DT125R FORUM

Aww that's awesome.

Glad you're getting out there on this motor and it's giving you some success

Such an iconic livery set on there as well. Looks great

Oh wow, what a lovely lovely DTR you have there. Please please please keep that original and no silly mods. That is a little time capsule there.

Sounds good listening to it on my phone.

If it pulls well and starts easy then in all likelihood it's a good motor congratulations

Hello,

Oh okay that sounds good.

There isn't exactly common problems with these bikes, if it's well maintained then they really do go on forever.

At that sort of mileage, and if it truly has never been opened, I'd expect the little end bearing to have worn excessively and rings need replacing. This will be tellable through a rattly top end from the small bearing and piston slap.

But again it's all down to how it's been treated.

The clutch baskets wear out over time so you can expect noise coming from the clutch area.

Other things can be like the bushes on the powervalves can be known go wear out. Again this will be proceeded by rattling noise from the top end. If the bushes are left to wear out so much they can have quite dire consequences.

All of these are minor really and shouldn't take any time all to address.

Look forward to hearing more about your endeavours, they're brilliant little machines when maintained properly.

Have you got access to a compression gauge? Can you measure the health of the engine?

I mean it could literally be anything.

You shouldn't be fouling plugs, ever...

So something isn't right there

Is it smoking excessively?

Are you losing coolant?

Are you losing gearbox oil?

I've had something similar when I fitted a cheap chinese knock off 'racing' coil, so make sure you have a genuine 3RM coil fitted.

Make sure the exhaust is cleaned through.

Make sure the airbox and inlet tract is cleared through.

Measure the HT lead resistance make sure it's within spec.

It sounds to me like the relay. So the starter motor button isn't wired directly to the starter motor as the starter motor requires a lot of current.

Instead the wire is connected to the relay and the relay activates the starter.

So I'd look in that general vicinity, sounds like it's starting to go faulty, which isn't bad considering it's age and the high amperage that it is subjected to.

These bikes are getting to an age where the clutch cush drive rubbers will start to wear out.

It's possible that this is where the rattling is coming from.

Whip the clutch cover off and try and rotate the clutch basket by hand. There should be no discernible play in it.

These rubbers sit behind the clutch basket

Sandwiched between the primary gear.

There were chaps on here that used to do something very similar but to the UK. Go down with a van and collect 5 or 6 bikes at a time.

Definitely worth while if it means you get the right bike.

My Dad imported a Lambretta GP from Brussells a few years ago, was no hassle.

Fair play that's mint.

Hello

Welcome to the forum

Yes, photo uploading is disabled as I host all of this myself and imagine hosting is expensive.

Imgur was the preference, but is now blocked in the UK and therefore cannot be viewed here

But yes a build thread would be awesome.

Very sick! That exhaust looks PHAT!

I am in the process of designing an airbox blanking kit which would plug the gap up nicely and then also house the battery/fuses. Although I've only designed it to replace the DTRE/X airbox.

Hi there,

Pretty sure the RPMs as far as the CDI are concerned are determined by the pick-up/magneto.

So when you switch the ignition on and off, the powervalve does a cleaning cycle. Once this cycle is complete and the engine is running the valve should return into its closed state.

If it is not, then it's possible that the powervalve wires have been inverted and the powervalve hasn't been adjusted properly. I feintly recall this being a common problem back in the day.

Interesting, what inlet manifold are you running.

Presumably the cylinder you have is a 3BN model on there. I wasn't aware they ran a 24mm carb, I thought the earlier models ran a 26mm round slide.

If you keep having problems then it might be worth sending the barrel off to someone lile PJME to have the O-Ring conversion...

@Pilot_LC Ideal Gas Law - PV=nRT. Pressure of a system is directly proportional to the temperature of that system. So if the thermostat is stuck, then the temperature goes up and therefore the pressure. The radiator cap bleeds this pressure to the overflow tank. Ergo explains loss of coolant.

As I say, one issue is the radiator cap spring looses tension so try replacing that.

I just use a cheap Chinese one on my DTR with a temperature sensor in it and it's been sound.

Another problem could be the thermostat as given up, maybe it's locked closed so it's not regulating temperature correctly.

The DTX comes fitted with a 3MB.

It's only the very early 89/88 models that came with the 3BN cylinders.

Otherwise all years ran the same cylinder. Surprising there isn't more availability given how many of them were made etc

@Pilot_LC 600km, are you sure you used a genuine head gasket and not the cheap white ones.

And it was definitely fitted in the right orientation.

Oh wow, well you'll be pleased to know not much has changed in the last 20 years for two strokes. Port tuning is as it's always been and fuel injection came a few years ago on nothing but the most elite machines.

These bikes are a doddle to get running, so throw up any questions you may have and we'll point you in the right direction.