nc21 tickover problems

[Neosophist]

nice one..thanks.
So it seems I have to have the carbs down to their total individual pieces to totally get my head round them.
I couldn't tonight . I gave up at 11pm and put them back together so I could be on the road tomorrow.
There coming apart again tomo night. Bring it.

Don't take them into 4 pieces, there is no point, you can't do anything else, there a real pain to put back together too

All you need to do, remove the tops and take out the slides and needles (remember which carb each part came from)

Remove the jets and jet holder (emulsion tube) and pilot jet.

Blast them all with lots of carb cleaner and find somebody with a compressor and blow compressed air through all the passageways.

The 3 holes make up the pilot circuit, while its idling they supply fuel, if they are blocked up it will idle rough, dont worry about a bit of black flashing aroudn there so much as long as the holes are clean.

[128bhp]

I'll need to have the idle adjuster machined out and tapped, as its idleing at 4k, then go from there. Its off the road till the weekend now, but thanks for the help, I'll let you know how its going.

[128bhp]

The Father in law has had the idea, fair doos to him that to not drill the adjuster screw out, but to drill and tap and put an adjustable bolt in the throttle twisty thing,.(terminology please).as trying to drill out the bolt would be far harder than drilling and tapping the alloy of the twisty thing.

[128bhp]

Hi folks, I thought I would let you know whats happening with the bike.
I bought the replacement carb rubbers from david silver. I had a right game fitting them, as they would not stay on the carb side, they would keep sliding off as if they wasn't on far enough. But with the restricters in the top of the rubbers they were on as far as I could get them. I finally realised that the rubbers were upside down. To look at them they seemed like they would go on either way, but no, there is a slight difference. so I simply turned them over with the restrictors now at the bottom and all tightened up well. It seemed that each rubber had a loose and a tight fitting end to it., and I found fitting the loose side to the carbs to work.
Hopefully that will save someone some time. I lost days on it.
Runs nice now. It still has a slight rising and falling idle. If I were to turn the idle adjuster(Had to modify as sheared off) so to get it to sit at say 3k revs, and found that the revs sat there solid and didn't go up and down, would that mean that it was not an air leak but a carb balancing job needed?

[bikemonkey]

Carb balancing and valve clearances I'd say

[Cammo]

To look at them they seemed like they would go on either way, but no, there is a slight difference. so I simply turned them over with the restrictors now at the bottom and all tightened up well. It seemed that each rubber had a loose and a tight fitting end to it., and I found fitting the loose side to the carbs to work.
Hopefully that will save someone some time. I lost days on it.

This advice is probably a bit late now, but the carb rubbers have the wording 'up' moulded into them them which indicates the direction to fit them...

[Neosophist]

To look at them they seemed like they would go on either way, but no, there is a slight difference. so I simply turned them over with the restrictors now at the bottom and all tightened up well. It seemed that each rubber had a loose and a tight fitting end to it., and I found fitting the loose side to the carbs to work.
Hopefully that will save someone some time. I lost days on it.

This advice is probably a bit late now, but the carb rubbers have the wording 'up' moulded into them them which indicates the direction to fit them...

Yes.

Also mount them to the ENGINE first, and clamp them up then push the carbs into them.

Id say you have an air-leak still.

Rising and falling is classic sympom.

At higher engine speed the airlea makes less difference as you need to pull in a lot of air.

Erm.. is the vaccum hose connected ok and the balnace screws all toegher.

Can be a bit of knack fitting them at first but once youve done a few its a doddle.

(dont overtighten the clamps alos.)