DT125R ARCHIVE

Jimi · DTR Member

Six weeks in and still not starting

tripr · Guru

had exaclty the same problem with my other engine to m8. is the piston in the right way did that new piston an that an still nothing . hope you get it sorted m8

Jimi · DTR Member

No, piston is in the right way. i really don't know what the problem is

bkray · DTR Senior Member

Kill switch?

tripr · Guru

i only say m8 is cos i changed everything before lookin at the piston cos the geeza i bought it off said it had just had a new piston so i trusted that but the div had only gone an put it in backwards.
we tried everything with mine m8 too but its still a non starter i had to give in an buy another engine in the end

Jimi · DTR Member

I wish it was as simple as the kill switch but thats not it. i think the problem is electrical. the ignition coil maybe

tripr · Guru

yeah i had that to m8 check ya pick up coil wiring mine had a break under the wiring to that was allowing the 2 wires to touch.
but that gave out a backfire saying that the timing was off.
and have a check of your woodruff key under your flywheel

Jimi · DTR Member

I'll check the sensor wiring. Sounds possible. It's just so weird that there is a decent blue spark and yet absolutely nothing. I wonder whether the thing might not actually be sparking in the cylinder?

tripr · Guru

yeah its worth a shot m8 cos it still sparks just not at the right time it needs to

StartSoIllFinishOn1 · DTR Member

I had the exact same problem with my partner's RS125, but luckily got it running again..

If the plug sparks out of the cylinder then it sparks in it, so with the spark all being well and petrol poures out (of the outlet pipe that connects to the carb) when the tank is turned on, then it may be a blockage in the carb or around the float valve.

When you cleaned the carb did you blow through it? If not then give it a go GENTLY to see if air passes through, if it doesn't then it's blocked.

If you did blow through when cleaning it and blew too hard then this can sometimes mess up the float valve, so not enough or no petrol gets through.

Let me know and I'll keep thinking, hopefully it's something simple. hmm

Jimi · DTR Member

Thanks very much for your suggestion. Maybe, as you suggest, it's carburation and not ignition.
The thing is, the plug is wet when I take it out. But then I guess the petrol/air mix could be wrong. Possibly a dogdy float-level setting?
I've blown through the jets and they seem fine. I'll set the float level properly this evening.
I'll keep everyone posted. It just can't be insoluble, can it?!

StartSoIllFinishOn1 · DTR Member

lol.. There has to be a way.. Don't let it beat you man! aww

Dingle001 · DTR Senior Member

Ok, so youve got a spark and you must have compression as you have had a rebore and the plug is wet. The only thing I can suggest is to re-check the crank seals. Stupid questions, but did you put them in the right way? Did you refit the collar over the crank on the clutch side? Are they the right bore size? As it was running before (although not well) I would guess it must be something to do with what you have done. Very easy to miss something. I think I might have asked you this before, but is the woodruff key on the flywheel ok? Good luck.

Jimi · DTR Member

I checked the seals. They are in the right way round - the flat side with the writing on it facing out. And I didn't forget the collar on the clutch side. I've also checked the woodruff key. No problem. But you're right: it could be something along these lines. Perhaps I've been stupid. Perhaps I'll have an 'a-ah moment'. But then maybe it's some niggly ignition thing. I doubt it. These are relatively simple engines. How can I just keep failing to get the wretched thing to start?