Dt125r 1998 electrical problem

[jjdpowell]

My dtr died on me on the way home from work it stopped sparking turned out to b cdi so got one off my bros bike which was running fine now its working but its very flat ant mid to high end revs and when i rev in not under load it misses at about 9k?? Any ideas would be great thanks

[Calum]

Sounds like powervalve. Does it operate when the ignition is switch on and off.

Try pinning it open and having a blast.

[jjdpowell]

Ye power valve is working as it should cleaned carb changed spark plug cut a bit off the ht lead and put cap back on

[Calum]

@jjdpowell So with it pinned open, it still feels dead.

So the valve may work correctly, but it might be a more restrictive cdi which retards it after a certain rpm so I need you to test it pinned open.

[jjdpowell]

@Calum hi calum tried it with pv unplugged and it has no power plugged it back in and ther is plenty of mid range power good throttle response just when the valve is open it screams but not going anywere seems like carb problem but only started since cdi change the bikes got a old round slide carb on it with a 145 main jet and ran quite well before cdi change i tried a 180 jet but just spluttered and valve wouldnt open i do have a 160 i could try?

[Calum]

@jjdpowell So to confirm then, with the valve pinned open, it has no bottom end (Which is what I'd expect) but it didn't pull hard 6K to red line.

Are you sure this is the correct CDI for your bike?

The round carb slide isn't the best, although it shouldn't be terrible.

It could just be worn electrical system not providing a healthy enough spark. For now you want to leave the carburettor settings alone, but rasther giving the carb a good clean.

The fact that the ignition system worn out leads me to think there is an underlying issue with the electrical system. Unfortunately it's a case of replacing the ignition system one item at a time to determine the source of the problem

The good news is, all these parts can be "Uprated" rather cheaply.

Starting with a decenet iridium NGK Plug. (BRE8S) I believe.

If it's still poor then you could try the HT Lead. NGK do a "Racing" Replacement. I put these things in quotes because this is what they claim, but when I've replaced them I haven't noticed a difference.

IF that's not it then you could try replacing the coil windings. There are some "Uprated" coils on the web.

All of the above should not cost you more than £30 to replace.

If they haven't solved your problem then it's something else. But those parts would need replacing in due course time anyway.