NC21/24 Project (re-opened from the back of my garage)

[bantam_dave21]

Hi all,

I'm new to the site and would rele appreciate help/tips/advice...

I've just un-earthed my NC21/24 project from the back of the garage. Its an NC21 (circa 1986) with the NC24 swing arm conversion.

In trusty V4 style, i've changed the oil, given the plugs a quick clean added some fuel and instantly shes popping and smoking - however not running correctly. I'm a college trained plant mechanic so not a total numtpy with the basics. The carbs are gonna come off thorough clean out of float chambers and jets etc. Will stick some new plugs in her. I'm also going to change fuel and vacuum pipes from the tap etc.

The bike was bought as a project and has never run properly and I'm not familiar with any common issues/hiccups these bikes have.

My questions for you the experts are: once the carbs are cleaned is there anything that requires specifically setting; float heights, choke plungers etc? Also is there any other common items of TLC these bikes need after being stood up for a while?
My main objective is to ensure she runs sweet and correctly before I commence the stripdown and rebuilding her back to all her glory.

Looking forward to your comments

Thanks
Dave

[Neosophist]

Strip and clean the carbs.

Set the float heights to 6.8mm (measured from base of carb)

Set pilot screws to 2.0 turns out as a start.

Check it has the rights jets and emulsion tubes.. work on one carb at a time as front / rears have different jets.

If its got 24 carbs it'll have 115's all around (the emulsion tubes with 5 holes go in the rear carbs) 4 holes in the front.

If it's an NC21 it'll have 110 / 112 jets (front / rear)


If it's been standing a while check all hoses and hose clips are ok and tight.. if it's stil got the original rubber brake lines i'd replace them along with the fluid.

The tyres are also probably well past their best.

Once you've cleaned the carbs put them back on (making sure the carb rubbers are ok.. they go brittle and crack, but there only £5 each for new ones)

Check and set the valve clearances while the carbs are off, it's easier with them out of the way... the valves are locknut adjustable so no shims to buy, easy job there.

Put the carbs back on and balance the carbs (adjusting carbs and valve clearnaces will require a rebalance)

should run ok now.

Only other problem your likely to get with the bike is that the reg/recs are made of chocolate and melt quite often.. when (not if!) it goes bang an R6 reg rec on and it'll be fine. It's worth checking the voltage at the battery when it's running with your current set-up.

Should be 13-14 volts.

[bantam_dave21]

Hi Neo,

It would seem by view of trusty VFR noise and popping is more of a poorly VFR popping and noise :-

Many Thanks for the reply. I have to be honest and say I don't know how to or can see anyway to set the float height, other than a rather crude amendment to where the needle valve sits on the float?
In any event, I've had them off tonyt and done a quick clean and check of jets and emulsion tubes etc (I have to say I read Cam's 'How to' whilst at work today which helped immensely, carbs off in minutes - excellent read) all seems ok but I'm getting little more than pops down the exhaust and no doubt out throught the carb inlet if I had left the filter off lol. The carbs are off again I'm taking them to work for a proper full strip and clean tomorrow. I've noticed a few things which 1.) make me want to give them a full coat of looking at and 2.) make me want to investigate every nut and washer on the bike. The cones on the carb inlets - 2 are fitted wrongly and obstructing air passages which can't be helping the starting/running. Choke adjustment on at least 2 of the plungers appears miles out again can't be helping. Also found loose earth while removing carbs at coil mounting bracket for front cyliners - all in all not a good mix right. But with the popping i'm thinking something electrical too could also be contributing here and possible only tryin on 3 or possibly two cylinders? Logic tells me popping (or backfiring - does that sound defeatist) without any other signs of life is probably more of a flooding bakcfire, perhaps not quite flooding but a build up of unburnt fuel. Theres been a poor repair to a wire from the ignition box under rear seat running to the front coils so there may be others lurking. After the proper clean tomorrow a proper check of sparks ect is in order I think.

Someones clearly had tinkering fingers in this one - so it was all getting stripped anyway I think I'm just going to do it sooner rather than later. Also i'm thinking it'll be far easier while stripped down to check valve clearances at the minimum with no doubt lots of other tasks eased too. The overhaul will give me time to acquire some vac gauges for balancing too - lol

The only positive thing in my short and only just beginning story is I only paid like £200 for this bike years ago so its like a freebie she WILL live again :)

thanks

Dave

[Neosophist]

Float heights are easy to set once you know how.

With the bowls off, tilt the carb at an angle so the float flops into the carb, you want it resting on the pin, not compressing the pin,





Like so... you then measure from the base of the carb (where the rubber gasket makes contact) to the top of the float-height.

In the pictures above a proper float height ruler is being used. I use a vernier caliper.



You bend the tang in very tiny amounts to adjust the hight.

6.8mm is factory height.

Float height guide

Measure the voltage at the battery when it's idling.

Get your carbs good and clean first.

Make sure there sealing around the rubbers too.

[bantam_dave21]

Hi,

thanks again ! So tilted to the side & closed needle, seems simple enough. Bending the tag was the only way I could see to influence the height just didn't know if I was missing anything. Will set floats up today while cleaning them out. Hopefully the improvements in carb/fuelling will mean any more issues I can focus my investigations elsewhere.

Update later hopefully

thanks

Dave