1999 yz250 Oil from Exhaust

[bk250]

I picked up a 1999 YZ250 last fall and only had a chance to ride it twice before putting it away for the winter. I noticed that both times I rode it, there was oil leaking from the exhaust. The first time was right at the engine exhaust/pipe connection which was corrected when I bought the missing rubber seals for the exhaust pipe. That just transferred the leak to the end of the silencer at the end of the second ride.

Everything I have read leads me to think that I need new oil seals in the crankcase. Does that seem right to those of you that know what you are talking about (unlike myself)?

Also, if I need to replace the seals, does it make sense to replace the bearings at the same time? Are there any other parts I should consider replacing while the engine is apart and the case split?

Thanks.

 

[ZOMBIE666]

if its thick black sludgy oil, its spooge. you'r just running rich


RE-JET

 

[KX250Dad]

The YZ250 doesn't have oil in the crankcase other than burn from the premix which lubes the rings/bearings. Only other oil in the crankpart of the case could come from the trans/clutch which can leak thru the seals so check your levels. You want the head pipe to seal against the cylinder, which it appears you've already discovered. Oil from the silencer end and between the silencer / pipe coupling is not uncommon, especially when riding the 2 stroke low in r's. Take the pipe off and look inside, I suspect you'll see a considerable amount of carbon and it may be wetted should you be running 30:1 with a cool plug. Times have change since '99 and guys like me who ride a 250 below 6000r's no longer carbon our power valve mechanisims closed, we simply have alot of spooge, to the point it comes out the power valve vent and silencer. If the oil you refer to is greyish it can only come from coolant which can only enter the firing zone thru the head or cylinder base to crank... check the coolant level as well.

Spooge is somewhat your friend at least you know your not running to lean. I wouldn't suggest any jetting mods until you get adequate run time and manuever from there. Average riders can use book spec on jetting. Point here is you need to develop a baseline to make jetting decisions.
Good Luck

 

[rmc_olderthandirt]

Like the others said, you bike is fine, it is normal two stroke oil out the exhaust.

If you are new to two strokes, in addition to the bike being new to you, then you need to pick up a few essentials.

First thing is that the oil/gas mix and carburetor jetting are connected. It is essential that you establish a gas/oil mix and stick with it. Once your oil mix is stable get your jetting right.

By chance, when you bought the bike, did the seller tell you what oil and mix he used? If you know that, then keep using it as there is a chance that the jetting was previously established for that.

If you don't know what it was before then pick one of your own. If you have a regular set of buddies that you ride with who also ride 2-strokes then I recommend that you choose the same oil and mix ratio that they use. This will allow you to share gas without any concerns. Unless, of course, your buddies are leeches in which case you might want to do something totally incompatible!

The oil out the exhaust is pretty much a fact of 2-stroke life. Running excessive oil makes the problem worse, and can lead to fouled plugs. Not running enough oil can destroy the engine.

Rod

 

[NWDirt]

I bought an 01 YZ 250 from a guy I never actually got to talk with so I decided to set the carb settings back to stock and used Yamalube at 32:1 as the book suggests. On slow trail rides, the black spooge was everywhere even dripping on the truck bed after the ride. Makes sense because the bike was made to be run at upper rpms in a supercross enviroment and I ride it on trails. I did the following:

I went through the process of getting it jetted correctly (great links on this sight) but the spooge kept coming, so I tried a few different pre mix oils. Finally settled on a 40:1 DUMOND mix with the best and freshest pump gas I could get. The Dumond oil made the bike slightly fuel lean even though I leaned the oil, so I rejetted the bike for the third time. For the riding I am doing, there is very little sign of spooge and recently when I had the power valve apart it was clean and nice instead of full of black oily crud. The previous post mentioned using the same oil as your friends and that makes sense as long as they are detailed enough to dial their own bikes in. Get it dialed in, one variable at a time, and then stick to it and the bike will run crisp and be relativly spooge free. Guys on here are more experienced with this than I am, but since I have the same bike and the same problem, I chimed in.

Dave

Oh yeah, after boring it out, jetting turned out to be a three ride experience to dial it back in.

 

[uts]

My old IT spooges too. I can't jet it any leaner either, or it runs cr%p. Go figure.

Anyway. it was leaking at the pipe/cylinder joint a bit. So I sealed it up. It didn't make any gain in performance, and now the spooge can't leak there, so it fills my silencer packing.
Fixing a leak has created more maintenance. Bummer.
At least my right boot doesn't get sprayed with the blackness any more.

 

[Solid State]

If the oil you refer to is greyish it can only come from coolant which can only enter the firing zone thru the head or cylinder base to crank...

Not true. There are other ways that water can enter the combustion chamber on a YZ250. I do agree the spooge issue is jetting related as you indicated.

 

[76GMC1500]

The spooge isn't necessarily an issue. It is my believe that if you have no oil carrying over into the exhaust, your powervalve is not properly lubricated. I like to see a little spooge at the end of the day. You probably need to repack your silencer, too.

 

[KX250Dad]

Not true. There are other ways that water can enter the combustion chamber on a YZ250

Solid State... unfortunately I've had issues with my '05 YZ250 and water in the cylinder/crank. Wound up either a warped head or errosion/pitting at the top of the cylinder cloose enough to the inner o-ring seal. Suspected when at temp (under pressure) coolant leaked from the jacket into the cylinder. Used some plastic metal and imagination and appears to have worked. Given the nature of this issue please pass on other water in crank avenues... I'd owe you one.

 

[Solid State]

KX250Dad,

I have chased this condition for years. According to Erik Gore, these mass produced cast cylinders (and heads) can leach water straight through the aluminum due to porosity of the metal. A cylinder and head swap would rule that out. Unfortunately, it did not in my situation ($249 plus shipping). Head gaskets (o-rings) and base gaskets are obvious candidates, but I'm sure you've ruled those out as well.

There is another source that is possible. If you study the exploded diagram for the left/right cases, you should see that the water pump pulls/pushes coolant from the right side case to the left side case to feed the cylinder up through the water jacket on the left side of the cylinder. There is a round channel in the front of the cases (internal) to facilitate this transfer. The cases, of course, are split down the center (really stupid but a universal approach) and the channel is sealed with liquid gasket and an o-ring. A leak in this area will put water into the bottom end and thus enter the combustion chamber.

Grey spooge may also be evident exiting the power valve vent tube and not necessarily the exhaust.

Good luck.

 

[bk250]

Thanks for all the advice. As I said I am new to riding so this is a steep learning curve for me. The oil I have leaking is definitiely black and thick, so I am taking that as a good sign from everything you guys have said. All I know from the guy I bought the bike from is that he used Klotz 50:1 oil, mixed at 32:1.

I am guessing I need to learn a lot more about jetting to put the rest of your advice to use. I do know the top end wasn't great last year so I had planned on pulling the valves apart to clean them and replace the piston and rings. Based on what I read here, I think I will pass on the lower end seals this season and see how things go. Any other advice before I start into this?

Thanks again.

 

[BSWIFT]

The spooge isn't necessarily an issue. It is my believe that if you have no oil carrying over into the exhaust, your powervalve is not properly lubricated. I like to see a little spooge at the end of the day. You probably need to repack your silencer, too.

Pull the pipe and wash it out with diesel, then repack your silencer. Repacking the silencer is cheap, keeps performance up and noise down. Jetting is not difficult, just time consuming.

 

[SHSPVR]

Have you check the float height if it getting to much fuel in the bowl it do that which was the part of my problrm I run in to.
It maybe a good idea to get a new float valve.

 

[NJGregsCR]

This thread definately puts my mind at ease. I had exactly the same question about the black oil from my exhaust, and some of the answers I heard were cracked reeds, and bad crank seal.
I just picked up a 97 CR250R and was concerned that I had a problem.
One buddy recommended using Golden Spectro 2 stroke oil @ 40:1 or 50:1 mix to eliminate the problem.
Any mix suggestions?

thanks,
Greg