Cough and Bang

[Dave McGowan]

So then..........Wonder if anyone has an opinion on the following..

I have been running my Z1B this year with no problems until recently.

I have noticed that in top gear around 4k revs the bike coughs and bangs a little.You can rev through it and the thing wants to fly which is good!It also coughs and bangs at similar revs in other gears if you keep a steady speed.

This problem has come without any reason that I can put my finger on.Last year I had the valve timing checked which required a new cam chain and a couple of shims to make good.The plugs are new this year with maybe 1000 miles if that on them.The spark is good on all.The petrol is new.I put on a new reg/rec this year to replace the old regulator and make redundant the rectifier (both were originals).The ignition is electronic and has been on the bike for 5 or more years
Other than that , there are no changes.

Does anyone have any suggestions on what to look at

[dek155]

sounds like to much air could be sucking in on the carb side check all rubbers for tightness muffle the filter box intakes engine should cut out, if still coughs screw in air srews a midges , each one seperate on a run could be only one cylinder you see it sounds like its fighting with the air somewhere hope this easy solution solves it dave

[Dave McGowan]

Thanks for the reply .I am running belmouths and I have to agree on the air theory based on an experience i had when on rubber came off no1 intake (where you plug yer vaccuum gauges in).

Sadly all are in place and the rubbers seem sound ,with no obvoius splits or gaps.
I will play with the air srews...all the way in and 1 1/2 turns out for starters??????

How about shite in the jets?
Dave

[Pigford]

Dave, could well be a bit of shite out of the tank, found its way into the carbs
Sounds like its fine on main jets, as its OK over 4,000 rpm & revs thru' it
Air jets out one & a half is about right. If standard carbs, can be a bitch to set up right tho.

[bollypne]

My A4 starts ok but seems not to be running on no1, rev to 4k and it starts to pop and bang a little. Is this probably the same problem of shite in the carbs.

[knut]

hi sounds just like my a4,pilot jets blocked in 1 & 2 having bike on it,s side stand probably doesn,t help (got no main stand),might be worth investing in a few carb repair kits ?10 each on ebay me tinks

[Dave McGowan]

Just dropped carb bowls and checked jets..blown through to clear them.No obvious blockage.Made an interesting observation whilst doing this.I have belmouths and the mesh on 1 and 4 was convex (as if blown from inside carb outwards).Took tank off to check and sure enough,1 and 4 both run off the same coil.............have not run bike out yet to check if carbs were a prob but also were under the impression a coil either works or it doesn't.
Anyone got any experiences in this field?
Dave