DT125R FORUM

@SpookDog

Sorry late reply, only got round to putting new plug on the other day but yeah no worries man

Replacement plug worked nicely. I replaced the regulator/rec and starter solenoid with oem parts as well and started lovely off the button. No more clicking from the starter solenoid or dodgy aftermarket rectifier going up in smoke

Cheers

I have the Dellorto VHSA 32mm Carburettor as found on the Rotax series of engines. I originally source a 4DL carburettor and saw another VHSA on eBay. I made a very good one from both of them, thinking at the time they were the same. They were not and therefore jetting on my DTR is WAAAAYYY different to that of the 4DL VHSA.

All I will say is, jet to suit, what works for my setup (bearing in mind how unique my setup is) may not be good for you.

But in essence, it's like a 140 main jet with a U13 needle (IIRC) But I bought the whole range. I don't run oil pump and have advanced the ignition + ported barrel with VForce4 Reeds and airbox delete with an underslung pipe. All of those will have factors on jetting so kinda take my setup with a pinch of salt.

I've had a few barrels done my Mick on my bikes. Both the 3MB000P and a 170 barrel and the difference in porting has always been night and day. The difference in performance is something else. I have never been great at actually "feeling" the difference.

Bikes with the dyno at the moment so I can post up how it gets on.

The base performance of the DTR is weak IMO. Compared to Aprilia/Cagiva barrels it is a very slow/detuned motor. Porting it may help, but you're very limited in what you can achieve with the standard setup.

In my experience, the DTR never favoured aggressive porting as it's best ridden in the mid range, due to its setup of being a trail bike. My fondest memories of the bike was probably when it was mildly tuned before I had it ported.

I was, at the time, 70kgs wet and that obviously accounted for most of the performance.

Now, coming in at more around the 90kgs, having the 170 kit makes the world of difference, but the bike has lost a lot of overrev. Now I pootle around at 4k and probably maxes it out at 10k.

It's setup lovely how it is at the moment and I cannot wait to get it back from the dyno.

Well I run RS 125 rear calipers on my stock DTRE master cylinder and the brakes are ace.

On the front I swapped out the mastercylinder with something more appropriate, for said reasons....

I would have a guess and say, we aren't sure. This isn't an LC Forum it's the R and therefore there isn't a wealth of information on the LCs unfortunately.

@SpookDog

Yes thank you, I thought the colours should match just when I got it they didn’t but still ran just making sure it’s all right

@R3L3_89 I wouldn't want to say. Take a look at Yamaha France parts lookup, key in your VIN(s) and check the numbers, they have a lot of details even for Yamaha products not initially sold in France:

https://www.yamaha-motor.eu/fr/fr/service-maintenance/parts-catalogue/

I think the gauge is pretty useless. My barrel heat seized before it ever reached the red! If it’s not giving usable information it’s no good.
I can’t remember exactly but I think the thermostat opens about 65* so that should be the ‘normal’ point on the gauge (dead centre) 85* should be ‘high green’ and 100* should be entering red…

It’d be easy enough to change the needle position using a potentiometer (variable resistor) Once it’s in the proper place read it with a multimeter and solder in the relevant resistor to adjust…

You’d have to do it ‘out of the bike’ though.
Put the temp sensor into a bowl of water heated to the relevant temp (use a thermometer) of 65, 85 & 100 and adjust the needle till you’re happy.
You’d have to remove the rev counter gauge and make a curcuit with a 12v battery…

@Rallyfinnen I think you might be right about the timing angle, one of my repeated measurements came out as cca 185°. I could have used the wrong technique when measuring; Shined a flashlight through spark plug hole and basically measured between the times I can see any light coming through, used the magnet rotor to set marks. A solid, definite number would be useful; my machine has a 3MB00 cylinder and a standard thin gasket, it is not marked with "P" and has never been bored or ported.

As for the temperature, I didn't get reliable numbers with a multimeter probe at the flange with the exhaust off, so I opted for calculating it via BMEP which turned out right around 7.10
The temperature would be lower at the middle of the pipe and even lower at the convergent cone, the highest temp is supposed to be right at the exit of the cylinder and if I'm not wrong, that's the part that creates the pressure wave.

Hi guys had mot today
Put a brand new plug in and ripped it to mot and back got 72.1mph on gps so pretty good! But wasn’t fully pinned, got home and thought I’d Chuck the plug after a 4 mile ride
What you think?
alt text

@R3L3_89

OK not what I was thinking, but very interesting. Never seen anything like that before…
It doesn’t look like any kind of method you could use for precision tuning though…

@SpookDog I'll inspect the power valve from the exhaust port and try to post pictures later, just to be sure
The bike feels fast and has good acceleration so there's a possibility that it's just my speedometer that's screwed up LoL

@SpookDog yeah that's cool as f

Thanks!

I'll be ordering a small piece of CFRP prepreg to form a chain guard next. I found a place that sell "test specimens" that just so happen to be exactly the size I need, for about £6.

How local are you to Dorset? Buy mine. Respoked/new bearings 2000 miles ago, nearly new tyres disc rotors and pads, ready to bolt straight in:

https://www.ebay.co.uk/itm/266386635256