KDXRIDER.NET

OK, I'm a 2-stroke noob...

How much (if any) oil spooge coming from where the pipe fits into the cylinder is normal?
I see in the fiche that the stock pipe has 2 O-rings and a gasket, does the FMF use the same parts?

(I'm running 40:1)

None.

Take it off, clean the connection up well by removing any old silicone and oil and put it back together using some high temperature silicone.

Check out this post:

http://kdxrider.net/forums/viewtopic.ph ... &highlight

CC put a picture of the recommended Permatex RTV black stuff.

The FMF pipes (Gnarley desert and woods, or torque and rev) both use the two O-rings as does the stocker. Also there is a copper washer that goes in the exhaust port that typically falls out when someone removes the pipe. Make sure you have one. I goop the area between the O-rings with blue RTV. there should be 2 springs holding the pipe in.

Awesome, thanks guys! It was dripping a little before but I had to loosen up the hangers and move the FMF outboard a little to get my shock off and on, now it's leaking more.

Definitely fix it. TO answer your question NO spooge should be coming from the exhaust spigot. A leak there becomes an intake leak of sorts on a 2-cycle with an expansion chamber.

fuzzy wrote:Definitely fix it. TO answer your question NO spooge should be coming from the exhaust spigot. A leak there becomes an intake leak of sorts on a 2-cycle with an expansion chamber.

Got it. I actually DO know enough about 2-strokes to understand that

I should have time to seal it up tomorrow and let it cure until I ride Sunday.

GRRRR....

Took the exhaust off - no copper gasket. It's not stuck to the cylinder or stuck to the pipe, nor did it fall off when I pulled the chamber off.

I think I know the answer, but would it be OK to just put it together with the O-rings and RTV and skip the copper washer? I was gonna ride Sunday and I doubt any place in town will have one in stock. I'll check though.

If it was MY bike I'd put it together and ride Sunday.

I'd think it will be all right for a couple more hours.

+1 get it together asap to give the RTV more than enough time to cure

Thanks guys. I was able to get the copper gasket - from the KTM dealer of all places. They are a great shop, and work on other makes too. About the only local place that caters to off road riders. Also picked up a spring puller tool.
This was after calling 3 of the giant "mega-low mart" all brands shops and getting " not in stock but we can order it".

Re: ' but I had to loosen up the hangers and move the FMF..'

You moved it back? Any movement of the pipe may result in an exhaust leak.

Spring pullers are great! I'd like both a 'T' AND an 'O' handled one, 'cuz I've used one when I'd rather have had the other, and vicey-versa..but one of EITHER is certainly better'n none.

If your bike is leaking at the pipe/cylinder joint, the pipe is almost certainly tweaked. It doesn't take much. I've tweaked a few pipes more'n a few times.

Not real hard to make the fit better. Use a couple of long leverage tools (jack handles, socket extensions, etc), place one in each end of the pipe, and force it in the direction it needs to go.

What direction?

With your silencer/arrester off, place your pipe in the cylinder, holding it only with the springs, them 'centered', you can 'feel' when the end of the headpipe is 'square' in the cylinder. If no part of the pipe is binding/hitting on something, it will tend to find its way by itself.

Now, hold up the silencer/arrester to it's mounting holes, note where the two tips are, where the pipe tip needs to be to fit the S/A without force.

Tweak the pipe to make that happen.

If you had trouble fitting either pipe hanger on (you couldn't fit a socket on the bottom nut, or the top holder was unduly stressed to make it fit) you will likely find THAT orientation is much better now, too.

It doesn't take much force. The FmF pipes may be 'Gnarly' 18ga. metal..but doesn't amount to much when it comes to strength. Better'n the 19ga. they used to use..but certainly not bulletproof.


Don't miss what Fuzzy said about the curing of the RTV. It takes awhile. You can heat it to quicken the cure process...say a troublelight (incandescent, not LED) hanging underneat...NOT a torch!

Rush it and you'll simply blow the stuff out of any spot you're trying to seal.

Get it gooped NOW..it'll be ready to ride tomorrow.

I think the fit is pretty close. This FMF is pretty pristine, no dents or anything. I was able to get the hanger bolts and silencer mounts in without difficulty. I'm sure I did make the leak worse (it was just a tiny amount before I moved the pipe), but all I did was remove the silencer, loosen the chamber hangers and push it to the right just slightly so I could get the shock out/in. Also - there was no copper washer and no RTV on the pipe/cylinder junction when I removed it.
I got it put on at about 12:30 CDT and I will wait at least 30 hours or so before starting it.

IF the pipe fit is perfect, IF the cylinder is in good condition, IF the o-rings/gasket are in place, the exhaust won't leak.

A brandy-new pipe fresh off the shelf may have a rotten fit. FmF is (in)famous for its poor quality control.

I think the copper gasket is more to protect the cylinder from the headpipe end, not so much to seal exhaust gas. At least I don't see any such combination..held together with a couple of weenie springs...to seal an exhaust.

I see you have a torque/woods pipe. That makes the pipe hangers a lot easier to get to even if the pipe IS tweaked 'cuz the pipe itself is a good bit smaller than the rev/desert pipe.

Happy trails!

#$%^#*#^#!!!!

I fired it up Saturday after 30 hours of curing and all looked good. Rode it up and down the street a little.
Hauled it to the riding area Sunday am and it leaked right away.
I'm going to check/tweak the fit and replace the O-rings. Next time I'll use the Ultra Copper RTV ("Suggested Applications: Exhaust header flanges, slip fit exhaust pipes, and mufflers") which is supposed to be better for etreme high temps than the black ("Suggested Applications: Valve covers, oil pans, intake manifold end seals, timing covers, transmission pans").

Use whatever color you want..the black works just fine.

Don't know...but my first guess would be a cleaning problem..meaning it wasn't.

Second guess: Bead not big enough.

Third: Too much movement after pipe placement.


Clean it real good, use a nice fat 1/4" bead, after it's all bolted up, use your finger to cove the joint.

It'll work!

Good luck next time!

1. It was squeaky clean, used brake cleaner (on a rag on the case of the cylinder port). Even used my headlight LED flashlight and wore my glasses.

2. Could be. I was scared to goop it up too much and have RTV squeezing out everywhere.

3. Probably a factor. How the hell do you not move it around without 5 arms (I have 1 1/2 arms)?

tbirdsp wrote:1. It was squeaky clean, used brake cleaner (on a rag on the case of the cylinder port). Even used my headlight LED flashlight and wore my glasses.

2. Could be. I was scared to goop it up too much and have RTV squeezing out everywhere.

3. Probably a factor. How the hell do you not move it around without 5 arms (I have 1 1/2 arms)?

1. WoW. I can hear the squeeks from here!

2. There is quite a bit of room at that joint. Other bikes are much tighter, particularly those that are oppositely maled/femaled..the end of the headpipe being female, the cylinder male. Point is, it will take a good-sized bead to fill the gap on the KDX. If you DIDN'T see it squeezing out pretty good, there likely wasn't enough.

3. Test fit it dry. Know what bobs-n-weaves you'll need to do before the end of the pipe is gooped up. Have your spring tool and springs handy. I've held my pipe in place with my knee/knees while I attach the springs. Said before...but if there's a lot of waggling that is required AFTER the springs are clipped, the pipe is tweaked. Maybe a good time to enlist the help of the sweetheart. A brief lesson in taking firm hold with just the right amount of twist and push upon insertion and then squeezing it tight to the cylinder. She might get that pipe mounted just fine!

"....the help of the sweetheart. A brief lesson in taking firm hold with just the right amount of twist and push upon insertion and then squeezing it tight to the cylinder. She might get that pipe mounted just fine!"

A lesson within a lesson: I have no idea how you mind works but I like it!

Well...'ya see...that's your first mistake (you saying you have no idea I mean). Well...on this thread anyway.

You know very well how it works.

You see......the secret is...it don't work at all!!! And to any extent it ever perchance DOES work..I have no idea about how that happens neither!!

I think I have something above the exhaust outlet leaking too, maybe the "center valve cover"? Does that cover have pressurized exhaust behind it?