20 Most Recent 2004 Derbi Senda SM 125 4T Questions & Answers

Hello! How did you solve it?

Adjust the mixture screw outwards about half a turn at a time to make it richer it is running too lean at the top end

sounds very much to me as the cylinder is shot, they do repair kits but i personally would change it you cant take risks with brakes.

Sounds like your chain is stretched and not fitting the sprocket properly or is just too loose. Check your front and rear chain sprockets for wear and ensure the teeth are straight. Check to insure the chain fits snuggly on the rear sprocket. As a chain stretches over its life, it won't fit in all of the teeth on the rear sprocket. This will cause the chain to ride up on the teeth at higher RPMs and jump (causing the feeling of a jolt or **** as it grabs again). Typically, the chain should have no more than an inch or so of play when properly adjusted.

check for spark at the plug. no spark? check for wet electrical connectors. yes spark? drain float bowl of gas. water may have entered during cleaning process. Shoot carburator cleaner into carb inlet and try to start engine.

the fule tank has a vent pipe fitted in it if the pipe is blocked or traped this is causing the fault

The fuse box should be very near the battery. Start there. Next check the wires where they plug together at the tail light. Next look for loose or dirty connections. Now look for any abraded wires. Next look at the key switch, is power getting through the switch? You do have good light bulbs don't you? If your bike has a headlight, often multiple circuit connections are inside the headlight housing.

If the bike has knobby type (bumpy tread) they do make noise.Just be sure they have the correct air pressure in them.
Try to support the bike so you can manually spin the wheels like if the bike had a center stand.Feel while turning, to see if the wheels feel to tight or loose.And try to feel any play in the wheels. Or hear any stange noise.
While your are at it go ahead a drain the oil and change it with a good quality oil. The bike should have come with a book to tell you what type oil it wants.Dont be afraid to change the oil more than it is suppost to be.They dont hold that much oil and the shifting of the gears will generate alot of break in metal dust that needs to come out of the engine.
To say if you made a mistake in buying the bike remains to be seen because their is no history of the Chinese bikes in this country.
If I could ride the bike I could give you a better opinion.
Another thing you could do is, while riding the bike with it makeing the sound,pull in the clutch and put it in neutral.Is the feeling gone?
This can help to be sure the noise is not engine generated.

Two other things to try. Make sure the battery terminal connectors are absolutely free of buildup. Then place your battery on a long slow charge. If it is not sealed, checkto make sure plates are all well covered with distilled water.

Finally, hook the battery charger up to the battery and move the selector up to start, say 50 amps. Try that. If you still have nothing but clicks, and all bolts and nuts are tight, time to look at the starter itself.

Sirwriter

try a different plug or a new one and get back to me

I understand that Honda's have this problem when they warm up. Try slowing down a bit more before shifting into first.Also, ensure you are kicking it all the way down past neutral. If the problem occurs from a standstill, try rocking the bike back and forth in neutral as that sometimes does the trick.