valves

[ant75]

hi all, could any1 tell me when the valve clearances need checking(or can you tell when their naffed) many thanks
merry xmas

[Neosophist]

The Honda service manual states that the valve clearances should be checked every 16,000 miles / 24,000km / every 2 years whatever comes first.

Check them when the engine is cold (below 35c)

There not difficult to do and worth checking if you don't know when they were last done.

As they wear the clearances become smaller.. this doesn't let the valve open properly which can burn it out.

If the clearances are on the loose side you'll hear a tappety sound from the top end.. worse when warm.. the NC30 is a little tappety anyway but no where near as bad as the ZXR's.

[ant75]

ah thanks for that think il have a look over the xmas hols,mayb that could be me problem with it not revving out properly bought the bike with genuine 12 thousand miles on the clock.

[Cammo]

mayb that could be me problem with it not revving out properly

I doubt that valve clearances will cause this.

It will more likely be fuelling (lean) or electrical issues in my opinion, both can cause this.

[ant75]

cheers cammo,ive tried running the bike without the fuel tank, and just a bottle of petrol connected to the fuel pipe and blanked the vacum hose off still the same. cant find anything in the wireing it just throws out flames when letting off throttle.

[Neosophist]

cheers cammo,ive tried running the bike without the fuel tank, and just a bottle of petrol connected to the fuel pipe and blanked the vacum hose off still the same. cant find anything in the wireing it just throws out flames when letting off throttle.

Too rich, unburnt fuel in the exhaust.

Do you have an airleak on the exhaust system too? ie.. stuffed collar / crack... this will make the problem worse.

Have you checked / set the carbs?

[ant75]

did have a hole on top of 1 of the down pipes had a new collar welded on it,had the carbs set up balanced new jets and gasgets to original spec spark plugs are new densos they came with the bike.

[Cammo]

In my opinion, and based on what peeps post up in this site, not revving out is usually caused by one of 2 things.

1. Fuelling - running lean. This can be caused by a number of things and not just inadequate jet size. When owners fit 'high-flow' (e.g. any non-Honda) air filters, chop parts off the airbox, remove the airbox snorkel or the rubber flap in front of the airbox it can all cause the bike to run lean and consequently not rev out to redline. When lean the symptoms usually get worse in each higher gear.

If all above is in place and original, you'll need to physically check inside the carbs yourself to see what jet sizes are in them - that's the ONLY way you'll be sure of what's in them. When you say carbs were set up to 'original' spec, if 'original' 110 size main jets (as standard on 1989 model bikes) were put in in it can run lean and not rev out properly, I've seen this before....

2. Electrical problems. These bikes have a poor history of an inadequate charging system which can manifest itself as all sorts of running problems. Backfiring is one of these symptoms (as unburnt fuel gets burnt intermittently). You'll need to use a multimeter and check the charging system all over, it's quite simple but important to do all checks and write down the measurements. Dodgy coils (you can check these with a multimeter) and cdi's can also cause issues, but this is not as common as a faulty charging system.

A document outlining the charging system checks can be found here: http://www.400greybike.com/docs.htm

Lastly, have you actually ridden this bike or are these problems happening when the bike is stationary? If this is happening when stationary there are a couple of other things I would check, but get back to us on above first.

[CMSMJ1]

I'd also add, that to try and rev a bike out on the stand is bad news.

[ant75]

thanks for the reply cammo, il do the electrical checks over the week ive got off work,it has 115/and 118 jets its a 91 model? j reg not ridden the bike as no tax and mot. cmsmj1,wot can happen to the bike revving it on the stand? cheers guys for the info.