How To Fix a 2 Stroke Motorcycle Exhaust Leak

– Hey guys this is Justin
with Rocky Mountain ATV MC, and I’m gonna show you how
to keep your two stroke exhaust from leaking and making a mess. All right if you ride a two stroke, you’ve probably noticed
some black nasty oil leak out of your pipe,
either where the pipe meets the cylinder or where
the silencer meets the pipe. If you’ve never experienced
that, you probably will at some point. Now that oil is simply
just unburned pre mix, it’s totally normal, if
your bike’s running rich, you’re gonna see a lot more of it. But it’s totally normal and most often you’re gonna see it where the pipe meets the cylinder. And it just makes a
nasty mess when it starts to leak. The reason why it starts
to leak is because you have O rings that
sit between the cylinder and the pipe, and as the engine vibrates the pipe vibrates, those O rings wear out, and the oil starts to leak. All right, so before I
change out the O rings on this bike, I wanna give you a few tips. Now, whether you’re
changing out the O rings on an old pipe or you’re
putting on a brand new pipe, these tips are gonna help
you get the most life out of your new O rings. Now the first tip is to
check your pipe mounts. This bike has two mounts. One up here, one down below. And it’s really important to check those because they do wear out over time. A lot of times the pipe
gets a little tweaked and you can actually break those mounts. And if those mounts are
wore out, missing or broken, the pipe’s going to move a lot more, vibrate a lot more, and those O rings are not going to last very long. So always make sure your pipe
mounts are in good shape. All right, my second tip, just
like with the pipe mounts, check your pipe springs, if
your pipe springs are wore out, stretched out, broken,
they’re not going to hold the pipe to the cylinder very well, and again those O rings aren’t
going to last very long. All right and my third tip, may seem a little bit hokey to some people but it works really well and
it makes a huge difference, and that’s the use of silicone. So I’ll actually use some
high temperature silicone, put it around the O rings, and that silicone not only helps seal the pipe on a little bit better but it
also adds a layer of protection against vibration that wear out O rings. So it makes a big difference and I also use a little bit of silicone
between the silencer and the pipe to prevent any leakage there. Now to show you how to do that I’m gonna be installing a
raven O ring and spring kit. I really like this kit
because the O rings are made of viton rubber,
which is a really durable heat resistant rubber so
these work really well. And the raven springs
are really heavy duty, and they feature a swivel head on one end which makes them really
easy to align and install. So let me show you how to get these on. All right, the first thing
I’m gonna do is pull off the side plate so I have
access to the silencer. Then I can go ahead and
remove the silencer. Now I can go ahead and
remove the pipe mounts. Now I’m ready to remove the springs. I’m gonna be using a tusks spring puller. These things are inexpensive and they make pulling springs a lot easier. If you’re gonna try to
do with a screwdriver or pliers, you’re gonna end
up with bloody knuckles. All right, with springs
removed I can pull this pipe. Now it’s always a good idea
to clean the cylinder before you put the pipe on, especially
if your pipe was leaking. So I’m just gonna spray a
little contact cleaner in there. And kinda wipe it off with the rag. All right so I’m gonna be
putting a different pipe on this bike, so I’m gonna
make sure it’s real clean. If you’re putting your old pipe on, you wanna make sure to
pull those old O rings out and then we can ahead and
put the new O rings in. So I’m just gonna slide
them into the groove here, so once those are seated
in their grooves like so, I’m gonna go ahead and
put a little silicone on. Now you don’t wanna go
crazy with the silicone, obviously you don’t
want it obstructing the pipe, but I’m just gonna
get a little on my fingers, rub it around the O
rings, and the nice thing about this permatex, high temp silicone is it comes off really easy. So when you pull your pipe off again, you gotta clean everything up, but the silicone comes off fairly easy. With a little bit of silicone in there I’m ready to put the pipe
back on the cylinder. Once it’s in place, I
can attach the mounts. Now one thing I wanna
point out is I’m gonna loosely attach these mounts at first. Once I get everything
in place and the springs in place, silencer in place, I can tighten everything up. Now I can go ahead and pull
these springs into place. Okay, with the mount and springs in place we can put the silencer on. Most two strokes are
gonna have a rubber seal that seal the silencer and pipe together. But they still leak, so I
like to use a little bit of silicone. So I’m going to slide the rubber boot back out of the way and then I’m going to apply silicone to the back of the pipe and then I can slide the
silencer on to the pipe and then I’ll pull the rubber boot back over the joint. With all the bolts in place loosely, I’m going to tighten all the mounts up, starting from the front
and work my way back. And finally I’ll put
the sideplate back on. All right guys, so there you have it, hopefully some of these tips help you out. And help prevent making a black oily mess on your two stroke. Be sure and subscribe
to our youtube channel for more how to videos
and product spotlights and check out our website, for all your parts and accessory needs, including the O rings,
springs and tools I used in this video. Thanks for watching.


  • can you please do an updated tire change video while being mindful of not ruining the rim finish

  • Im really early 2nd

  • Where the silencer and pipe meet, what is the part number for the rubber boot?
    02 YZ250

  • You guys should do a video on how to fix the fmf "slip fit" header to muffler leak , paid over $800 for a exhaust that is designed to leak ? I don't think so

  • I've been using copper seal on my 2 strokes for a long time and it works great. Awesome video!

  • good idea with the silicone will be trying this next time as my 300 tends to destroy orings fairly often

  • Wow perfect timing for me I've been battling a leaky head pipe for a few weeks now. I'll definitely use the high temp silicone! Thanks for the video guys!

  • I can't praise the spring puller enough. That thing has saved me hours of pliar struggle over the past year.

  • Do you guys sell a power valve rebuild kit for my 2000 yz125

  • Maaan I thought there was something wrong with my 2 stroke since it was leaking that unburned premix I thought it was gear oil or something.

  • can this prevent the bike from running properly? I have an old Yamaha I'm fixing up and it leaks where the head meets the cylinder

  • i had a question with my 2 stroke like i have a lot of that oil in my pipe and i just smoke and smoke not from running rich but from all that oil during out i think is there a way for me to get that stuff out?? plz let me know

  • If you can see smoke coming out where the pipe meets the cylinder, are you losing any note-worthy performance?

  • This man surely likes Silicone.

  • Dude, why you are not wearing safety glasses? If you're a professional mechanic that doesn't mean you don't need them 🙂

  • Hey awesome video!! My bike doesn't have any orings between the cylinder and exhaust. I have a KTM 360 97 model, is there anything further I could do besides the springs and hi-temp silicone? Thank you.

  • great tips!! will try that on my cr250r!

  • Where can I get a rubber boot my bike doesn’t have one

  • where do i get new pipe mounts?

  • Hey i see your using silicone, i have a yamaha dt 50 and im gonna do the same thing with my exhaust soon but i wanted to ask is it okay to use heat resistant glue instead of the silicone? A friend of mine who is an old motocross racer used somekinda heat glue on my bike when he helped me Change my exhaust wool

  • Thanks for having the parts I need for my cr125 build #rockymountianatv #teamhonda

  • Josh Turnquist

    Hey do you know where I can get a rubber boot for my 2004 cr125 2 stroke

  • LOL, @3:25 that radiator overflow hose is scorched meat from laying right on the header . Dude, you have got to ziptie that hose to the frame with the same black strap you use for the stator wiring.

  • Don't forget the pipe bearings!

  • I just put a new fmf gnarly pipe and fmf turbine core 2.1 on my 2018 yz250x a few days ago and on today’s ride I now have the splooge problem once again (like I did on my last fmf equipped Yz) .And in addition to that , the silencer is leaking oil out of the rivets! Never had an issue with the stock pipes, but I’ll definitely try out the silicone trick. Any ideas on fixing the rivet leaks would be appreciated. Btw , my bike runs excellent and jetting is pretty spot on. Thanks in advance for your response.

    Btw, the spring puller looks epic!

  • Can a leaky exhaust at the cylinder decrease power and make it difficult to stay in the powerband?

  • the oil on my bike leaks from the exhaust itself. do you think its the same problem?

  • Mulligan Repairs

    Why does my expantion chamber come loose it of motor every time I put it back in?

  • Can you ride your dirt bike temporarily until you get it fixed? Or no? Bad idea?

  • When i pull my headerpipe off, and I’m cleaning it, and I take the O rings out, Will I need new o rings? If so what are they called? Just headpipe o rings?

  • Michael Harris


  • Michael Kastner

    Always wear safety glasses- you need to follow your own advice. Do as i say not as i do

  • Ive changes the o rings and the springs ?? Still leaking

  • I’m having the same problem with my kx125 but every time I start my bike it runs for 3 minutes then shuts off. Can anyone please help me figure out what’s wrong

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