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Old 22-10-2014, 04:52   #1
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How do you "Break" a Carburetor

We have invested more money in our little Yamaha 2.9 2 stroke than its worth. This last go around has been interesting. We had a bad batch of fuel and it dirties the carb. I pulled it apart and cleaned it as I have several times in the past. Threw a new plug in it and fired it up. It ran but would not come up to full power, stuttering is probably the best word to use here. Worked on it again but could not improve it. Bit the bullet yesterday and took it to a Yamaha dealership for repair.
I set a limit on what could be spent without an email back to me and I got an email saying the carb was "broken" and needed replacement. That was new information so I went down to the shop to talk with the mechanic in my broken Spanish but when that quit working I had a young lady to do the interpreting.
Long and the short of it, its got nothing to do with the jets, nor the float, nor any adjustment. He tells me its inside the casting of the carb and needs replacing at a cost of 330 Euro or something north of $500 bucks. I packed everything up and took it back as I'm buying a new larger engine when we arrive in the Caribbean anyways BUT....

Have any of you heard of such a thing as the mechanic describes????
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Old 22-10-2014, 05:16   #2
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How do you "Break" a Carburetor

Hi, never heard of it !
Those little carbs are basically a float chamber, diaphragm , choke plate and ports.

The only thing that is inside the casting are the various ports, so I can't see what he is saying is broken ? But maybe the language barrier doesn't help.

I had problems similar the other day with a 10hp. Tried the carb cleaner but still no great so took it to the local OB guy who said that the modern fuels are a nightmare and that the only real way to get the ports clean is with an ultra sonic bath. Luckily my wife had a small one for her jewellery which worked wonders.
Needless to say it took some grovelling to explain why I wanted to put my OB part in her bath !!




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Old 22-10-2014, 05:21   #3
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Re: How do you "Break" a Carburetor

No in the end we did understand each other as I pointed to each piece on the carb and gave it the English and Spanish names. What he pointed to was the interior of the castings which of course may be plugged a bit inside. I will take your advice when I have an opportunity to get the carb cleaned with an ultrasonic bath. Thanks, Cheers, Robert
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Old 22-10-2014, 06:01   #4
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Re: How do you "Break" a Carburetor

If the carb casting has a hairline crack, it can suck false air. This could easily be the cause of your stuttering and the lack of full power performance. The crack my be so fine that it doesn't leak gas (or be in a place that does not see the gas)


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Old 22-10-2014, 06:26   #5
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Re: How do you "Break" a Carburetor

Be careful of which jewelry you put in an ultrasonic, it can loosen stones in their mountings, and I think even destroy some stones, Opals come to mind, but not sure.
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Old 22-10-2014, 06:31   #6
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Re: How do you "Break" a Carburetor

I don't know about it being broken, but your symptoms are of a clogged high speed jet or as mentioned a possible air leak. Stumbling and not idling are of course low speed symptoms, but you come off of the low speed and onto the main very quickly (adjustment screw only adjust low speed).
Since this is a two smoke, it's easier to diagnose, when your at high power and it's stumbling, is it smoking, or is the smoke gone?
Do you know how to take plug readings?
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Old 22-10-2014, 07:50   #7
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Re: How do you "Break" a Carburetor

I had an issue with my jet boat, an elbow on a line was clogged causing pressure back up to the carb. just a thought?


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Old 22-10-2014, 08:21   #8
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Re: How do you "Break" a Carburetor

Sometimes it is "safer" for a mechanic to replace something rather than try to fix it. Fixing it costs labor and it may not work.

Then you have a dissatisfied customer and you must continue investing your time to make it right.

The world is a replacable place these days. I understand why the guy wants to replace the carb. Especially after the owner had it apart and together.

No slight against you but that's a mechanic's reality...

If it were me, knowing now the mehcanics diagnosis, I would take it apart again myself and go over it with a magnifying glass and a very bright light.

There are also dyes you can put in the fuel, run it for a couple of minutes and case cracks will show up immediately when you pull it again and take it apart.
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Old 22-10-2014, 08:23   #9
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Re: How do you "Break" a Carburetor

When its stumbling along the smoke is normal. It has very few moments at low power that it runs smooth here and there. It sounded at first like a bad plug so I changed it but same result. Remember I took this into a large Yamaha dealership and they supposedly checked the carb as I told them I cleaned it and the jets but I didn't have pressure air I used carb cleaner and really fine wire to clean the jets and to me it was all good and its not the first time I have cleaned carbs but its the first time I got this result. Their answer was that after a proper inspection the carb could not be fixed as the damage was inside the housing where you couldn't get to it. I'll have another go at it when we sail to the Caribbean in a few weeks. I just never heard of a carb that couldn't be rebuilt and my only choice was to replace it. By the way as much as I love Yammi's I wouldn't give you 2 cents for these little buggers, real pain in the butt.
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Old 22-10-2014, 08:35   #10
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Re: How do you "Break" a Carburetor

put some sea foam in the tank, run it for a while and see if it clears up, also pull off and check all hoses and connectors for clogs. sea foam available at wal-mart. the biggest issue is with the gas we are forced to use. also replace any filters.

a mechanic told my mom she needed a new throttle body on her car, turned out the electric fuel pump was losing power and it was running dry, go figure?


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Old 22-10-2014, 09:19   #11
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Re: How do you "Break" a Carburetor

I just replaced the carburetor on my Honda 2 hp. I tried cleaning it several times to no avail. I went to the dealer & he said cleaning just does not work. They have given up trying & now just replace the carburetor which turns out to be cheaper anyway if you're paying for their labor. The carburetor was around $128 from the dealer & $88 from boats.net so I bought it there & it fixed the problem. I did try replacing the main nozzle/jet but that did not work either. It's easy to replace the carb on these little motors & well worth the cost. I use non-ethanol gas & add stabil & Pri-G. I also try not to let the gas get more than a month old although the stabil is supposed to help with that.
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Old 22-10-2014, 10:04   #12
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Re: How do you "Break" a Carburetor

Quote:
Originally Posted by raybobsky View Post
put some sea foam in the tank, run it for a while and see if it clears up, also pull off and check all hoses and connectors for clogs. sea foam available at wal-mart. the biggest issue is with the gas we are forced to use. also replace any filters.

a mechanic told my mom she needed a new throttle body on her car, turned out the electric fuel pump was losing power and it was running dry, go figure?


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Old 22-10-2014, 10:05   #13
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Re: How do you "Break" a Carburetor

chevy dealership Newburgh ny.


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Old 02-02-2015, 02:32   #14
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Re: How do you "Break" a Carburetor

If it's a two piece carb, a body and a horn or top.
They can warp out of shape allowing air to be sucked in resulting in a too lean condition.
If it's a single casting , it's probably got something stuck in a passage and may not be cleanable.



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Old 29-04-2015, 16:24   #15
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Re: How do you "Break" a Carburetor

When you do get a new motor, install a lawn mower-type filter in the line between the tank and the carb. Many have NO FILTER except a strainer in the tank, and that is just silly. Replacing a $3 filter between 2 clamps about once a year is a very easy thing! Best $3 I ever spent on a motor.

Probably not dirty fuel, probably you got water in the fuel through the vent (possibly seawater), which gelled up with corrosion products and corked a passage. So keep the fuel dry, close the vent when not in use, and use an anti-corrosion additive like Biobor EB or Seafoam.
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