Possible crank seal leak

[cspinner]

Hello,

I recently purchased a 1992 KX80 which just had a new top end put in (0 hours on it).It is jetted completely stock, idle air screw out 2 turns. Upon start up, white smoke billows out the exhaust and is more intense when the throttle is opened a bit --like a crop duster. I warmed it up for about 10 minutes idling and cracking the throttle a bit, but I'm not sure if that was really warm enough. The pipe was dripping black spooge. When I pulled the plug it was dripping black and wet. The bike has no problem starting and holding idle. Cracking the throttle 20-30% make a low throaty and bogging sound, which make sense giving the richness.

I tried adjusting the idle air mixture screw, but it didn't have any effect. With stock jetting and it being only 40F outside, I figured it'd be on the lean side if anything. So I suspect the following:
1. the crank seal is going bad and tranny oil is making its way into the combustion chamber
2. the guy who installed the top end did something wrong? He said he heavily lubed the cylinder, piston, rings with pre-mix oil when he put everything together. (I've heard people swear by dry assembly) But wouldn't that have burned off after a minute or two? Also, compression test after running for a few minutes looks good, around 180PSI.

I did not know how it ran before the new top end was put in so I'm relying on current symptoms to diagnose the issue. I'm relatively new to 2 stroke bikes in general so any help (even obvious advice) is appreciated. I'm not sure what I should expect to see running 10 minutes idle with blips after a fresh top end. Maybe this is normal? I plan to take it for an hour ride in a few days, but the place I ride is far so I want to get a feeling whether this is normal first.

Other questions:
1. Can I rule out leaky crank seal by draining the tranny and running the engine (not riding) to see if the amount of smoke changes? Is that safe?
2. If it is the crank seal, are they accessible from the clutch cover or do I need to split the case?

Thanks!

[KDXGarage]

MOVED to "Other Bikes" subforum

Welcome to the forums.

[KDXGarage]

DO NOT drain the oil and run it.

Check your coolant level. White smoke can mean coolant. Check the sight glass on the transmission, if it has one. If it is very milky, then it may be leaking.

[royadams]

A better way then running with no oil, is running benol 2 cycle oil in the transmission. If its leaking you will smell it a mile away.

[cspinner]

Coolant and oil level is still good. Exactly where it started, but I'm skeptical 10 minutes of idling would really affect it

The oil still looked fresh, not milky.

I also since discovered that the can has zero packing in it. That explains why it was so loud

Just for kicks I pulled the left side cover and confirmed there was no leaking out the dry seal.

[G22inSC]

Pressure / vacuum test if you can and definitely a fresh repack on the silencer.

[Julien D]

Don't run it without oil. There are still meshed and spinning gears when in neutral.

Leak down is the best way, but if you're not losing any oil in the transmission when riding, what makes you think you could be burning it? Just the smoke? That's probably more of a jetting issue or gunked up exhaust. The ineffective airscrew indicates a problem in fuel/air delivery issue as well. Possibly poor jetting, or something wrong in the carb.

[cspinner]

It took a lot of setup but I performed a leakdown test and the results were acceptable. So I turned my focus back to the carb and what I found was troubling... I used permatex #2 gasket maker on the float bowl to replace the old cracked gasket . It is rated for gasoline, but still it looks like it emulsified and made a mess of the inside of the carb. There were bits and pieces in the float bowl. I stripped the carb again, cleaned everything, and used a homemade paper gasket on the bowl. No leaks, no mess.

It was around 70F today, beautiful! I took the bike out for a couple hour ride today and it ran much better (no more billowing smoke) now that there's no gasket junk in the carb. the bike pulls hard after a certain RPM. I mean you can really feel it kick in, but drags down on the low end. The pilot circuit is obviously still running really rich and I prob need to drop the needle a click. However I am satisfied with the main jet. Then I did some more technical stuff in the woods...Ended up fouling the plug after a little while at 1/8-1/4 throttle.

I'm on the stock pilot jet (55) with the mixture screw 2.5 turns out. I know stock jetting is on the richer side, but I'm concerned it still fouled the plug. Note this was the same plug that ran the bike for 10-15 min at idle mentioned in the previous post. Should I try for a smaller pilot? How many increments power should I try?

[KDXGarage]

I used permatex #2 gasket maker on the float bowl to replace the old cracked gasket . It is rated for gasoline, but still it looks like it emulsified and made a mess of the inside of the carb. There were bits and pieces in the float bowl. I stripped the carb again, cleaned everything, and used a homemade paper gasket on the bowl. No leaks, no mess.

If you don't mind me asking, how many hours did you spend chasing it down after that?

Try a new plug and adjust air screw to try to tune.

[G22inSC]

Hope you got all the Permatex out of the carb. Every passage, jet, nook and cranny, etc. If not and a piece plugs a jet, it will give you fits.