NC30 fuelling

[matt_vfr]

Hi guys... just had my nc30 serviced and rejetted etc, its got ethos pipework with a blueflame twin exit oval can and its just had 117.5 jets all round. When i first got it back its ran beautifully but now it feels a little rough, and if i ride it for a little while it starts misfiring, a bit like its flooding, and its awful. If i rev it a bit , after a while it seems to clear and is fine for a little while. I doubt its something wrong with the jetting as the guy used to work for redline honda. I know for a fact that the fuel tap is dodgy as it lets petrol through even when its turned to off... would this cause it? It didnt used to do this before i had it rejetted apart from it did something similar when the rear ignition coil died, but it did not like to rev then, whereas it does now! Anyone have any ideas??

Cheers,

Matt

[CMSMJ1]

What jets were in it before? Has anything else changed? Have you changed anything airbox/filter etc related?

117.5 would seem to me possibly lean for your pipes and with that I would expect it to rev nicely but for it to then stop feeling as nice is dodgy.

It has got rich..so either choke stuck open or filter is dirty?

Pop the tank off and have a look!

[wullvfr]

check the plugs and see what signs they are showing,are you getting any back-firing or black smoke from the exhaust at all?

you said it ran fine for while and then started to run like this,so it may be another problem other than the jet sizes!!!!

like cm says have a good look and see if there is any obvious signs..........

maybe check the plugs are sparking good,it could be an ignition/electrical problem but it does seem a little suspect that it has happened a short while after the carbs were done.


william

[Sligeach]

i get the exact same symptoms when i put the race can on my bike.
it will cruise along ok and then when slowwing down like at a round about, it will bogg down and almost stall.
if i put the OEM can back on, i never get the same symptoms.
so my 2p is that it is fuelling/jet related.
117.5 all round is it? does seem a little lean for aftermarket pipework and can

[matt_vfr]

Right, well when i had it done it went in for a full service as well, so its had new plugs and filter, air filter etc etc... theres no black smoke from the exhaust, just the usual bit of steam you get when starting it from cold which clear after a while. Not really any backfiring except the occasional pop from the exhaust on the run-off. When you ride it for a bit it starts to feel fluffy (doesnt seem so bad if your up and down the rev range, more when you stick at a constant speed for a bit) and if you then try to accelerate it misfires and holds back for a bit and then seems to move after a load of coughing and spluttering. If you then slow down and pull the clutch in to rev freely its still not happy and splutters for a while but seems to clear to some extent after some revving, although not fully. Another strange thing is when its doing its thing, if you try to open it up more, once it clears a little it will quite happily rev all the way to the top, its only really while its staying at the same speed

It seems to be when it gets warm it starts to behave like a biatch!! Left me stranded last night at the brook street roundabout (M25/A12) cos it started missing along the A12 and when i pulled onto the sliproad i pulled the clutch in and the engine died... tried to start it again and the battery went dead before it would start (only about 5-10 seconds or cranking) so i had to push it into a petrol station and call the AA to come and sort it out... 1 hour and 15 mins later he comes, jump starts it and it ran perfectly!! Started going home and about 5-10 miles down the road i could feel it getitng fluffy again but managed to get it home thankfully!

The thing that makes me think its not the jetting is that when it works it runs beautifully, and did so for a week after it went in, and then it started doing this... also as i say, the guy i sent it to knows what hes doing cos he used to work for redline honda and spent many years racing nc30s.

Ive just had the thing apart and cant find any obvious problems, but checked the regulator against the table of values in the haynes manual and the connections between the yellow terminals all show around 2-3Mohms instead of 30-500Kohms, so is it possible this has died? would this cause such a problem?

Thanks for the help guys,

Matt

[viper_biker]

Is it cold where you are? It has the symptoms of carb icing as well. I had this a few years ago and it sounds just like what you are describing. If everything else has been replaced for new ie plugs, filters and a Dyno set-up and jetted correctly then that would be the next viable explanation.

[matt_vfr]

One other thing, when i open the petrol tank, the water that collects around the edge falls into the tank, and ive had to fill up a couple of times this week, could water in the carbs do anything? My dad reckons the water will go to the bottom of the tank so it surely it should go through first, be a shit for a while and then clear?!?! Dunno if this is relevant but if i describe everything im guessing ive got a better chance of someone coming up with a sloution!

Matt

[CMSMJ1]

I think you are looking at electrical issues if you say the reg rec does not have the right numbers when tested. Riding it on a charged battery is all good...but then when it starts to die it can feel like you describe. I would test the charge rate of the battery at 5k revs (should be 14.5 or so volts)

worth a punt as so easy to check

[matt_vfr]

its pretty much bang on 14.5V not sure whats going on here now, does that mean that the rectifier is fine? Also, about the carb icing... its not that cold around here, it was a lot colder when i got the bike back from the mechanic, plus ive been using it in london for the past 2 weeks so its not really cold there at all!

Matt

[Sligeach]

the more posts you make the more i am convinced the bike needs the jets changed as it is running lean.
i have been running the OEM can on the ZX6 all winter and its been super. just in the past few days i put on the race can and in the mornings it is an absolute pig, bogging down when going to overtake, and just being a bit of a whore after cruising at the same speed for a while, like a approaching roundabouts.

however in the afternoon its much better. so may say this is carb icing, but i know in my case its the jetting is incorrect and when running lean, the air mixture is wrong, and the cold air is even wronger, but its not true carb icing, as silkolene fst pro doesnt cure it, either does premium petrol.

the other trick you can pull is the old kill switch one, it is dangerous, irresponsible and may damage your bike, but its another way of testing to see if the bike is lean