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Ranwell1, Small Engine Technician
Category: Small Engine
Satisfied Customers: 10304
Experience:  I Own a Lawn Mower Sales and service business (37years). Have 2-cycle and 4-cycle certification.
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Troy-Bilt TB475ss trimmer. Starts and will idle, pull trottle

Customer Question

Troy-Bilt TB475ss trimmer. Starts and will idle, pull trottle a little bit, the line starts to rotate. As soo as I give it a little more throttle it dies. Cleaned carborator, fresh gas. No aitr in fules lines. Left idling for 5 minutes no stall, as soon as giver it some throttle slowly accelerates, but just as it nearsa full speed. dies???
Submitted: 5 years ago.
Category: Small Engine
Expert:  Ranwell1 replied 5 years ago.





the problem is still likely to be in the carburetor.



If you did nlt use a complete carburetor repair kit, then the problem is likely that the diaphrams are bad.



Also it could be a fuel line that has a snmall hole in it.


JACUSTOMER-a91oyj5r- :

Ran fine for about 45 minutes on Thursday. Starts and will idle fine. Pull thruottle partway will speed up, go to full throttle dies.


Also it could be that the fuel filter has falen off of the end of the fuel line inside the fuel tank. These will NOT run without the filter on the lone.



The problem is that the engine is not getting enough fuel.



I have a possible "QUICK-FIX" that I will send you......


JACUSTOMER-a91oyj5r- :

Where is the filter, inside the tank?


It is supposed to be attached to the fuel line that is in the tank.





I am having trouble getting the answer to past into this chat, so I am going to close the chat and open this question in a different format. Just refresh your browser and it will come up.

Expert:  Ranwell1 replied 5 years ago.

Most likely the problem you have is that the carburetor is restricted or plugged because of fuel that was left in the the carburetor while it was stored. Fuel CANNOT be used if it is over 30 days old. Also this old fuel will not burn correctly and will cause oother issues as well.

In many cases the carburetor should be removed and cleaned and rebuilt with a new carburetor repair kit.

Even if an engine is run dry, there will still be 10 to 12 drops of fuel left in the carburetor. This is what turns to gum and varnish and dirt and restricts the passages in the carburetor. Also keep in mind that even if this is a BRAND NEW unit, you can still have this same carburetor problem. This is because of the fuel that the factory puts into it when they are testing it. They then run it dry before shipping it. But there is still some fuel in the carburetor.

I do have a possible Quick fix for you, but you must use what I tell you.

DO NOT USE regular CARBURETOR CLEANER such as GUMOUT or something similar. These carb cleaners will ruin the rubber parts of the carburetor.

Here is the possible Quick fix.:

There is one good thing you can try. It is called "Mechanic in a bottle". It is usually available at Home Depot some Walmarts or many autoparts stores. Even some Mower repair shops. We cary it at my store. It is very new to the industry and is the very best.

Here is the website that should tell you more about it.

"Mechanic in a Bottle" is designed to help clean the carburetor without damaging the diaphrams and rubber parts like regular carburetor cleaner. Click on thes site above and it will tell you all about it.

This helps sometimes, but other times it does not.and the only solution is to to clean and rebuild the carburetor.

It is available t Home Depot and good mower shops.

It is also available at Here is their website info.

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

It actually breaks down the varnish and alcohol and water into its molecular components and it completely dissolves these substances. It DOES 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 "GUNK" 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 case 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 the 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. Many of the Justanswer customers have come back to thank me for telling them about it and it solved thier issues.

Here is some information that I got off their website.

Varnished carburetor? Fuel gone bad? Water in the tank & carburetor

causing corrosion from ethanol? "FIX THE UNFIXABLE" Mechanic In A

Bottle removes all varnish in the fuel system without having to remove

the carburetor from the machine. Add to your gasoline and you will be

able to clean varnish and carbon.

  • Restore old fuel by separating the hydrocarbon chains that have bonded

together since the fuel has deteriorated. An octane booster is added to

replace the lost octane in the decayed fuel. We do not use any metals in

our formula to increase the octane.

  • Remove carbon deposits from combustion chamber components

including the combustion chamber, piston(s), rings and valves.

  • Dual lubricants condition the rubber and plastic components. They also

rejuvenate and protect the rubber gaskets and seals that may have been

dried out from ethanol. After the fuel is burned in the combustion

chamber, a synthetic lubricant remains to lubricate the entire upper

combustion chamber, such as piston rings and valves.


Poor Running Engine:

No detrimental effects if overdosed.

Mix 2 ounces of Mechanic In A Bottle (MIB) to1 gallon of fresh gasoline.

Start engine and run for at least 10 minutes. Let engine stand for at least

8 hours before restarting. Continue use of mixed MIB fuel until gone. Use

Ethanol Shield all the time to prevent fuel related problems.

Non Running Engine:

Add 4 ounces of Mechanic In A Bottle (MIB) into an empty fuel tank and

prime the MIB through the fuel system into the carburetor. Wait at least 8

hours before draining contaminated MIB from the fuel system and

adding fresh fuel mixed 2 ounces MIB to 1 gallon of fresh gasoline.

Severely contaminated fuel systems let stand overnight or repeat if



Mix 1 ounce of MIB to 5 gallons of gasoline.

This is a fuel additive not a replacement for 2 cycle oil.

This helps sometimes, but other times it does not.and the only solution is to to clean and rebuild the carburetor.

Here is my comprehensive carburetor and fuel answer that may give you some ideas.

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 gasoline's contain MTBE and alcohol. (Ethanol) They turn to "Junk and garbage" very quickly. Alcohol is partially water (H2O). And they call it "Oxygenated fuels! It is the oxygen 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... and fuel stabilizers do almost nothing to prevent the fuel from going bad with the changes in today's fuels.

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 lawn mower business are due to this same issue. You most likely have dirt, gum, varnish...etc in your carburetor plugging up the small passageways and jets in the carburetor.

The carburetor must be removed from the engine. Clean all parts with carburetor cleaner and blow out all the small holes and passageways with compressed air. 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.

Wash the carburetor cleaner off of the metal parts by washing them in warm, soapy water then rinsing with clean water. Dry them by blowing it off with compressed air. Make sure that all the passageways are blown dry before reassembling.

Reassemble using a NEW carburetor rebuild kit.

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

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. 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.

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

If the carburetor still doesn't work correctly, you may have to take it to someone who has an "Ultra-sonic" cleaning machine. This machine uses carb cleaner and ultrasonic vibrations to get the very small passageways clean when traditional methods fail.

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

If you don't feel comfortable with this kind of repair I would suggest sending it to a reputable shop.

Here is a Carburetor rebuild process.

First make sure that you have the correct complete carburetor repair kit.

Now take special care when you take the carburetor make sure that you watch and remember exactly how the gaskets come off.

There are two types of carburetors. The "FLOAT" type carburetor and the "DIAPHRAM" type carburetor.

Below is the information for the float carburetor.

The Diaphram carburetor is very similar except that you need to remove the diaphrams and replace them. They wiill also have a needle and and sometimes a seat that need to be replaced as well.

Remove the float pin just pushes out...and remove the float..carefully.. so you can see how the float needle is attached...(Some of them have a small wire spring holding it to the will have to reinstall this spring when you reassemble the carburetor.

Remove the float needle

Next...remove the float valve seat. . Look around the carburetor and see if it has a small idle adjustment needle...remove this needle if it has one. You are now done disassembling the carb. DO not take anything else out of the carb.

Get a good carburetor cleaner....preferably with a small hose you can attach to the nozzle of the can. Spray the carb cleaner all over the outside of the carburetor. this will loosen the dirt on the outside while you clean the inside. Now spray the cleaner through every hole, and nook and cranny you can fine on the inside of the carb.

When you are finished with the spray,blow all of the passageway clean with compressed air from an air compressor. Also blow all of the dirt from the outside of the carburetor.

Next. Take the entire carburetor to the kitchen sink......Ok maybe it would be better to get a big you don't make your wife mad....and wash the entire carburetor with HOT SOAPY dishwater. This is to make sure that all of the carburetor cleaner is completely washed from the carb...(If it is not, you will deform the new gaskets and such that you install...even if it is dry.) Now rinse in clear watter and then blow the carb dry with the compressed air again.

Reassemble the carb using the identical parts out of the carb kit as you took out. install the float seat, then install the float needle and the float in the same position that you took them out. Check the float level after it is installed. Making sure that when the carb is upside down with the float in the up position, the float should be nearly level with the body of the carburetor. Now reinstall the bowl gaskets the same as you took them off. Then install the bowl nut with the small gasket under it. Reinstall the small idle needle if it had one.

There you are done.

Install the carburetor on the engine and you should be ready to go.

Customer: replied 5 years ago.

I just went out to check the filter. It was attached.


Expert:  Ranwell1 replied 5 years ago.

I understand, that was just a last ditch idea.

The real problem is in the carburetor. It MUST be cleaned and rebuilt.

Try the mechanic in a bottle First and you might find that it works for you. If not, then you will have to buy the compete carburetor repair kit.

There is ONE more thing that you might try, though.

Check the muffler screen. It may be clogged with carbon. Also check to makes sure that it is not clogged by a Mud dabber's nest. These wasps like to build nests in these mufflers.

If this is not the case, then you MUST rebuild the carburetor.

Customer: replied 5 years ago.

I replaced the fuel line and filter. The flash arrester screen is clean and clear. The carborator is also clean. I tried some ether engine starter, will start up, but agin will not run when acceerating. I can see that there is plenty of gas flowing in the new line. I have done everything that the user's manual suggest. I have adjusted the idle and can ramp it up to fast idle, but pull on the accellerator adn it stalls. Rebuilding the carborator seems bit extreme since it ran perfectly 2 days ago???


Expert:  Ranwell1 replied 5 years ago.

You can believe what you want, but the problem is in the carburetor.

I would first use the MECHANIC IN A BOTTLE. It will most likely fix the problem.

Drain all the gas out of the tank.

Put about 2 ounces of MIB in the tank. Prime the primer about 15 times. Then let it sit overnight.

Then prime it again about 15 times and let it sit overnight again.

Then fill the tanks with FRESH fuel...And I mean FRESH. Then push the primer again about 15 times. Then start the engine. It will most likely fix the problem.

If it doesn't, then you will need to rebuild the carb with a complete kit.

Customer: replied 5 years ago.
You didn't tell me much that I didn't already know or hadn't already seen in the troubleshooting manual. Certainly not worth what this web site was charging.
Expert:  Ranwell1 replied 5 years ago.

As I have said several times, if you did not rebuild the carburetor with a COMOMPLETE carburetor repair kit. Then is is NOT going to work. The diaphrams are likely part of the problem.Rebuilding the carburetor is NOT EXTREME. This is definately what your problem is.The information is very complete, but if you won't do what I have told you to do, the we have BOTH failed. Why ask for help and not take the advice?