78 ts 125 wont start

[JOE91]

I'm hoping that someone here knows enough to help me out. The bike is a 1978 ts 125, which in case you don't know is a 2-stroke and I can not get it to run! The carb is clean jets were removed and cleaned everything is clear the bike has good blue\white spark every kick has good compression, fresh gas, newer plug, tried choking while air box is off and on filter is good. Everything checks out to make it run, except it just wont run, maybe it was too cold out? it was 10 Degrees F when we were working on it and kicking it over, it would fire sometimes with starting fluid but not every time. I did have it running for about 30 seconds once. it ran good and took throttle well even though it was still cold before it died. Maybe there is something I'm missing or just don't know to check. I do not know when this bike ran last it sat in a junk yard for years before I got it. I know the fuel is getting to it, it seems like a spark issue but everytime I check its always sparking really well. Any help is much appreciated thank you in advanced

 

[tatu]

What are the main bearings like? Crank shaft seals? Take the points cover off and gearbox oil filler and sniff for petrol, see if there is any play in the bearing up and down. Base gasket in good condition? If the engine is severely flooded it won't start.
Fuel off, plug out, 1st gear full open throttle and run, spin the engine as fast as possible, a fresh new plug and try starting normally.

 

[Efordman]

I've been working on a Yamaha dt100 with the same problems. make sure you have a NEW plug handy and dip it in a little gas and kick it over and see if you get anything. also if you have a spark plug test light put it on and try it. I have had instances where the plug would spark out of the cylinder but not inside the cylinder because it wasn't grounding good enough. I cleaned the threads good on both and a new plug and fired up. check all your carb setting also to make sure it is set correctly. if it has oil injection the settings may be different if running premix through it. adding the oil to the gas beforehand will make it leaner so some adjusting may be necessary. depending on how the carburetor is the choke my actually add more gas instead of cutting off air so choking it by hand my help

 

[JOE91]

We've been choking it by hand have pulled the plug multiple times if we thought it was flooded even poured some fuel into the cylinder to clean it up a bit and then pumped it out. my next step is taking a look at the points and cleaning them and making sure they are set right, as far as the carb goes I have tried adjusting the idle but I haven't touched the air mixture screw. we did check the oil and there is no fuel in it. as far as main bearings and crank seals I have no idea if they are good yet or not. my question though is if the plug is sparking as well as it is wouldn't that mean the points are at least good enough to run?