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KTM idle is sky-high

  1. #26
    Lifer typeone's Avatar
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    Re: KTM idle is sky-high



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  2. #27
    Backwoods lobster boy number9's Avatar
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    Re: KTM idle is sky-high

    The new intake boot arrived and I pulled the old boot off. The crack does not go all the way through, so it's not the source of my issue.

    Unfortunately, the PO had glued the V-Force gasket to the intake, which means I've got to get another gasket from Moto Tassinari. (He's also used the wrong hoses for the radiator, because of course he has.)

    I've decided to go through the carb to see if my problem lays there. Unfortunately it's mostly held together with 3mm Allen screws, and I only have 2.5mm and 4mm . None of my SAE stuff fits, so I'll have to find a 3mm key tomorrow. I have the Harbor Freight ultrasonic cleaner, so I'll stick the carb in that. Should I order a new gasket kit, or take everything off carefully and not put any o-rings in the ultrasonic jobbie?

    In other news, I got the last of the new sticker set on the bodywork, and also installed an Enduro Engineering disc guard for the front brake. Front brake needs to be bled too...

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    '00 Honda VFR 800, '01 Subaru Outback, '03 Porsche 911, '05 KTM 300 EXC, '08 Ducati Hypermotard 1100S, '14 Honda CRF 250R

  3. #28
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    Re: KTM idle is sky-high

    I've never had issues with o-rings in the ultrasonic. Cork/paper gaskets/etc I remove carefully, but buna-n / viton / etc rubber is not affected by water. Now, that said rebuild kits for your carb should be fairly cheap, especially if you're already ordering other parts at the same time. If you're already in there and spending some money?

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  4. #29
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    Re: KTM idle is sky-high

    I also dump o-rings in the ultrasonic. I usually use tap water and a touch of simple green. Fookin' AMAZING what it does to a carburetor!

    KTM idle is sky-high-img_0047-jpg

    These babies went through twice and needed it.

    I did have problems with the diaphragm on some CV carbs shrinking once. I think that was the heat, not the solvent or ultrasonic.

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    Last edited by nhbubba; 09-11-17 at 07:25 AM.

  5. #30
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    Re: KTM idle is sky-high

    I like the 'fancy' un dyed, no fragrances Dawn dish detergent and distilled water. No chance of simple green etching anything if I let it cook for longer periods. Takes a bit longer, but I'm ok with letting the ultrasonic do it's thing while I putter with other stuff.

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  6. #31
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    Re: KTM idle is sky-high

    Thanks guys. Any recommendations for a carb gasket/rebuild kit? RMATV is my go-to and they don't seem to carry one that will work...

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    '00 Honda VFR 800, '01 Subaru Outback, '03 Porsche 911, '05 KTM 300 EXC, '08 Ducati Hypermotard 1100S, '14 Honda CRF 250R

  7. #32
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    Re: KTM idle is sky-high

    Here are a bunch of photos of the carb post-ultrasonic cleaner. I probably need to run it through again to get the last of the crud off.

    I didn't take the choke off before cleaning it. I took the idle adjusting screw off by accident, whereas you wanted me to take off the air control screw. Oops. Guess I'll have to remove that and re-clean it...

    Float gasket looks a little worse for wear, but other than that everything looks good to my untrained eye. Idle jet looks like *40 and main jet looks like *165, I think the funny asterisks mean they're genuine Keihin.

    Rebuild kits seem to be few and far between. K&L have the 018-2539 kit for about $60, but it doesn't include much. A new OEM bowl gasket and new OEM float needle is $25 from RMATV. Should I just do that? The fueling seemed to be pretty good before, so I'm not sure I need to change jets & needles.
    Attached Thumbnails Attached Thumbnails KTM idle is sky-high-img_0591-jpg   KTM idle is sky-high-img_0590-jpg   KTM idle is sky-high-img_0594-jpg   KTM idle is sky-high-img_0593-jpg  

    KTM idle is sky-high-img_0592-jpg   KTM idle is sky-high-img_0589-jpg  

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    Last edited by number9; 09-11-17 at 05:00 PM. Reason: idle adjusting screw confusion
    '00 Honda VFR 800, '01 Subaru Outback, '03 Porsche 911, '05 KTM 300 EXC, '08 Ducati Hypermotard 1100S, '14 Honda CRF 250R

  8. #33
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    Re: KTM idle is sky-high

    I got it running! Cleaned everything up, new o-rings, re-used jet and needle.. started after a couple of kicks.

    I've still got a couple of issues. The biggest one is that, maybe 50% of the time, the carb will spit gas (through the bowl overflow vent) if the bike is stopped. Turning the fuel tap off stops it, of course. What did I likely do wrong here? I was really careful with the float tang as to not change the height, and the float needle looked great -- no scoring or ridges.

    The bike also sometimes, maybe 20% of the time, will stall at very low speeds in high gear even with the clutch pulled in. I think I need to fine-tune the mixture to sort that out, though..?

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    Last edited by number9; 09-18-17 at 10:23 AM.
    '00 Honda VFR 800, '01 Subaru Outback, '03 Porsche 911, '05 KTM 300 EXC, '08 Ducati Hypermotard 1100S, '14 Honda CRF 250R

  9. #34
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    Re: KTM idle is sky-high

    Float needle isn't seating. If you take the carb off, drain all the gas out of it and blow into the fuel inlet with the carb upright you should meet little resistance. If you turn the carb upside down and blow in, you shouldn't be able to. I'm betting you'll still meet little resistance. This may explain why you're flaming out at low RPM, it's likely getting way too much fuel as the bowl overflows. Gotta fix that before you chase mixture settings.

    Potential causes: (All needle references here are to the float needle)
    - Float height is set wrong
    - Needle seat is beat all to hell (not anticipating this is the issue)
    - Needle seat is dirty still
    - Needle tip is overly hard from age, deformed, etc
    - Needle spring is gummed up or otherwise not working

    Carb off, bowl off, time to inspect. The needle tip should be slightly soft rubber and not have any obvious indents/etc, just a cone coming to a point. The little plunger on the top of the needle should be springy with no stiction. If either of these are false, toss that needle and replace. To test, bowl off, float out, carb upside down, put the needle in place, lightly rest a finger on the plunger so you feel it compress and test that you can't blow in the fuel inlet. Once that is working you'll need to verify the float height setting. Lots of good vids on that.

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    771 Racing -=- FaceBook
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  10. #35
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    Re: KTM idle is sky-high

    There is some grit under teh float needle causing the fuel pissing. Or perhaps the needle itself is worn out. inspect the tip...

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  11. #36
    Lifer Chippertheripper's Avatar
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    Re: KTM idle is sky-high

    just the tip.

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    Cliff's Cycles KTM LRRS 560x retired, PSTR 317 B-vet, NETRA enduro B-vet

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  12. #37
    Backwoods lobster boy number9's Avatar
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    Re: KTM idle is sky-high

    You guys are the fucking best.

    Quote Originally Posted by Kurlon View Post
    Float needle isn't seating. If you take the carb off, drain all the gas out of it and blow into the fuel inlet with the carb upright you should meet little resistance. If you turn the carb upside down and blow in, you shouldn't be able to. I'm betting you'll still meet little resistance. This may explain why you're flaming out at low RPM, it's likely getting way too much fuel as the bowl overflows. Gotta fix that before you chase mixture settings.
    This all makes sense. Thanks Josh!

    Potential causes: (All needle references here are to the float needle)
    - Float height is set wrong
    - Needle seat is beat all to hell (not anticipating this is the issue)
    - Needle seat is dirty still
    - Needle tip is overly hard from age, deformed, etc
    - Needle spring is gummed up or otherwise not working

    Carb off, bowl off, time to inspect. The needle tip should be slightly soft rubber and not have any obvious indents/etc, just a cone coming to a point. The little plunger on the top of the needle should be springy with no stiction. If either of these are false, toss that needle and replace. To test, bowl off, float out, carb upside down, put the needle in place, lightly rest a finger on the plunger so you feel it compress and test that you can't blow in the fuel inlet. Once that is working you'll need to verify the float height setting. Lots of good vids on that.
    The needle looked good, no ridges or anything that I remember. But I didn't really check the hardness or the stiction, so maybe I just need a new needle.

    Quote Originally Posted by Paul_E_D View Post
    There is some grit under teh float needle causing the fuel pissing. Or perhaps the needle itself is worn out. inspect the tip...
    Quote Originally Posted by Chippertheripper View Post
    just the tip.

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    '00 Honda VFR 800, '01 Subaru Outback, '03 Porsche 911, '05 KTM 300 EXC, '08 Ducati Hypermotard 1100S, '14 Honda CRF 250R

  13. #38
    Soul Rider Paul_E_D's Avatar
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    Re: KTM idle is sky-high

    Quote Originally Posted by number9 View Post
    You guys are the fucking best.

    This all makes sense. Thanks Josh!

    The needle looked good, no ridges or anything that I remember. But I didn't really check the hardness or the stiction, so maybe I just need a new needle.



    Just remember, if you play that game too long, you can end up with a minivan...

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  14. #39
    Backwoods lobster boy number9's Avatar
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    Re: KTM idle is sky-high

    Quote Originally Posted by Paul_E_D View Post
    Just remember, if you play that game too long, you can end up with a minivan...
    Oh, don't worry, I'm still practicing.

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    '00 Honda VFR 800, '01 Subaru Outback, '03 Porsche 911, '05 KTM 300 EXC, '08 Ducati Hypermotard 1100S, '14 Honda CRF 250R

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