NC30 revving issues

[Jarlly]

Hi again

So, swapped both HT coils over with replacements from ebay (the replacements were in spec, mine definitely weren't) and popped the plugs out. They were all exactly the same- a half or full turn too loose and the threads covered in oil (also present in the bottom of the plug holes- icky). They cleaned up nicely so I did the gaps and put them back in. I'd guess they're fairly new as there's minimal erosion.



She starts better but the nasty high revving problems are exactly the same :/

Today she gave up again shortly after starting. I dropped my weight on her a few times and she started up right away, which makes me think stuck float (good call, neo). What would that look like when I’ve got the carbs off and how would I fix it?

[Neosophist]

carbs right way up, push the floats up so it closes the pin, when you loose your finger they should drop down and not stick closed.

only real thing that causes that is either gummy shit on the float pin, or crap in the actual float needle orifice.

If you put the float pins out the slides will come out with the pins, check they are all nice and clean and nothings gummed up.

i think theres some fiters in the carbs too so worth checking those.

[Jarlly]

Ok, it's been a while, but I've got a partial fix to the high revving stuff. It went when I swapped the plug in the front left cylinder with a new one (looked worst) and charged the battery (maybe this isn't in as good condition as I assumed!), so I'll be doing the rest of the plugs at the weekend. I also just had a dyno run, fuelling is as good as I could hope to achieve, and it's clear that trying to draw power (lights on full) causes nasty misfires:

http://s23.postimg.org/g1p4lhee3/vfr400 ... n_1401.jpg

(pretty impressed she still makes 57bhp!)

I've changed the reg/rec to an R6 one that holds steady at 14v so a little surprised that the plugs are struggling for power. Will be checking wire resistances also.

[Neosophist]

it shoudl run perfect without a reg/rec / gennny at all.. ie total loss for at least 30 mins or so on a full charged battery.

I suspect you have a shitty connection.. usually the earths are the first to go this requires more power to overcome the resistance.

clean up the earthtags is a good start. theres only a few on the bike

[Rascal]

Out of interest how where you checking the coils where in spec?

[Jarlly]

multimeter down the two spark caps, checked resistance. Also did resistances without the plug leads on, all results were on the high end for the new coils and leads, but nothing was insanely out of spec (unlike my old plug leads!).

Interestingly (!!) she looses significant power (it could even be 2 cylinders) in the rain, and makes a noise somewhat like there's arcing electricity between 6 and 8k at full throttle. I'm wondering if one of the leads has a hole in it or similar.

Will check earths and tidy up this weekend, see what happens...

[Cammo]

Interestingly (!!) she looses significant power (it could even be 2 cylinders) in the rain, and makes a noise somewhat like there's arcing electricity between 6 and 8k at full throttle.

Good idea to do those electrical checks.

I'd also check that the two cdi plugs are plugged in firmly, and that the spark plug wells are not holding water (the drain holes can get blocked up).

[Jarlly]

FIXED!!!

So, turns out swapping the coils wasn't a 100% fix. I replaced a duff lead and good coil with a duff coil and good lead! Put the original coil on (kept the newer leads) and she's at 100%. Such a fun bike to ride, with the problems I'd totally forgotten how good she was in the first place!

Interestingly the duff coil resistances are 2.8Ohms and 13.7kOhm. So, 100% in spec.