Cynic

Can't really say, i have only ever had bikes with liners, i don't know how the coatings fare with scratches in them. Just open her up for a lookie see. I would expect the bore to be better than the piston as the coating is VERY hard but like i said. Never messed with one. TOO new for me. Sorry. I suppose it depends if you want a reliable bike or a money pit i suppose. A YZ is no shrinking flower and demands respect and a few bob. The engines are rated for hours rather than miles. Don't get me wrong it will run for probably a couple of thousand equivalent road miles (depends how good you are) but not a lot more, you are sacrifising reliability for performance. 2003 YZ must be getting on for 40HP when a really good DT125 will have maybe 20HP and wont rev nearly so hard.

You have the bike listed on your profile as a 2k4 thats just a chassis number prefix common to DT Mx's, if its a 1981 bike its a 4J4 chassis number 2k4-020101 onwards. If it is an early bike then it would be a 2X2 with a chassis number 2K4-010101 onwards.

Not meaning to interupt here but have you done anything with the carb, bigger main or lifted the needle? Not an expert on the water pumpers but when i was a snotty teen and we pegged the valve you needed a 240/250 main or no good.

So long as you have everything 125 from the cases up you will be fine.ie Head Barrel Piston Little end Gudgeon Pin Gaskets Also you will need to re jet the carb, your carb will be a VM24ss carb ID 3U500 the 125 had a 22mm and a24mm carb over the 3/4years it ran for so for safety's sake these are the specs for a 125 f which had a 24mm carb. Carb ID (for reference purposes if you are ordering parts)2N400 Main jet 125 Main air jet .5 Jet needle 5GL8 3rd groove from the top Needle jet N-4 throttle cutaway 2 Pilot jet 22.5 Starter jet 20 Float height 21mm Idle speed 1350-1500 As to the oil pump, play that by ear. If she's smoking a lot adjust it if you must but i would be tempted to leave it alone if at all possible. Little bit of extra oil won't hurt, certainly better than to little. You will find the 125 is lacking quite a bit in the 2-5000rpm range compared to the 175, but so long as you let it rev it does around the same flat out. You just have to turn down the mechanical sympathy a little. Hope this helps.

The demon bay would be your best bet. Where all of mine have come from. DONT buy and engine on chance unless its stupidly cheap and contact the seller too ask LOTS of questions. I'd check with PJME first. There are companies that can rebore and replate, or fit liners to engines but you will have to spend some google time tracking them down. Like i said ring some of the companies up, they are the experts and providing you approach them properly, i imagine they get no end of "can you tune my bike to a billion BHP for £4.50". They are running a business. But asking PJME is they can fix up your barrel/piston is likely to get a good response.

These are the people i've used before, on reccomendation. Sensible prices for first class work. Cheap rebores will cost you loads in the long term. PJME

Owing to the way a 2 stroke works there is always positive pressure coming from the transfer ports so it is very difficult for it to travel that way. They are also quite small. The exhaust on the other hand effectively sucks the charge from the cylinder as it helps draw the fuel air mix onto the piston. Some of this ends up in the pipe and is forced back with the backpressure in the pipe. That back pressure wouldn't lift the bits back into the pot. If your really botherd i'd have the front pipe off and see whats inside it, most likely its in the u bend at the bottom of the pipe.

Unless your very unlucky the bits will have gone straight out the exhaust port, one of the perks of a 2 stroke Stick a new plug in and it should be well again. And dont leave it so long without a once over, the YZ's are not designed like a road bike they need hugs and cuddles to keep them sweet (ie, fast)

He wasn't a stranger, but fcuk me that was a drive. Do a full day at work and when i'd normally be thinking of going to bed i'm setting off on what turns out to be 400 odd miles in the pissing rain. Got to bed at 0400, (i normally get to work arond 0330)Tuesday was a total veg out and it knocked me all week. Once i could have done a 24hour stint and been fine with a couple of power naps, boo getting older Anyway better now.....

Sorry people, remember the scoot that was living in my garage, well the pilot is a long time friend of the family, we get on very well with her daughters family who have been living with her for a while now. Thing is she's going to take the stairway to heaven anytime soon, sometime in the next 24hrs at the latest guess so sorry if i'm a bit hit and miss for a while. Off now to exceter to pick up one of their family that can't get back.....

You wouldn't say that if you'd seen what that thing goes like, he'll be there in 20minutes (if he stops for a smoke)

Done a few, bikes, V8's in my land rovers and a couple of gearboxes. Hard fought experience learned from my father and patient reasearch. None of that consisted of a blunt open ended question without so much as a hello.

Next time you pass some road works, ask for a go on their:- whacker plate, paddy's pogo, patch tamper, delete as applicable. It would be about the same as a 650 single cyl 2 stroke.

Short answer Yes. As far as it goes the exhaust is THE critical component on these engines. Minor exhaust issues can rob masses of power. If you lose 2-3 hp from something when you only have 8 or 9 to start with its going to hurt. You MUST get the exhaust to seal properly, if not the bike wont be running properly as instead of drawing unburnt charge back into the cylinder you will pull in air which will mean your bike running lean at the most critical point in the power. I will also cause hesitation.

You have a 1973 AT3, engine numbers ran AT1 201101 to AT1 232651, engine and chassis numbers should match. It should be Brigade Blue if it still has the original paint. The 72 AT2 was Mandarin orange with the 71 AT1-C being Brilliant red. The frame prefix for all these bikes is AT1 HTH

He he , oops. Does sound like a leak of some sort. When you say it runs ok have you actually ridden it.

Ok thats an hour of my life gone from a mouse click,got to 21, the birthday level is lamely amusing.

What do you mean push the choke in to turn it off?

Same as its always been since the first 175, 66.0mm 3 official oversizes at .25, .5 and .75, the aftermarket do upto 2.0mm extra.

I've got 3 rides One is expensive, noisy, and dangerously unpredictable. Then there is the DT and the TDR

I've got 3 rides One is expensive, noisy, and dangerously unpredictable. Then there is the DT and the TDR

TDR has gone in a sulk, i think its got the arse cos ive been messing with the DT. The spark just vanished this morning, thankfully 500yds from the house. Not a fuse, not plugs or the cap. Its gonna play hardball. Who said bikes aren't like women...... I bet the wife would be fine if i rode another..

Not really a good frame choice for that kind of thing. The backbone of the frame is relatively low/ the MX frame is worse so you can't do anything about the motor height. Maybe lower the bottom cradle but then you will have chain issues. Also the sheer weight of something like a XS650 will crush the life out of the DT sus. Something 2 stroke is it really, DTR motor would be pretty easy as the lc frame isn't all that far from an aircooled frame bar the suspention and they are very tunable with big bores (see cardboard dave) Or track down one of the DT230 motors. Maybe go really nuts and squeese a dt400mx motor in there, or something YZ, bearing in mind the (hum)drum brakes.

Ahemm cough cough,

Why take a picture of the gas tower in northampton (top picture) dave. Can't say its that interesting tbh? And if you ended up on the gasworks roundabout you took a bit of a detour . Could have called into mine for a coffee on the way through.