Rebuild time! (Crank seal failure) ((Questions))

[p.caudilljr]

I acquired a 96 kdx 200 about 3 months ago and have been going through the neglect of the previous owner getting it running. Got to a good point I thought and did a camping/riding trip to Fort Sage OHV near Doyle CA and the bike was phenomenal, super fun and very capable. Put it in the garage for about 3 weeks then decided to go on a little ride last weekend and was having a bog from idle to a little over 1/4 throttle. Almost like I needed to downshift. Thought it was elevation/jetting related since I was going from about 5000 ft to 8300 ft. Got back home and realized heavy smoke from the exhaust and I'm pretty certain it's pulling transmission oil through the crank seal

Since splitting cases is the way to tackle this, what should be ok my list of things to replace while I'm there? I would like to not have to worry about anything other than regular maintenance for a bit. Thinking might as well do top end too.
So far I have this stuff on the list:

-crank bearings
-tusk engine oil seal kit
-inner clutch cover gasket
-tusk/wiseco pro-lite piston and gasket kit
-tusk clutch kit with heavy duty springs

[ss109]

Before doing any of that please do a leak down test to know for sure. Test not guess!

[KDXGarage]

Welcome.

Vacuum and pressure test to check the engine BEFORE tear down.

[p.caudilljr]

Welcome.

Vacuum and pressure test to check the engine BEFORE tear down.

Your correct about the testing, guess I let my bummer mood get the best of me and I'm assuming the worst haha.

I'll go ahead and do a compression test and leak down test this weekend before anything else, what is a vacuum test??

[SpruceItUp]

A vacuum test just pulls a vacuum in the engine instead of applying pressure to it. Some seals only spring a leak one way with pressure or vacuum, so only doing one test can be inconclusive. Since the engine has periods of vacuum and pressure in the crankcase while it's running, it's best to test them both.

Now, you don't actually need an expensive setup to do this, I made one from a handheld vacuum and pressure pump for bleeding brakes.
Something like this:

(My amazon link is not working, at least not for me, so I attached a photo)

And then I used an adapter from my compression tester to connect the hose to the spark plug hole. If your adapter has one, remove the schrader valve stem.

When you have that together, make sure you put the piston at bottom dead center so the pressure and vacuum can get past the piston and enter the rest of the case, and plug the exhaust and intake. Also, I've read you don't want to pull more than 7 inHg (vacuum) on the cases. I've pulled more in the past, but I stick to 7 now. And no more than 5 psi of pressure.

I ended up making this specifically for the KDX as removing the airbox on it, or at least the E series, takes more work than I'd like if I'm just testing. I had made a another that goes in the intake for my 125 that works just fine as well.

[p.caudilljr]

A vacuum test just pulls a vacuum in the engine instead of applying pressure to it. Some seals only spring a leak one way with pressure or vacuum, so only doing one test can be inconclusive. Since the engine has periods of vacuum and pressure in the crankcase while it's running, it's best to test them both.

Now, you don't actually need an expensive setup to do this, I made one from a handheld vacuum and pressure pump for bleeding brakes.
Something like this:

(My amazon link is not working, at least not for me, so I attached a photo)

And then I used an adapter from my compression tester to connect the hose to the spark plug hole. If your adapter has one, remove the schrader valve stem.

When you have that together, make sure you put the piston at bottom dead center so the pressure and vacuum can get past the piston and enter the rest of the case, and plug the exhaust and intake. Also, I've read you don't want to pull more than 7 inHg (vacuum) on the cases. I've pulled more in the past, but I stick to 7 now. And no more than 5 psi of pressure.

I ended up making this specifically for the KDX as removing the airbox on it, or at least the E series, takes more work than I'd like if I'm just testing. I had made a another that goes in the intake for my 125 that works just fine as well.

Thankyou! I will get that vacuum pump on the way and see what we are looking like. I did a leak down and compression test(135psi)when I first got it and it passed but I'm wondering if it is more likely to leak the other way like your saying. The bike sat for a long time after being rode hard. Got to a spot were it was running good and now this thought it was a little too good to be true just tossing it together and getting the jetting set up right haha

Hopefully have some numbers this weekend on the tests. Thanks for the help.

[Chuck78]

135psi is a bit on the low side, I would say it's time for at least to top end refresh and inspection, but only after doing a leak down test as the other members have stated, to determine the condition of the bottom end seals.

Also, I would strongly advise against using a Tusk seal kit. Use OEM or equivalent name brand seals, not a generic low-cost aftermarket kit, same with engine bearings.
As for the top end kit, I would recommend Wossner forged pistons over Wiseco every time, but also, OEM 200 pistons are great, especially if you ride in cold or high elevation areas and go back and forth in elevation and temperature often. Cast pistons are better for colder temperatures or drastic elevation changes with temperature change.
OEM or Cometic on the gasket kits. Cometic does not stock their own gaskets (everything is made to order if you order direct from them), but distributors do. Cometic will also custom make any gasket on the bike for you out of any material and any thickness requested that is non-stock. The MLS head gaskets are much preferred over the CFM 20 composite gaskets with a steel fire ring. I never like to use the steel fire rings on aluminum heads or cylinders only Multi-Layer Steel.

[p.caudilljr]

So compression is still sitting at 135 psi.
Leak down test was a fail, dropped from 6 psi to 3 psi after 6 minutes, small leak from my exhaust plug though. No leaks anywhere else I could spray. Slathered some grease on the leaky plug and had similar results of psi drop.
Vacuum test I went from 10inHg to 8.5inHg in ten minutes.

Before these tests I fired it up for a couple minutes and had the same terrible thick smoke that filled my 2 car garage almost instantly and reeked of burning oil

[Chuck78]

Have you tested the ignition components yet? While I definitely think you are due for a top end job, many bikes are still moderately rideable with that compression, pointing to the fact that you may have multiple issues and the compression is not your greatest issue. I would do an ohm test on the ignition source stator coil as well as the high tension ignition coil. The CDI box is a challenging one to test, and they generally are quite reliable although they do fail.

With a leaking compression plug in the exhaust port, it's difficult to trust the test results, but you may have a leaking crank seal still with the exhaust plug leak fixed, if no other areas showed you leaks externally

[p.caudilljr]

I have not tested ignition components yet and it probably couldn't hurt, but my overall issue doesn't seem like an electrical issue. It's the extremely heavy smoke that pours from the exhaust that is concerning me. I am going to drain transmission fluid and see if there is a significantly less amount than what I put in.

I went through the bike(carb and tank clean, fresh gas, new fork fluid, new transmission oil, coolant flush) when I got it and then put about 100 miles of pretty hard riding on it before this heavy smoke started

[Chuck78]

I wouldn't entirely rule out a change in ignition timing or performance, electronically speaking, but they failed right crank seal will definitely consume a considerable amount of oil and leave quite a smoke screen. This happened to me previously. The smell was evident that it was burning motor oil or gearbox oil, depending on what oils you use, and smells quite different from 2T pre-mix. I use Shell Rotella T4 in my gearboxes, and it clearly smelled like burning motor oil. I had to top off my gearbox mid ride in order to keep riding, and the bike ran pretty terribly really until the gearbox oil level was low and it was no longer leaking through the crank seal, then, the performance picked up quite a bit. That engine got shelved after that ride.

[p.caudilljr]

I have Shell rotella t6 in there now. And it is definitely oil burning from the exhaust. Like I had said before it did have like a mild bogging issue the ride I realized the smoke pouring from the exhaust, but the other 80ish miles I put on the bike tuning the carburetor, once the carburetor was jetted correctly it ran great with no bog and lots of power.

I am 99% certain my right side crank seal is out. I really would like to know other than crank bearings and crank seals, is there any other bottom end components that I should either buy or check while I have the cases split?

[Chuck78]

I am 99% certain my right side crank seal is out.
...other than crank bearings and crank seals, is there any other bottom end components that I should either buy or check while I have the cases split?

If you open up the cases, I would epoxy the curved grooves or "windows" cast into the crankcases underneath the ignition stator plate, they circle around the crank bearing area, and are known to be thin castings that often have porosity, as there is a steel insert cast into the cases there, so any porosity in the aluminum casting can end up causing a slight leak that seals will not fix. You generally just need to rough them up with sandpaper and degrease them really well, and use JB Weld or other similar epoxy to fill those grooves.

You should also inspect the shift dogs on all the gears, measure the shift forks for wear, possibly replace the counter shaft bearing, the one adjacent to the front sprocket, potentially replace the clutch actuator bearing in the clutch case housing, rebuild the water pump, etc.... and of course crank bearings and a crank rebuild while it is apart.
Also, make sure your counter shaft sprocket splines are in good shape, and look for a good used one if not. They are the same from '89 & up on the counter shaft, but the input shaft of the gearbox is different for the E Series (I'm guessing due to different clutch basket interface).