whats wrong with my carbs?

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trying to balance carbs.
1+2 and 3+4 are balanced as pairs, then the 2 pairs are balanced.
i backed the screw all the way out of 1+2 carbs trying to adjust them with a cheap gauge and finally managed to get the screw back in today, i superglued it to the screwdriver to get it started off!

the problem im having is the adjustment screw is having no effect on 1+2 carbs.
carb 1 is on the bottom of the scale(Morgan carbtune) and carb 2 is on the top. and turning the screw is having no affect.

what have i cocked up?
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current bike Yamaha Thunderace.
its old and fat, but its a damned good ride. the bikes not bad either.

[Nutty]

Maybe try to gently "bottom" all the Pilot Screws and then bring them out 2 1/2 turns each and take it from there, that should be standard measurement, then carry on with the balancing

[Nobby the Bastard]

Are you sure you don't have a leaky rubber or two? 8tll make it almost impossible to balance them.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[Islander]

[Pete.]

If the butterfly spindle is worn it'll leak air through the bushes but that will be obvious.

Have you done the vales and compression check? If one cylinder is low on compression or has tight valves it won't be firing as well as the next and if it's not firing as wll it will be producing less vacuum.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

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how do i go about checking for air leaks?
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current bike Yamaha Thunderace.
its old and fat, but its a damned good ride. the bikes not bad either.

[Pete.]

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i think ive isolated the problem. the butterfly valve on cylinder 1 is not closing fully. im able to push it down about 1mm when it should be fully seated

does anyone have an idea as to what could be causing this? i cant see any obvious debris.
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current bike Yamaha Thunderace.
its old and fat, but its a damned good ride. the bikes not bad either.

[stinkwheel]

Is there still a little free play onthe throttle cable or do you need to back it off a touch? Or back off the idle adjuster?
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

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have just checked the cables and there is free play on both.
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current bike Yamaha Thunderace.
its old and fat, but its a damned good ride. the bikes not bad either.

[Pete.]

My next step would be to pull the carbs and sort them on the bench. Get the carbs off, cables disconnected etc. Wedge up the four plungers (or if you're brave pull the tops and extract them). Hold all four up to the light and see if you can adjust them so that the crescent of light under each butterfly is equal.

If you're lucky all that's wrong is that you've got the adjusters too far out of whack. Set all of the balance screws to the tabs are dead centred between the two springs and go from there.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

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removing the carbs from the bike is a scary thought, im worried ill do even more harm.

looking at the manual it seems quite involved. the coolant has to be drained before you can even start.
____________________
current bike Yamaha Thunderace.
its old and fat, but its a damned good ride. the bikes not bad either.

[Islander]

[Nobby the Bastard]

If thats scary don't ever try and reshim a genesis engine....
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[Pete.]

[Bhud]

Bite the bullet and do it properly.

Start from scratch. Carbs off the bike, valve clearances DO, renew any dodgy carb-to-engine rubbers (replace fuel line and any vacuum line at the same time, regardless of whether it's needed), then go through carbs and get them done. Valve shims first though.

1) Carbs clean and all passages that you can reach: clean.
2) Do you need to split carbs? Check by blowing down the fuel line tube while tilting it, for blockages (there will be resistance if there's dirt). If not, then leave it and don't split (more trouble than it's worth sometimes).
3) Float levels reset to factory spec.
4) Check jets and emulsion tubes are clean, especially pilot jets.
5) CV carbs: check diaphragms carefully, and replace where there are any tears.
6) Are your slides scored and are they sticking because of this? First things first: blast all your springs with carb cleaner, because return springs get clogged with dirt. After that, they should return smoothly. If not, then you MUST check if your main needle is bent. It should drop straight back into the main circuit. Is that OK? Then I (personally) don't have much of a problem with a dab of oil on the slides. See if that makes a difference. Beware though, that if it's wear in the throttle bodies (carb barrels) you will need new ones, or the problem will reappear in the winter.
7) Bench sync of carb bank.
8) Reinstall carb bank, get engine warm, then properly sync.

May take a bit of work but once it's done it's done. Just one of those things with bikes: a bodge/fix will do most of the time but not all the time. Sometimes you've got to go right through it. Good luck.

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would love to do the valve clearances Bhud, but thats way beyond my capabilities
____________________
current bike Yamaha Thunderace.
its old and fat, but its a damned good ride. the bikes not bad either.

[Nobby the Bastard]

[Zen Dog]

[Nobby the Bastard]

His fault for not adding it to his numerical list.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[Kawasaki Jimbo]

[Fizzer Thou]

You will not need to drain the coolant so as to remove the carbs.

I found it easier to leave the throttle cables attached to the carbs.Just take the throttle apart at the handlebar and unthread the cables through the frame.You will thank me when you do this as the cables are a b'stard to reattach otherwise.

When removing the cam cover to check the valve clearances I found it a lot easier to drain the coolant so as to pull the radiator forward for better access to the cams,which need to be removed as and when the shims need to be changed.

The cost of doing shims on an engine like this will be upwards of £350-£500 if taking to a shop to be done.If you choose to go that route then remove as much of the bodywork as possible as you will be charged for this.

I have seen the post on the exup1000.co.uk forum
I am on there as YAMAEXUP
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Just talk bikes.What else is there?

Always have a 'Plan B'

[Pete.]

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