carb cough?

[hugeduck]

every now and then keep getting what seems like a thump underneath the tank and the bike nearly stalls, heared people call it a carb cough, it doesnt really bother me TBH but if it going to do damage to the engine i'd rather fix it sooner rather than later! any ideas what its is? cheers

[VTRDark]

That's what is known on these as a carb cough, or on Superhawk forum as a carb fart.

It's where part of the incoming charge through the carburettor detonates inside the airbox- possibly a tiny bit of glowing carbon blown back through the inlet valve or exhaust valve into the airbox. The valves are actually open as the piston starts to rise in the bore, and the incoming charge starts to fill the chamber due to the incoming fresh charge gas intertia in the stack and airbox. If the outgoing charge is still burning, or a small glowing bit of carbon is able to ignite the incoming charge early, it burns back into the airbox.
You can feel it as a single bang through the tank, as well as hear it, and sometimes it causes a stall.

Usually when the bike is warming up, at low revs, as the throttle is opened.
It can be improved by balancing the carbs, as has been suggested, by setting the tickover a little higher than would be normal, around 13-1400 rpm, and also by fitting an ignition advancer.
It's not fuel-related; it's a result of huge carbs and the cam timing/ignition timing./quote]

As well as balncing the carbs I have found that adjusting the TPS helps as well which sort of relates with the ignition advancer that tony mentions.
http://www.vtr1000.org/phpBB3/viewtopic ... or#p222504

You may also be running a bit on the lean side.


(:-})

[Stratman]

Get the carbs set up as Mr Honda intended, make sure that they are balanced and it will do it very rarely. My tickover is set to about 900 rpm and it doesn't do it, nor does it cut out. Had the old girl for 12 years now, so I might know her quite well

[hugeduck]

cheers guys, so does it cause any damage? the bike runs perfect for me so not going to mess with the carbs unless i have to

[tony.mon]

No damage, unless you sit too far forward......