nc21 tickover problems

[Neosophist]

As cammo said, the older rubbers are not available, NC30 ones should be ok and are avaiable.

viewtopic.php?f=24&t=14524

This is the guide.

Ignore all the bits about the NC30 mods but the carbs are very simliar, will show you how to get them off and clean them etc.

Use it as a reference.

Jetting will be 110/112 if it hasnt been messed with with the 110s in the front and 112s in the back.

[128bhp]

To think that two hundred years ago, books were being burnt to stop us learning.
This internet is fuckin awesome.
Thanks all.

[speedy231278]

Yeah, but no-one had invented motorcycles, so there was nothing much worth reading about!

[Neosophist]

Yeah, but no-one had invented motorcycles, so there was nothing much worth reading about!

If they hadn't burnt all the books in the dark ages then imagine how developed the bikes might be now!

[andy1472]

Hi there.

Make sure your float valves are in good working order too. I put 4 new ones in mine and cleaned out the float valve seat filters. Two were blocked and 1 had come away from it's seating position.

It's great fun leaning to do your bike yourself and that in turns gives you more of a chance of fixing it if you break down somewhere.
I knew nothing about carbs until my dad who has restored bikes for 42 years taught me a lot. Take your time, take pictures if you aint sure to refere back too. Personally I'd source out a secondhand fuel tap off ebay. You can get them for around a tenner, change it back to how it's meant to be.
Set yourself up a good clean bench. plenty of light and give it a good clean and check. Neo is right, people who know fuck all about carbs mess with them and fuck them up. My needles were all over the shop in the wrong places and some screws were rounded off. I hate rounded off over tightened screws grrrs. Luckily my dad brought me a full set of donor carbs so I got a very good working set from the two.

Good luck matey. Hope you sort it out.

[128bhp]

Hi there Andy, I set the float hieghts, and they seem to operate ok. If it doesn't run great I'll change the floats. Where can I get floats from?
I got the rubbers today and took the carbs off. One of the main jets had fallen/unscrewed out and must have been sat under the float.
I got some sealer and sealed the bowl covers back on after a clean.
I was scratching my head for ages trying to work out how to get the carbs back on the rubbers, until I worked it out that the carbs had to be split/ loosened.
Really enjoyed the job, bloody marvelous.
Just finished getting it back together 11.45pm. so I'll try and start it in the morning.
The chap at the garage who put the restricters in said the problem I had with the revs slowly returning to idle could only be sorted with new carbs . When he tried to get it going, would he have had to set the carbs up to compensate for the jet being out, as he obviously didn't know. I have no clue as to set them up as yet. Do they have to come off to set them?

[Cammo]

I was scratching my head for ages trying to work out how to get the carbs back on the rubbers, until I worked it out that the carbs had to be split/ loosened.

The chap at the garage who put the restricters in said the problem I had with the revs slowly returning to idle could only be sorted with new carbs .

I have no clue as to set them up as yet. Do they have to come off to set them?

You shouldn't need to split/loosen the carbs to get them back on, doing this will make it difficult to fasten them properly to each other when in the bike and could cause more issues.

Slowly returning to idle could have been related to the jet missing/sticking the float or pilot screw setting out of adjustment, whatever it is it can be certainly be fixed. It's easiest to set the pilot screws with the carbs off the bike.

[Neosophist]

The guy who told you that shouldn't be a mechanic.

He either

1. Knows the real issue and can't be arsed to sort it and is fobbing you off

2. Doesn't know what is causing it and is clutching at straws.

Either way its the sign of a truly shitty mechanic.

Any mechnicac knows that reputation goes a long way, so they could at least do you the courtesy of telling you the truth.

A slow return to idle is THE classic symptom of an airleak... when you shut off the throttle the bike can still suck in air through the leak (which is actually like having the throttle still open) so the revs stay high for a while.

Restrictor washers shoulndt really affect the idling of the bike, only at part / full throttle when it may be too rich.

Providing.

1. Your carbs are clean inside and assembled properly
2. There are no air leaks
3. Valve clearances are in spec
4. Carbs are balanced

it should run like a swiss watch.

Having a jet not scrweed in will REALLY mess up the running big time.

Providing you have no air-leaks and the vaccumn tap is working, starting these bikes from dry carbs can take a while.

FULL choke, no throttle at all.

Crank the bike (tap on of course) for 5 seconds (count) then wait 3 minutes. Crank again and it should fire.

The tap only opens when the vaccum is applied (engine cranking over) and becuase the carbs are empty from a strip it takes a while for fuel to drain down into the carbs and fill them up (gravity fed)

Let us know how you get on.

[128bhp]

Yeah, the mechanic said that the parts in the carb were worn. I asked him what can be done and he said"nothing".
I think because I had him fit the restricters, he thought thered be no way I'd have the carbs off and stripped, Thanks to you guys I did.
The rubbers are on now and its been cleaned out, and float heights checked, runs nice. It is a pig to start everytime though, I have to gradually pull throttle bit by bit otherwise it would cut out. Is there a tickover screw on these or do you adjust the throttle cable ends.
I took out a plug and it says ngk cr9eh and a 9 under it.(edit; I see the spec actually doesn't have the r in the code its c9eh-9) for extended high speed riding. I assume that means its for the track and I should put in u24fe9 instead.

[Neosophist]

it will most likely be fine, perhaps your plugs will foul a little easier but time will tell.

It cuts out becuase of low revs? Then adjust the idle speed, yes there is an idle adjuster on the carbs.

Is your choke working and are you using it?



Look here you can see it right by where the throttle cable connects (black spinney thing) Turn it up a bit and see how it helps.

Finally.

I see the mechnic offered some explantion, maybe I was a bit quick on slating him, but did he say what was worn? There isnt a great deal on the NCxx carbs that wears out but it is possible.

Anyway, hopefully youve fixed it :D

Remember to balance them after setting up the idle speed for a super smooth tick over