XR600R - Keihin carb slide sticks, throttle sticks off idle


22 replies to this topic
  • thumpasaurus

Posted July 07, 2004 - 01:20 PM

#1

On my XR600 with it's stock carb, I have trouble controlling my throttle coming off idle. For a while I thought it was my cables, but it's not. I finally traced it to the carb itself and the slide in particular. My theory is that when the engine is running, pulling a vacuum through the carb body it causes the slide to [@#$%&*!] slightly in its bore. When you turn the throttle it sticks then pops loose. I think the popping loose is the time it takes for the slide to get straight..

Anybody else ever notice this? Is my carb just worn out? I took a turn or two out of the return spring and that helped but it still bothers me, especially in tight going. Any advice appreciated.

dan.

EDIT:
"causes the slide to c-o-c-k slightly in its bore" (meaning to get out of alignment w/ the bore) The TT software bleeped me out for that. dirty mind or what? :thumbsup: :devil:

  • AzMtnThumper

Posted July 08, 2004 - 04:41 AM

#2

A sticking throttle has got to be scary to say the least. If your slide and your bore of the carb are both nice and smooth, the only other thing I could think of would be maybe the linkage attached to the slide is binding???? :thumbsup:

  • thumpasaurus

Posted July 08, 2004 - 05:57 AM

#3

A sticking throttle has got to be scary to say the least.


Not scary, it doesnt stick open. It's more irritating as it sticks as you try to roll the gas from idle. Makes precise throttle control difficult. It definitely has to do w/ the slide sticking while under vacuum from the motor. with the motor off the throttle operation is nice and smooth.

I've done some digging and it seems like it is a common thing and a big reason people go to other carbs. I hate to spend that kind of money ($400) on a carb, but it's a lot cheaper than another bike. I see you have a 600. Is the carb stock, and if so does your throttle open smoothly from idle?

  • AzMtnThumper

Posted July 08, 2004 - 07:57 AM

#4

Yeah, I'm using the stock carb and have had no problems with it (once I sorted out my jetting for the various elevations that I ride in). No problems with any sticking of any kind. Maybe someone like Barnum's could give you some insight.

  • thumpasaurus

Posted July 08, 2004 - 10:24 AM

#5

Yeah, I'm using the stock carb ... No problems with any sticking of any kind...


So maybe my carb is just getting worn out. It is the original 92 and lord only knows how many miles are on it. I'll keep an eye out for a late model carb on ebay, or maybe try a 650R carb since people are throwing them out like crazy.

thanks.

  • stir-it

Posted July 11, 2004 - 04:38 PM

#6

my brother just got a 95 600r and the throttle is sticky right off idle also. any fixes? :thumbsup:

  • thumpasaurus

Posted July 11, 2004 - 05:26 PM

#7

my brother just got a 95 600r and the throttle is sticky right off idle also. any fixes? :thumbsup:


I've been having the problem for years. After taking the carb and throttle apart many times, I determined it was the slide/and or carb body that was worn. the slide no longer fit snugly and when all the way down the engines vacuum would pull it towards the intake slightly.. That causes it to be out of alignment and to stick when you try to roll it on. Replacing the slide is expensive, and I'm afraid half the problem in the body of the carb. :devil: FWIW, I was able to lessen the problem by:
- keeping my idle slightly higer
- taking one or two turns out of the throttle return spring.
but it is still aggravating :awww:

I talked to Rob Barnum as advised here. He confirmed all the above and recomended a Edelbrock. I just can't stomach spending that kind of money on this old bike.

There are XR650R carbs all the time on ebay, so I thought about trying to use one of those and even started a thread about it the other day. Got one response from someone who had done it.
..Here..

I decided to bite the bullet and buy a new carb/throttle (Mikuni TM40). Got it all from XRsOnly < $200 or less than half the Edelbrock. Let you know how it goes when I get it.

  • JetPilot

Posted July 12, 2004 - 03:46 AM

#8

I have the same problem with the vacuum making the carb stick off idle, its perfectly smooth when the bike is not running, but really sticks when its running, obviously the vacuum is holding the slider down at idle. Will the Edelbrock fit a 1993 XR600R ?? Is it a pain in the arse to install ? Modifications, etc ?

  • redryder03

Posted July 12, 2004 - 04:15 AM

#9

I have the exact same problem with my 04xr650r. I posted about it on this forum a while ago. I am just living with the problem for now. Turning up the idle seems to help a bit. Considering the Edelbrock but it seems people are haveing some problems tuning them also. It really sucks tho. Apparently it doesn't affect all carbs but it definitely got me. I also am sure it is a vacumn thing.

  • thumpasaurus

Posted July 13, 2004 - 06:15 AM

#10

I have the same problem with the vacuum making the carb stick off idle, its perfectly smooth when the bike is not running..Will the Edelbrock fit a 1993 XR600R ?? Is it a pain in the arse to install ? Modifications, etc ?

Rob Barnum recommended the Edelbrock for my 92, and said he would send it jetted for my bike setup/elevation and that it would be a drop in replacement. Based on his reputation around here I'd believe him.
:thumbsup:

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • HairyScary

Posted July 13, 2004 - 08:03 AM

#11

One thing I had in mind to try someday if the opportunity arose was to run
a slightly different ACV spring in the 600 carb. The ACV (air cut valve)
is that funky diaphragm thing on the side of the carb about the size of a
quarter. It controls air flow in one of the pilot jet passages. The idea
is that when you let off the gas and initiate engine braking, the high
vacuum conditions cause this valve to close off the air flow in the one
pilot circuit which makes the mixture richer and will stop the exhaust
popping and backfiring like your neighbour's harley.

Anyway, the point is that introducing a richer mixture during decel also
reduces the engine braking effect, and hence the peak vacuum obtained
during deceleration. At normal cruise setting on flat ground you would
have somewhere in the neighbourhood of 20 inches of vacuum, but at a higher
RPM with the throttle closed and no ACV it is probably closer to 30.

If you've ever rode a 650R, you will notice it doesn't exhibit anywhere
near the same engine braking as the 600R did. I don't currently know if
the 650R ACV is sprung to actuate at a lower vacuum setting, or if it
simply has a larger percentage of the pilot air go through the ACV.
The other thing about the 650R is that it uses a pilot jet with smaller air
bleed holes. If you know anyone with a 650R, chances are they will give
you their stock 65S pilot jet - the stock 600 pilot (62) is considered
lean for sea level, so instead of going to a 65 or 68, it would be
interesting to try a 65S in there and see if that helped any.

Somebody said the "S" series pilots for the 600 (99103-MAG-0xx0) are
slightly leaner than the 650R "S" series (99103-MBN-0xx0), but richer than
the generic non-s versions for all bikes (99103-437-0xx0), but I haven't
ordered a MAG pilot to confirm this. I would have hoped all pilots marked
with a 65S would be created equal - otherwise if you pull one from a parts
bin, you'd have no idea what you have!

So if you didn't want to buy a carb, and were game to experiment a bit, I'm
sure you could sort something out. Depends on how much time and screwing
around you are willing to invest in it.


~
:thumbsup:

  • JetPilot

Posted July 13, 2004 - 11:23 AM

#12

Very informative stuff Hairy :awww: , but what you are addressing is not the problem we are having. The problem we are having is the throttle sticking off idle :thumbsup:... The amount of engine breaking and popping is a totally different issue. Our problem is caused by the vacuum created at idle, not the mixture or anything like that. I will just go with an EdleBrock from Barnum if it gets to bad.......... :devil:

  • XRMANU

Posted July 13, 2004 - 11:41 AM

#13

http://www.enduro-st...e/xr/xrtune.htm
http://www.danzl.at/...xr_vergaser.htm

  • redryder03

Posted July 13, 2004 - 12:13 PM

#14

Ya it looks like both those links provide good info. If I only knew what they said :thumbsup:

  • XRMANU

Posted July 13, 2004 - 08:07 PM

#15

A little hole in the carbslide (at the right spot :devil: ),takes the vacuum away :thumbsup:

  • thumpasaurus

Posted July 14, 2004 - 03:29 AM

#16

A little hole in the carbslide (at the right spot :devil: ),takes the vacuum away :thumbsup:


Do you have the particulars on this? Specifically, how big a hole and where to make it. Also, have you tried this yourself? I have a new carb coming, so I could experiment.

thanks.

  • XRMANU

Posted July 14, 2004 - 10:53 AM

#17

Look @ the drawings in the links: a 2mm hole in the frontside(and middle) of the slide ,23mm from the top....

I did the mod to 3 or 4 XR600's,they all run great.If it doesn't work for you ,close the hole with epoxy or something :thumbsup:

  • gamorg02

Posted July 23, 2010 - 10:24 PM

#18

Look @ the drawings in the links: a 2mm hole in the frontside(and middle) of the slide ,23mm from the top....

I did the mod to 3 or 4 XR600's,they all run great.If it doesn't work for you ,close the hole with epoxy or something :smirk:



reviving an old thread, i have an xr250 showing the same things, does this work? anyone try it? its wicked f'n annoying

  • HeadTrauma

Posted July 24, 2010 - 08:31 AM

#19

Periodically oiling the slide and bore helps. No need to remove the carb; just go in through the top. I have heard from others that a dash of two-stroke oil in the fuel makes a difference too. I don't want to deal with extra carbon over the long term, however, so I just lube the carb directly.

So maybe my carb is just getting worn out. It is the original 92 and lord only knows how many miles are on it.


This is a big contributor to a sticking slide. The older the carb, the more prone it will be to sticking due to the likelihood of having more use and wear. The original carb on my '95 isn't bad(I still have to oil it once in a while, though). I have a spare that I suspect came off of an older bike, it has seen noticeably more use, and is a lot more prone to the off-idle stick. "Drier" fuels like alcohol(E85 in my case) aggravate the problem.

  • gamorg02

Posted July 24, 2010 - 11:50 AM

#20

Periodically oiling the slide and bore helps. No need to remove the carb; just go in through the top. I have heard from others that a dash of two-stroke oil in the fuel makes a difference too. I don't want to deal with extra carbon over the long term, however, so I just lube the carb directly.



This is a big contributor to a sticking slide. The older the carb, the more prone it will be to sticking due to the likelihood of having more use and wear. The original carb on my '95 isn't bad(I still have to oil it once in a while, though). I have a spare that I suspect came off of an older bike, it has seen noticeably more use, and is a lot more prone to the off-idle stick. "Drier" fuels like alcohol(E85 in my case) aggravate the problem.


Thanks for the reply. Quick question, you said I don't have to remove the carb. Not sure how to get to the top (assume you mean the slide lever assembly) without removing the carb as the frame would be in the way.





Related Content

 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.