DT125R FORUM

Yeah, I certainly think it's worth a shot. I can't see it making too much difference one way or another

Hi @kristóf,

Mmm, problem indeed. This is worsened by the fact that this carb was only fitted to your year of DT. I don't know what the LC's ran and later models used a 28mm flat slide.

I can't imagine the thickness needs to be spot on, should match what other carbs use for thickness, possibly 0.1mm I'd have thought. See what others recommend though as I've just pulled that figure out of thin air and don't have my verniers handy.

Oh that's really cool!

Well it looks well loved for, it's an appreciating classic that's for sure.

I don't know of anyone who's done that conversion. The common one from back in the day were the Polysport conversions, but they're more enduro so not designed for peak brightness

Oh okay...wow, errmm the KTM one is quite ugly to be fair.

I was thinking you were showing a picture of your bike with it already fitted and was thinking! Yeah that looks sweet.

Your bike looks really tidy to be fair. The DTX/RE headlight is a lot better than the DTR headlight, is there something you're not getting out of the current headlight. Not only does your bike look sweet, but the light should be decent out of it.

I'm sure the KTM LED headlight will be even better though.

Yes, the air leak will definitely not be helped by not plugging up the oil inlet on the manfild, albeit a tiny leak.

Yes the '88 DTR ran the TMS26 carb not the TM28 carb found on all other years.

That said, I am not aware of any other changes. So finding a suitable inlet manifold (probably can still be had new) and the airboot shouldn't be hard. But finding a genuine Mikuni 28mm is trickier.

A split in the carb boot is not ideal, but it won't be the source of your problem. I'd just smear some silicone onto it and allow that to harden.

Crank seals are common causes for air leaks, as well as the gasket on the inlet manifolds (once you sort the oil connector out).

Spray some WD40 around the general vicinity and if the revs drop back to normal then you've found your culprit .

A crack in the airbox won't manifest itself as an 'air leak' as it's before the carb. Obviously you are bypassing the air filter and that's not ideal, but the engine will behave normally as you're not running the engine lean since air will still rush over the carb and pick up fuel.

You can run without the airbox just fine.

But yeah, sourcing a new carb boot would be ideal

3MB-14453-00

That's the part number

Or fit a later dtx/re one and bung the YEIS or source the YEIS.
3RM-14453-00

With the choke on and it being cold, I'd be reluctant to rev it past 6500.

The 2000 models were heavily restrictive, so going over it all and ensuring it's full power and healthy would be where I'd start.

See @scrimsmustang's guide for derstricting.
https://dt125r.co.uk/topic/3492/yamaha-dt-125-r-derestriction

Do a compression test, make sure the engine's healthy. Check all the air ways, that the exhaust is free of water/oil. That the airbox is clear and the filter has been changed. Check the carb and jets make sure that they're all clear and not blocked.

I'd pin the powervalve open for the moment, just to eliminate it from being a problem source. This will drastically reduce power low down, but should rip roar to the red line.

Jetting needs to be done to suit. With the upgrades you're proposing, I doubt it'll be enough for just a main jet. You'll be looking at a needle and idle jets as well.

It is always my recommendation to jet to suit, I can't help here as I've never ran Athena on the stock carb.

You will get benefits from a bigger carb, but the TM28 is a decent carb so you can always look to upgrade it later if you feel it's not quite working for you. For context, people tune RD350's with 28mm carbs, so I wouldn't be rushing out to replace yours on a whim.

I use the TZR 4DL carb (Dellorto VHSA 32mm) on my ported Athena set.

I run the Romeu Enriques pipe on my DT. It's been absolutely solid, not a spec of rust and I've had it 10+ years.

The DEP one will rust no matter how hard you clean it. I had great success with both pipes, but I've stuck with the Romeu pipe.

Well the extra CC's definitely helps with wheelie power. The CDI gives it a much need whack up the bum. The DEP not only massively reduces the weight (especially over the front end) but increases midrange.

The porting work is something else. Porting is almost always a compromise, you don't get something for nothing as they say.

The 170 does benefit from a port, and I mentioned in another thread, port matching will be required anyway, and the cylinder benefits from have the spigot machine to remove the obstruction into the DTs inlet air waves.

You do those mods, and you'll have a lovely packing machine, that's for sure!

CDi is an absolute must if you're going modified.

Having done most things on my DTR, I'd go ported Athena all day long. Stage 2 sounds good to me.

The extra displacement just gives it a good punch, at the cost of overrev.

If you're after a fast 125, ditch the DT platform and get yourself an Aprilia RX/MX/SX/RS Rotax bike.

But if you want a faster DT, then the above is a good option.

Get the Athena 170, Zeeltronic Ignition and a DEP pipe and you won't be disappointed.

Bang for buck, a Rotax engine is going to be cheaper, but as I say, if you want to keep the DT, then that's a good option.

That is really lovely!

I like the colour scheme and graphics kit on that as well.

Welcome to the forum

@hotshot-iii @aragian Gawd! I made the mistake of buying a chinese "racing" coil and that caused me so much grief. A fresh DTR rebuild and I was plagued with running issues which I couldn't get my head around.

Wasn't until my brother bought his RD 350 and he took it in for a Dyno where the chap refused to run the bike due to the coil and suddenly it hit me!

I exclusively run Zeeltronics on all of my bikes, but getting genuine CDIs is getting harder to come by.

I'm amazed you've managed to break so many though, that's almost unheard of.

Swapping the CDIs is pretty common, the main thing is making sure you get a CDI which supports your powervalve system (either 3 wire or 5 wire units).

Not all CDIs are equivalent, the 3RM CDIs were decidedly the less restrictive of the pack, but good luck finding one of those these days.

Yeah decent, 450 is a good step up too!

I must admit, I've had my DT for 15 odd years, so the thought of selling up is unthinkable.

Such a dependable little machine.

Hi @aragian,

Oh cool, that looks pretty tidy to be fair? That could fetch a nice price, shame you need to sell it for uni and you can't sit on it, as these things are appreciating classics!

Yes your DT will be autolube. If it wasn't... you'd have known by now.

You'll need to keep an on eye on the two stroke level and refill it as it gets depleted.

Hi Mohamed,

That is a cool looking bike you have there.

I am not too familiar with the newer models as it's not something we get over here and I don't know what performance upgrades are available in your region.

Definitely like to see more of what you do to the bike though!

Welcome to the forum.

Hello there,

As far as I was aware the Yamaha DT was discontinued in 2007 instead Yamaha makes rhe WR series.

That looks like a cool looking bike though, would love to know more about it.

I take it you're in the Asian market, hence why this is still available. I didn't know that the bike was still being produced there.

I'd almost argue the bike's styling is closer to the 80's LC model vs the earlier 70's model, with the bike using an aircooled design over the liquid cooled variant.

Sorry I can't be much more help than that, still cool bike though!

@hotshot-iii That's a very cool video and local to me too!

A crated Banshee, wow what a museum piece.

I had no affiliation with the Banshee prior to this build, but what a machine and what an era for motorcycling. All lost to time now and kids these days won't know the joys of machines like that.

@HOTSHOT-III Yeah and the tuning possibilities for the RD is all thanks to the Americans and the love for the Banshee.

I just think it's amazing that an engine basically designed in the 60s was used competitively all the way up till today.

Wow a Banshee new in crate, that's silly! They command good money now for a Banshee.