DT125R FORUM

Yeah, I hear that the bargains at Lidl get great reviews.

@HOTSHOT-III Would definitely like to see that. Would make for an interesting build for sure.

I was surprised to see cast pistons in this kit, but apparently I have to junk them anyway to go with the stroker kit I bought as the wrist pin offset is different.

So I've got a few more things to buy before this is called done.

Been saving for months to purchase this!

With Christmas and what not it was a difficult item to purchase.

Athena 392cc big bore, with the hot rods kit this will take this up to 421ccs.

Brand new gearbox layshaft and a 1st gear tall conversion to duot.

Snooping around the house I found these items

I shudder think what I spend on these things and I don't even remember half the time!

This is a sort of budget build though.

I ummed and arred but I was just going to reuse the handlebars that came with this bike. They're in pretty bad shape, but easy enough to replace should I want to put some prettier ones on.

Front wheel fitted, front brake disassembled, need pads and it'll be good to go.

Front tyre looks good, so happy to reuse this for the moment. Just needs pads.

I would have got the rear wheel fitted, but ran out of steam.

Save that for next weekend.

Frames back and painted and no signs of rust, so it's reassembly time...again.

Engine is in no dramas there.

Triple clamps bolted together with nice grade 5 titanium bolts.

I haven't reconditioned the forks, the stanchions are rough but the rebound is solid.

New headstock bearings, for anyone who is looking...(Future me)

Aprilia ETX Head Stock Bearings:
NTN 4T-30205 Tapered Roller Bearing Cup and Cone Set 25x52x16.25mm

Aprilia MX125 rear swinging arm fitted, it measured almost half the weight of the one that was on originally.

Need to give the fork bottoms a good clean and the wheels then I should be able to roll the chassis.

Forum patch and updated, if you're having issues try clearing out your browsers cache.

I had the same battery that came with my bike up until 2019 until I misdiagnosed a problem to the battery. So that was 9 years of service and I don't know how long it was on the bike before then...

I'd definitely be looking at getting a genuine regulator, I had a lithium battery go up in smoke when I accidently fitted a Chinese regulator to my RS

Never heard of it. Have you got a link?

Well are you sure it's beyond repair? I mean it has to be pretty bad for that to be the case?

Wow really? That's savage. It's aluminium, how corroded could it be!

Well I wouldn't be paying £200 for what is effectively a shit caliper.

I'd be finding something similar or off another bike.

But I'd probably just rebuild the one you have, looks like lots of listings on eBay for rebuild kits available.

I certainly wouldn't be paying the prices they're asking for on Fleabay.

Yamaha don't make calipers, Nissin are usually their preferred supplier. So I'd be looking at other Yamaha's of a similar era that used the same brake setup and grabbing a caliper off of one of those.

Possibly a YBR or something. Check the part numbers for compatibility:

Yamaha, DT50R (3MN1, 1989) 999 A, 1989, DT50R (3MN1, 1989) 999 A, Europe, Yamaha black FRONT BRAKE
Yamaha, DT50R (3MN1, 1989) 999 B, 1989, DT50R (3MN1, 1989) 999 B, Europe, White FRONT BRAKE
Yamaha, DT50R (3MN1, 1989) 999 C, 1989, DT50R (3MN1, 1989) 999 C, Europe, Solid endurance blue FRONT BRAKE
Yamaha, DT50R (3MN2, 1991) 999 A, 1991, DT50R (3MN2, 1991) 999 A, Europe, Yamaha black FRONT BRAKE
Yamaha, DT50R (3MN2, 1991) 999 B, 1991, DT50R (3MN2, 1991) 999 B, Europe, Deep violet FRONT BRAKE
Yamaha, DT50R (3MN2, 1991) 999 C, 1991, DT50R (3MN2, 1991) 999 C, Europe, Deep violet solid 1 FRONT BRAKE
Yamaha, DT50R (3MN2, 1991) 999 D, 1991, DT50R (3MN2, 1991) 999 D, Europe, Purplish white solid 1 FRONT BRAKE
Yamaha, DT50R (3MN2, 1991) 999 E, 1991, DT50R (3MN2, 1991) 999 E, Europe, Spanish white 2 FRONT BRAKE
Yamaha, DT50R (3MN3, 1995) 999 A, 1995, DT50R (3MN3, 1995) 999 A, Europe, Yamaha black FRONT BRAKE
Yamaha, DT50R (3MN3, 1995) 999 B, 1995, DT50R (3MN3, 1995) 999 B, Europe, Purplish white solid 1 FRONT BRAKE

A quick look on Fowlers suggest the DT50R ran the same brake.

New Part Number: 34X-2580T-00
Old Part Number: 3BN-2580T-01
https://www.fowlersparts.co.uk/parts/4159462/dt125r-3rme-1999-060-a/front-brake-caliper

What's the matter with the one that's on there? Can't you just rebuild it?

I'd leave the jetting alone, Yamaha spent a lot of R&D in the jetting.

You should be running the bike with the snorkel in as it's adverse to performance to remove it.

Make sure that the carb boot is clear of any debris.

Do you have the Snorkel fitted? Is there anything obstructing the top of the airbox?

I think this based off what you've told me. Sounds like giving it more air has resulted in night and day performance. Ergo, it's intake related.

@facundo-duarte Yes that's correct.

On later models Yamaha fitted two YEIS bottles.

One to the inlet manifold, and then one to the carburetor boot. You've removed the one fitted to the carburetor boot.

It sounds like not enough air flow to me.

If you remove the air filter/carburetor boot altogether you can see if your problem goes away and that tells you it's the airbox.

Sad times You still doing this on your sisters drive?

Go with what @SpookDog said. If you removed the YEIS from the Carb Boot...your carb settings should be okay (perhaps a little lean), since you're not altering the air after the carburettor, merely increasing flow over the carb. If you remove the one on the inlet manifold then yes it'll be a huge air leak, but you didn't....

So that to me sounds like poor flow through the airbox system. So remove the airbox lid and give it a good clean. Make sure the snorkel isn't obstructed etc.

There is no memory in the CDI to my knowledge.

A weak battery will cause issues with the powervalve, so will things like fault rectifier and bad stator etc.

But just wanted to start simple.

Have a look at @scrimsmustang guide on derestricting your model.

https://www.slideshare.net/slideshow/derestricting-the-yamaha-dt125-r-1988-through-to-2007-scrimsmustangs-classic-yamaha-restorations/32127545