I've just got a Yamaha dt 125 R, I think it's a

SOURCE: yamaha FZ 750 FM

It sounds like the idle screw is not set right., but if your going to clean the carbs anywyas. Clean them, sync them and see how she runs, if still doing the same thing the idle screw needs to be adjusted. The RPMs should be between 800 to 1200 while idling. If your bike is an older on it will most likely sit around the 1200 rpm at idle.

SOURCE: No power at low revs but works a treat at higher revs.

Hi mate it seems your powervalve is turned up fully, It can give u power on top end ,middle,and bottom end of revs.With it being a 87 a manual valve you will have to take off your exghust off.Now take a look into your engine through your exghust manifold and turn the power valve round ,you will see the hole in which the burnt gases escapre gets bigger or smaller by adjusting this gap you will find the perfect riding style for you (agressave or plesant ) remember to tighten all nuts up ,as you dont want your valve spinning round cus it will shread your piston and rings to death. hope this works
scotty

SOURCE: 1987 rm 125 starts and idols fine, bogs out on take off!!!!

Pull the slide out of the throat of the carb then move the clip at the top of the needle down one notch, two if needed. This will richen the low end fuel mix.

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SOURCE: yamaha DT 125 2003 Main beam headlight keeps

i have well, had a very similar problem, my headlight kept going on my 1990 dt125r from 1990 to 2003 the engine is the same so i feel it may be the same fix, the regulator/rectifier stopped working properly and was alowying to much power to get to the headlight and blew it, i got a new regulator/rectifier for around £30 ish, you could tell when it went caus the higher you reved it the brighter the light got until it blew not like when it gets brighter from tickover, it was just proggesive and just kept getting brighter the more you revved it, hope this helps

SOURCE: i have a dt 125 lc 1987 just changed the piston

You have several possibilities;

• The slide in the carb is not closing properly,
• The throttle cable is stretched or kinked so that the cable is binding up.
• The rubber seals mounting the carb to the manifold are old, hard and cracked. This lets extra air into the fuel making it lean which makes the engine go nuts. The original seal was broken when the carb was removed from the cylinder.
• The reed valves are cracked, chipped or broken.
• The new head gasket is not sealing properly and is sucking in air. You DID tighten the head bolts in a pattern, a bit at a time, and you DID use a torque wrench, didn't you?
• The timing is pre-set, you have no points or condenser. You may have messed up the timing by trying to adjust it.
• Can I get a “very helpful” rating on this answer?

Testimonial: "very helpful"