Hi guys, i have a 1989 nc30 but its not running right Its starts quite freely but struggles a bit to rev sometimes, sounds a bit like a misfire and occasionally it only idles on 3 cylinders! When i try and ride it, if i try and pull off by letting the clutch out slowly it will cut out!! If i give it plenty of revs and clutch slip it will go but letting the clutch out reasonably fast results in the revs dropping and really really slow pulling off!! Then when its going fast it doesnt want to rev past about 8000 at times, but sometimes it will, just a bit slowly... still sounding a bit like its misfiring! However, yesterday i put a tankful of shell v-power in and when i started it up it was incredibly free revving and pissed off up the road out fo the petrol station... and then went back to its old problem!!! To cap all this off, i got about 90 miles out of a full tank so its drinking as well!!! Since the guy i bought it off (relatively cheaply thankfully ) had stored it for about 5 months i figured it could just have that varnishy stuff inside the carbs so i put a can of motrax fuel system cleaner in it hoping that would work and while it seems to have cleared it a little bit, its far from fixed! Does anyone have any suggestions as to what is up with it??? Anyone had a similar problem??? ....Before i got and dismantle all the carbs!

Cheers,

Matt

Check your rectifier before you start to dismantle anything. That can cause some strange running issues. Borrow a haynes manual and a multimeter, thats all you will need.

Yeh ive heard about these being a problem but the guy told me hed had it replaced not so long ago... but then i guess you cant trust anything a seller says really lol! Ill give it a go tonight!

I would say it is dirty carbs.

Probably one pilot jet or drilling is blocked with fuel corrosion.

Strip the carbs and soak with a carb cleaner, YAMAHA do a good one
then blow out with compressed air.

Dont poke wire down the jets, but a brisstle from a brush is ok if all else fails.

Dave.

What he ^ said :) . I very much doubt it's the rectifier.

yeah i wouldnt worry about the reg rec......dirty carbs by the sounds of it,it all makes sense with it being laid up for 5mnths.get them off and cleaned and see if it makes a difference :D

you have checked the plugs are producing a decent spark havent you? if not id try that before i stripped the carbs down

my 89 nc30 ran like a bag of crap when i got it....wouldnt rev freely and would stutter at around 8-9k and then splutter all the way to 11 then it would rev a bit more...

i changed my airfilter and it helped a bit....but changing the jets sorted the problem right out! 122's and 120's now it revs fine.

recently it played up again at 8k....my airfilter was so blocked it was unreal....turned it upsidown and tapped it on the ground and so much grit etc fell out....put it back now she runs right again!

check and clean your airfilter
strip your carbs and clean the jets!

Thanks for the advice guys, ill be stripping the carbs down and cleaning all the jets etc a bit later in the week when i get back from house hunting! My dad reckons that its shit in the carbs as well, which is also causing one cylinder to flood and misfire... hopefully itll be a reasonably easy fix! Ive had a good check over the bike and the engine sounds mechanically sweet, the spark plugs are pretty much new as the guy i bought it from said, and the air filter looks fine... its not new but theres plenty of life left in it still!! Cheers for the help!

Matt

Right, well i had all the carbs off yesterday and cleaned them all up... on the whole they didnt look too bad but cleaned them up anyway and had them back on. Went out on it today and it did seem a bit livelier when i first got out on it, and it was accelerating rather nicely for a while, but as soon as i tried to open it up a bit it decided to bog down again and splutter! So i stopped and put it in neutral and gently revved it to clear it out and it was good again! Kinda like its flooding... what the hell is wrong with it!!! I have no idea now! Does anyone have a clue whats wrong with it?? Weak spark perhaps? Is this a side effect of a dead reg/rec??? Cheers for any help!

Matt