NC21 Wont start after 1 year of staying

[demerdzhiev]

From which passages to blow i out exactly? I was thinking about that method but didnt have a compressor at the garage, but i think it is worth findig one and doing it, even after cleaning them with coreselin.

I found a whole new set of carbs from a man in bulgaria who sells his bike on parts for 30$

Couldnt resist that offer and told him to sent them tomorrow.

[Neosophist]

aha new carbs might be good.

every passageway.. the most comon to block up is the pilot circuit.. if you unscrew the pilot fuel screw (be careful to amke sure you get the screw / spring / o ring and small washer out.. they often get stuck in the hole.. even a foot pump with soccar ball adapter will be ok.. get some carb cleaner in there and blow (be careful of eyes)

the pilot screw hole goes to just by the butterfly.. you will see 3 small tiny holes.. they need to be clear for the bike to idle properly.

[demerdzhiev]

In mine case the three little holes are behind the butterfly therefore these three holes work when the butterfly is opened, and in front of the buterfly there is one little hole.

By behind and in front of i am talking from the point of viewing as i am on the side of the cylinder.

should i do it with float bowl on and jets on or first remove them?

[Neosophist]

thats the holes.. the bigger one is probably for the choke.

remove everythign from the carbs and blow through the holes and then blow in where the pilot jet and main jet / jet holder goes.

make sure to check you have teh correct jets in each carb and pilot screws are set to the right amount of turns out as well as the float height is set correctly and it shoudl run nice

[demerdzhiev]

Sooo i cleaned them and reassembled them and there is nothing leaking, at first cylinder #1 got flooded because the the float was stuck i guess but after i knocked the float bowl gently with a piece of wood it was fine.

But the engine still doesnt run, and it still backfires through the carbs.

Is it possible that the plugs give spark (Checked) but they still be faulty? From the beginning i was concerned about them.
there may be spark leaks or the timing of the ignition is f*cked up.

[Neosophist]

igntiion timing is set therough electronic so very rarely to go out of problem

its hard to start with no airbox..

full choke and no throttle at all.. if you even open the throttle slightly it wont start

[demerdzhiev]

What do you think about the plugs ? they give a spark but i dont know when the previous owner had them first, and if they arent worn and by the threads i read i saw a lot of people with plugs that give spark and still by being changed the engine fires.

Is it possible that i have mistaken the coil-cylinder connections, and does the nc21 share the wasted spark thing where it gives a spark to both rear/front cylinder simultaneously?

[Neosophist]

nc21 has 4 separate coils.

plugs should be ok, lift up the vaccum diaphram, open the butterflys by opening the throttle and pour a litle fuel down each cylinder and try and start it.

[demerdzhiev]

soo i was right, changed the plugs and everything is ok. F*cking vfr and plugs, how can they give a spark and still aint worth shit.

Now i have to adjust the carbs, but first i have to change the diaphragm. Tomorrow it should be here. After i change it i will put the tank and seat ot their place and try to adjust the idle, whats the perfect idle rpms? 1000? should i adjust them only from the idle adjust screw which opens the butterflies? Ofcourse after i have made all the idle screws 2 turns out?

[Neosophist]

soo i was right, changed the plugs and everything is ok. F*cking vfr and plugs, how can they give a spark and still aint worth shit.

Now i have to adjust the carbs, but first i have to change the diaphragm. Tomorrow it should be here. After i change it i will put the tank and seat ot their place and try to adjust the idle, whats the perfect idle rpms? 1000? should i adjust them only from the idle adjust screw which opens the butterflies? Ofcourse after i have made all the idle screws 2 turns out?

no no ...

you are turning the wrong screws!

there are several "screws" on the carbs.

get the carbs off and check them all first and it will run spot on and save you having a biek that starts but runs like crap.

First off you need to check the main jets and slow jets are clean, did you remove them and clean them?

I think the NC24 runs 110/112 jets? Smaller jets go in the front carbs and larger jets go in the rear carbs.. easy to get them mixed up..

the jet holder that the main jet screws into has air bleed holes in the side.. if you have a set with more holes in them they also go in the rear carbs.

Next you need to set the height of the float inside the carb.. you can measure this, it needs to be 6.8mm on each carb.. if you dont have the proper measuring tool you can use an old plastic card like a credit card / gift card etc.. you need to cut a section of it that is 6.8mm high.. then tip the carbs at a 45 degree angle.. you want the float to rest on the spring pin of the float valve but NOT to compress it.. if you put them upside down it will squash the pin in and your setting will be wrong.. then use a small flat screwdriver to bend the tab that the float pin is connected to until the height is ok... see the picture



Then first off you have the pilot screws.. there are one on each carb so you have 4 in total.. these adjust the fuelling at idle to each carb. The stock setting is two turns out.. so screw them all in gently. do not use force.

Next unscrew them 2 complete turns... if screw looks like this (-) ---> (|) -----> (-) = half a turn, so 2 full turns.. put a dot on a screwdriver handle to make counting easier.

Once you have all 4 of them done you can look under the carbs.. there are 3 hexagonal shaped screws on the linkages, these are the balnace screws and they sycnhronize the carbs.. the proper way to set these is with a set of vaccumn gauges to measure the engine suck while its running.. if you dont have a set of these then you can google search "balance carburettors drill bit method" to find a guide on how to set them quite close with a drill bit.. this is important to get a smooth idle so take your time with it, bike will thank you in the end.

last setting is the idle speed adjuster.. there is only 1 of these and its the plastic turnable by hand scrwe.. use this to set the idle after doing all theabove.

Idle speed is 1,300rpm and stock plugs are C8EH9