Question about Troy Bilt Tb70ss Gas Trimmer

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TB525cs trimmer runs until it is accelerated-surges then dies

This is a 4 stroke engine. with a previous TB 4s model I could open and clean the carb (not dirty) and that would solve this mysterious problem. I tried the same on this model with no success. It is as if there is an auto shut-down if the engine reaches a certain RPM. Like it can't maintain a constant fuel supply for the throttle increase given. There is a difference in the position of the choke settings of normal operation and getting it to run presently. I strongly feel this is a carburator issue and will attempt to clean it and the fuel filter again.

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Check the fuel lines for cracks/breaks. If they are o.k., then:

You will need to disassemble the carburetor and spray with carb.cleaner. Make sure the small screen is free of debris. (Should be able to see daylight through it.)

Use a Den Tek Brush, (,to clean the small portals in carb. These portals can become blocked. Reassemble and start.

If the carb. parts are more than 4 years old, you may have to replace them.

If you need further assistance, just let me know.


Posted on Jun 28, 2009

  • Jim Parker
    Jim Parker Jul 01, 2009

    Did this solution solve the problem?




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Engine starts & runs at idle. Dies when switched to RUN & wont accelerate.

Sounds like its a fueling issue. With small tool 2 stroke engines when you pull the throttle you actually increase the amount of air the carb gets. In turn, this rush of air through the venturi of the carb draws more fuel into the cylinder. If your engine is cutting out or wont accelerate this is generally because the engine is either getting too much fuel or not enough for the fuel/air mix to burn effectively. It could also be air getting into the fueling system by means of a damaged fuel line or carb diaphragm. By all means clean the carbon from the exhaust and clean the air filter, they can only help the running of the engine. Hope this is of some help.

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If you rebuilt the carb did you turn any of the screws on the carb while cleaning or take out, you might have just the low idle screw closed a little to much open half turn and see what happens. If you look at the carb where needle screws are located on the side,if you have two screws it will be stamped with an " L " and?or an " H " next to each screw. If you only have one screw then turn that one, to left to get more fuel. Good Luck...

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I have a Toro 4 cycle gas trimmer that won't stay running. Starts, then sputters, then dies. I've changed the oil, drained fuel & put in new fuel.

check to make sure the air filter and the fuel screen are clean, the screen is the little white plastic piece on the end of the hose in the tank. if it is still sputtering try cleaning the bell out on the carb. it is the little metal cylinder on the bottom of the carb where it holds the fuel until it evaporates into the engine if it gets clogged the engine will not run properly.

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Hi, I have a Victa Tornado Plus Whipper Snipper that starts straight away and it idles but it won't rev up. When you try and rev the motor up it sounds like it is under load and the trimmer head only moves...

Hi and welcome to FixYa, I am Kelly. I know this is a 26 cc petrol engine on your trimmer but do not know if it is a 2 or 4 stroke engine. If you are in AU then it would be a 2 stroke. There are a few things that can cause this.

If you engine has a primer bulb.... Hold it depressed hard while trying to increase engine speed. What your trying to do by doing this is prevent air introduction via the primer bulb if it has a pin hole in it. If you can get normal speeds bu holding the primer bulb depressed HARD the primer bulb has a pin hole in it and must be replaced.

Also look inside the fuel tank at the fuel collection tube end. Usually there is a screen inside the tank. Some times the screen becomes coated with gunk and it has to be removed from inside the tank for cleaning.

If your carb has a fuel shut off on the side of it... unbolt the fuel manifold and pull the bolt out of the manifold. Models with this type of fuel shut off have a screen inside the manifold that has to be pushed out of the manifold and cleaned.

If after checking all of the above you still have the problem then it is time to remove the "L" fuel mixture screw on the side of the carb. BEFORE removal... rotate the screw clockwise counting turns until it JUST barely closes. Do not turn it tightly closed as the end of the mixture screw needle will break off inside the carb and you will have to replace the carb.
Then rotate the mixture screw ccw and remove it. Spray carb cleaner into the mixture screw hole to remove any debris.
IF your carb only has an "H" screw perform the same procedure above but for sure clean both the "H" and "L" mixture holes with carb cleaner. Wipe off the needles too.

Install both screws CW until closed and then reverse the number of turns CCW you counted before removal for EACH of the 2 mixture screws.
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Start the engine and let it warm up briefly. Attempt to increase speed slowly to full speed. If the engine hesitates open the "L" mixture screw less than 1/8 th turn and try again. You should note a change in performance after rotating the "L" Mixture screw ccw. Begin rapidly throttling up the engine after EACH adjustment until the engine no longer hesitates or tries to stall upon acceleration from idle.

RUN the engine at TOP SPEED. Adjust the "H" Mixture screw until you get maximum engine rpm. You will NOT hurt the engine but it must run at MAX speed smoothly.

CHECK acceleration from idle to MAX again. re-adjust "L" mixture if necessary.

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This should get you going again. If you need any more assistance or you still have the problem after performing the aboe please respond here with any updates.
Thanks for choosing FixYa,

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