Know instance where mesh was placed over normally unrestricted carbies to stop ingress of small stones etc, engine ran rich and poorly on top end until mesh was removed. In another case air filter was fitted to another normally unrestricted cardy and same result. Both engines were designed by the manufacturer to run unrestricted. I know NC30 normally has a filter but not sure all filters are the same. Removing your non OEM filter cannot hurt.

vfrman wrote:It IS set to standard jetting!

I think he means 115/118. I'm running a 112/115 jetting after having similar problems but your a/f ratio fluctuates a lot in addition to the average being low so I don't know what the problem is.

Yeah thats what i meant, 115/118 mine hated 118/120, it was doing wat yours is, mega rich and wouldnt blip on the down shift, has foam filter and twin exhaust pipes.
Cheers
Ian

Morespeedvicar wrote:Yeah thats what i meant, 115/118 mine hated 118/120, it was doing wat yours is, mega rich and wouldnt blip on the down shift, has foam filter and twin exhaust pipes.
Cheers
Ian

Oh. I thought you meant what the manual says is stock.

vfrman wrote:

Also, WTF is happening at the top end of the rev range?

Steve, there's something seriously wrong with the bike judging by your a/f ratio.

Based on how rich the bike is through the entire rev range (extremely) it's likely that it's fouling plugs and causing spark to break down at high revs. This could be caused by a number of things.

It sounds as though your carb setup is reasonably close to what you would want (minus the needles - ditch them and go back to standard or Rick O's road needles). It's very unlikely that an issue with your carbs is responsible for running this rich over the entire rev range, best to look elsewhere for the cause.

It would be worth performing a compression test on the engine before looking any further for a fix. Bores or rings could be worn allowing oil through which will affect the a/f ratio.

Check to see that the oil level isn't overfilled either (or that there's no petrol in it if you've hrc'd the fuel tap or got stuck floats - it's happened to me before).

The k&N air filter won't be helping the 5k dip, go back to a standard air filter to improve that slightly, but I think you have bigger problems than this right now!

vfrman wrote:It IS set to standard jetting!

which would be awesome at sea level. At your altitude drop a size or two, and put the air filter back to stock.......

Mike Norman suggests I clean the carbs well, inspect the tank for crud, and drop 4 sizes...

vfrman wrote:Mike Norman suggests I clean the carbs well, inspect the tank for crud, and drop 4 sizes...

When you have the carbs off check the back of the intake valves for oil or oil sludge on them.

vfrman wrote:Mike Norman suggests I clean the carbs well, inspect the tank for crud, and drop 4 sizes...

I'm with cammo, actually have time to look at the thread today and woah its running mega rich.

You dont have a mouse or something blockin the airbox off do you?

Since its proven on so many bikes what a good known base setup is then I think thats what you should be aiming for.

As cammo has said, oil level and rings are good to check. Are your float heights ok? How does it feel when running, I should imagine its flat and boggy? Pilot screws are ok, choke isnt stuck on? (all levers return back ok.)

dirty carbs usually get blocked up so stop letting fuel through rather than ovrfuel but you cant have too clean a set of carbs, and might spot anything else.

Yo VFRMAN go for 110's all round
TRUST ME