Hi i have a 1987 dt 125 lc and the engin run s then stops

Maybe you need a new battery.

The cause of this in most gas engines is a plugged jet in the carb. It must be taken apart and thoroghly cleaned. The jet must be unplugged with a stiff wire or paper clip if it will fit. Carb cleaner alone will not do the trick.

sounds like the stator coil in behind the flywheel there are some electric tests for the stator but not allways correct I would try a stator

Hi there, you likely still have the restrictor in the exhaust header. Mine was the same, they are shipped like that as standard. Take the exhaust off the engine and remove the the concentric tube that's in there (you need to cut it out). Instant +100% power, if that is your problem.

Check your CDI

hi,most two strokes run a gear oil in the gearbox,unless specified by the manufacturer dont use engine oil as it is not heavy enough,i use a 75w gear oil in my nsr 250 and it works fine..cheers

It would be best if the whole carburetor were soaked in carb cleaner and then blown out with compressed air. You could have a plugged up passageway in the carburetor. If you take this route and use comercially available carburetor cleaner, DO NOT put any rubber or plastic parts from your carb in the carb cleaner as it will ruin them. As for the jets, make sure you can see light through them. I usually take a strand of copper wire (like from stranded automotive electrical wire) and run it through the jets to make sure they are clean.
If this fails to correct the situation, check the engine's compression. Low compression will cause the engine to not run at low RPM. You need to see at least 140PSI of compression (throttle wide open) in order for the engine to idle. If the compression is low, adjust the valve tappet clearances. If this fails to bring the compression to a normal level, then the engine needs internal repairs.

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?

had exactly the same prob with my dt 125.

In the fuel tank there were two filters that had become a little blocked with small fragments. I replaced both of these, aswell as the petrol tank and now works perfectly.Worth replacing with every service.

Also make sure the amount of fuel to oil is correct because if there is too much oil it leaves a small layer of oil on the spark plug which gets thicker when the engine cools. When you dip the spark plug in petrol and put it back in it obviosly makes a large enough spark to remove the oil, but repeats itself when the bike cools.

Hope this helps

Andrew