back fire bad on #1 cyl

  • hydrolazer
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back fire bad on #1 cyl

21 Jul 2019 05:20
#807913
at idle it back fires,,,high rpm really big loud back fire... I pulled off the plug wire and it stopped till I put it back on. the carbs were rebuilt 5k miles ago with no issues...it is getting worse now...I suspect an air leak...any ideas????? tia
\'79 kaw 1000 ltd

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  • hardrockminer
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Re: back fire bad on #1 cyl

21 Jul 2019 05:30
#807915
Have you checked valve clearance and compression?

What air intake system? What exhaust system? What carburetors? How are they jetted?
I have several restored bikes along with a 2006 Goldwing with a sidecar. My wife has a 2019 Suzuki DR 650 for on and off road.

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Re: back fire bad on #1 cyl

21 Jul 2019 08:34
#807923
a complety stock 1979 kz 1000 ltd jardine exhaust....just started trouble shooting a few mins ago,,,,mikuni carbs
\'79 kaw 1000 ltd

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  • SWest
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Re: back fire bad on #1 cyl

21 Jul 2019 08:55
#807924
Exhaust leak at the head?
Steve
Z1b1000 1975 Z1b
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229

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Re: back fire bad on #1 cyl

21 Jul 2019 09:29
#807925
i pulled #1 plug and it indicated a rich mixture,,,,black smutty plug but not oil fowled...I cleaned it up and will retest
\'79 kaw 1000 ltd

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  • SWest
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Re: back fire bad on #1 cyl

21 Jul 2019 09:47
#807926
Check the spark plug H/T wire at the cap for corrosion.
Steve
Z1b1000 1975 Z1b
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229

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Re: back fire bad on #1 cyl

21 Jul 2019 09:52
#807927
VM26SS carbs. If they came with the bike the idle mixture stock setting is full clockwise.
I have several restored bikes along with a 2006 Goldwing with a sidecar. My wife has a 2019 Suzuki DR 650 for on and off road.

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Re: back fire bad on #1 cyl

21 Jul 2019 09:56
#807928
the h/t wire has no corrosion,,,,thanks for the tip!
\'79 kaw 1000 ltd

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Re: back fire bad on #1 cyl

21 Jul 2019 15:34
#807944
I cleaned the plug and it only back fired once....I rechecked the plug and it was kinda black again...this bike does rest all the time on the side stand,,,could it be a float issue? sticking some maybe
\'79 kaw 1000 ltd

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  • Patton
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Re: back fire bad on #1 cyl

21 Jul 2019 19:52
#807950
Patton wrote: Backfire through carb is likely due to an intake valve failing to fully seal when supposedly closed.
Could result from such conditions as insufficient clearance, burnt or broken valve, or damaged valve seat.
Some of the combustion inside the cylinder escapes past the supposedly closed intake valve and shoots back through the intake port and on through the carb.



Hopefully, the mating surfaces between the valve and seat are undamaged and will again provide complete seal when closed, given proper clearance required to enable closure when seated.

Continued operation with insufficient clearance is one reason for burnt valve faces and valve seats.

Good Fortune! :)
1973 Z1
KZ900 LTD

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Re: back fire bad on #1 cyl

29 Jan 2020 17:23
#818205
very late reply back....the culprit was both coils had old age heat cracks.1-4 coil was really bad....the were replaced and problem solved
\'79 kaw 1000 ltd
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