DT125R FORUM

How much of a diffrence did the 5mm widening of the port make?
I've just completely rebuild my engine. (Gearbox, bearing, new piston) Already have 320km's on it and it's pretty solid. The 170 kit is a huge improvement over the 125. Is it worth messing with the ports?

Anyone ever thought about using ceramic bearings? I found them for the wheel bearings. But out of curiousity why not use it on the inside of the engine? As i seem to understand they are in every way superior over the normal steel bearings? (Except for the cost )

@calum Any recommendations on a crankshaft? While everything is open I want to replace it anyway (Has some small grooves where the bearing is). Best with original or aftermarket?

@theportingmaster The jetting was extremely rich. Apparently there are 2 sorts of mikuni jet 'sizes'. In my carb there was a 250 mikuni jet. So i ordered aftermarket 250-300 for the Athena kit to test with. But the aftermarket 180 size is the same as original 250.

It was overlay rich while tuning the carb until i figured this out.

If you got a excellent low milage gearbox for me send me a message with some details. Really appreciate it
I looked at new original parts but it's a little expensive for my student wallet

Hey guys thanks for the replies. It's probably the harder break in tha caused the damage. I only had 300km's on it and probably forced it with the top speed run.

I also opened the gearbox and seem to have stripped a gear. Lots of heat was Involved.
I included some pictures below. I've never seen damage like this before. Is this normal?

https://imgur.com/a/BH66681

@Calum
This looks like an overheating issue? But shouldn't the damaged be at the exhaust side

So i started opening her up. Everything looks fine gearbox wise this far. I'll split the case asap but I have to wait for a flywheel puller or ask my local Yamaha dealer to pull it for me.

Pulled the Athena 170 cilinder and head, both are already damaged. No clue why. Bottom ring is completly stuck, also explains why it had very good compression (full weight to kick it over) after the first testrun +- 10min it was 10 times easier to kick over.

https://imgur.com/a/tfHwLKW

@calum
Thanks, i'll keep that in mind. Gonna try and get a first look today.

So I installed the Athena 170 kit. And after tuning the carburator, i took it out for a top speed run (148kmh in gps). The front sprocket 17 made the bike much more enjoyable, power wheelie in 1 & 2 after shifting. Overall great fun. So i decide to go on a late night drive for fun .

On the highway at +- 120km/h I lost 6th gear . So i put it in 5th gear, i was just at the exit i needed so i slow down, try to give it some gas to get of the highway but after 50m the gears dissapeared. Still 1 of 2 gears somewhere when standing still, but didn't drive it home.
6th gear always sounded different than the other gears ever since i bought the bike 22.000 km ago, the added torque probably pushed it over the Edge.

So I was wondering if anybody has an idea on what to look for when in open her up .
Or if possible, some tips on where I can get reliable original parts or if there are reinforced kits I can order?

@yammieguy I don't have experience with arrow exhaust systems. But I do have a Gianelli which was great for peak power. And a Athena which has more low rpm power, less peak power
Now I have a custom one and sounds perfect. And great power all the way

@markus-w
That sounds real nice. Please keep me up to date

@Calum
I got very lucky. I bought it 6 years ago and looking back it was the deal of a lifetime. By far the best 125 I could've bought. And I got it very cheap

@markus-w
I'll look into this. Now that i think about it the spacer is not that difficult we have a CNC machine at work to build electrical panels that van do this no problem.
Just have to find a mill now.

1mm enough? Or better with 1.5mm, 2mm? I only found 1mm on eBay .
Honestly I have no idea

@Calum
Stock dt125r with gianelli pipe and silencer.
And the destriction with the wire behind the Dash.

She pulls really well. But had a leaky connection between the silencer and pipe which lost a lot of power.
Also had a small oil leak at the shift lever. So decided to rebuild the while bike while waiting on my custom one I ordered from Henriques

@Calum
I got a custom build pipe ready.
Zeeltronic also ready
All the jets for rejetting

I am planning to put the bike back together with the new pipe. Go to the dyno.
Change to the zeeltronic, prepare some maps. Go to the dyno
Change to the 170cc and after a solid break in back to the dyno.

To get a good idea of what gives the most difference

This is a dyno from my current setup
(Can't get the picture to work though)

@Calum
I'll check it out, don't really have a Mill available. So i'll have to look for someone to do it for me. Spacers are custom build? Or you happen to know if anyone is selling them?

@Calum
Yes i saw this one. The best solution would probably be a spacer but I would prefer a 'simple' porting job.