Need opinion on 94 kdx250 piston

[hlewis]

I know that you can't see it all that well. But does the piston look to be ok and the cylinder walls. I just bought the bike and I'm completely new to 2 strokes and I don't think it is running exactly the way it is supposed to. Also I'm getting a huge amount of spooge coming out. It has an FMF gnarly pipe on it and a stock (I think) Silencer with the guts completely removed from the end of it. I put in a 40 pilot jet and a 155 main. It has a UNI filter in it that is super glued together ( a new on is on it's was). Also I've ordered new Boyseen reeds and a R1367H needle. The FMF pipe does not seem to fit properly. Is there a way to tell if this is the right pipe. It has a funny bend in it. I took it off to make sure that the crush washer and o rings were in there. Which they were. But I'm still getting gunk spitting out around the exhaust port. I tried packing the silencer with pipe insulation and that seemed to kill the bike completely. It is running and it is a ton faster than my XR250 but like I said before I'm not sure if it is running correctly as this is the first KDX I've ever riden. Let me know what you guys think.

Here is a youtube viceo of the piston through the exhaust port. The streaks you see is oil. It does not appear to be messed up. Also there seems to be a lot of gunk built up in the exhaust port. Is this normal.

http://www.youtube.com/watch?v=3Brpf6sne98

Here is a picture of the bend. Does this look correct?


Here is the spooge



Here is the bike. Someone did a really sweet spray paint job!!

[kdxmaniac]

for one..........check the compression! we cant tell by looking at a video thru the exhaust port.

list of stuff to check.


1} check compression......if lower than 130, rebuild and forget the rest
of the list!
2} check air filter
3} put new plug in
4} check jetting
5} check crank seals

[rbates9]

Did you check your compression? (With a gauge)

Have you checked you jetting?

Some one else could tell you better but it looks like an after market silencer, repacking it should not make it run worse.

Looking at a pipe off the bike can't really tell you much. When it is on the bike is it going into the exhaust port squarely? Not cocked to one side or up or down.

[hlewis]

Jets were changed by me and the compression was around 145.

[hlewis]

How do you check the crank seals? Everything else had been checked.

[plotski]

145 is the MIn operating tolerance for a kdx250 compression should be between 145 and 220.....you need rings at the very least. Do you own a service manual for this bike yet? If not...get one! They are invaluble sources of information!

[hlewis]

Yeah I do have a manual and for some reason I thought that I read the minimum was 120 so I thought I would be ok for a while at 145 but I went back and looked and saw where it actually is 145-220. Thanks for your help. It's easy to miss things like that and why I thought I would ask on here. While I'm changing the rings do you think I should change out anything else or just wait and see what it looks like?

[scheckaet]

I'd get a new top end just for piece of mind since you don't know how long ago and how hard the bike was ridden.

[Julien D]

replace piston and rings, inspect cylinder plating for damage or wear and re-plate if needed.

[kdxmaniac]

there is a easy way of checking crank seals.....

1} take the stator/flywheel cover off, and see if there is oil in it.
2} if the bike was running.......you can start it up, take the trans vent
hose, stick it in a cup of water, rev the bike a few times.....
if it sucks water out of the cup....you have a bad clutch side.
if it blow bubbles.......................you have a bad stator side.


on the compression, was you holding the trottle wide open while kicking?
my buddies kx250 has 140lbs compression, and pulls him {325lbs! } fine.........but, it is was MY bike, i would tear it down and do a top end{ after cheaking crank seals}. the spooge you have in the pics kinda make you wonder whats going on. the reason i said below 130 is because, if the compression is that low, they are a dog to ride.

[hlewis]

Well I rode it today for a couple of hours and with the new jetting it has almost stopped the spooge. I'm running Kawasaki oil at 32:1. Everything seemed pretty good. Never fouled a plug and lugged it around quite a bit. Love the power that it has. Seems at least twice as powerful as my old xr250. I'll definitely look at putting a new piston and rings in as well as the reeds, new air filter, new needle jet, and possibly modify the slide. And also the 88 kx250 gasket.

[Julien D]

you can start it up, take the trans vent
hose, stick it in a cup of water, rev the bike a few times.....
if it sucks water out of the cup....you have a bad clutch side.
if it blow bubbles.......................you have a bad stator side.

How do you figure a bad LH crank seal will affect the pressure in the transmission in any way? You do realize that barring a leaking RIGHT HAND seal or some leak in the engine cases the crankcase is completely isolated from the transmisison, yes?

Blowing bubbles OR sucking water from the cup would BOTH indicate a leaking RH seal. This test method would NOT evidence a leaking LH main seal in any way.

Just saying. And besides all that, the BEST way to determine if your main seals are leaking is via a leakdown test.

[rbates9]

you can start it up, take the trans vent
hose, stick it in a cup of water, rev the bike a few times.....
if it sucks water out of the cup....you have a bad clutch side.
if it blow bubbles.......................you have a bad stator side.

How do you figure a bad LH crank seal will affect the pressure in the transmission in any way? You do realize that barring a leaking RIGHT HAND seal or some leak in the engine cases the crankcase is completely isolated from the transmisison, yes?

Blowing bubbles OR sucking water from the cup would BOTH indicate a leaking RH seal. This test method would NOT evidence a leaking LH main seal in any way.

Just saying. And besides all that, the BEST way to determine if your main seals are leaking is via a leakdown test.

+1/2....... If one crank seal was bad would you bother splitting the cases to just fix the one?

[kdxmaniac]

i didnt know the trans was isolated from the crankcase ......
no, i wouldnt bother splitting cases to change ONE crankseal{ thats why i run ktm,s......you dont have to split the cases to change crank seals! and ktms are MUCH easyer to work on{when the tear up}

i dont know how the cup method works, but it does. i have a leakdown tester, but not everyone has one, and the cup method is just a easy way to tell.

[plotski]

Good stuff...all of ya'all! I am with the group that says throw a top end at it...I would....if you are going to open it up anyway...you might as well. Just make sure you open it first....mic the piston and cylinder..before you order your top end set!! you never know what someone else may have already done as far as a B...C...or even D piston and rings...not to mention possible overbores!! Save yourself some headaches and look before you leap!! Just a suggestion.

And on the crank seal thing...my vote is..one bad they all bad! And if I am splitting cases I am most likely gonna throw bearings in for good measure...just sayin! LOL

[hlewis]

Great information. I was on the verge of ordering a new piston and started thinking that I should definitely check before I order because you are right you never know what someone else may have done.

Yes I did hold the throttle open while kicking it on the compression test.

[Julien D]

Very true. For that matter, I'd never want to replace my main seals without replacing bearings. In my experience leaking main seals are caused by worn main bearings 99% of the time. If the main seals are leaking, it's time to split and rebuild the bottom end.

[hlewis]

So does anyone know where I can find an R1367H needle? My local Kawasaki dealer called today and said that it was no longer made.

[exbee]

So does anyone know where I can find an R1367H needle? My local Kawasaki dealer called today and said that it was no longer made.

They're still made, I bought one last winter, pretty sure I got it from ronayers.com

[fuzzy]

I love my $25 harbor freight leak down tester.