Backfires

My bike (K75S, 1988) seem to do a lot of backfires. What could be the
reason and how do I sort it out?

 

On 13 Nov 2005 00:34:44 GMT If you fall from a tree,leave your anger

1st thing I look for with,"Backfires" are exhaust leaks.Most common
cause IMHO.

 

Shep© proposed

How do you find those? Plugging the back [1] and watch where the smoke
comes out?

[1] well, not completely of course

 

Wet your fingers and wave them around the exhaust pipes.

If it's anything like the K100s I've had... you will need to soak the
exhaust nuts in plus gas for a couple of days, heat the nuts red hot and
hammer an under-sized socket onto them to get them off without shearing
an exhaust stud.

Another common place for leaks is where the header pipes meet the
collector box.

 

[Snipped Text]

Yup, that happened to mine, didn't blow at all it just backfired
occasionally. Quite good if a cage was following too close

 

ISTR a tale from a regular poster here (possibly Prawn or Weggy) of a
backfire resulting in a london taxi being torpedoed by a silencer off a SOB.

SWK may be along to confirm this.

--
Dan L (Oldbloke)

My bike 1996 Kawasaki ZR1100 Zephyr
M'boy's bike 2003 Honda NSR125R (Going)
Spare Bike 1990 Suzuki TS50X (Patio Ornament)
BOTAFOT #140 (KotL 2005), X-FOT#000, DIAABTCOD #26, BOMB#18 (slow), OMF#11

 

[Snipped Text]

Excellent.

 

Hah, found it.

It was Buzby on UKRMC:
http://groups.google.co.uk/group/uk...d68c8a634?q=torpedoed&rnum=1#6e54661d68c8a634


--
Dan L (Oldbloke)

My bike 1996 Kawasaki ZR1100 Zephyr
M'boy's bike 2003 Honda NSR125R (Going)
Spare Bike 1990 Suzuki TS50X (Patio Ornament)
BOTAFOT #140 (KotL 2005), X-FOT#000, DIAABTCOD #26, BOMB#18 (slow), OMF#11

 

K100s were known for the odd backfire - I'd guess that K75s were the
same.

Having said that, mine only did it very occasionally on the overrun
above 2000rpm. Below this is where the FI cuts back in. The idea is
that above 2K on the overrun the injection switches off completely to
save fuel and increase engine braking; the side effect is virtually
pure air getting to the exhausts, rather like an exhaust leak.

If it does it excessively then as others have said, probably an air
leak to the exhausts, probably near the cylinder itself. I *think*
this is because the bounced negative pressure waves are at their
strongest here and more air gets sucked in as a result.

 

** waves **

 

<points at unsnipped post and stripped out attributions>

Sort it out Buzby, eh?

 

On 13 Nov 2005 01:54:20 GMT If you fall from a tree,leave your anger

The old trick is to get an old towel/piece of heavy cloth and soak
it/Damp it with water.Then wrap it around any of the areas you suspect
or the pipes and joints area by area and rev the bike.If you find an
area you have got this around and the backfiring stops or lessens,then
you have an area to address.

This does not however discount other possible causes but is a quick
and easy,"Troubleshooter"

 

Oops. I followed a SOB along Marleybone Rd/Westway on Friday night that
was backfiring about eavery 30 seconds or so. Reading this has made me
realise I should probably have gone passed him rather than staying
behind.

Certainly gave the cagers something to think about! ;-)

 

Shep© proposed