Carb Sticking


14 replies to this topic
  • Jon-D

Posted March 23, 2006 - 02:16 PM

#1

I have a 93 XR 600 that the carb sticks slightly when attempting to open the throttle while the bike is running. When enough force is applied to over come the sticktion the throttle opens up somewhat abruptly which could become a safety issue. When I bought the bike the guy said this has never happened before so I thought the cables were going bad. After inspecting and lubing the cables, the carb worked smoothly until the motor was running. I believe it is the vacuum that is preventing the slide from working smoothly because the carb only sticks when it is running. I saw that there was some discussion in a previous thread about this, but what is the solution? Do I need to replace my carb or slide or both?

  • CFAmD7G

Posted March 23, 2006 - 05:29 PM

#2

Do you notice interference working the throttle with the engine off?

  • Mudshark

Posted March 23, 2006 - 06:04 PM

#3

Do you notice interference working the throttle with the engine off?


After inspecting and lubing the cables, the carb worked smoothly until the motor was running.


Sorry Jon-D, I can't offer much help with this.
Have you had the slide out of the carb? if not, take it out and see it
it is worn badly or not, this would at least tell you if it's the slide sticking.

  • daddyk

Posted March 23, 2006 - 06:29 PM

#4

I'm experencing the same thing with mine. Especially when in high vacuum situations i.e. shut of the throttle into a corner and want to roll it on out of it and you have to pull hard and then it "jumps" a bit. I found here, I think, a site that recommends drilling a 2 mm hole in the slide to relieve vacuum. Haven't tried it yet though. The site is http://www.enduro-st...e/xr/xrtune.htm
Only problem is it's in German. You do speak German of course. :thumbsup: If you do a search of this site with 'sticking throttle" you'll find it.

  • Mudshark

Posted March 23, 2006 - 08:18 PM

#5

I'm experencing the same thing with mine. Especially when in high vacuum situations i.e. shut of the throttle into a corner and want to roll it on out of it and you have to pull hard and then it "jumps" a bit. I found here, I think, a site that recommends drilling a 2 mm hole in the slide to relieve vacuum. Haven't tried it yet though. The site is http://www.enduro-st...e/xr/xrtune.htm
Only problem is it's in German. You do speak German of course. :thumbsup: If you do a search of this site with 'sticking throttle" you'll find it.


Cool, so the net effect is that the vacuum now ends up at the top of the
slide via the hole, having the effect of “lifting” the slide under extreme
vacuum situations.
I guess with the weight and spring it would never lift it, but would make it
easier to lift, hence making it feel smoother.... just pray that the seal at
the top of the carb never leaks, or it would cause endless problems for you
with extra air getting into the mix.

  • Jon-D

Posted March 23, 2006 - 08:23 PM

#6

Interesting solution to drill a hole in the slide to relieve the pressure. There must be a simple fix that would not require drilling the carb since most other people have not experienced this on their bike. I have not had my carb apart but I have a feeling that the slide or walls of the carb are warn down and causing the sticking.

  • Mudshark

Posted March 23, 2006 - 08:37 PM

#7

Interesting solution to drill a hole in the slide to relieve the pressure. There must be a simple fix that would not require drilling the carb since most other people have not experienced this on their bike. I have not had my carb apart but I have a feeling that the slide or walls of the carb are warn down and causing the sticking.


Agreed, But I think the hole will prevent most of the wear by getting rid of
the vacuum problem before it causes the wear. It could still help in your
situation though.
Any how, like I suggested, pull it apart and take a quick look.
If it is worn, maybe getting one of these pumper carbs to replace it would
be a good idea?

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  • Jon-D

Posted March 23, 2006 - 09:10 PM

#8

I wonder if the vacuum is only part of the problem. I am starting to think that the flow past the slide is pulling it against the walls of the carb and causing it to stick. At closed throttle the slide is near the bottom and the moment (or torque) is greatest because the pull on the bottom of the slide relative to the carb/slide contact point is at its greatest (that was a mouth full). At open throttle the moment is less due to the decreased distance between the bottom of the slide and the slide/carb contact point. Of course the flow is greater at open throttle so this may disprove my theory.

...just thinking out loud.

  • Jon-D

Posted March 23, 2006 - 09:20 PM

#9

Any how, like I suggested, pull it apart and take a quick look.
If it is worn, maybe getting one of these pumper carbs to replace it would
be a good idea?



ya, that's what I was thinking. The only problem is that my cheap gene is telling me to try and fix the carb before buying another one.

  • daddyk

Posted March 24, 2006 - 06:13 AM

#10

We must be related I have the same gene. I'm going to see if I can live with it as is. If it bothers me to much I'll try the slide drill. If that doesn't handle it I have a 38 mm Mikuni Flatslide I'll try fitting. The flatside will need some re-jetting but I hear the work well.

  • creeky

Posted March 24, 2006 - 06:44 AM

#11

I gave up a some good time ago trying to "fix" the stock XR600 carb. It can be made to work better than it comes from the factory, but still never worked to my liking. I have also tried Mikuni flat slides, they are better, but still not what I like. I have been using Edelbrocks for about 10 years or so, they improve the 600's overall performance considerably, no jetting hassels, and deliver slightly better fuel economy. I'll spend the bucks every time.

  • MotoGoalie

Posted March 24, 2006 - 11:33 AM

#12

Re; The sticking carb.

...you have a 13 year old dirt bike.

I would take the carb off of the bike and COMPLETELY dissasemble and clean it, first thing,. It's amazing the accumulation of small grit over time.

Also, you mentioned you lubed the cables. That's important and


Clean and lube the throttle tube.

I have to do all this about once a year to keep it to my liking.

  • Jon-D

Posted April 22, 2006 - 04:56 PM

#13

OK, I removed the carb and slide and during inspection I can see that there is a little wear on the slide as well as the bore in the carb. the carb also had some green varnish from sitting too long near the bottom of the bore (next to the bowl end). I cleaned everything as best I could and then gently polished the slide and bore. the bore is not perfectly polished and shinny like the slide, but enough to make it feel smooth to the touch. I applied 2 stroke oil to all moving parts including the slide itself and reassembled. I also applied sealant around the top plate before installation to ensure a good seal. I rode today for the first time and the throttle worked like it should. I don’t know if it was the polishing, the oil, or a combination of the two that made a difference but the carb worked like it should.


with reguard to drilling the slide, it should not be nessassary because at the base of the slide there is a small hole that will equalize the presser between the top of the carb and the intake section.

  • socalduner

Posted April 23, 2006 - 05:50 AM

#14

Can you let us know if your fix lasts more than a couple rides, I would think it would return once the oil is gone. My 97 does it to and I am thinking about getting the edelbrock carb to solve the problem and gain 5 hp at the same time. Im sure my wife would like it better to save the $400. :thumbsup:

  • Jon-D

Posted July 13, 2006 - 11:28 AM

#15

Can you let us know if your fix lasts more than a couple rides, I would think it would return once the oil is gone. My 97 does it to and I am thinking about getting the edelbrock carb to solve the problem and gain 5 hp at the same time. Im sure my wife would like it better to save the $400. :ride:



in about 10 hours of riding the sticking has returned. i plan to remove the top off the carb this weekend and add a little 2-stroke oil. kind of disapointing, i was hoping it would be fixed.





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