The KTM300 Thread

[sanjoh]

Originally Posted by Just John

Yikes !
What main jet ?
If you lean the bike over 45 degrees,does fuel come out the over flows ?

Exactly!

Not sure on the main jet.

No overflow, when leaning it over.

Starts first kick without choke, when hot or cold, thinking the low end/pilot is stinky rich.

[RideFreak]

Originally Posted by HellSickle

Thanks guys. My local KTM shop says the SX head is what Slavens used to put in his mule mod. Funny that the head cost is less than a new piston. As long as I'm doing the top end, I'll put on the SX head.

Any tips on jetting? I've been riding my 300 like a diesel. Great low end torque, then it starts to stutter at contant low throttle a few thousand RPM above idle. This causes me to short shift for cleaner running, and I'm only using a very narrow portion of the RPM range and shifting a lot to stay in that range. It rips up high, but I seldom have need for that kind of power on single track. I think I need a smaller pilot jet.

In moab I had a 165, 38pilot, it's got the JD kit and I'm not sure on the needle color but it's what they recommend for 5K' (I run that 1 clip leaner). Ran very clean through the dieseling on 5MOH, ran clean in the few sections where I could get on it. There was still a little spooge running down from the silencer though. I find that setup good to about 10K' and then I can feel it needs a little leaner pilot and probably needle too but it's not so bad I'd change it unless I was spending some days up where you live. For 5MOH I ran the green spring with the dolly 2 turns in (late hit), In the desert I run a red spring flush, exact opposite, wide powerband that comes in early and smooth, nice for the sand.

With the SXS head I find I can run the back a tooth smaller (13/49) the extra grunt works nicely with a little more gear.

Sometimes you'll hear "pipe knock" on decel with a higher com head caused by too lean cond (not enough fuel when the throttle is suddenly shut down), if you run in the a/s 1/2 turn that will usally solve it.

[CO/WV]

I am planning on getting a 2012 300.... I live at 9600ft and I am not a mechanic.

1) For weekends in Moab will it run fine without rejetting 9600ft to 4600ft I assume I would richen the fuel oil mix a bit

2) of course rejetting is better....... how long would it take your not expert mechanic brother to rejet the bike?

[DougZ73]

The KTM..back in its natural habitat...sadly, not for that long.


I just got back from a short test ride. Good news..I made it back. Bad news..I broke the bike. It died coming back on road, two streets away from house. While rolling at speed ...I jumped it going to start it again. It wanted to stall on low end...I did not let it.

Got it in driveway and thought it was just lack of fuel. Put in on reserves and tried kicking it. Kicked waaay to easy. Hummm compression issue.

Praying it was a loose spark plug..I pulled the seat and tank to check. Plug was fine. I suspect with the difficulty I had putting top end back together..something was wrong with rings...and they probably broke on ride home. With kid coming ..this shall sit till spring. Ugh. KTM's

[HellSickle]

Originally Posted by DougZ73

The KTM..back in its natural habitat...sadly, not for that long.


I just got back from a short test ride. Good news..I made it back. Bad news..I broke the bike. It died coming back on road, two streets away from house. While rolling at speed ...I jumped it going to start it again. It wanted to stall on low end...I did not let it.

Got it in driveway and thought it was just lack of fuel. Put in on reserves and tried kicking it. Kicked waaay to easy. Hummm compression issue.

Praying it was a loose spark plug..I pulled the seat and tank to check. Plug was fine. I suspect with the difficulty I had putting top end back together..something was wrong with rings...and they probably broke on ride home. With kid coming ..this shall sit till spring. Ugh. KTM's

"Ugh. KTM's" ?!?!?! Sorry, it sounds like a possible issue with your mechanic. If you had issues getting the rings in place, you should have dashed out to the tool store & picked up a ring compressor.

I don't mean to be harsh. I've made my share of expensive mistakes. Sometimes the purpose in our life is to serve as a warning to others.

Sometimes I'll tell the story of the CB750F build and the "Llama Incident"

[DougZ73]

Originally Posted by HellSickle

"Ugh. KTM's" ?!?!?! Sorry, it sounds like a possible issue with your mechanic. If you had issues getting the rings in place, you should have dashed out to the tool store & picked up a ring compressor.

I don't mean to be harsh. I've made my share of expensive mistakes. Sometimes the purpose in our life is to serve as a warning to others.

Sometimes I'll tell the story of the CB750F build and the "Llama Incident"

Do they have piston ring compressors for two stroke motorcycle motors?? I have used rings compressors when rebuilding four strokes, but never heard of one for a two stroke. The KTM manual I have never mentioned one either.

This is the third two stroke top end I have done, and never used one. Not sure how you would get it out?? Usual method is to hold rings with hand, and then lower cylinder down onto piston, while squeezing the rings.

Its not like a four stroke, where the piston and connecting rod goes in from top of head, and gets bolted around crank journal. In two stroke, connecting rod does not come out unless you take whole motor apart.

Maybe I am missing something.

[wayno]

Originally Posted by DougZ73

Do they have piston ring compressors for two stroke motorcycle motors?? I have used rings compressors when rebuilding four strokes, but never heard of one for a two stroke. The KTM manual I have never mentioned one either.

This is the third two stroke top end I have done, and never used one. Not sure how you would get it out?? Usual method is to hold rings with hand, and then lower cylinder down onto piston, while squeezing the rings.

Its not like a four stroke, where the piston and connecting rod goes in from top of head, and gets bolted around crank journal. In two stroke, connecting rod does not come out unless you take whole motor apart.

Maybe I am missing something.

Ive taken 2 stroke apart for craxcked head bdfor to put new one on and I had no ring compressor then but was back in 80's

[HellSickle]

Originally Posted by DougZ73

Do they have piston ring compressors for two stroke motorcycle motors?? I have used rings compressors when rebuilding four strokes, but never heard of one for a two stroke. The KTM manual I have never mentioned one either.

This is the third two stroke top end I have done, and never used one. Not sure how you would get it out?? Usual method is to hold rings with hand, and then lower cylinder down onto piston, while squeezing the rings.

Its not like a four stroke, where the piston and connecting rod goes in from top of head, and gets bolted around crank journal. In two stroke, connecting rod does not come out unless you take whole motor apart.

Maybe I am missing something.

2 or 4 stroke, when doing top ends I generally just pull the cylinder. Ring compressors don't care if it's a 2 or 4 stroke.

With that said, I've never used a ring compressor. I've always well oiled things and jiggered the rings thru the taper at the bottom of the cylinder. Because of the requirement to align the rings with the pins on the piston, a 2 stroke is usually more difficult. I'll probably be visiting Harbor Freight to get a ring compressor for my upcoming 300 top end job.

The most difficult top end I ever did was a V4 honda. The cylinder banks were cast into the upper case. You had to align all the pistons as you brought the upper case & cylinder down. After that project, I vowed never to own a bike with more than 2 cylinders.

Currently shopping for a KTM 950/990.....

[DougZ73]

Originally Posted by HellSickle

2 or 4 stroke, when doing top ends I generally just pull the cylinder. Ring compressors don't care if it's a 2 or 4 stroke.

With that said, I've never used a ring compressor. I've always well oiled things and jiggered the rings thru the taper at the bottom of the cylinder. Because of the requirement to align the rings with the pins on the piston, a 2 stroke is usually more difficult. I'll probably be visiting Harbor Freight to get a ring compressor for my upcoming 300 top end job.

The most difficult top end I ever did was a V4 honda. The cylinder banks were cast into the upper case. You had to align all the pistons as you brought the upper case & cylinder down. After that project, I vowed never to own a bike with more than 2 cylinders.

Currently shopping for a KTM 950/990.....

Take a video of how you do the 300 top end, with a ring compressor. I'd am really interested in how you'd go about it.

The only way I could see you using a ring compressor, on of these motors, is to use it, to insert the piston, down into the cylinder, from the topside, push it down enough to expose just the wrist pin hole, and then try to put the combo down over the connecting rod, and insert the wrist pin and clip(s), that way, through the connecting rod. Even if that is even possible with motor in bike, I am not sure. Somehow, I doubt it. I know I barely had room to get cylinder on from top, while trying to compress the rings with my hand, and slide down from above, the normal way I know it and have done twice already.

[HellSickle]

Originally Posted by DougZ73

Take a video of how you do the 300 top end, with a ring compressor. I'd am really interested in how you'd go about it.

The only way I could see you using a ring compressor, on of these motors, is to use it, to insert the piston, down into the cylinder, from the topside, push it down enough to expose just the wrist pin hole, and then try to put the combo down over the connecting rod, and insert the wrist pin and clip(s), that way, through the connecting rod. Even if that is even possible with motor in bike, I am not sure. Somehow, I doubt it. I know I barely had room to get cylinder on from top, while trying to compress the rings with my hand, and slide down from above, the normal way I know it and have done twice already.

Actually, I have done a variation of this on 2S before. I've installed the piston into the bottom of the cylinder, then mounted the piston onto the connecting rod. This allows you to carefully put the piston into the cylinder while it's sitting on the bench. It does make it awkward trying to get the pin clip into place. Having a helper to hold the cylinder in place is useful.

I think I see the issue with the ring compressor. There's not enough space below the cylinder to get it in and out of there. What's really needed is a half-height ring compressor. I'm wondering if just a hose clamp couldn't be used on the 2S?

[DougZ73]

Originally Posted by HellSickle

Actually, I have done a variation of this on 2S before. I've installed the piston into the bottom of the cylinder, then mounted the piston onto the connecting rod. This allows you to carefully put the piston into the cylinder while it's sitting on the bench. It does make it awkward trying to get the pin clip into place. Having a helper to hold the cylinder in place is useful.

I think I see the issue with the ring compressor. There's not enough space below the cylinder to get it in and out of there. What's really needed is a half-height ring compressor. I'm wondering if just a hose clamp couldn't be used on the 2S?

Ah ha..you now see the issue...which is why typical SOP is just to use your hand. And that method has worked or me a couple times before.

At the end of the day, it probably was my fault...as I had to take the cylinder off three times to change the gaskets and get the proper Z setting. What a PIA. Once I got the proper gasket on there, the rings/piston gave me a hell of a time going back into the cylinder. Although it did seem OK, once I finally got it.

This time, I'll be pulling the motor for sure. The nice thing about these two strokes..they make it pretty simple to pull motor.

[Just John]

Originally Posted by DougZ73

Ah ha..you now see the issue...which is why typical SOP is just to use your hand. And that method has worked or me a couple times before.

At the end of the day, it probably was my fault...as I had to take the cylinder off three times to change the gaskets and get the proper Z setting. What a PIA. Once I got the proper gasket on there, the rings/piston gave me a hell of a time going back into the cylinder. Although it did seem OK, once I finally got it.

This time, I'll be pulling the motor for sure. The nice thing about these two strokes..they make it pretty simple to pull motor.

What do you suspect went wrong ?
I don't see anything gained by pulling the motor out.

[DougZ73]

Originally Posted by Just John

What do you suspect went wrong ?
I don't see anything gained by pulling the motor out.

I suspect the rings were not seated correctly, when I finally got the cylinder on. Potentially not being lined up on the locating pin like they should have been..at least one anyway. Probably rotated, caught one of the port edges, and broke off. Potentially gauging the cylinder wall. The compression went somewhere, so best case, its just the broken ring, worst case, messed up cylinder wall.

Pulling the motor will make it easier to get cylinder on correctly, for me anyway. When I did the top end on a YZ125, I did it on bike and had no issues. This motor, I have done out of frame, and had no issue. This last time, motor was in frame, and I had room issues. Not sure why...but I did.

Also, if I have to send cylinder out to get redone, I'd rather have motor in house, and not out in weather*temp) changes in shed.

[DougZ73]

On a side note, I did watch a bunch of vids this morning with the KTM 300 EXC in them, and my bike does sound normal.....you know, when running.

[RideFreak]

Originally Posted by DougZ73

On a side note, I did watch a bunch of vids this morning with the KTM 300 EXC in them, and my bike does sound normal.....you know, when running.

I do the z setting with the rings off, figure out the gaskets and install the rings just prior to final reassembly. I've seen a ring compressor that would work on the 300 (about 1/2" top to bottom) but truthfully once you figure the cyl install out, proper installation takes a couple seconds. Now the piston pin clips are a different story, the stock KTM units are a huge PITA. Why did they go away from the old style that worked with a pair of needle nose plyers.

Yeah I know, the old ones are still available.

My hardest cyl install was a VW waterboxer, seperate cyl liners that fit down into a non removable waterjacket that pretty much blocks all access for a mortal like me.