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Old 11-11-2012, 12:06 AM   #1 (permalink)
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955 Throttle body butterfly sticks

My 2000 955 is running really well - now I have dumped the old air filter in favour of a K&N. I can confirm the fitting on the K&N is a bit of a bear..they are NOT made 100% right and need some "love taps" to seat in the airbox.
Did a mixed week of commuting and some 30 miler hot runs to test the consumption - got 201 miles before the orange light came on. Did a 2nd week of pure commuting - got 179 miles...and just completed a 2-up with wife 200+ mile ride - which included a 60ml section of twisties through a gorge. Got 215 miles and the light hasn't come on yet! Looks like another 5 miles or so. Happy with that!
Anyway - while fitting the air filter - I rechecked the throttle balance - which was good..but noticed no 1 throttle butterfly flap was sticking shut. Feels like it is wedged on a groove. Had to push it free. If I let go of the throttle so it SNAPS closed - it will stick it everytime and I have to wiggle the throttle grip furiously to free it up.
Before I go back in AGAIN...can anybody offer some tips for sorting this? Do the screws mounting the flaps loosen up to realign the flap? They are split and spread on the underside I noticed - but guessed they are adjustable..? What about the "roughage" I can feel with my finger in the throttle cavity..? Should that be dressed up somehow?

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Old 11-12-2012, 08:40 PM   #2 (permalink)
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Quote:
Originally Posted by Trade_nancy View Post
Do the screws mounting the flaps loosen up to realign the flap?
No, they're supposed to be there for the life of the bike. More than likely you'd have to drill them to get them out. I doubt if it'd do any good; I can't imagine the plate has moved in relation to the spindle. Easy way to check - open the throttle fully, grip the throttle plate and pull to see if it moves in relation to the spindle.

If there is any movement it would most likely be the spindle and throttle plate moving together within the throttle body. I'm not familiar with the separate throttle bodies on a 2000 but if you do have any up/down movement of the throttle and spindle then that would probably indicate serious wear where the spindle bears at either side of the throttle body.

A more likely cause of the sticking would be a broken return spring. Maybe you checked that already but you didn't say if you'd removed the throttle body and inspected the spring.

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Originally Posted by Trade_nancy View Post
What about the "roughage" I can feel with my finger in the throttle cavity..? Should that be dressed up somehow?
I'd assume that "roughage" has been there since the bike was new so that would only be causing a problem if something else was amiss.
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Last edited by champ87; 11-12-2012 at 08:46 PM.
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Old 11-13-2012, 01:50 AM   #3 (permalink)
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Thanks for the response.
No - I didn't check the spring while in there. I'll do that soon. This doesn't cause me operational problems (yet) as the "sticking" only occurs if I slam the throttle shut. I'll wait till I have more energy and an empty tank and go back in have a look.
I asked about the screws as I read someone else's thread here - saying they had problems with throttles going out of balance - so they had a dealer look at it and they "loosened off" the butterfly screws, realigned the butterfly and fixed the fault..so it seemed. Go figure.
Mark

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No, they're supposed to be there for the life of the bike. More than likely you'd have to drill them to get them out. I doubt if it'd do any good; I can't imagine the plate has moved in relation to the spindle. Easy way to check - open the throttle fully, grip the throttle plate and pull to see if it moves in relation to the spindle.

If there is any movement it would most likely be the spindle and throttle plate moving together within the throttle body. I'm not familiar with the separate throttle bodies on a 2000 but if you do have any up/down movement of the throttle and spindle then that would probably indicate serious wear where the spindle bears at either side of the throttle body.

A more likely cause of the sticking would be a broken return spring. Maybe you checked that already but you didn't say if you'd removed the throttle body and inspected the spring.



I'd assume that "roughage" has been there since the bike was new so that would only be causing a problem if something else was amiss.
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Old 11-13-2012, 01:18 PM   #4 (permalink)
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I second the Champ's suggestion to check the return spring.

If it's not that, my '08 Sprint has a set screw (stop) that limits the butterfly closed position so that it can't bind/stick in the bore of the throttle body.

I wouldn't recommend it to just anybody but you're on the right track with loosening the butterflys on the shaft then snapping them closed to seat. That's how I do it. It's not easy because the TB needs to be removed and the stakes on the old screws ground off. The key to getting the screws out is to use a phillips bit that fits the screw head. Be careful the shaft is brass. For better flow, replace the screws with ProBolt stainless dome heads cut to length then LocTite. You can also see that the shafts were narrowed and the leading edges of the shaft and butterflys were beveled. This was all part of the throttle body mods and port-matching that Power-Tripp described.

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Old 11-13-2012, 05:32 PM   #5 (permalink)
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If someone is influenced to attempt to remove the TB butterfly screws, they ought at least to use the correct screwdriver. They are JIS, not Phillips. Both appear very similar but there is a difference. They are usually available at the RC hobby shops. Especially the shops that deal with RC helicopters.
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Old 11-13-2012, 05:56 PM   #6 (permalink)
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If someone is influenced to attempt to remove the TB butterfly screws, they ought at least to use the correct screwdriver. They are JIS, not Phillips. Both appear very similar but there is a difference. They are usually available at the RC hobby shops. Especially the shops that deal with RC helicopters.
Hey!! Old,..but not so dumb = good call, thanks. Brass screws are a bastard if u have an ill-fitting tool..been there and buggered some inside carbs before...but I hope to avoid tearing into those screws..if it's not a broken return spring, I'll likely leave them...unless problem becomes worse. But did wonder as those are threaded screws and split - if they can be backed out a bit if one clamps the split ends back together somewhat..loosen the scew back a turn..?
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Old 11-14-2012, 10:27 AM   #7 (permalink)
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Throttle cables adjustment and condition should not be assumed.

I agree with checking the spring first, then checking the butterfly shaft travel limit screw, providing it has one.

Squeezing the staked split ends would probably allow removal of the screws, but most likely they would come out at the expense of the threaded holes in the shaft. Best bet, as previously suggested, would be to grind them flush, without contacting the plate. Then, on re-assembly I would use red locktite since the threads in the shaft will still be compromised to some extent.

If it were me working this problem, removing the plate for adjustment would be my last consideration. I would first inspect the bore "roughage" to determine if it was a bore defect or merely deposits. Then, as Champ suggested, my next inspection would be the tb spindle/shaft bore condition. Of course, these steps would be after initially verifying a travel limit screw. The problem definition definitely sounds like butterfly over-travel, for which most tbs have a travel limit screw.
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Old 11-14-2012, 03:14 PM   #8 (permalink)
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[QUOTE=oldndumb;2424627]Throttle cables adjustment and condition should not be assumed.
Ahhh,..yes I agree...could be a likely culprit as I did replace the throttle cable about 5 months ago...
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Old 11-16-2012, 11:12 AM   #9 (permalink)
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Quote:
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...could be a likely culprit as I did replace the throttle cable about 5 months ago...
Throttle cable would affect all 3 throttles. Elevens' and OnD's suggestion to check the limit/stop screw sounds good.

As elevens said the 1050s have a stop limit screw. It's on the throttle cable bracket at the right hand end of the throttle body assembly. As you can see from elevens' photo your 2000 is different becasue you have separate throttle bodies. Looking at the parts diagram I can't see a limit screw but maybe the sync screws serve that purpose.
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Old 11-16-2012, 11:47 AM   #10 (permalink)
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Here is good pic of the older TBs



#1 is on the right in this picture
(that view as it is mounted on the bike would be looking towards the rear)

Can you confirm is this one and not the one at TPS end?
Are you saying that 2 & 3 begin to open, but 1 remains closed?
or that 1 sticking is causing all three to remain closed, but 1 is the plate that you feel the issue with?

I would be more inclined to believe something in the linkage rather than the plate itself that is sticking.
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