Picked up a 1978 Yamaha DT 125 from Maximus today. Spent the afternoon out in the shed going over it to see what I'm in for. So far it looks like ths:

1. Fuel tank is rusted inside, need to clean and probabaly line it with something.
2. Brake lever perch is split, can probably get one off Ebay.
3. No spark, plug wire was broken off inside boot, half-ass rigged it, but still nothing. Need to pull flywheel to look at points and condensors.
4. Forks seem to be out of alignment, hopefully not bent and an easy fix.

Waiting on Clymer manual to get here before I go much deeper, should only take a couple days.

I had a 1975 dt125. Looks like you have some work ahead of you, but that can be fun. I restored a 1975 gt80 last year.

cool bikes guys

Good news first:

I have a weak spark. I put a plug tester on it today and got a weak spark when kicking it over. I need to get a 27mm left-hand thread flywheel puller to get into the breaker plate and check that out. I took the head pipe and expansion chamber off and sprayed some starter fluid into the carb. I kicked it over and was rewarded with 3 pops, which means there is some fire in there. I got a brake lever and perch from Pete's Cycle for $10 that will work, although it's for off road bikes so it doesn't have a mirror mount. Got the front wheel tracking straight by loosening all the bolts and giving it a couple kicks.

Bad news next:

The fuel tank has some holes rusted through the bottom, nothing a little JB Weld can't fix, but still a minor setback. The big problem is with the title. The guy who Max bought the bike from filled out the buyer section of the title and never went ahead with titling it. So, as of now, it looks like a may not be able to get a title in my name. However, if any of you know any way around this, I'd appreciate the help. I would think a licensed dealer might be able to work some magic on it, but I haven't looked into that route yet.

I used international title service for lost titles for my gt80. I got a maine plate with no title. Maine does not give titles to bikes under 300cc. But they will give you a letter that will allow you to get a regular title with your home state. http://www.its-titles.com/ But this was for a bike with no title. If you have a title of some sort there may be a way around it.

I also used one of the title services to get a title on a bike I bought with no title. They don't need to know that you actually have the title but with inappropriate information.

My first full-size bike was a '73 DT 125. I'm not nostalgic at all for that bike, it was plagued with constant troubles, including setting the wiring harness on fire.

Disassembled and cleaned the carb today, found a lot of gum inside so everything looks better now. Put it back on the bike and poured some gas down the fuel line into the carb. Kicked it over and on the 3rd or 4th kick it caught and ran for about 5 seconds, enough for all the dash lights to power up. I still have a weak spark, so I'm waiting for the magneto puller to get here(Monday hopefully) and I'll change the points and condensor just for good measure. I went to a lawn & garden shop and got a new end and boot for the spark plug wire, however, the wire seems to be a little loose at the coil too, which is bad because it doesn't appear to be something I can replace.

I also patched the holes in the tank with JB Weld, and am going to use Kreem to clean, etch, and line the inside of the tank tomorrow. I think the next thing I tackle will be the transmission and clutch. I'm going to start by draining the old oil and replacing with some new stuff. I don't want to pull the side cover off the engine and replace the clutch if I don't have to, so I'll see how this goes. The chain is a little rusted and has some noisy spots, but I'm going to soak it in lightweight oil to see if it loosens up. If not, a new chain isn't too expensive, but then I'll have to get new sprockets too.

My new carb "secret weapon" is to boil it with laundry soap. Yeah, outdoors on the grill coz it stinks. Make sure you get all the rubber bits out, and you might want to dump the water out through a fine strainer in case little parts like washers come loose.

The other suggestion is that JB weld will only temporarily solve the tank problem. The only way to truly fix a rusty/leaky tank is to weld in new metal.

I ordered the points and condensor today, should be here Wednesday or Thursday. The magneto puller got here today, so I pulled that and found the crank key was broken, so I'll have to pick one of those up when the other parts get here. The points are shot, heavily pitted and blackened, which makes me wonder of the magneto spun on the crank a little throwing the timing off.

Removed the rear wheel to inspect the chain and sprockets closer, they're in desperate need of replacement. The chain has a couple tight spots, but overall isn't too bad. The rear sprocket is badly worn and the teeth are saw-toothed. The front sprocket is also saw-toothed but 3 of the 15 teeth are broken off.

Here's the deal with 2-strokes that a lot of people don't know: they run just as good backwards if you set the timing correctly.

Crappy old points ignitions could wear so they were firing close to TDC. Sometimes when starting, or running at very low RPM - like just before it stalls climbing a hill - the motor will switch direction.

This is real hard on the flywheel key.

IMHO, you'd do real well to adapt some type of electronic ignition to that motor -- they sell kits for small engines (go-kart racing) complete with rotors, sensors, and ignition modules.

http://www.msdpowersports.com/karts.html