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My Tecumseh HM 8 hp motor over revs than stalls. It must be

Customer Question
My Tecumseh HM 8 hp...
My Tecumseh HM 8 hp motor over revs than stalls. It must be primed again to start. Won't maintain working rpm.
Submitted: 5 years ago.Category: Small Engine
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Answered in 2 minutes by:
1/8/2012
Technician: James W, Small Engine Troubleshooting Expert replied 5 years ago
James W
James W, Small Engine Troubleshooting Expert
Category: Small Engine
Satisfied Customers: 3,708
Experience: 7 years as Mechanic & Parts Manager for Brother who has Owned Lawn & Garden Repair shop for 35 years
Verified

James W :

Greetings, My name isXXXXX and I am here to help the best I can. My goal is 100% satisfaction. Let's get started.

James W :

what method did you use to clean the carburetor

James W :

because it STILL seems like a carb problem

James W :

also, do you have exactly the model number, type number and spec number of the engine?

James W :

would it be an HM80 rather?

Customer:

dissassembled, sprayed with carb cleaner, sprayed ports with compressed air

Customer:

yes HM80

James W :

there are many ports, tiny holes, etc

James W :

that need to be probed with a tiny stiff wire such as from a bread twsit tie

Customer:

revs really high when I open up the throttle

James W :

It is running too lean and the governor is trying to adjust

James W :

when it does all it can, then it dies

James W :

pay particular attention to the bowl nut / main jet

James W :

As engines sit or get older, fuel that is left in the carburetor can turn to gum and varnish and cause this and other problems.


Also, any gasoline that was left in a gas can for a period of more than 30 days must be discarded because it also has begun to turn to varnish.


Today's gasolines contain MTBE and alcohol. (Ethanol) They turn to "Junk and garbage" very quickly. Alcohol absorbs water. And they call it "Oxygenated fuels! It is the oxygen (and the water) that breaks down the organic compounds in the fuel and turns the gas to "Garbage" (Gum and varnish) The fuels we had just a few years ago had no alcohol in it and would store for longer periods of time before going stale.


Fuel stabilizers do almost nothing to prevent the fuel from going bad with the changes in today's fuels. The whole point of a fuel stabilizer is to form an oily film on the surface of stored gasoline whether in the tank or in a gas can. The idea was to keep oxygen away from the gasoline to prevent breakdown. Since the fuel is already oxygenated, the fuel stabilizer concept is null and void. These fuels start to degrade immediately upon the addition of the ethanol.


Do not buy gas from the "Discount" Stations. The discount stations get a reduced price on gas because they may be buying fuel that is nearly 30 days old already. You may be getting fuel that's nearly stale right from the pump when buying from a discount station. Purchase your fuel from the well-known stations such as Shell, BP, Sonoco, Phillips 66 etc.


More than 70% of all of our repairs in our small engine repair business are due to these same issues. You most likely have dirt, gum, varnish...etc in your carburetor plugging up the small passageways and jets in the carburetor.


The carburetor will need to be cleaned and overhauled as well as the rest of the fuel system.


 



  • If you plan to do the work yourself, take pictures with your digital camera or at least make a drawing of where all the linkages, gaskets, and component parts go. Correct reassembly is critical.

  • Remove the carburetor from the engine.

  • Remove all of the non-metallic parts since the carburetor cleaner will cause them to be disfigured decompose and plug the carburetor as time goes on.

  • Clean all parts with carburetor cleaner. You will want to SOAK the non metallic parts in a cleaner bath.

  • Blow out all the small holes and passageways with compressed air.

  • Use a tiny stiff wire such as is found on the twist tie on a loaf of bread or on a garbage bag to open all tiny passageways found in the carburetor such as in the screw, nut, or jet holding the bowl of the carburetor on (if it has a bowl). Make sure to look for tiny holes in the bottom and side threads of the bowl nut or nozzle a make sure they are clear with the wire.

  • Wash the carburetor cleaner off of the metal parts by washing them in warm, soapy water then rinsing with clean water.

  • Dry all carburetor parts by blowing it off with compressed air.

  • Make sure that all the passageways are blown dry before reassembling (you do not want water back in the carburetor).

  • Reassemble the carburetor using a NEW carburetor rebuild kit.

  • NOTE: DO NOT TRY TO REASSEMBLE WITHOUT USING A COMPLETE CARBURETOR KIT! You will just end up having to do the job again.

  • Find the Model, type and serial or code numbers off of the engine and take them to your local dealer to get the carburetor repair kit.

  • ALWAYS clean the fuel tank and replace the fuel line when doing this repair or you may have to do it all over again. The inside of the fuel line disintegrates over time and these small pieces of rubber will plug up the carburetor too. Dirt and water from a dirty fuel tank will also plug up the carburetor. If this happens, you will be starting over again from the top.


In an Emergency such as a blizzard where you cannot get out to buy a carburetor kit until the plows come through, or during an emergency power outage and you need a generator running even if it runs poorly, you might try the following if your carburetor is the type that has a bowl. Sometimes this procedure works:


While the carburetor is still mounted to the engine:



  • Pinch the fuel line with a pair of vice grips to stop the fuel from going to the carburetor.

  • Remove the bowl nut (or nozzle from the bottom of the carburetor and let the fuel drain from the bowl.

  • Carefully remove the bowl from the carburetor without letting the needle and seat and float fall out of position (if it does, no big deal, but you will have to reassemble it, which is harder with the carburetor on the unit).

  • Dump all of the Gunk out of the bowl and put the bowl back into position.

  • Use a tiny stiff wire such as is found on the twist tie on a loaf of bread or on a garbage bag to open all tiny holes in the screw, bowl nut, or nozzle that was holding the bowl of the carburetor on (if it has a bowl). Make sure to look for tiny holes in the bottom and side threads of the bowl nut or nozzle a make sure they are clear with the wire.

  • Reassemble and see if you got lucky.


You may be able to finish the job at hand then clean and overhaul the carburetor correctly when you have more time and a new carburetor overhaul kit.


The nut that holds on the carburetor bowl has several small holes in it. Some are on the sides and one may be in the end. In order to completely clean the carburetor correctly, you Must clean these holes with a tag wire or a jet drill. (If a jet drill is used, DO NOT use a drill that is bigger than the hole or the engine will run too rich.)















 





 



 



View Full Image



 


If you don't feel comfortable with these kinds of repairs, or if the carburetor still doesn't work correctly after your attempt, I would suggest sending it to a profession repair shop with a reputation for having friendly, knowledgeable, experienced service technicians. It would be best to take it to someone who has an "Ultra-sonic" cleaning machine. This machine uses a very mild carburetor cleaner in concert with ultrasonic vibrations to get the very small passageways clean. This method is very effective even when traditional methods fail.


Here is where you can get an inexpensive "Ultrasonic Cleaning Machine"


http://www.harborfreight.com/catalogsearch/result?category=&q=ultrasonic+cleaner


There is a New Product that you can try which is guaranteed to work or your money back (per the manufacturer).


http://www.b3cfuelsolutions.com/html/mib.html


It is designed to help clean the carburetor without damaging the diaphragms and rubber parts like regular carburetor cleaner. Click on this site and it will tell you all about it. http://www.b3cfuelsolutions.com/html/mib.html


The mechanic in a bottle is NOT a conventional carburetor cleaner.


It actually breaks down the varnish into it molecular components and it completely dissolves. It DOE NOT clog up the jets as conventional carburetor cleaners do. Conventional carb cleaners just loosen the varnish and the varnish particles will go into the jets and filters and clog them up.... usually causing much more problems that was originally there. The conventional carb cleaners also will loosen the "GUMK" that has formed in the gas tanks and cause all of that gunk to go through the carburetor as well.


 


The Mechanic in a BOTTLE is a completely revolutionary product that will in many cases alleviate the need to tear the carburetor down and rebuilt it..... unless there is mechanical wear and tear that would require that parts be replaced.


 


In addition, the special formula actually is designed to soften and restore the rubber parts in the carburetor such as the needle and seats and gaskets.


 


Mechanic in a bottle is NOT a cure-all but it can help customer get going in many cases without them having to tear the carburetor apart. If the customer is NOT mechanically inclined, it might save them a trip to the repair shop.


 


Yes I was very skeptical about this product when I first was introduced to it, but the Distributor demonstrated it and we have tried it on many occasions with terrific results.


Otherwise you will have to clean and rebuild the carburetor.


Please feel free to ask follow-up questions so that we can always arrive at the correct solution. We want you to be 100% satisfied.


 

Customer:

ok, should I try cleaning the carb again?

James W :

Absolutely, and use a carb kit... The instructions (all 100 lines) are above as I just sent you

James W :

you are on the right track.. You just misses something

James W :

this book in PDF format

James W :

will help you KNOW exactly what to look for

James W :

It has photos of the holes in the bowl nut an elsewhere must be probed

James W :

it has photos of the holes and orifices in the bowl nut AND eleswhere whcih must be probed I mean.

Customer:

ok

James W :

I will be available and will be notified via email of your replies and follow up questions

James W :

even after I switch the question to Q&A mode rather than chat and after you ACCEPT

James W :

I will be glad to help futher

Customer:

ok great. I will give it a try

James W
James W, Small Engine Troubleshooting Expert
Category: Small Engine
Satisfied Customers: 3,708
Experience: 7 years as Mechanic & Parts Manager for Brother who has Owned Lawn & Garden Repair shop for 35 years
Verified
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Technician: James W, Small Engine Troubleshooting Expert replied 5 years ago
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James W, Small Engine Troubleshooting Expert
Category: Small Engine
Satisfied Customers: 3,708
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Experience: 7 years as Mechanic & Parts Manager for Brother who has Owned Lawn & Garden Repair shop for 35 years

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