KTM Forums banner

1 - 17 of 17 Posts

·
Registered
Joined
·
50 Posts
Discussion Starter #1
we've had a 1996 300 exc for a few months. ran good. maybe got 4 tanks of fuel through it before today. Last ride we noticed oily pipe and figured we needed to do a muffler re-pack. I'm sure that's just a coincedence. I also think power was down too.

so today it started. ran for about 5 minutes. my son may have heard a knock. It lost power. He revved but it just did a slow death. Kickstarter may have rattled on pipe just before.

now it doesn't run and the kickstart is seized. coolant is quite low aswell. we had checked coolant before the ride, so it should only have went down in very short time.

where do I begin? could I be lucky and only need piston & cylinder? what happened to cause this?

also, if I need to find parts, what years are compatible to 1996? I was thinking of a full out swap. who is the cheapest KTM parts seller?

thnx
 

·
Administrator
Joined
·
14,818 Posts
The 1996 - 2000 300 two stroke KTM all use the 54630405144 cylinder, so
it's safe to assume that means pistons etc.

I've found Munnracing is the least expensive online KTM parts guys out there.

http://www.munnracing.com/
 

·
Registered
Joined
·
1,624 Posts
Ceasing is never good, usually you'll need to clean up the cylinder as well, so prepare to send it out for honing and coating.

In this case, my guess is, the rings went bad. The spooge coming out the tailpipe is also indicative of blow-by and a rich fueling situation. That means, it wasn't burning the mixture properly, a very common sign of bad rings. On the bigger bore bikes, when the rings go bad, more friction is generated from the piston slapping around in there and it tends to over-heat things very quickly. Usually within seconds, the motor could go catastrophic on you. The original owner could have installed the piston backwards as well... that would have caused a similar issue.

One word of advice on 2 strokes, always check the combustion chamber pressure using a standard PSI pressure gauge. Start the bike, warm it up and then check it. You should be upwards of 200psi on that motor and if your less then 120psi when warm, then the rings are toast. I never "assume" the rings are OK on a used 2 stroke, I always check them because 9 times out of 10, "hours" don't mean anything, your just trusting the original owner.

In terms of parts places, I've been ordering recently from ktmpartswarehouse.com and they've been super friendly and excellent pricing. You want a vertex aftermarket piston, so you can buy that anywhere you want, don't need to be a KTM dealer or something.

Good luck! Can't wait to see what the cylinder looks like! Make sure you make a note of which direction the piston was installed as well.
 

·
Registered
Joined
·
50 Posts
Discussion Starter #4
thanks for the info guys. Tye, you rock!!

I won't know anything until the jug gets removed. If kick start is seized, what is this going to be like to remove cylinder?

I'll try to post pics as requested, but this job won't get done for awhile; too many projects ahead of it. sucks for the summer though.
 

·
Registered
Joined
·
1,624 Posts
thanks for the info guys. Tye, you rock!!

I won't know anything until the jug gets removed. If kick start is seized, what is this going to be like to remove cylinder?

I'll try to post pics as requested, but this job won't get done for awhile; too many projects ahead of it. sucks for the summer though.
Pop the cylinder bolts off, yank on the cylinder until it comes loose. Then place the cylinder on top of the studs and work the kick start until the piston comes loose. ;)

Yea been there, done that, sucky situation. Its very unusual for KTM's to cease like that, its for sure a problem with the build in my eyes.
 

·
Registered
Joined
·
50 Posts
Discussion Starter #6
took it apart. the cylinder had an arrow pointing to exhaust port so i think it was good that way.

The top of the cylinder was broken and chipped away. very scuffed on the exhaust port side. Machinist said it was definitely heat related and immediately suspected straight gas, or incorrect mix. Sorry, I forgot to take pics and now it sits with machinist. I will get pics of piston when I get it back. Guessing he's tried to see if he can save cylinder.

Machinist also noted no oily slop on exhaust port, which he thought was indicative of heat/straight gas. The irridium spark plug looked black to me, not brown or light brown.

My son insists he used the mixed gas and I recall seeing him dump the gas from our 2-stroke container, the same gas he had already used a full tank from. I am skeptical that it was the gas. Where can i take a sample to confirm mix or ratio? I'd really like to know.

My cousin has rebuilt many KTMs. He says the waterpump seal can fail and suck down coolant quick, causing heat damage. But I should see the coolant in the tranny oil (which I'm not seeing). Coolant was almost empty when we discovered the seized piston. I dumped the tranny oil and it is clean, brown and oily, I see no milky appearance, and no evidence of coolant mixing in with it.

Mostly, I want to correct whatever cuased this. I will also dump the fuel in my car if that is my problem and just mix a new batch. But I still can't wrap my head around fuel being the issue. i used amsoil 50:1.
 

·
Registered
Joined
·
1,624 Posts
Yep, over heating will do that for sure.

How did the rings look? How ceased was the piston?

You might have just been low on coolant the whole time and it might have been bad coolant, which happens. If the water pump seal fails, the transmission oil would be mostly water, because the total amount of coolant exceeds that of the transmission oil.

The problem honestly might have just been a cracked cylinder. My 125 has a cracked cylinder as well, right where the powervalve goes. Cylinders can get cracked very easily if they over-heat multiple times. So perhaps this particular motor has had problems with it in the past, ya never know.

In regards to the "premix", honestly the first things to go bad will be the rod bearings, top and bottom. So the first thing I always do with a ceased motor is do once I get the piston loose, is check those bearings. If they're loose as a goose and discolored, then you know there wasn't enough oil in the mixture, pretty straight-forward.

One more thing to think about... maybe the air filter wasn't installed properly. I've seen that happen and dirt has entered the system, which has caused similar ceasing. However, you would see a little trail of sand/debris through the carb, reeds and scratches on the cylinder and piston.

Ohh well, man you just don't have any luck with these pumpkins! :(

I'm sorry your having such crazy problems, it sucks. These motors have been bullet proof in my view.
 

·
Registered
Joined
·
50 Posts
Discussion Starter #8
the head slid off quite easily. Not as bad as it felt from trying to force it with kick start. maybe one way moved better than the other?

the rings... not sure what to say. they were melted into the piston groove. I'll get pics of that.

I believe the previous owner ran low on coolant once, from a hose leak or something.

he did just change the air filter but not sure if he got a chance to dust the engine.
 

·
Registered
Joined
·
1,624 Posts
Some people don't understand the importance of an air filter, so maybe the filter is just old. But I'd really have a long-hard look at the filter and carb, see if you find any dirt build up anywhere.

The rings melted into the ring groove is simply over-heating. The question now is how and fix the problem before it happens again. I wonder if there was any water in the crank side of the case.
 

·
Registered
Joined
·
50 Posts
Discussion Starter #10
this was a brand new, pre-oiled filter, fresh out of the bag. I usually have 2-3 air filters per machine. We ride some dusty areas at times. So it's easier to have a fresh filter ready, and clean the other one later.

but i hear ya, I've cracked open some pretty disgusting airboxes and filters and wondered what the owner was thinking. it needs more attention than oil changes.
 

·
Registered
Joined
·
5 Posts
I seized the motor on my '99 300 EXC after a rebuild... Over looked a the Wrist pin circlip being fully seated and gouged a massive line in the cylinder and the side of the piston. I went to rockymountainatvmc.com and bought new piston and rings (set 2) and founded a company on the internet called USchrome.com out of Wisconsin.

You have to send the new piston and rings with the jug. 100$/per cylinder, they re-welded the jug, bored to factory specs, and sealed it with the Nikasil that KTM used, and went as far as gaping the rings for me.

I love USchrome.com if I ever had a seized motor that is right will go no questions asked.

They did such a great job I couldn't tell where the weld was, I almost thought they sent me a new jug. It was wonderful. After rebuilding the motor properly it runs like new.

Depending on how spanked the jug is I would suggest sending there.
 

·
Administrator
Joined
·
14,818 Posts
USchrome.com out of Wisconsin.

I love USchrome.com if I ever had a seized motor that is right will go no questions asked.
Great 411.

Can I sticky this thread (canucklehead) ?
 

·
Registered
Joined
·
1,624 Posts
Just an FYI: I don't think its worth putting money into a cracked cylinder. Usually when cylinder has gone through enough trauma to crack, its damaged in ways that you might not be able to see today. However, up the road, they usually have issues from my experience.

I've had pretty good luck finding used cylinders that are in good shape. ;)
 

·
Registered
Joined
·
50 Posts
Discussion Starter #14
I checked their site and it looks like it'd be closer to $250-300 to get a cylinder repaired and NiChromed.

yes, you can sticky this thread if you think it'd help someone.
 

·
Registered
Joined
·
15 Posts
Hey there . Another thing that can cause your symptoms are lean lean conditions. As in a air leak. Check your reed gaskets are not letting extra air into chamber. Have also heard of stator oil seal letting air in and leaning things out. Good luick
 

·
Registered
Joined
·
50 Posts
Discussion Starter #16
I ended up finding a complete motor from a '99. I put in new piston and had cylinder honed. ran good but was a bugger on cold start. Once running it was easy to re-start. anyways, sold it about 2 months ago as my son wasn't riding it anymore.
 

·
Registered
Joined
·
15 Posts
I have had similar issues

Hi there I have a 99 380 sx and have had a similar issue. After two pistons and two re nikasiled cylinders I found the gasket between the alloy reed spacer and engine casing was Letting in Air. I had first travelled nearly Six hours trail riding before it first seized. This was because it was tight slow riding and I never really punished the engine. As soon as I had some open space it seized.After a lot of searching I found that One part of gasket was brittle and had fallen away. This let more air in and leaned bike out. Hense high temp and seizure near exhaust port. Check all parts post Carb. Also check oil seal on stator side of crank is ok as this can leak air as well. Good luck
 
1 - 17 of 17 Posts
About this Discussion
16 Replies
5 Participants
MeanKilleen
KTM Forums
KTM Forums is the forum community for dirt bike motorcycle enthusiasts covering the KTM Duke, Sport minicycles, Off-road bikes, KTM 1190 RC8 and all KTM Motorcycles.
Full Forum Listing
Top