Back from the dead

[V1346]

I recently was lucky to find a '69 steel tank 125 which had been sitting for 30+ years.  The engine was stuck tight with a burned piston and I suspect that is why is sat.  I've dipped the carb and it is all clean, replaced the piston and put everything back together.  My question is what else should I do before I hook up the coil, put some petrol in the carb and kick it over?  How about initial carb settings?  Are these engines prone to burning pistons?  What about electrics?  I know they are basic but should I spend some time looking at resistance in the coils, etc?

TIA,

Bill

[Paul Danik]

Bill,

   You probably already checked the aircleaner, but if not those old filters usually are pretty bad from age. I always doubble check to make sure the slide is hitting bottom properly in the carb before firing up an engine.   The air screw on the carb should be about 1 1/2 turns out for initial starting. You may want to put a fuel filter in the line to catch anything that may be hiding in the tank and comes loose with vibration. I never heard of very many burned pistons back in the day, make sure you are running the proper heat range sparkplug. The book says the timing should be set at 3 - 3.5 mm BTDC.

Hope this helps.
Paul

[tofriedel]

Paul gives you excellant advise.  I would also drain and replace the oil in the engine and do the same with the forks.

Tony

[slvrbrdfxr]

Bill,
Probably one of the most important things is to ensure that the kill switch is working properly before attempting to start the bike just in case something serious goes wrong. One other item would be to blow some compressed air through the exhaust pipe to make sure it's unobstructed. It's surprising how much dirt and debris that can be packed into a pipe by mud dobbers and mice. Good luck and let us know how everthing turns out.
Dave McCullough

[linglewn]

Bill,
No one has addressed your comment that the piston was "burned" and stuck. Hopefully you made sure that corrosion and/or aluminum was removed from the cylinder before you put in a new piston. Also, if the burned piston was actually "holed," you need to be concerned about aluminum in the lower end bearings. Any racing engine can hole a piston if run too lean for extended lengths of time. Most folks don't jet dirt bikes extreemly lean and are on and off the throttle, so holeing the piston isn't a common problem. Good luck.

Nelson Lingle
73 Jackpiner
71 DKW 125

[MattyQ]

I had recently read on a motor cycle repair site , that if you run a two stroke for a long periond of time at the same speed it can freeze up even a new piston .  This was his theory at least , that had seen it happen . I had wondered about it , as far a my six day enduro went , riding it on the street from time to time. [?]

I have a stuck piston on one of my mx bikes , not sure how to get it unstuck ? Put some oil in the piston , still no luck ?

Matthew Quinlan

[brian kirby]

Put some heat on it, if you have a stuck piston your not saving it anyway. Try a penetrant like PB Blaster instead of oil too.

Brian

'72 Six Day (on loan from Ernie P.)

[V1346]

It lives!!!!!  That was the main goal before moving forward. I did not want to spend money if the engine was going to be big money.   These little suckers really bark, I forgot how nice a 125 and expansion chamber can sound.

Thanks for the assistance all and I'll be looking for parts and advice as time allows.  

Bill

[V1346]

OK, question number 2-

The tank is full of 2 stroke oil and gasoline turned to varnish from President Ford's term.  How should I go about flushing this thing out?

[Lew Mayer]

Use just what you would on varnish.
Lacquer thinner. It works pretty good.

Lew Mayer

[Rain Man]

Pull the engine and send it to Doug W. [8D]

Raymond
 Down East Pentons

[tomale]

Good to hear it runs, I would be very concerned about the crank seals. A bike of that vintage, the seals are bound to be hard, even if they run does not mean that they are in good enough shape to continue to be servicable. I had a seal go out on one of my bikes and did not know it.. it was the seal on the clutch side. I first began to suspect something when I ended up going to a large pilot jet for my standard setting, I later after I had taken the top end off, I found a large amount of oil on the crank. It was time for a top end anyway so we split the cases and replaced the bearings and seals, wow what a difference.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
75' GS400 (finished project bike)
72'sixday (project bike)