NC30 running on 3.

[mitchyboy01]

Hi guys, been a lurker here for a while but now I need your help....pretty please!

Anyway, I'll introduce myself. I'm Mitch from down in sunny Kent. Bought my NC30 last August and have only ridden it a few miles. Maybe 30 at most. Here is pics for you all.











I have owned 2 NC30's before but usually I pay a garage to do the work. I am a lot more patient than my younger days so I've decided to have a bash at maintaining/fixing this one myself.

I have pulled it from the garage today after booking a track day for April 12th. The bike has to be running well by then or I'm going to be gutted. I knew the bike had been running quite rough and today found that the front right cylinder header is only getting warm unlike the rest which are scolding hot. On initial fire up it heats up quite quickly but then levels off at a temp I can just about touch.

I have swapped the plug from the misfiring cylinder to another but the problem still persists on the same cylinder. I have a receipt for new plugs from a month before i purchased the bike. I tested resistance on the coils. Rears were 4.1 ohms primary and 24.15 ohms secondary. Fronts were identical.

Pulse generator coil gave me 428 ohms.

Both front plugs had a small amount of oil at the tops of the threads. Not sure if this is normal.

There is a flat spot when riding between about 8-10,000rpm which may be related. The bike feels very down on power from my previous NC30's.

I found that the ignition lights were only coming on intermittently when turning on the ignition. On further investigation I found some very bad solder joints on the back of the switch so a new replacement has been ordered.

What is your advice on my next step guys? Any help is greatly appreciated.

Mitch.

[mitchyboy01]

Any ideas anyone. I now have the carbs off and planning to check the settings and clean them tomorrow. The fuel filter looked like it had began to melt when I removed it! The airbox has had some mod done. Could this be causing the flat spot? Shall I return it to standard? Pics of filter and airbox below. Thanks.


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[VtypeV4]

I think your fuel filter has 'reached the end of it's useful life' if I'm being honest!

As for your airbox, there's a flappy rubber part that sits near the mouth but I can't really see what's going on with your pic. They need this as I'm sure you know having had '30s before, they're very sensitive and funny about even small changes to their breathing and fuelling. This might explain your 8-10k rpm issue. Mine pulls really strong from 9 up to 13k. It will happily bang into the limiter but is best in that range.

I get the spot of oil on the threads of the plugs too and my bike doesn't burn oil so I assume I have a slight cam-box gasket leak. I wouldn't worry too much about it.

Have you checked your main jet isn't blocked? Had that with the Mrs' Bandit as it would idle fine on all four then I'd open the throttle and drop onto 3 cyls. That has Keihin carbs too which seem quite stroppy on occasion. Never had bother with Mikunis.

[mitchyboy01]

Hi, thanks for the reply!

I did own an RC30 in 2006 but realised that riding it like I stole it I was eventually going to kill a classic so I took the money and ran! I'm still over the moon that I got to really put an RC30 through its paces against all my mates on younger machinary. Anyway back on the subject!

With regards to airbox, if you look at the top of the picture you can just make out a gauze that has been stuck over a hole that has been cut out of the plastic. I'm sure this is a common mod as my old one had the same mod but was set up professionally. Im pretty sure this bike has had a DIY job so I may just return it to stock and follow the jetting guide on here.

I have a friend who owns a car garage so would you recommend I get him to use compressed air to clean my jets? Also after removing the float bowls will I need to order a gasket set or can I reuse the old ones? I'm quite tight for time so the less I have to wait around for parts the better. Would any motorcycle shop stock fuel filters? As you say, mine is feeling a little sorry for itself lol

Sorry for the barrage of questions!

cheers, Mitch.

[bikemonkey]

That fuel filter is probably part of your problem.

It is not needed.

As the NC30 uses a gravity fed fuel system (and already has a filter in the tank and each carb) adding an inline filter can seriously slow down the flow.

As for it being one cylinder that's the problem, I'd be investigating that cylinders carb, and all the others whilst I was at it.

[mitchyboy01]

That fuel filter is probably part of your problem.

It is not needed.

As the NC30 uses a gravity fed fuel system (and already has a filter in the tank and each carb) adding an inline filter can seriously slow down the flow.

As for it being one cylinder that's the problem, I'd be investigating that cylinders carb, and all the others whilst I was at it.

Thanks. Definitely going to bin the filter. If I get time today I'll have a look at the carbs. Do I need a gasket set or can I reuse the gaskets?

[bikemonkey]

Personally I always buy new gaskets each time.

You can re-use the gaskets if they are in good enough condition, just add a very thin smear of petrol-resistant gasket goo

[arsey30]

As for it being one cylinder that's the problem, I'd be investigating that cylinders carb, and all the others whilst I was at it.

Exactly, if it runs well on start up, I expect it is still on choke, so the pilot circuit is bypassed.
Clean the jets [pilot blocks easy as it is tiny] and air ways, including the 3 tiny holes where the butterfly touches the throat of the carb with compressed air and carb cleaner, paying attention to that cylinder running colder.
I have found most poor running on NC and RC is carb blockage, although the NC plugs foul easily if the engine does not start quickly.

Most other faults will affect 2 or 4 cylinders.

[NGneer]

for getting rid of the inline filter. Not needed and only going to cause problems rather than solve anything and go back to OEM on the air filter / flow set up.

If you havn't run the bike much over the last 8 months a good carb check won't take too long and will serve you well.My advice is to just do one bowl/carb at a time so you don't get mixed up and yoyu can always compare with another one if you get lost.

As for cleaning your jets, having an airline handy is nice...but not essential. I use some of the "TeePee" interdental brushes and a can of keybord 'compressed air' cleaner.....or just blow 'em if I have no can of air. The TeePee bushes are brilliant for this as they can get right though the jet and give it a propper scrub out...


As well as the jets check the rest of each bowl as old petrol can turn to shalac(spelling?) inside the bowls and generaly gunge things up...
eg turning this to this with just a bit of petrol and an old tooth brush.

As for the bowl seals etc - yes you can re-use them if they are in reasonable condition, but whilst you are doing it, why not do a proper job and treat then to some new seals..(viewtopic.php?f=64&t=39681)

Finaly either check the plugs are properly clean before you refit them - or treat it to a fresh set for the summer.

Keep us posted on how you get on and enjoy the track day

[mitchyboy01]

Fantastic posts guys. A great help. I feel a lot more hopeful now. Not sure if I will have time today but I will post my findings and update when I can!

THANKS!!