1994 KDX200 Problems - Low Power, Oil Drip from Exhaust, Hard to Start

[BigO1980]

I recently rebuilt a 94 KDX200 from a box full of parts I got from a guy off marketplace. It was a combination of me and a local mechanic that finished off the build after I ran out of time. Everything is all back together now and the bike runs, but I'm experiencing the following problems:

- Hard to Start, the air filter and carb are spotless so I do not believe it's either of these
- Will not idle without throttle, adjusting air and pilot screws does nothing
- Compression feels low even though piston and rings are brand new and cylinder is fine, very easy to kick over
- When riding through the gears, power is low. it will rev high but engine is not delivering nearly the power it should be
- black oil leaking from exhaust port. all of the correct gaskets and washers are in place between the exhaust and cylinder
- black oil leaking from crankcase overflow

I'm concerned that I have a crank seal issue, but wanted to check with others to see if there's anything else I should be doing / checking before I resort to taking the entire engine back apart to look at them.

thanks!

[SS109]

I would do a leak down test. That will confirm if you have a leak somewhere. The oil coming from the crankcase overflow, low power, hard to start, lower compression makes me think the case halves are not sealed properly from one another.

Burnt oil out the exhaust, even if you used new o-rings on the pipe, isn't that uncommon. Pipes get tweaked from dropping and crashing the bike and don't fit quite like they should after that leading to the leak. I use high temp silicone along with the o-rings to get a perfect seal now.

[brademan76]

Silencer packing?

[KDXGarage]

Pipe and silencer / spark arrestor may have had oil pooled up in them when you got it.

I would look up pressure / vacuum testing.