Question about 2004 Yamaha TW 125
The bike will suddenly loose power and **** or shudder or even just grind to a halt at about 50mph. At times it regains power but sometimes the throttle is useless until the bike has been switched off and restarted.
Hi, Richard_dunn and the usual suspects are:
1. Severely discharged or a damaged battery must have 12.5 volts or more and be able to pass a proper "LOAD" test if necessary, you may have a preliminary reading of 12.5 volts or more but little or zero amperage the battery is faulty and must be replaced, AGM batteries fail in this scenario more so than lead acid batteries.
2. Faulty alternator/generator and or voltage regulator.
3. Loose or corroded battery terminals and or cables especially the "NEGATIVE" cable, look for loose, corroded, or broken connectors inside the cable harness at "BOTH" ends.
4. Faulty main circuit breaker or ignition switch, check for loose connections and continuity.
5. Faulty system and or ignition relay, check for continuity.
6. Faulty ignition coil, ignition/electronic module.
7. Faulty CKP, CPS, CMP, MAP, TPS, or BAS sensor, corroded, loose or broken wire connector pins/sockets.
8. Throttle cables and or idle speed improperly adjusted hot idle speed should be 950 RPM to 1000 RPM.
9. Faulty neutral, side stand or clutch lever safety switch.
10. Fuel tank empty
11. Fuel tank contaminated with ethanol sludge.
12. Water or dirt in the fuel system, or clogged filter.
13. Restricted, blocked or kinked fuel line.
14. Faulty fuel pump.
15. Faulty pressure regulator.
16. Faulty or clogged fuel injectors.
17. Lean angle switch is faulty or needs adjustment.
For more information about your issue and valuable "FREE" downloads that you need please click on the blue links below. Good luck and have a wonderful day.
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YAMAHA TW125 Owner Manual
Posted on Jun 15, 2017
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Posted on Jan 02, 2017
SOURCE: yamaha tw 125 2
ALWAYS have a fire extinguisher at hand when working on carburetors.
Remove the water trap bowl at the bottom of the petcock, (gas valve). Is there any water or trash in the bowl? Drain a cup of gas from the tank. Is there any water or trash in the cup? Dump it, clean it and re-mount it, ( not all bikes have a water trap bowl ).
Drain the carburetor. There should be a screw on the lower side of the carb float bowl. Remove the screw then replace it after the fuel drains. Turn the gas back on and wait a minute for the carb to fill with gas. Install a new stock NGK spark plug and try to start the engine. If the bike doesn't start and run properly then shut off the gas and remove the carburetor from the engine.
Remove the float bowl and clean the entire carb with a spray carb cleaner from the auto parts store. Wear protective goggles to avoid getting spray in your eyes. Spray into all the little airways and fittings in the carb. Remove the idle screw and the air screw on the outside throat of the carb and spray into the screw holes as well.
< < READ CLOSELY > >
Be sure to put these two screws back in the same hole they came out of. IMPORTANT > do not tighten these two adjusters down. Only screw these in until they LIGHTLY seat. Now turn each adjuster one and one half turns outward. Put the rest of the carb back together, clean the air filter and install the carb. Let the float bowl fill then start the engine. If the problem is still there, the float height needs to be reset. If possible take the carb to a dealer and let them put a float gage to it. Probably cost $15 but call and ask before you take the carb in.
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Posted on May 06, 2009
SOURCE: yamaha tw 125
The noise you hear is valve clatter. You should not adjust your timing chain. Instead get a manual and find the vlave clearances for that bike. (Ex. The exaughst valve may be .006" and the intake valve may be .004") Then you'll need a feeler gauge, and to do this you'll remove the valve covers and get the engine to TDC (Top Dead Center) This is where the piston is at the very top of it's stroke and both valves are shut. (compression stroke) You must then loosen the rocker arm nut to the point that you can insert the feeler gauge between the rocker arm and the top of the valve run the nut down tight to the feeler gauge and then pull gauge out and repeat on the other valve.
Posted on Aug 24, 2009
SOURCE: 03 yamaha tw 125cc, bike wont go
Could be a number of things....but sounds like it might be fuel starvation. Check your fuel filter and maybe replace it. Check and make sure there is fuel flowing to the carb. After that you would have to service the carb.
Posted on Oct 23, 2009
They are listed in the service manual.
You can download a free one at
Posted on Nov 21, 2009
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