin float needle and jets out that harborright machine gets HOT
 

herler

LawnSite Fanatic
I just clean them with carb cleaner but when it comes to using a kit I just replace them whole.
 

dboyd351

LawnSite Bronze Member
Location
Cape Charles, VA
My brother has the cheap harbor freight ultrasonic that can only use water and soap but not solvent. Is that good enough? Thanks for the tip.

I have the cheap HF one, too. It works fine and you can use degreasers like simple green, purple power or totally awesome in it. That or dish soap are all I've ever used. Guess I meant use a degreaser, not a flammable solvent.
I do run it thru multiple cycles with the heater on, changing the water if it gets very dirty.
 
OP
S

stuck

LawnSite Member
Location
albany, ga
Sorry for reuping this but is the plastic primer bulb plate, plastic 90* fuel elbow, and those siliconed plugs ok for the heated ultrasonic cleaners? I'm talking the harbor freight one.
 

dboyd351

LawnSite Bronze Member
Location
Cape Charles, VA
I'm sure they are. I have not done those specific pieces, but I put diaphragms, adjustment needles with rubber cones and such in the ultrasonic cleaner all the time. Doesn't hurt them at all. It is a good idea to apply fingernail polish over the welch plug covers (is this the silicone cover you are talking about?) to re-seal them anyway.

I use the Harbor Freight one - Item 95563.
 

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