Possible carb problem - high revs

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Azazel
Posts: 39
Joined: Tue Feb 08, 2011 4:24 pm
My Bike: ZXR400 L1
Location: Nottingham

Possible carb problem - high revs

Post by Azazel »

Hey everyone - it's been a while.

Thought I would go for a bit of maintenance over the winter:

Carbs removed and cleaned, new plugs, valve clearances checked (were a mess), oil and coolant change, filters etc...

After firing her up yesterday I noticed that she idles at about 2.5K with the idle screw off!
Couple of things which might be causing it but advice would certainly help narrow it down:

- The throttle body doesn't sit all the way down when the idle screw is off. Probably around 5mm off of the resting point (if that's what it is)
- The carbs are yet to be balanced (insufficient equipment)
- The mixture screws are set to standard (2.5 turns out) - do they just need adjusting?
- Checked carb rubbers - no leaks
- Nice tight seal around airbox

Is there anything else anyone could suggest that could potentially be causing the problem at all?
Help most appreciated

Many thanks :smt001
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banner001
Track day God
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Posts: 2589
Joined: Sat Sep 24, 2011 3:27 pm
My Bike: ZXR400 L4
Location: Nuneaton

Re: Possible carb problem - high revs

Post by banner001 »

im guesing that someone has screwed your balancing screws all the way in/out so thats why the idle is so high - you have too much air going through and this is creating the vacuum that is allowing the bike to rev so high.

i am in coventry if you fancy a ride down the M1 and we can get your bike fettled? i have a set of carbtune ballancers here as well as JIS screwdrivers, air tools, paddock stands...whatever you need really :D
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003
Azazel
Posts: 39
Joined: Tue Feb 08, 2011 4:24 pm
My Bike: ZXR400 L1
Location: Nottingham

Re: Possible carb problem - high revs

Post by Azazel »

WOW! Thanks for the offer - would love to have a ride down!

Not sure when it would be possible though thanks to our always fantastic weather. Would you want some ££?

Is there a method I could go through to sort this myself without balancers? (just so I can have a tinker)
I know it's going to need proper attention at some point.

Will the carbs need adjusting when I stick my race can on?

biggrin
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banner001
Track day God
Track day God
Posts: 2589
Joined: Sat Sep 24, 2011 3:27 pm
My Bike: ZXR400 L4
Location: Nuneaton

Re: Possible carb problem - high revs

Post by banner001 »

get me a few nice beers, is all i ask for.

you can try to do a "seat of the pants" adjustment, just make a note of how much you turn each adjustment screw so you can set it back to standard if necessary.

any adjustments to the airbox or exhaust will require adjustments of the carbs.
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003
Azazel
Posts: 39
Joined: Tue Feb 08, 2011 4:24 pm
My Bike: ZXR400 L1
Location: Nottingham

Re: Possible carb problem - high revs

Post by Azazel »

Can you believe I had to google "Seat of the pants" - honestly had no idea what you were talking about :smt003

Beers is in some respects more valuable than ££ so no problem - thanks again.
Might have the money to buy some balancers before i manage to get down to you but will keep in touch anyway.

Going to do some research into adjustments for the race can so thanks for the advice :)
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