black tar coming our of silencer

yz 144 sst pipe shorty silencer if it matters. I noticed after riding three times i have a black tar like substance leaking out the pipe. It not dripping out and falling but i see a think build up on the silencer. I only noticed it three time and all times have been after either slow trail riding or doing 2nd gear most of the time at the track. is this normal and if not what is it?

its a 2 stroke, its just burnt premix aka spoog (?)

You gots the spooge. Jetting, float height, mix ratio, packing, top end condition, etc. all play into this. :bonk:

i bet jetting

my kx gets a coat just thick enough for dost to stick after a weekend, i used to have a kx100 w/ less than 5 hours on the motor and it made alot of spooge.

Oh I thought spooge was the green oiley booger looking crap. I will check the top end first I guess since I know nothing about carbs.

Like I said this has only happened 3 times after slow speed riding. Could a worn out ring cause this?

The slow speed riding is probably what did it.

I'd say fiddle with your carb first. It's probably the problem, and jetting is easy to do.

Not trying to be a dick.... but if you dont know your way around a carb, then you probably dont need to be tearing into the top end looking for the problem. Even if you are jetted properly if you are poking around at low rpm you will get spooge simply from the lack of heat that the pipe produces when its below not making power.

i hear you chop but thats a stupid comment. I should not pay some guy either to look at it cause from what i read on here half the time they dont know either at the shops. But thanks for the advice, i assuemd it may have just been from slow speepd but just wanted to make sure. i try to run it hard and see what happens

I dont know my way around bikes bts cause im new to bike and have not dove into that yet. I have no natural mechanically ability at all but am learing. I already tore the top end down twice and can do it in less than 3 hrs now.

Ok so if you have torn a top end down twice, this will be easy for you.

You've drastically changed your exhaust flow (by putting on the SST and the shorty) so you probably need to change you jetting. I'm assuming you're running stock jetting.

Go to your dealer, and get a 48, 45, and 42 pilot. Also get a 178, 175, 172, 170, 168, and 165 main jet. This should only cost you $35-$45. If you don't want to lay out that kind of cash up front get at least the 48, 45, and 178, 172, and 170.

Changing out the main and pilot is easy, just loosen up the carb boots, then rotate the carb towards you. It won't go all the way but it will go far enough to access the 17mm drain bowl nut. You may need to tkae off the case saver to get the nut off, I do.

Once you do that the main is the 6mm hex jet, and the pilot is the one you can access with a flat blade screw driver. If your screwdriver is too big head to sears and get a small flat blade craftsman one. It should only cost a few bucks.

Only change one jet at a time, one size at a time, and see how the spooge level is impacted.

Once you get the procedure down you can do the job in less than 15 minutes. It takes me 20-25 but that includes time for testing the change to make sure it doesn't cause the bike to run too lean.

The SST pipe has a bad track record for trying to get the jetting dialed, there is a post by moto814 floating around that talks about that pipe

Found it


Originally Posted by moto814

The FMF SST pipe is an amazing pipe.

Why is it amazing? Because in just about every case, it will work WORSE than the stock pipe that came on the bike.

The SST uses a restrictive reverse cone and pressure bleed to intensify the return wave and lower the initial flow out the stinger section of the pipe. What that in turn does is increase piston crown temperatures and make jetting difficult at best.

Now increased piston crown temperatures can be compensated for to some extent with richer jetting. But, by doing that you are defeating the purpose of the pipe, and negating any power gain you may have gotten from the pipe in the first place. Why are increased piston crown temperatures bad? Well, in some cases they are not. You see most bikes are jetted horribly rich from the factory, and raising the piston crown temps in this case will "fool" the engine into thinking it is jetted leaner than it is. Which will in some cases improve power. But in most cases, it will just cause slightly better throttle response and an increase in the spooge out the back of the pipe.

After all that you may be thinking: "well this doesn't sound so bad, why are they saying this pipe is no good?" Good question. Here's the answer. Because of the restrictive nature of the pressure bleed from the pipe, it does not evacuate as efficiently as it needs to. This combined with the piston crown temperature increase yeilds jetting that is too rich. So now you have a pipe that "fools" the engine into thinking it is leaner than it really is, but also makes it much richer than it was previously. Here in lies the second problem. It makes jetting a nightmare. If you jet it by feel, you will be jetting richer, and compounding the too rich condition even more, making the bike run like a slug. If you jet it leaner, you will be increasing piston crown temperatures even more resulting in an engine siezure. Catch-22 anyone?


the sst sucks heres a dyno graph to prove it (on a 65)


i think spooge and pump fuel go together.

If it's only doing it during periods of prolonged slow riding, it's probally not a problem at all.

No big deal man, don't sweat it.

That little wetness on the outlet is normal during mild cruising.

When you are taking it easy you are on the pilot and lower section of the needle often.

Check the air screw for position. Back it out 1/2 turn at a time from 1.5 to 3 turns out and see how it runs.

As long as you don't get a throttle bog off closed throttle, it's ok.

This will increase the comb. temps. at 0-1/4 throttle if you're rich and help

clear that up if it only happens when riding easy.

No big deal either way, but the leaner A/S-pilot setting may clear it easily.


thanks everyone. I have a question. Is the cold weather going to effect this? Its been about 50 degrees out lately.

today I took it out and rode it for only 5 minutes. I pretty much just ripped it down the street and back and noticed its spitting oil and was still leaking some. I snapped the throttle and got a bog for a second and i noticed i had the same thig happen at the track the other day. I also notice some smoke coming out of the pipe after i shut it off and a funny smell. This happened onne before months age the first time i saw the spooge but it went away until last week.

At the track the other day when i snapped the throttle and bogged, but that was after babying the bike, second gear riding then getting on it. after i got on it it cleared it up. Today when it bogged i was in 3rd and hit it and got the bog, i let off and did it again and it did not bog

Oh and btw i got the bike with the sst and shorty already on it. What is a good pipe for the bike with the shorty combo for more bottom end since i am 195 pd rider?

First, it is normal for a 2T to bog the first couple of throttle applications after warming up or babying it

as the oil in the crankcase pooling is blown out and burned out.

Secondly, it takes more than a few minutes to get everything up to operating temperature

and most 2T's will smoke and blow some oil until they are at full operating temp.

It's also possible you have some oil pooling in the pipe from repeated cruises,

take the expansion chamber off and swish some raw gas in it, let it sit, swish it again and dump.

You might be surprised at the goop that comes out.

If you were rich, the cold will make it better as you'll now be leaner with denser air.

It may take a little longer to get up to operating temp, but if it's still

bogging after a couple of laps, you're too lean.

Pipe wise, the DEP is supposed to be the hot overall 144 pipe.

But something to consider is if you want more bottom-mid, you might even try a

stock pipe because it's set up for less flow. It should perform more toward the bottom-mid with the 144.

You'll also pick up some bottom mid from leaning the pilot-needle on the stocker.

Don't know what your settings are for the 144 but it's something to consider.

But it's a small bore 2T so you're going to have to rev it regardless :bonk:

Edited by carver

thanks again i will do this to the pipe and as soon as i get time, either tuesday or thrusday i will try to see what i am dealing with jet wise and update this thread and hopefully be able to ride the bike by then for harder, longer ride.


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