DT125R FORUM

Hi there bud,

Sounds like a reed switch issue to me, or powervalve.

I've never done it myself before, but my understanding there seems to be two different ways of doing the reed switch, so double check that the reed switch has been applied correctly.

The other thing that causes this exact problem is where by the Powervalve closes in the higher RPMs limiting power. This is really easy to test to eliminate rather than figuring out the reed switch problem.

Allow the powervalve cleaning cycle to occur, and turn the ignition off when it's fully open, then disconnect the powervalve. This will leave it in the fully open position. You'll notice a large drop in performance at the lower RPMs, but the bike should come alive at 6K rpm and red line hard.

If this is not the case, then it's likely the reedswitch is a problem.

All of this assumes that the engine is in a healthy state. And that the ignition system is all up to scratch.

Obviously there are a multitude of factors that cause loss of performance, but assuming that the engine is good condition, that's where I'd start.

Frame has been repaired by my Dad all welded up and he's managed to paint it for me as well.

So this has been a big help and will at least allow me to throw the bike back together.

He has gone to extensive efforts on this well, as well as welding the frame, he has purged the frame of any remaining acid that was left in by the previous powdercoaters.

Followed by then filling the frame with Waxoyl to ensure that it doesn't happen again.

![][(https://i.imgur.com/lXe8Hcx.jpeg)

By no means a perfect job, the bike was never intended to be concourse (hell my DT is looking worse for wear now having been refurbished nearly 10 years ago).

But overall he's put a lot of work in for me and I'll be glad to have it back and rebuilt.

Hopefully get this back next month and then start reassembling it

Also took delivery of the Gianelli (Now Arrow) end can to compliment the expansion chamber.

Those links work fine for me. The '88-04 models are relatively the same so should be good. Otherwise the Haynes manual is very good,

@Alexwych Have you tried searching?
https://dt125r.co.uk/topic/3258/yamaha-dt125r-200r-workshop-manual

Well something doesn't sound right, are you just the pull start is operating efficiently? Might not be noticeable with the spark plug out but exacerbated with it in.

Can you turn the flywheel by hand with the spark plug in? Use a drill and some lube to make sure it's moving freely. I mean the fact it rotates by hand with the spark plug out is odd, two strokes don't typically make so much compression that its hard to turn over.

Hhmm, yeah that's not ideal that.

I've not seen this before and if it's never done it before you touched the brakes.....

Hello there and welcome.

Oh awesome congratulations!

Is it a UK model? How many miles has it done?

Is it ready to ride or do you need some work to get it there?

Throw up any questions and I'm sure we will get some answers for you.

My graphics on my RE are TMX. Fitted them about 8+ years ago and they're still holding up really well.

@BalnAndCantGetUp Yeah, the problem is, is the way they are and what are you have are two different things.

The way Yamaha intended the machine, and the way it ended up varied from its release in 88 to its discontinuation in 2007. I am merely recommending putting it back to how Yamaha originally envisaged the machine makes a lovely bump in performance with minimal degredation in reliability.

So in the DTRE/X they put a huge honeycombe restriction in the exhaust expansion chamber. They gimped the YPVS to retard post 10K RPM, and the reeds are just a nice to have as they're cheap and easy to fit.

That's all I was getting at. I had/loved mine in stock trim for a good while before I started fettling with it.

IMO, leaving your DTRE bone stock is the way to go. I don't think mine was ever better.

There are several really nice upgrades that I'd recommend doing and leaving it at that.

• Zeeltronic Ignition System
• Improvement in the midrange and over rev
• DEP Exhaust System
• Improvement in mid range and over rev
• Carbon Reeds
• No noticeable improvement, but cheap

Leave everything else bone stock, no carb adjustments needed for any of the above and you'll be left with a full power 125 as Yamaha intended with Yamaha reliability.

But that's something to consider in the fullness of time

Hi George!

Awesome, DT125X 2005 is an awesome bike! The Honda MTX is also a cool bike.

If you want to share photos you'll need to upload to another site and cross link it.

Have you got any plans with the bike? Or are you just using it as a vehicle?

That's the conversion problem isn't it!

The other thing I've seen people do is to press out the steering stem from the DTR triple clamps and into the conversion triple clamps of your choice. However if the stem diameter is different then you'll need a shim/cut to fit it into the conversion triple clamp.

This is quite a destructive process if you're cutting and you won't benefit from taper roller bearings up top. But it's an alternative approach.

The bearing cup method is the simplest approach and is easily reversible.

https://dt125r.co.uk/topic/17/usd-conversion-bearing-cup-method

My Dad did this on his VW Split Screen van so that all the doors used the same keys.

He just spent the time and recoded the barrels on the lock that matched the genuine key.

You'd need to be familiar with how locks work etc, but if the the barrel is dismantleable, or you can find a barrel which fits, then it should be possible.

Hi Andy!

Fab!

My Dad has a DT400B that he's been in the midst of restoring for about 8 years now.

I think he has all the parts, but he's since moved on to a Vespa and Lambretta obsession!

But I'm hoping he'll throw the DT400B back together and talks of passing it on to me

This is predominantly a DT125R website, so knowledge about early models is very limited.

But of course we're all motorcyclist enthusiasts so we welcome any bike really.

Although, admitably, traffic has plummet in the last 12 months.

Yeah looks like it's in need of some TLC.

When the bikes in neutral all the lights should be on.

As I say, that bike looks like it's got a lot of issues and working through those by restoring it to factory is what I'd do.

If the original ignition coil was faulty, replace it with a 3RM genuine one. I fought this battle when I rebuilt my DTRE and then put it into storage. Years later when I got it out of storage, and everything was new on it, it took me ages to realise it was the non-genuine coil.

I was having neighon similar symptoms. It would run from cold then, after a short ride, wouldn't rev.

I only realised it was the ignition coil when my brother's RD350 was fitted with the same type and the mechanic scoughed at it saying how they basically get saturated with voltage and can never recover. So once they're depleted they provide a weak spark.

So as I say, that would be my first port of call.

Anyone have any idea what’s going on and what I could t try to get the bike going?

I think this is probably your problem. Instead of addressing the issue which caused your bike to fail the first time around, it sounds (going from your description) that all you're interested in is getting it going again, which unfortunately, on a 19 year old bike, probably isn't enough.

Why did it fail the first time round? Once you understand that, you'll be in a better position to address the follow on issues.

What made you think it was a coil? Did you measure the impedance between the primary and secondary coil and it was out of tolerance? What were those measurements? Did you replace with a genuine 3RM coil? Those Chinese aftermarket ones are only worth throwing in the bin, they do not work!

It sounds like there are two issues here, one is sounding ominously electrical, the other clearly mechanical and until you strip the bike down to investigate and eliminate you'll continue to have problems.

The DTRE in stock trim is an incredibly reliable machine, but that said 20k and you'll going to want to do some TLC overhauls.

The engine failed last year and damaged the barrel, well there is no real reason it would do that unless the maintenance schedule wasn't adhered to. Or the oil pump failed. The problem with the latter is throwing a new piston/barrel at the problem doesn't fix anything and is money wasted. If it was just worn rings and you were hammering it then that's just lack of maintenance.

I could throw you a whole raft of potential solutions but sounds like your bike is a bit of a basket case.

Because of this there is likely a whole host of things that your bike could be missing and botched so diagnosing is a bit of a rabbit hole. My advice put the bike back to factory OEM spec and go from there.

Why do the plugs keep failing? Are they black sooty? Has the oil pump failed and just throwing copious amounts of oil at the engine fouling plugs, is it because there is no YPVS and it's thrown the settings off.

But throwing in some simple checks, probably:

• Neutral Switch/Clutch Switch/Side Stand Switch
  • A combination of this will cause the bike to start in neutral, but kill the engine if in gear is detected.
• Ignition Barrel
  • Aftermarket ignition barrels corrode and break down and result in erratic behaviour
• Ignition Coild Fly Lead
  • As above
• Faulty CDI
  • As above
• Lazy battery/Faulty Stator
  • The engine requires power to run, if the stator is failing or not being rectified correctly then you'll find problems running

I can go on, but really you want to tear the bike down, do a compression check, make sure the engine is healthy, that the airways are clear, exhaust, intake, airbox etc. Carb isn't blocked.