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Discussion Starter · #1 ·
Hi, I would like to know what are these screws on the VN900 throttle body? They look like they miht be are/fuel mix screws but since this is a fuel injected bike I would't think they should be that.

PS:
One of those got lost and when looking at the parts manual those look like they are not sold separetely, so how can I get a replacement?

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IIRC (it's been a long time) you remove the little black caps next to them, hook up a sync tool (just like synching multiple carbs) and adjust the idle vacuum to the level spec in the service manual making sure they are both as equal as possible. Check your service manual for a section called 'synchronizing the throttle bodies' or something similar.
 
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Question- did you mess with them and lose one or what? Why would you need a replacement?
 
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I would order one from a Kawasaki dealership and be done with it. It will save you a lot of grief, this kind of thing you can order online, and get it delivered to your home. ;)
 

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They are indeed Air Bypass Screws and used to sync the Throttle Bodies at Factory connecting an electronic syn tool to the Stubs under the Black Caps, Once performed they need not be adjusted again through out the life of the Motorcycle.
This seems to be standard practise with Kawasaki Biggish Twins.

In the real world where things are not all equal they can be synced using a Generic Vacuum Guage, It matters not where they sit on the scale as long as they are both sitting at the same level.
One wonders why they aren't capped off like they did years ago on USA Models and maybe other Countries.
On a side not they are not available as seperate components so a used set of T/C's are requred to rob one from..
 

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Thanks for that great info, Greenisbest! To the OP, since the screws should be identical and since you still have one of them, it looks like your best option is to take it to a machine shop and have them make you a new one.

It may be helpful to the shop if you could also bring the throttle body with you so they can make sure the thread fit is correct.
 

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Discussion Starter · #13 ·
IIRC (it's been a long time) you remove the little black caps next to them, hook up a sync tool (just like synching multiple carbs) and adjust the idle vacuum to the level spec in the service manual making sure they are both as equal as possible. Check your service manual for a section called 'synchronizing the throttle bodies' or something similar.
I've looked several times thru the servise manual and I don't see any section explaining this or giving me a value that I should aim for... does someone have an idea of a ballpark number to aim for?
 

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Get the motorcycling idling within the idle range listed. if it is idling smoothly, leave it alone. If you just put them in, I would star by turning them in till they just touch, do NOT overtighten them or even snug them up, just till they seat. I would then turn back each one 1.5 turns. Start the bike, adjust it till it idles. if it is idling smooth, then you are all set, if not, turn one of the screw maybe 1/4 turn and see if it matches with the other one. Always rmember the last position you left. If you adjjustment doesn't work, then put it back, and try the other carb. a Carb Sync tool helps with this a lot, as you can adjust the screw and look for an increase in rpm's ( slight increase) then back off 1/4 turn, then do the same with the other one, matching the rpm's. Essentially you adjust one carb and that becomes your reference carb, you then bring the other carb into sync with that one. If you rpm's have increased, then lower the idle. If they drop, increase your idle, but stay in the idle range of rpm's. Like I stated, a carb tool really helps out with this. The above method will get you very close though. When the bike gets hot, you may have to do an adjustment again. If you have only one gauge, you can fabricate a dual set up using fish tank valves and plastic "T's" to make a selector and match up the carbs that way. To get it exact, you will need a vacuum sync gauge, and after that, never need to touch them again. ;)
 

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Kawi made 5 different VN900 models in 2009. We need to know which one you have.
You are a spectacular amount of wrong. There's the base/Classic, LT which was just a Classic with accessories, and the Custom. Even the SE wasn't that special. It was actually just testing the waters for blacked out models to cheap out on chrome, but they upsold people on it to mitigate economy of scales. Following Kawi tradition, it's not even relevant even which year he has for 99.9% of things.

I had to adjust my throttle bodies after 40k miles and removing the secondary plates. It helped with bucking during engine braking at low RPM even though it had been idling pretty smoothly.
 

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Wow! Those bikes only made 50 HP!! I sincerely think my Briggs and Stratton mini bike could give one of these a run for the money. I found 3 models listed, but that's still really not so important for such a blasé motorcycle. IMHO. ;)
 

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Sometimes people in the U.S., me being one of them, are "Amero-centric". I've travelled much. Spent a month in Montreal and another in Quebec. 2.5 months in England, and a month traveling through Europe. Montreal and Quebec were like 2 separate countries! :)
 
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