All seems to drive and pull great but when taking the foot off the gas and decelerating she gives the odd BIG bang. Could this be the air filter clogging and making it over fuel or any other suggestions short of getting it on a rolling road when money isnt that good at the moment.
Air leak in the exhaust
On over run my engine pops a bit
zx9r carbs
Pops from the exhaust are caused by weak mixture rather than rich mixture. I think you get undetectable miss-fires, which leave fuel and air in the
exhaust with the inevitable result.
Rich mixtures don't leave any air (oxygen) in the exhaust. This surprised me too.
Perhaps it is a bit weak through the whole range, and worse when you take your foot off. If this were the case you could richen it up (raise needles
a notch). What do the spark plugs look like?
Matt
Will it have anything to do with changing the exhaust to the R1 can?
I was under the impression you would have to change the jetting when changing from the originol can.
Jetting. I've had all sorts of issues with it in the past. I too would reckon on having to alter it a bit after a new exhaust.
surely its just unburnt fuel in the exhaust burning off?
It was doing it before changing the can. The original can needed repacking and so put the R1 on it whilst I get it done. But it was happening with
both. I'll check the plugs tomorrow.
Cerbera... as it was yours in the past I wanted to ask you if there was a power commander fitted at one time as theres an empty bracket next to the
battery. Also noticed in some of your older photos there was something running up the top middle of the engine thats not there now?
Ahha found the photo here
Image deleted by owner
[Edited on 31/1/10 by FFTS]
That bracket near the battery has always been there since I owned it, so don't know what it was initially intended for.
I posted that photo from somewhere else asking what that bit I circled was. Can't remember the answer but it will be in the thread where you
found the picture, but it's not a photo of the Loco, or Beccy as you call her 
There has always been a bit of popping on overrun but I don't recall any loud bangs on lift off.
[Edited on 31/1/10 by cerbera]
The circled bit is a sort of recirculating valve. Takes the crankcase vapours and puts them back into the air box. Was cleaning out the garage yesterday and mines in the bin right now. I've never used it.
Thanks for that.
Just to be clear she NEVER backfires whilst accelerating ONLY on overun whilst coasting and no gas on.
[Edited on 31/1/10 by FFTS]
Looking at that photo and seeing how disgracefully untidy the garage is, and poorly aligned the rivets are on that MK, I'd say the photo was from
matt.c's archive
The red circle is the breather connection which I beleive allows air to be drawn from the air box through the reed valves in the head (under the two
rectangular covers on the head) and into the exhaust via openings in the ports to reduce "popping" on throttle shut off /decelleration.
I Took reeds out on mine and fitted blank covers over, and it pops on overrun with the standard can.
The popping is unlikely to be anything to do with fuelling since our carbs were set on a rolling road, however this doen't by implication mean
your carbs are set correctly.
I've read another thread somewhere that said to block them off (It think it was Hellfire)
Are you saying you blanked them off but still got popping? Did you resolve it in the end?
Mine have always been blocked off but the onlt time I've had popping is when the mixture and jetting needed fettling.
Out of interest have you checked your plugs? I've been dealing with a backfiring 3000GT which turned out to be the plugs.
Got a long plug spanner from fleabay on the way so will let you know in a few days.
Should've said mate. I'm nipping to Chorley Friday hopefully you could've had a go at my socket.
quote:
Originally posted by mistergrumpy
Should've said mate. I'm nipping to Chorley Friday hopefully you could've had a go at my socket.
if i had seen this post you could have borrowed mine