DT125R FORUM

@SpookDog
The center bolt on the puller used the exact same thread size and pitch as the crankshaft, so I could screw on a much too small puller (for that flywheel) that fits nicely on the shaft.

After further testing I could confirm it was M27 x P1.0 L so I'l order one such as that, but deeper than the one I already have... But with easter being a national holiday nothing will ship until earliest tuesday.

Also emailed a Swedish firm doing work on cylinders an they could bore it out an supply a new piston for a decent enuff price, I'm ready to pay a bit more just so I can actually ride the bike these few months of the year with good weather xD

Meanwhile I am also working on my 2 other bikes, the daily-driver scooter have a clogged mainjet so it's real slow on it's acceleration... Need to get it on the lift an clean the carb.
And the big heavy bike is being prepped for summer MC wacay, getting some sidebags for it, an swapping the bearings for the stearing, it keeps locking itself into a bad position an makes it hard to drive safely..

@SpookDog
This is an 1989 bike from Sweden, registered as a 3MB with 3MB in the chassi-number, but the engine says:

If I keep the cylinder I will get a 3MB piston yes.

@Calum Ya sure? The picture shows 2 of them, but the text says 18X1,5Mm, and it's def bigger than that. With the set I had either a 26mm or 27mm would fit, though they where not deep enuff to let me screw them into the flywheel without also screwing it onto the crankshaft.

I was gonna take the bottom end apart but instantly got stuck at the flywheel. I have a box of pullers but none of them deep enuff to catch the threading of the flywheel before engaging the crank. I tried looking in my Haynees manual, and googling "DTR 125 R flywheel puller" but I didn't find anything in the book, an got conflicting results online.
My best guess is that I need M27x1 Righthand thread, is that correct?

Also looking closer at my engine I saw that the case is a 3NB while the cylinder and head is 3MB, so a previous owner have already swapped the cylinder at least once.
After reading some threads here about the difference that seems like a good thing?

As @SpookDog said I also checked the head and gasket for any signs of blowby but couldn't see anything suspicious.

Checking for play on the conrod it seems to move a fair bit side-to-side, but nothing front-to-back, I think it's good enuff to use, though I will still need to remove the sides to check the gaskets.

@Calum Right, good, then I should be able to look for any company in the area doing engine restorations.

Instantly found a pair on google saying they do motorcycles, for boring out a MC cylinder they wanted 1100 SEK or ~110 Euro

Googling for pistons they seem to go for about 100 Euro, CMSNL seem to stock oversized ones as well which I suppose I would need for a bored out cylinder...

However it's just a step up to the Athena 125cc Cylinder kit (~450 euro) including a new top, pins an gaskets as well.
(Though if the bottom end needs rebuilding as well one might wanna go the longer route, and relocating some budget to the crank)

@SpookDog Do you know if the cylinder is nikasil coated on the 3MB engine or could anyone doing work on cylinders fix it? Cheapest alternative would be to get just a new piston, keep the cylinder, and maybe send the crank off to be rebuilt, smack new seals on everywhere an change the oil...

@SpookDog I poured a lot of coolingwater on the floor when dissasembling so that should'nt have been the problem...
But I had problems last summer with the water cooking off, so maybe that was just a precursor to this. I thought it had to do with me running tapwater for a while until I bought a bottle of premix an swapped it out, but maybe the engine was just always running too hot.
Right didn't think of the seals on the crank... I turned the engine over with a drill, without the cylinder an whatnot to listen for noices. It sounded allright to me but broken seals would not make any sound so I should def check that.

@Calum Lean eh... So should have used a bigger mainjet then...

@mhbikesnbits Barrel? Like cylinder? This should be the original cylinder and piston, I've never changed them and power feels like what I would expect from a stock engine. Original exhaust and carb as well.

Edit:
Off course when I removed the top one of the screws for the waterpipe broke off, so now I also goto deal with that. Another reason I was looking at cylinder-kits that includes a new top, I don't have the correct tools to do this correctly, any time I have tried drilling a broken off screw before the hole always end up off-center...

1.5 years later...
I did get the bike together an rode it quite a lot last summer.

We got some sunny weather a few weeks ago so I took it out for the first time this year for a day-trip, on the way back it all went down-hill though!
Was doing about 110kmh on the motorway when I suddenly felt like someone applied my brakes, the engine shot out a whole lotta oil through the breather tube so I thought some seal had broken. Immediately applied clutch an pulled over. Heat gauge showed max-temp, and before i turned the engine off it made a real racket.
Since I was kinda stuck where I was, I waited for the engine to cool down and it actually started, I drove to the next exit witch was only a few hundred meters ahead, at a very slow speed.
Actually drove it home but kept a bare minimum speed, all the while making a real bad grinding noice.

Back home in the garage I could take it apart and instantly found this removing the top:

Removing the cylinder the piston didn't look very nice...

Checking the cylinder it looked a whole lot better:

Looking at the crankshaft I could see a spot where it got real hot:

Bluing the metal.

Now I am not sure why this happened an where to go from here.
Have been looking at a buncha different options like aftermarket cylinderkits, local shops specialising in repairing cylinders an pistons, original pistons...
But not sure what to do, or even if there is more damage, have yet to split the case.
Any tips here would be apriciated, both how to fix this and if anyone has insight in why it happened in the first place. (Not enuff cooling? Not enuff 2stroke oil? Just bad luck?)

I am looking at a Athena front pipe exhaust, but wondering if it does anything for me with the rest of the engine stock? And would I need to combine it with a new muffler to get anything?

My org front pipe has some damage from being laid down by previous owners, so if there is no downside I could make it look nice at the same time with a new pipe.
If, however, it performs worse than stock if I don't also combine it with bigger carbs, porting or big bore then I need to think about it.

DTR 125 R -89

@SpookDog
I got a powder coating gun from a webstore selling tools, they also sold paints in a few colors, so I got red, black, silver and white so I would have what I would need for the bike.
Swedish store: https://verktygsboden.se/pulverlacksprutor/pulverlackeringsspruta
Costs about 160€, and the colors are between 14-35€ for a kilo each.
Then we got a old kitchen stove with a extra wide oven from someone who was renovating their kitchen, so we have a dedicated powder-coat oven in the garage.

I can't reuse the sand when I am blasting outside, it gets spread with the wind and mixed in with the soil.

I would have to make a somewhat sealed container both me and the frame could fit inside, where I can somwhat easy collect the sand from the floor.
Its not super expensive... I found 25kg bags later for about 100kr or 10€
But I estimated I would go through so much sand to get all the nooks and holes on the frame, it doesn't seem worth buying that, instead paying someone who have a blasting room to do it instead.

@Calum Thats very cheap. Yes, they told me they would outsource it as well, I just assume it gets more expensive when there is another party who needs to get their profits.

Last weekend I started preparations for the repaint, my thinking is, as soon as I get the frame back from the painters, I can start mounting pieces, get fewer stuff in boxes, and try mounting any new pieces I buy.
I found a company in town who does powder coating on big things like MC frames, but when I emailed them I wasn't sure exactly what parts I would need painted and thus they couldn't give me a price estimate.

Now that the whole bike is apart, I can see that the only things they will need to do is the frame, swing and tank.
Anything smaller I will be able to do myself.

Here you can see how the frame have been partially painted by a previous owner, very shoddy work, and the primary reason I want to get it repainted.

They only painted where it was easy, and they used a brush, not a spray. So its very uneven.
And, I want the frame to be original white and not black.

I started with a wirebrush to take off most of the stuff, and then the plan was to sandblast it outside. But that turned out to use a whole lot more sand than I was planning on, didn't get even 5% done and I had used up a 14kg sack.
The powder coaters I contacted previously asked if I would need to have them sandblast it for me, and I had hoped to do it myself to keep cost down. Looks like I will at least have them do the frame...

The swing and tank fits nicely inside the sandblasting cabinet, so those I can do myself no problem.

I had previously tried powder coating small things at home with great result, the foot pegs looks like new after sandblasting and a coat of black.

There is numerous small pieces on the bike I will have to either repaint the same color, or another color to better fit the look I am going for.
But right now I am focusing on the big things I need to outsource.

Have you powder coated a frame before? What did it cost you?
Previous googling in forum posts gave me 2000kr or about 200€, but I doubt that included any sand blasting.
I am hoping I can get these things done for 300€ or less, but quality will cost, I rather spend a bit more now for a job well done than having to do it again in a year or two.

Bought a DT125R -89 as my first motorcycle and have had a good time riding it, but a lot of things isn't to my liking so have been renovating it.

It was originally a white framed blue plastic one, but previous owner had painted plastics black, and painted the frame black, wherever it was easy to do so. It frankly looked like crap, so now I took the whole thing apart, gonna sand-blast it and get it powdercoated white again.

I am not gonna recreate the original look but instead I am aiming for the white/pink design that seemed to be a thing in the middle of the 90's.

For that to work out, I am gonna need some new fork-gaiters, and I feel like I have been looking all around the internet but I can barley find any gaiters that seems to fit the DT125R, even less pink ones... If anyone got links that would be appreciated.
If I can't find pink ones, at the very least I would like to get red ones, currently I have black ones.

Hazardgraphics, that I bought a reproduction decale-kit, have pics of what I am aiming for:
http://hazardgraphics.co.uk/projects/1991-yamaha-dt125r-pink-blue/

I found someone who sold reproduced pink seat-covers, with Yamaha text, so already got one of those.
Also found someone selling new production plastic pieces, so got all 4 side-covers. They where not as thick plastic as the original, but the originals I have have been repaired in many places already an doesn't look to good, so I am happy with what I can get.

Another thing I am looking for is good looking square mirrors, if anyone have tips on that I'd appreciate it.

This is how it's currently looking, or well, before I took it apart down to the frame last weekend!
Lot's of work left, hoping to get it looking real nice ready for spring in April.