Classic, well they say nothing last forever.

I'd change it at the recommend service interval, if nothing else, restores lost power.

Did you see my Cagiva Raptor. Nothing wrong with that engine on the face of it. Started on the button and ran really well. Last year I decided to do the service interval.

Turned out the piston had a hairline crack in on top of the piston crown and down the gudgeon locator...ticking time bomb.

I had a barrel replated, new piston/rings and the bike was utterly night and day in terms of performance. The thing absolutely flew.

Then a few weeks later it was really struggling to run. I went on an overseas trip and came back when the temperature had drops some, then the engine just died.

I haven't stripped it enough to figure it out yet, but at 30 PSI, prognosis is not good. I whipped the cylinder head off and the piston/bore are in good shape. My guess is the crankshaft seals have given up. The restored new power was just too much for them and they've let go.

Another one for another time

@Stevie-Wonder They're ace, they'll sell you a GPX TSE250R engine which bolts straight in, and other stuff like a cone-shaped shim which fits on a DTR crankshaft under the flywheel to enable running it in a DTRe bottom end.

Oh that's cool, though my brother ran a 38mm Keihin on his 2001 DTR. Just heated up the rubber and stretched it over.

https://www.youtube.com/shorts/bOGAEzTaBgI

There has to be somewhere in Europe that ships to Bosnia?

@HOTSHOT-III

Absolutely! The low to mid range is really quite something. I’m cruising at 55 @ 5K rpm so nicely, I’ve just got a new 18T front sprocket to try. I’m hoping it’ll make me rev it more. I’m riding it like a 4/ single at the moment!
I’ve upped the oil to just about 2.5%. I’ve been limp mode riding before now. I’ve just gotten over a spell of the pilot jet and main jet being partially blocked! (I thought the new CDI was failing!) it seems the paper-like filter was shedding micro fibres!
New tap, new pipe, new filter!…

Now that I can say it’s running properly! I’m going to get the auto lube refreshed and put back on…

Thanks for the info! Priceless!! 👍 …

@SpookDog Do you still have plain bolts and copper washers in your carb warmer hose connections? If so this could be the culprit. The official Yamaha procedure for bleeding the cooling system is to remove the carb warmer hose where it joins the thermostat housing (i.e above the actual thermostat), then fill the rad whilst watching for coolant to come out of the tube with no bubbles, then refit the tube and fill the radiator to the brim with the bike vertical. If your carb warmer circuit isn't operating you'll have a small air pocket below the thermostat until it opens.

I'm not a huge fan of the carb warmer circuit as IMO it's not really cold enough to warrant it in the UK and it makes getting the carb off a right PITA if you like experimenting with jetting, float heights etc. But it has another useful function which is to make the cooling system self-bleeding by allowing it to bypass the thermostat during refilling (this is why bikes like the 350LC without a carb warmer circuit have bleed bolts on the sides of the cylinders). So the best compromise I found was to just run a single hose directly from one banjo to the other, retaining the self-bleeding and not having to disturb the cooling system if/when taking the carb off.

I've never primed the expansion tank circuit and I'm not sure it would be necessary because as the coolant expands in use and travels down the tube, it would probably expel any air present anyway. But I guess you could by filling the tank, then putting a long tube over the filler hole to avoid ingesting any antifreeze and blowing through it until coolant comes back out the tube and fills the rad to the brim, then sticking the rad cap on quick and topping up the expansion tank. And definitely fill the rad slowly as @OllieDTR said.

TBH I'd try refitting the carb warmer banjos first and see if you're still getting an air gap in the rad. When I sold Greta the other day Liam asked to see the coolant level as I mentioned I'd replaced the head gasket when I bought the bike, so we took off the rad cap to look and the coolant was right to the brim after being ridden a few thousand miles (including getting quite hot off-road a few times) and being in my living room for over two years.

DTRE/X are the same as the DTR except they came with an electric start instead of a kicker. The stator and cranks are therefore different but everything else about the engine is the same.

It's only the 4GW TZRs and 4DL TDRs that came with the 4FU cylinders to my knowledge. There may have been other designations that came with 4FUs but none in DTR configuration.

I always wanted to try it out myself and a few units back in the day. Never did though, I am happy to park DTR development for the time being, happy enough with the Athena 170 kit for the moment.

@Vcelicka

Happy for you bud! 👍 …

If you can afford it get a NGK rubber (red) ‘racing’ cap and an NGK Iridium spark plug. They are the Bogs Dollox! 😜 …

@OllieDTR No? Jetting is normally easy as pi.

But apparently, as I found out on a recent dyno session, my entire setup is jank 🤣 Not terribly convinced. They sent me home on a completely broken/dangerous bike...

@OllieDTR Not sure of the thickness but along with the cylinder base nuts and studs, these are fasteners worth buying genuine from Fowlers.

It's a good question, 70 sounds about right for the coolant temperature, not sure about temperature at the spark plug.

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.

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…

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?
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@SpookDog

Hi mate yes I’ve done it on this bike I’ve got now, it’s a dtre engine in a Dtr frame, it’s really simple. @Calum did a post about it and what you need! Here you go

https://dt125r.co.uk/topic/13/kick-start-conversion-dtre

Thanks to all the help offered i solved the issue it was the cables not turning the valve the right way it was closing instead of oppening , tomorrow im gonna do a topspeed test thinking of hitting atleast 120-30 kmh

I think the main thing are the piston rings bedding in.

I haven't worried about it too much. 50 miles if it's just a top end. But I am quite happy to rebuild the engine prematurely.

@89dt125nick

Drain the coolant properly before and when you take off the head take some pics. You want to see where it was leaking from the coolant jacket into the bore. Also look for the root cause, head gaskets don’t usually blow unless there are overheating issues, or (in my case) misfire problems…

Buy a price of plate glass10mm x 30cm x30cm to lap the head clean and smooth…

Don’t buy a shitty head gasket, get an Athena, Vertex or genuine head gasket…

Part 1 on the first link and an o ring needed. Joint 10v-12446-00
Thanks mate