The KTM300 Thread

Discussion in 'Thumpers' started by GasGas300, Jan 11, 2010.

  1. RideFreak

    RideFreak Torque Junky

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    Here's a page one bump.

    Everything here's been in lockdown for a couple weeks, it was nice to get out and sling a little dirt.

  2. cal08

    cal08 Long timer

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    Cheers. Made my morning. All the best to you.
  3. solo rider

    solo rider Adventurer

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    Great footage with killer music!
    Loved it RideFreak.
    RideFreak likes this.
  4. Gordy

    Gordy SUPPORTER

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  5. sacto929

    sacto929 Been here awhile Supporter

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  6. SierraCB

    SierraCB wadahp

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    Still looking for some help from the gurus. I can't track down whats goin on with my bike. I initially wanted to tune out this sort of weak idle downhill stalling issue but now I've realized I had other issues.

    My air screw only likes being 1/4 turn out from all the way in, regardless of pilot jet. 38, 40, now 42 (which seems very rich for 5k elevation?) If it goes any more out I get a lean bog and the idle is really up and down and hangs.

    I've cleaned the whole carb, reset float height replaced all the jets, tried a richer needle setting, new air screw o ring and washer etc. Checked for air leaks also. It's almost as though the pilot jet has no effect, lol.

    I attached a couple videos to show the symptoms maybe just maybe someone knows what's up!

    42 pilot, Red #4 needle AS 1 1/4 turn out.



    Now at 1/4 turn out from all the way in.

  7. Gordy

    Gordy SUPPORTER

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  8. SierraCB

    SierraCB wadahp

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    Hmm definitely possible. Actually the first i've seen that. It does explain how going up in pilot size is having no effects. I did just try to start it at current setting and now the choke is acting weird! Anyone else??
  9. RideFreak

    RideFreak Torque Junky

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    Another possible cause that's going to sound odd but some 300s have had low speed (off-idle) fueling issues due excessive air getting past the O-rings on the powervalve pivot shaft. They always seem to leak oil but I'd never heard of running issues being traced to it. But there's a whole thread on it over on KTMTalk, I think the OP on the thread I was reading solved it with slightly larger orings. They always seems to leak oil so leaking air isn't a big stretch. Something to keep in mind.
    alvincullumyork likes this.
  10. SierraCB

    SierraCB wadahp

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    good info! Not something i'm hoping is the issue as i've been focused on the carb and wish it's the carb! A lot more disassembly on that side... Yikes
  11. BikePilot

    BikePilot Long timer

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    Can air get in via the o-rings with out going through the exhaust port?

    I haven’t spent time with a Kehin since the 1990s, but they were generally pretty trouble feee.

    Have you messed with the needle? Maybe it’s lean and the rich pilot and air screw is compensating a bit.

    Otherwise I’d look for air getting into the motor where it should not. A sloppy slide to carb body fit can cause this. If air leaks by that’s like having the air screw wide open and will lean it out. Too much will also weaken the signal over the pilot jet and make it ineffective.
  12. Jodaddy

    Jodaddy Been here awhile

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    Can you just check the float level with the bike running by filling up the over flow hose and visually see where it’s at? Maybe hook up an auxiliary fuel source. Fuel line maybe deteriorating and plugging the inlet.
  13. RideFreak

    RideFreak Torque Junky

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    Yes, the boost ports are also controlled by the power valve, those are the tiny little cylinder's with the cutaways that have the half of a gear on each one, they are almost a direct path onto the crankcase via the transfer port. At small throttle positions vacuum goes up and is essential factor in pulling fuel up through the pilot circuit. When air is introduced via another path the vacuum signal drops at the carb and it doesn't pull as much fuel, low end suffers. In Sierra's situation the screw position doesn't matter if it's got a 40, a 38 pilot according to him, that tells me it's not a jetting issue but something else. Gordys solution is the easiest to implement and that'd be my first check. I'd never dealt with the orings as an airleak issue before, I always change those when I do a topend and I never let them go too long. The thread discussing the owners issues and it's eventual resolution is well documented. He only went that direction when nothing else worked and that ended up fixing his problem. I only mentioned it after Sierra indicating the airscrew issue (same setting for 2 different size jets) which we know isn't normal. Changing the pilot jet should have a significant impact on the air screw setting.

    Also a bad reed valve can have similar effects, that's another easy check.
  14. Junglejeff1

    Junglejeff1 Long timer

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    Really enjoyed that and one of my favorite bands.Were is that at as that type of riding is in my bucket list.
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  15. Anatoli

    Anatoli Pale rider

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    Our regular Wednesday ride was rain or sleet all day. My riding buddy brought a slick little Echo top handle gas saw that was about half the size of my 017 Stilhsaw. Despite the small size we were able to cut through some pretty big 20” timber. We refueled using premix fuel drawn from his carb equipped 2018 TE 300. The light weight means that the bike’s handling suffers far less when it is on the front mount. One needs a sharp chain and high chain speed to make it work.

    E9775F1B-B799-433C-96C7-4AEF263D4366.jpeg
  16. Gordy

    Gordy SUPPORTER

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    Was it here or was it elsewhere that some guys got defective S3 air screws (the ones that are knurled) and they were leaking air and messing up the pilot circuit?
  17. RideFreak

    RideFreak Torque Junky

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    I didn't hear about that issue, sounds like a major FU that the defective screws would make it into customer bikes. Poor QC.
    alvincullumyork likes this.
  18. SierraCB

    SierraCB wadahp

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    I grabbed a new AS just in case, even though it looks totally brand new. Might as well try.
  19. Rusty Rocket

    Rusty Rocket Life behind "Bars"

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    That looks exactly like the saw I carry. It fits in my knapsack.
  20. Junglejeff1

    Junglejeff1 Long timer

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    I had 2 bad ones that I purchased at same time(this summer).one on the TRS and one in the KTM.I have used them before with no issues so must have been a bad batch.very loose fit was the problem.They were replaced for free and no issue with replacements.
    Bitingdog and Gordy like this.