engine issue

[matty_boy]

The NC30 has started to pop and fart, not when the power is put on but when the engine is coming down the rev's. It is a bit like a back fire but it is popping, i think it might be a little to much fuel or fuel not being burnt, but has any one got any ideas why ?


Ta Matty

[Cammo]

i think it might be a little to much fuel or fuel not being burnt, but has any one got any ideas why ?

That's why it happens. Check that all carb settings are correct. Exhaust air leaks might also contribute, make sure everything is sealed (if it's a sprung aftermarket system, use gasket sealant, etc).

Depending on your setup (carbs and can), you might not be able to totally eliminate it.

[randallbass]

also if your not confident with pulling apart the carbs first off i would check your plugs start it for a while and let if cough and splutter then kill the engine remove plugs.... if there built up with carbon and wet then u definatly have to much fuel going there,
might be your needles and diaphrams are dirty and getting jammed as the engine revs are dropping, if the bike has been running well for a while and nothing has been modified or altered then id say a good clean of the carbs will get ya going as they dont usually detune them selves they just need tweaking
cheers Tim

[matty_boy]

Yes this is what is was thinking, it was doing it before the new system was put on.

Could it be signs that the carbs need to be balanced ?

[randallbass]

have u cleaned your air filter recently?
check your airbox for oil.
if a filter clean and air box clean doesnt help take the carbs off, check the rubber boots the carbs fit onto the engine for splits and such, remove the fuel bowls and check your float heights and jets (take note of size of jets) are not blocked, if your float heights are right n jets are clear then remove your needle and diaphram (dont loose the springs) and check diaphram condition and needle for grooves and stuff. if there ok screw in your pilot screws (flat head screw driver right on the float chamber side of carbs) screw them till they bottom (dont go crazy, just so it bottoms, not tightly!!!!) count the amount of turns should be around 2 to 2-3/4 turns, make shore their all the same.
after those checks and a good clean re-fit everything and see if that helps if not then yer you need to syncronise them lolz read the haynes manual or go the mechanic its a little tricky hope this helps mate
cheers Tim

[chrisxr]

reasons for major back fires on over run are cause via either air entering exhaust post combustion or the main one is the adjustment of the pilot air screw. usually for a stock setup the manual recomends 2 1/2 turns out from closed but if the bike pops when throttle is closed (all else being correct) wind the screw in 1/2 turn on each carb to lean out the closed throttle circuit. Best way to adjust these idealy is to start at say 3 1/2 turns out run the bike at about 2000rpm then turn the screw clockwise until you here that cylinder pick up speed keep going until that cylinder starts to missfire at them rpms then turn back to you are back at the highest rpm. It takes a little skill in doing this listening for that cylinder but once you have it its easy. do the same on all carbs if when you have done this the bikes rpms hang a little higher ie 1800rpm (after reving) then drop down to 1000 rpm you will need to richen the screw slightly (counter clockwise) on each carb to the rpms become stable. If when you have done this your bike still pops on over run you have either exhaust gas leeks/ a poorly designed exhaust system or a more serious fueling issue. If you have your carbs off screw in a set of 116 (front)/118 rear main jets for astraight through end can you wont be far wrong with that

[matty_boy]

Thanks lads i will give them a bash.

I am at the track day tomorrow so i will look in to it there, or when i get home.

I have just fitted a full Tyga system but the bike was doing it before then, so i dowt it is a issue with the exhaust leaking.
Plus i have just fitted new seals in the headers with the new system.


ta Matty.