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From time to time I come across carburetors do not run properly no matter how much I have cleaned. I am sure I have cleaned every possible holes and passages but still not running right. Does this happen to you?

New carburetors are under $20 from many sources now but I still feel bad not be able to fix the old one.
 

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With the welch plugs removed, there really are no areas that cannot be cleaned. If the carb is still not running right, start looking for warped mating surfaces which can allow air to be sucked in between the carb and engine, worn throttle/choke rods and bores or even hairline cracks in the carb body itself.

But when new carbs are so cheap, is it really worth spending 8 hours fiddling with the old one?
 

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The other issue is that it seems, to me at least, that some carbs never allow the engine to run right no matter how clean they are. Due to emissions restrictions, it seems like some of these carbs are jetted to never really deliver a decent mixture to the engine resulting in the engine running poorly.

I recently tried a Chinese-made adjustable carb on my LH195SP. It ran markedly better at idle and WOT (though I never had a chance to try it in snow) after adjusting the mixture. I had to take that carb off and toss it because no matter what I did it did not stop leaking fuel (needle valve...) but it showed that the engine could run smoother with some degree of adjustment dialed in.
 

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I've had some carbs that just won't run right, they've been the ones with the non-adjustable jets. I've picked up an Oregon carb off ebay that had the right choke and throttle linkage and was for the size motor I was working on. I've had great results doing that.
 

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Discussion Starter #7
I got one from Harbor Freight. I am not so sure it works that well. I use the gallon size carburetor cleaner from Advance Auto Parts. I have read people use Simple Green HD. Do you think that gives a better result?
 

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I got one from Harbor Freight. I am not so sure it works that well. I use the gallon size carburetor cleaner from Advance Auto Parts. I have read people use Simple Green HD. Do you think that gives a better result?
I've had good results with Simple Green HD. The cleaning solution selection definitely makes a difference.

I've read you're not supposed to use flammable solvents in an ultrasonic cleaner. When researching this, I don't recall much discussion of people using the more "traditional"/dedicated carb cleaning solutions when using ultrasonics.

The HF model runs for 8 minutes, I think. I ran the carbs for an hour in my cleaner (not the HF one). So I'd run multiple cycles, with the solution hot, for better results.

I was amazed at the results with ultrasonic. Things went in fairly nasty, and came out looking almost new.
 

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Some can't be fixed according to ...How to Rebuild a Tecumseh Carburetor " After the carb is off the engine there is one thing you need to check before going any further. Remove the float as above. Now hold the choke and throttle butterflies so that you can shake the carb without them making a sound. Shake the carb and listen for it to rattle. If you do not hear the rattle, the emulsion tube is stuck. This tube is sealed into the body of the carb during manufacturing and can not be replaced. The carburetor will need to be replaced. Also if the aluminum body of the carb is corroded inside, any rebuild will only be a temporary fix. Once the corrosion has started it can not be stopped."
 

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Do you mix water in Simple Green HD? 50-50?
Where do you buy Simple Green HD?
Yes, but I use dishwashing liquid, a couple drops. So, with simple green, you may add a few more. I figure, it's easier to run the machine longer, and not cause damage or get the most effectiveness out of it, with the least.
 

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Regarding leaks from Chinese carbs; I find that any carb cleaner or brakleen or acetone, etc will swell the seats making them leak(not seal). I test all these carbs first dry upside down with my Mityvac to see what the popoff pressure is on the seat. Should hold a couple of psi before popping off. I don't have the official Tecumseh leak detector listed below, I just make sure the seat is in fact sealing against the needle.

Excerpt from Tecumseh Service Manual:

Needle and Seat Pop-Off Test
To test the pop-off pressure, remove the carburetor from
the engine. Be sure to drain any fuel into an approved
container. Invert the carburetor and remove the float bowl.
This test is best performed when the carburetor is placed
upside down and level in a soft jawed vice. Lift the float
and needle assembly off of the seat in order to place a
drop of WD-40 on the tip of the needle or on the seat surface.
Reposition the float and needle assembly. Using the
Tecumseh Leak Tester part # 670340, connect the high
pressure regulator to the low pressure regulator and attach
the clear low pressure air line to the carburetor fuel inlet.
Apply approximately 5-6 psi of compressed air, close the
gate valve and disconnect the low pressure guage from the
high pressure guage. Monitor the low pressure guage to
make sure the needle shouldn't drop below 1.5 psi before
1 minute of time elapses. If the minimum of 1.5 psi cannot
be maintained for this period of time, then replacement of
the needle and seat is required
 
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