This one's for Neo

Just been stripping down my spare set of carbs ready for ultrasonic cleaning. Apart from a missing choke mech, it all seems ok. Or does it?......

Started on the rears, removing the floats and jets. Main jet only has 4 holes in the emulsion tube Checked out all the others and they are all the same Can't tell what sizes they are though as I can't see any markings on them. The other jets are all #35 so they are fine.

Am I right in thinking the mains should be 5 port on the rear? Is it 110 front and 112 rear or 112 all round on the later carbs? Think I'll be getting some new mains anyway so just wanted to check. Will standard sized jets be ok with OE air filter and Dic system?

I posted a thread but nobody stickied it detailing every revision of NC21 / 24 carbs.

The early NC24 carbs had 112/115 jets.
The later NC24 carbs had 115 all around.

What jets are in your carbs?

There are also several revision of emulsion tubes on the various models.

viewtopic.php?f=24&t=22317&start=0

This should help :)

If you have the same tubes all around I wouldn't worry. But if you have 110 / 112 jets this indicates NC21 carbs.

How do I actually identify the jets? There don't appear to be any markings on them.

BTW, I got the carbs off a 400GB member in the Midlands


EDIT: BTW, where do I need to plug in vacuum gauge extensions on the V4 carbs? I've only ever done inline carbs before and never Keihin.

You'll need screw in take-off adapters.



On the barrels just below the carb rubbers you'll see a philips screw with a washer, unscrew these and you screw in a take-off adapater for each one.

There not all in the same place so look around.. one is hiding behind the thermostat for cylinder #4

If you don't have the take-off adapters morgan carbtune sell them quite cheaply.

The little jets should have the size stamped on them, maybe around the edge?



Mine look like this...

I've got take off stems that screw in but I can't find the screws you mean. The only screws I can find are the drain screws on the bowls and the mixture screws just above the bowls, both are slotted screws.

The only philips screws I can find are those that hold the carbs together and those that hold on the bowls and diaphragm covers.

Carbs are marked up VD and have 32mm ports so they are definitely NC24 carbs.

Found the ID on the jets. 112F and 115R.


And I think I've just realised that you mean the take offs are on the block and not on the carbs?

Yes there early NC24 ports.

And yes the take-off parts are on the Barrels not the carbs.

Look where the rubber attaches the carbs to the engine and just below those.

There on the corners for cylinder 1,2 and 3 but on the side for cylinder 4.

For reference 1 is bottom left, 2 is top left, 3 is bottom right and 4 is top right when sitting on the bike.

the screw for number 4 is hidden from view by the thermostat (you dont need to remove this to get the screw out)

Ta Neo. I may venture out into the frozen garage tomorrow to balance my carbs then

No worries,

Unless you have very small hands or some fancy bendy stuff with a 7mm socket on the end or an angled screwdriver you may struggle as the balancing screws are underneath the carbs in the middle of the V.



Morgan also sell this, at £42.00 it isn't cheap but it does have many uses and makes balancing the VFR carbs a doddle.

Warm the engine up, set the idle to about 1600 and balance them there.

You can't adjust carb on cylinder 2 (top left) as this is the master, all the other carbs should be adjusted to match it.

All balanced now

I took the carbs off to check everything out and noticed that the screws that hold them all together had become loose and causing the butterly arms on the R/H carbs not to meet the throttle arms properly. Must not have tightened them up properly last time around and with the persuasion needed to get the trumpet bowl on it must have shaken them loose.

Anyhoo, tightened them all up and reset the butterflies to a balance-by-eye state and got the gauges on before putting the carbs and tank back on. Started her up and left her to warm up for ten mins.

Came back and... well bugger me if the carbs aren't balanced to within the width of the needle on the gauge A slight tweak and they're now pretty darned spot on. Adjusted the idle to around 1400rpm.

It's much better now but still hunts a little, fluctuating no more than about 75rpm every now and again so I think I may need new carb rubbers soon.