1989 NC30 track bike few issues

[Haydn]

Hi,

I've not posted on here since last year but I've recently started getting the bike ready for the track day season and need some advice on a couple of things.

First up Fuelling.

I know the NC30 can be sensitive when it comes to fuelling but I'm not sure what's normal and what's not.
It seems to be running rich, smells rich with heavy black deposits in the exhaust, had to use a baffle at donington last year and it was thick black on removal. Looks like a standard air filter with just a Gibson end can. I changed the spark plugs last year and put NGK ER10EH in. The standard ER09's that came out didn't look overly black which ads to the confusion. On track it struggles with many flat spots in the rev range. At the moment I don't know what jets it's running. Any advice would be appreciated.

Second issue front wheel alignment.

I had a very small off last year at Cadwell. Went on to the wet grass and lost the front. Low speed but bent the rear brake lever and sent the right clip on into the tank. I've straightened up the clip on but on close inspection, the front wheel isn't centred when the top yoke is straight. Now it could have always been like this but it's a bit of a coencidence. It's only minor but definitely off to one side. Im hoping if I loosen all the pinch bolts i might get it running true again. Any help would be appreciated.

Thanks
Haydn

[Cammo]

I know the NC30 can be sensitive when it comes to fuelling but I'm not sure what's normal and what's not. On track it struggles with many flat spots in the rev range. At the moment I don't know what jets it's running.

Normal is lovely smooth linear torque and no fuelling hiccups. If yours isn't like this then yes, you have problems. Good news is that all issues can be sorted, it just takes some time to find the culprit.

Does it run the standard airbox and honda air filter? Rubber flap installed in front of the airbox? If all of this is present then I would suggest you need to take the carbs off, open them up and see what's inside (main jet, pilot jet, needles etc). Report back with what you find.

Also, because electrical issues are so common on these bikes, it's always a good idea to do some simple checks with a multimeter to ensure your electrical system isn't responsible for these symptoms. You can find a good charging system guide here: http://www.400greybike.com/docs.htm

I've straightened up the clip on but on close inspection, the front wheel isn't centred when the top yoke is straight. It's only minor but definitely off to one side. Im hoping if I loosen all the pinch bolts i might get it running true again.

This is usually caused by twisting of the lower yoke fork clamp, happens easily. You might be able to get it straightened, or just get hold of another lower yoke.

[Haydn]

Hi,

Sorry for the late reply but I've only recently had the time to work on the bike.

The bike is now straight, loosening all the pinch bolts was all that was needed to align the from wheel back up.

I've posted a few pics of the airbox below. It's running the standard honda air filter, but I have a few questions. There doesn't seem to be a rubber flap in front of the airbox anywhere but there is a plastic extension part which almost seals to the headstock, I'm surprised the air box can get enough air tbh. Can you just confirm where the rubber flap should be? Also there are two pipes go onto the back of the air box. The area they pipe into has a large hole at the bottom so these two pipes are just venting to atmosphere. Is this correct?

When the bike is cool is bogs down really bad at 9k rpm. Once it's warm the issue disappears however the bike feels very flat generally. I've never rode another nc30 nor have I rode a bike with 60bhp for many years so I could just be expecting too much from it. Doesn't explain the 9k flat spot or the heavy black deposits in the exhaust though.

Any help would be appreciated.

Thanks
Haydn

[CMSMJ1]

I reckon ER10 plugs are bastards and don;t really do much for us. I've never had anything but ballache with them and they are prone to fouling.

You are going to have to check your carb settings by the sound of it - check the choke not stuck open for starters

[Cammo]

You'll have to remove the carbs and check what jets and needles are in there.

If you're unsure how to do this, the carb jetting guide here should help (it's not a huge job): http://www.400greybike.com/docs.htm

It doesn't matter that those 2 pipes vent to atmosphere, they're the carb slide air displacement pipes that just push the air out when the carb slides move up.

[Neosophist]

why is one of those pipes clear?

and they dont usualyl vent to atmosphere, there is a small foam filter goes in there to filter the air going to the carb sliders.. I dont think it makes any difference personally thought.

Your bike sounds very badly setup.

Follow cammos carb guide. Carbs off and stripped and full setup to the letter.. 115/118 jets are a good place to start.

Check your existing stuff.. its amazing how years of people trying to make the bikes a little better ends up in them being ruined, often with stuff in the wrong carbs (most parts, jets needles and holdes are different front to back)

Oh and use stock plugs.. unless you get it red hot for long periods often they will just give you grief

[magg]

No mention of the scoop that fits over the radiator that directs the air flow to the air box.

[Neosophist]

What magg is trying to say in some round about fashion is that there is a heatguard / air scoop located at the front too, if thats missing it can cause running issues at higher speeds.



Number 15 in this image

[Haydn]

Thanks for all the replies. The airbox radiator front scoop is there. Only leaves a very small gap either side of the frame for air intake though. I take it this is not the airbox rubber flap mentioned earlier? I can't seem to locate that.

I'm not too sure why one of the carb pipes is clear but this bike has been a track bike for years so there's a few non standard parts on it.

I will strip the carbs down and see what I have in there, and change the plugs back to 9's. how much does a slip on can affect these bikes because that seems to be the only mod at this stage.

Thanks again
Haydn

[Drunkn Munky]

Not a lot really, maybe go up 1 jet size from stock depending on how free flowing it is