need tuning/troubleshooting help 97' 300 EXC


12 replies to this topic
  • jagxtype

Posted July 21, 2009 - 02:51 PM

#1

KTM 300 EXC 1997
42 idle jet
172 Main Jet
R38C Needle
Stock Pipe w/ fmf turbine core silencer
Other mods unknown
enough compression i can barely kick it. (assuming the top end is good)
fairly clean power valve

The bike has a lot of trouble starting. Once started it has great low end snap, but anything other than that it is sluggish and smokes ALOT and never really revs all the way up. Pulled the spark plug and it was black so i started with cleaning the carburator and replacing the spark plug. Rode it around and no difference and pulled the new plpug and it was already black within minutes. Tried moving the needle down and still no difference. Set the float lower...no difference once again.

anyone have any idea how to solve this problem? im desperate to get it fixed!

  • Mike in Fresno

Posted July 22, 2009 - 08:01 AM

#2

could be many things, bad ignition, stuck PV, jetting way off, seal leaking

also post this in the 2st section

  • D1k

Posted July 22, 2009 - 09:12 AM

#3

KTM 300 EXC 1997
42 idle jet
172 Main Jet
R38C Needle
Stock Pipe w/ fmf turbine core silencer
Other mods unknown
enough compression i can barely kick it. (assuming the top end is good)
fairly clean power valve

The bike has a lot of trouble starting. Once started it has great low end snap, but anything other than that it is sluggish and smokes ALOT and never really revs all the way up. Pulled the spark plug and it was black so i started with cleaning the carburator and replacing the spark plug. Rode it around and no difference and pulled the new plpug and it was already black within minutes. Tried moving the needle down and still no difference. Set the float lower...no difference once again.

anyone have any idea how to solve this problem? im desperate to get it fixed!


What mixture are you using for the gas/oil ?

How does the bike idle ? Can you let it idle for 1 minute straight without touching the throttle?

If it won't idle by itself, might be bottom end seals need to be replaced. Also, how are the rubber components in the carb. That year carb might have to be rebuilt completely.

  • jagxtype

Posted July 23, 2009 - 10:33 AM

#4

What mixture are you using for the gas/oil ?

How does the bike idle ? Can you let it idle for 1 minute straight without touching the throttle?

If it won't idle by itself, might be bottom end seals need to be replaced. Also, how are the rubber components in the carb. That year carb might have to be rebuilt completely.


45:1 amsoil dominator with 93 octane. Well I can get it to idle for one minute... Just not respond In the top end. Just lots of smoke and sputtering.

  • D1k

Posted July 23, 2009 - 11:21 AM

#5

45:1 amsoil dominator with 93 octane. Well I can get it to idle for one minute... Just not respond In the top end. Just lots of smoke and sputtering.


Blocked main jet or electrical problems me thinks. You may have to get values for the cdi and stator/pickup and test them out.

  • jagxtype

Posted July 26, 2009 - 02:14 PM

#6

Well despite having good compression I took the jug off and the whole top end of the bike was destroyed. The piston had a crack all around th front. It is a wonder the bike was running at all and that the piston didn't shatter. The piston and the jug have deep scoring.Could be the problem.

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  • jackrichmond100

Posted August 06, 2009 - 03:53 PM

#7

Pilot 42 is fine from 0 to 4000 elevation.
Stock needle - clip in 2 slot from the top.
The main jet is ungodly rich! That is why it won't even rev. How do I know this? I bought a brand new 1997 (still have it) and - even though I felt it to be insane - I had to lean the main jet ALL the way down to 160 for 0 elevation (and 158 main for 4000 ft. and clip in top slot of stock needle)

As far as I am concerned, it is unforgivable for KTM to jet their bikes for 10,000 feet below sea level!!!!!!!!!!

Here is what I suggest - since 160 (I know!) sounds outlandish. Buy a 165, and 162 and a 160. Install the safe 165 and you will see that the bike will at least now rev out - but only after blubbering heavily through the mid range revs. Next, to the 162, there will be much less blubbering. You should then have a big smile on your face....

Go to 160 and live with that baby (at sea level).

I have lived with and raced mine for 12 years now and it runs perfectly.

Just don't get crazy and run a 155 at sea level on a flat out run. You will lock it up (I know firsthand). At sea level, 158 is too close to being too lean.
Just don't do it....

Happy revving!!!!!!!!!!!
Jack


KTM 300 EXC 1997
42 idle jet
172 Main Jet
R38C Needle
Stock Pipe w/ fmf turbine core silencer
Other mods unknown
enough compression i can barely kick it. (assuming the top end is good)
fairly clean power valve

The bike has a lot of trouble starting. Once started it has great low end snap, but anything other than that it is sluggish and smokes ALOT and never really revs all the way up. Pulled the spark plug and it was black so i started with cleaning the carburator and replacing the spark plug. Rode it around and no difference and pulled the new plpug and it was already black within minutes. Tried moving the needle down and still no difference. Set the float lower...no difference once again.

anyone have any idea how to solve this problem? im desperate to get it fixed!



  • jackrichmond100

Posted August 06, 2009 - 06:34 PM

#8

I think I forgot something. I am pretty sure 12 years ago I also changed out the needle for the next leanest (the leanest of all). So if you are still using the stock needle you will want to put the clip in the top slot for sea level. You will know because the 2nd slot will cause the engine to "diesel" (run rich) as you accelerate with 1/3 throttle (mark the throttle grip with chalk or something like that.)

The next leaner needle which I have installed in my bike is simply "one slot" leaner than the stock needle. That is to say, if you put the clip in the top slot of the stock needle - and ride at 4000 feet elevation - your engine will diesel - but don't worry, it shoud not foul the plug. It takes a LOT to foul the plug - like the 170 or 172 or 175 main jet. Throw those evil things away when you are done.


KTM 300 EXC 1997
42 idle jet
172 Main Jet
R38C Needle
Stock Pipe w/ fmf turbine core silencer
Other mods unknown
enough compression i can barely kick it. (assuming the top end is good)
fairly clean power valve

The bike has a lot of trouble starting. Once started it has great low end snap, but anything other than that it is sluggish and smokes ALOT and never really revs all the way up. Pulled the spark plug and it was black so i started with cleaning the carburator and replacing the spark plug. Rode it around and no difference and pulled the new plpug and it was already black within minutes. Tried moving the needle down and still no difference. Set the float lower...no difference once again.

anyone have any idea how to solve this problem? im desperate to get it fixed!



  • jackrichmond100

Posted August 06, 2009 - 06:45 PM

#9

P.S. I don't recognize the R38C needle. I think my came with a N85ED or something like that. Anyway, play around with the clip settings at 1/3 throttle.

P.P.S. don't be afraid of hurting the engine while trying to figure out the jetting - just don't run it for 20 seconds flat out wide open if you really believe it might be too lean.

P.P.P.S. Also as time goes by, your silencer can pack up with two stroke oil and stifle the high rpms. My did. I took it to the shop, mystified. They were mystified too and they finally took the silencer off and it suddenly once again ran beautifully. Loud by beautiful. This happened to me after running the same silencer for 8 years. I put on a new FMF turbine core. LOL.

QUOTE=jagxtype;8382463]KTM 300 EXC 1997
42 idle jet
172 Main Jet
R38C Needle
Stock Pipe w/ fmf turbine core silencer
Other mods unknown
enough compression i can barely kick it. (assuming the top end is good)
fairly clean power valve

The bike has a lot of trouble starting. Once started it has great low end snap, but anything other than that it is sluggish and smokes ALOT and never really revs all the way up. Pulled the spark plug and it was black so i started with cleaning the carburator and replacing the spark plug. Rode it around and no difference and pulled the new plpug and it was already black within minutes. Tried moving the needle down and still no difference. Set the float lower...no difference once again.

anyone have any idea how to solve this problem? im desperate to get it fixed![/QUOTE]

  • jackrichmond100

Posted August 10, 2009 - 10:46 PM

#10

If the exhaust (front) side of the piston is messed up only, make sure the power valve is not touching the piston/rings as the piston goes up and down. Slowing move the piston up and down by the ignition nut and listen. If you hear it touching, adjust it on the "shifter side" of the power valve. Improvise using flat feeler gauge stacked on each other to the external, moving power valve mechanism. Or take it to the shop and let the pros do it.


Well despite having good compression I took the jug off and the whole top end of the bike was destroyed. The piston had a crack all around th front. It is a wonder the bike was running at all and that the piston didn't shatter. The piston and the jug have deep scoring.Could be the problem.



  • jagxtype

Posted August 11, 2009 - 09:13 PM

#11

will def check that out. i think the wear was on the sides. someone decided to drill oil holes on each side of the piston right outside of the powervalve contact area and that is where all the damage was. No oil holes this time around... obviously they do no good.

  • jackrichmond100

Posted August 12, 2009 - 12:02 PM

#12

Holes definitely not needed.
Sea level jetting:
Main 160
Needle - clip in top slot (or 2nd down)
Pilot 42

  • ktmfred300

Posted August 15, 2009 - 09:17 AM

#13

In my 96 I ran a R1468NS Honda needle part # 16201-KZ4-000 which is much leaner and a straight taper a 50 pilot and a 180 main due to the leaner needle. Make sure the power valve is set right and the exhaust is clean and repaced. My bike ran perfect for the 4 years that I had it.




 
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