2 stroke power loss

[need2understand]

oh, it took several kicks to get to 120. If we were to base it on just 2 kicks, it'd be much lower.

[Delboy]

Another thing to check.....That series DT250 was notorious for the silencer chambers clogging with carbon and seriously restricting power. I had some success with heating mine with a torch and hammering it to get the carbon out, but the best solution I ever came up with was to cut the stock silencer off of the tail pipe and weld a YZ250 can onto it.

As suggested do a leakdown test, its going to tell you more than simply measuring the compression. The compression was only about 6.5:1 on those anyway as a 2 stroke only makes compression from when the exhaust port closes, not over the full length of the stroke so if the port has been lifted by 1.5-2mm - as was a common mod - its hard to tell exactly what the compression should be.

Is it running weak? That would indicate an air leak.... as they were also notorious for the left hand crank seal letting go.

[DoubleJ]

As for the exhaust being maybe plugged. Take it off and plug the inlet and fill it with a mixture of caustic soda and water and let it sit. Rinse out well next day and reinstall. Use gloves and face shield as that stuff will burn the **** out of you. A potato makes a good plug!

[Stewart]

i have used the potato trick before....when somebody stole my parking spot, years ago, i jammed a potato in their tailpipe. on a cold winter's day,i watched them try to start their car to no avail, i laughed so hard when the tow truck came to take the car away. true story! oh ya, i did this before beverly hills cop, the bananas don't work, thats hollywood for you.

[need2understand]

Ok, I got to work. Used lye on the exhaust and for good measure, put a torch to it: it's clear. Took engine apart and cross hatched cylindar, new rings. Getting compression of 135. Bike still runs like crap. Took a look at the spark and when I expected to see a bright blue spark, I saw a white-ish spark. Replaced the ignition coil. No change and the spark looks almost the same. Thinking about replacing the CDI at this point...

I also bought a flywheel puller and had a look at the crank seal and it looks new. It's in there tight. Thinking of replacing it anyway because I bought an extra.

No visable damage to the reeds.

Any other ideas or should i fork out more cash for the CDI? Thoughts?

Edit: Anyone know a link to instructions on how to replace the crank seal on the mag/flywheel side?

[Frank the Tank]

so you're sure you have no leaks?
i dont see the cdi as the problem.