DT125R FORUM

I mean....

As I say, I can't see how this doesn't affect performance!

Only use genuine coils. The cheap orange ones simply don't work so make sure it's a genuine one.

@Yaya97422 Vert/noir

From my experience, the catalytic converter was so restrictive that I cannot fathom how it possible could not have an adverse effect.

I do think, leaving your pipe standard is really ideal, especially as these bikes are appreciating classics. Instead, just grab yourself a DEP pipe and be done with it, the weight saving alone is worth it!

Do you have a powervalve fitted or is it fixed?

It's in my experience that my DTR never started without choke, so that's normal. It needs to get to temperature and then you can remove the choke.

Sounds like you need to strip and clean your carburetor, based off what you've just said.

It could be float level height if it's just shutting the fuel off before it's even getting a chance to get into the bowl.

Strip the carb, removing the atomiser and properly clean the carburetor in and out, being careful not to damage it as the components are brass and delicate.

The engines are very basic and provided you've got compression, spark and fuel ,it'll run.

If you can confirm that it's got spark and fuel, then check the compression for the engine, should get around 140PSI. Anything below 90 PSI and your engine is going to need an overhaul.

What year and which bottle?

Early models only had the YEIS that goes into the inlet manifold.

Later models had that ones that go into the carb boot.

I don't recall them mounting to the frame however, it's merely attached via the carb inlet and the carb boot.

Lot's of information on this site already.

I find going to Google and use site:dt125r.co.uk 4bl derestriction better than the internal search.

https://dt125r.co.uk/topic/3102/derestrict-yamaha-dt-125-r-1997/66?page=4

It does depend on what region you live in, but the easiest way to get full power is

• Zeeltronic Ignition
• DEP Pipe

Make sure you've got 3MB cylinder head (3BN denotes you've got a combustion ring head that benefits from machining out). But otherwise you'll be laughing!

There are wiring diagrams and manuals around on this site.

Try searching using the built in search.

Another great tip is using Google

In Google search engine do site:dt125r.co.uk wiring diagram 6 wire and let Google indexing do the heavy lifting.

Float valve height sounds like it needs adjusting.

I can't say I am very familiar with thise pipes sadly.

I have been away from the tuning scene for these bikes for many years now. It's been years since I've even ridden my DT to be fair.

The DEP pipe is tried and tested and I was really impressed with it.

Here in the UK, they typically rust before too long. I always cleaned mine when putting it away and it held up well.

The one in the photo looks similar that it's mild-steel, so you'll want to get that painted before you fit it.

I run a Romeu Henriques pipe on my DTRE. I've had it since 2011 and there isn't a blemish on it as he made mine out of Stainless. It's also not cracked in that time either.

I went for underslung due to my setup, but he does wrap arounds also.

So the mounting points on the frame differ from the DTRE/DTR.

Whilst the engine is basically identical, so the actually performance/shape of the pipe won't be affected by the later design, the frame mounting points are different.

It's worth noting, the very early DTR's ran a 3BN cylinder, so there are subtle differences in actual engine specifications. Can you confirm that you're running a 3BN cylinder? Or the revised 3MB cylinder?

I can't remember whether or not the fact the mounting points differ was a deal breaker or not, or in other words, did it cause it to foul the frame.

My gut instinct is no and you should be okay, if you can make a couple of brackets.

I've done something similar with my Aprilia ETX, where I have put a full arrow system off of the SX models. The engine is the same, but I've had to fabricate up some brackets to get it to fit.

The most easiest carb to get ahold of is probably a Dellorto PHBH 28mm. Found on restricted RS's, they're widely used and reknowned for being easy to jet.

I run a Dellorto VHSA 32mm carb on my DTR.

The reason I've gone with this carb, although rarer and harder to find, is that they were factory fitted to the TZR 125 RR Belgarda which effectively ran a DT125RE engine. Which just gave me nice confidence that it was a solid choice to make.

One for sale here: https://www.ebay.co.uk/itm/178501570394?_skw=Dellorto+VHSA+32&itmmeta=01M4B4V0QQEPEYJMTHPDP73MJH&hash=item298f85cf5a:g:QzEAAeSwwDVqqknx&itmprp=enc%3AAQALAAAA8GfYFPkwiKCW4ZNSs2u11xCsZ9R43qCdhmBbcO8vd2J2b6UmsaleZzaYCXtHKDFciw7JJKWAv%2BVU1RMnsTcB6BR1oQISPasgAcqE0jvZsRV6c%2FlVyBaJXcN8rrE44oBe2oSQMMj8qAaObD%2Fbe28WiBSFTDYhptWeveTmzxQZ09RFGD7JnvJgWfjWhS4BRVr1FAcIy%2FVPcCRof3cnpiW1FFNAA8NGpOV3g7ZB2Ofvh56ymFldlS74mqGTajYR3fy53FzAnXiqxtqLCFu%2F4or12IxEXL%2B%2BYXIOMAsOoLkx2wRBM6v%2BZd63q%2FuxmzX2SAEqnw%3D%3D|tkp%3ABk9SR4iN7OSiaA

Another great carb, albeit harder to tune, is the VHST 28mm.

So keeping the size the same as the Mikuni, but this time Flat Slide instead of Round Slide like the PHBH.

Remember, bigger is not always better. Going from 28->32 doesn't necessarily mean more performance. Fair enough if you're giving the engine a tune up, but if your plan is to keep it relatively stock, then sticking to 28mm isn't a bad idea.

Hi there,

I would leave the carb settings alone. DEP themselves don't even recommend changing the settings for their setup.

There can be several factors for poor running, a lot of this is well documented on this forum.

Probably the key one here that I am sure @hotshot-iii would say is the emulsion tube in the carb. Often gets overlooked and clogged.

Cleaning it verbatim won't help, it'll need pressing out and properly cleaning, before reassembly.

Zeeltronic easily the single best upgrade for my DT

Disc guard looks great.

Yeah sadly these bikes aren't going to pull your arms off or anything. They're pretty decent at what they are though however.

Lovely colour scheme on yours for sure!

Well the best thing to do is to check to ensure that the thermostat is working correctly. You can remove it and place it into a sauce pan and check to see if it correctly opens at the right temperature when left to boil.

If your daily commuting the bike, then leaving the thermostat in is advisable. Yamaha know what they're doing.

If you start tuning the bike and pushing it beyond its original specifications, then you may want to consider removing it.

The thermostat isn't just there to aid heating up of the engine, it also has a role in providing pressure in the cylinder head to avoid pocket stagnation of gases. So it's actually important it's fitted.

I just noted that these engines do run warm and removing the thermostat allowed my bike to run at a more consistent temperature when under load.

DTRs do seem to run very hot in my experience. Always have, wouldn't worry about it.

My Aprilia RS usually sits around the 60 degree mark, I run a Vapor Trail Tech unit on my DTRE and it's ready 110 before!

To combat this, I removed the thermostat and now it sits around the 60-70 mark, just note you do really need to be careful when warming them up to ensure you don't cold-seize the engine.

Yeah okay, well that sounds like you've ruled out all most of the basic things.

I've had this before with a faulty ignition coil. These can still be bought brand new from Yamaha and I highly recommend going for genuine coil over an aftermarket one. The aftermarket one I had led me on a wild goose chase trying to figure out the intermittent fault.

You can measure the coil to see if it's within tolerance, what I was finding was that from cold it would work a treat, but once under load and warmed up, it would fail to fire above 4k RPM.

So it could be a worn out ignition coil, however unlikely that may seem.

Other than the stator/pickup, there really isn't a lot more to these engines to get them running.

The side stand sw and the whole interlock chain should be good. I even bypassed all of that by grounding the blue yellow wire to the CDI directly

If I had to guess, that's probably your issue.

I see this time and time again with the side stand switch. My brother had a similar problem on his 2001 DTR many years ago now. My advice would be, if you're struggling to figure out a problem, get it as close to factory as possible, otherwise you're going to be chasing ghosts.

No a mechanically unhealthy engine wouldn't necessarily affect spark, but given how you described riding the bike and it cutting out, indicates that you had spark.

Okay, well it's good to know it's unlike to be water corrosion But still check those connections anyway to make sure they haven't vibrated themselves to pieces.

Ensuring good connection between that block is essential.

As I said previously, triple check the neutral switch, clutch switch as well. If they are vibrating loose they will cause intermittent problems.