Popping or spitting out of carbs

  • ewolpert
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Popping or spitting out of carbs

21 Apr 2015 09:48
#669004
Hey guys. My 78 KZ650B is running, but has developed a new problem. When throttling up (or down) from about 1/6 throttle up (only under load or in gear) I get a popping, backfiring or "spitting" out of the carburetors. This was not happening and is new. Before you ask, I have pods but stock jets and I do not own an airbox. The valve clearance and timing have been checked and adjusted. I have no idea what the cause or solution to this particular problem is.
Eddie
78 KZ650 b2a

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  • SWest
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Re: Popping or spitting out of carbs

21 Apr 2015 10:13
#669010
Lean or air leaks. When I do jetting, I tell the client or myself to run it for at least 100 miles. Sometimes it will lean out. That just means the engine is breaking in and wants more fuel.
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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  • 650ed
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Re: Popping or spitting out of carbs

21 Apr 2015 10:23
#669011
Running pods with stock jetting is a bad idea. The engine will run lean and hot - not a good thing. Either rejet or get a stock airbox & air filter. Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)

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Re: Popping or spitting out of carbs

21 Apr 2015 11:01
#669014
What I've seen here is guys putting on pods, 4/1 exhaust all at the same time and wondering why the bike won't run for SHT. Go one size up (pilots and mains), see how that works with one item only, then add the exhaust or pods and start again.
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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  • KzChop82
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Re: Re:Popping or spitting out of carbs

21 Apr 2015 11:48
#669018
Steve has this bang on- just did this same thing great result.
I had to go up an extra pilot size for mine- buts that's probably unique to my setup.
I was having trouble with idling.

Also- make sure your carb boots are creating a really good seal and you retorque your head nuts after the heat cycle.
Clinton, NJ
Custom chopper, 1982 KZ 1000 M2 CSR engine, K&N Pod Filters

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  • KZB2 650
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Re: Popping or spitting out of carbs

21 Apr 2015 12:19
#669021
17.5 pilots, nettle up a notch and 117.5 mains are about perfect for mine. Ran the same only with 112.5 mains before I went with the 700 kit and 750 cam.

Air screws out 1 and 3/4 a turn too ....... will get them closer this summer with the color tune hopefully. make sure you have good carb holders too, new ones were money well spent I feel.
1978 KZ650 b-2
700cc Wiseco kit 10 to 1.
1980 KZ750 cam, ape springs, stock clutch/ Barnett springs.
Vance and Hines Header w/ comp baffle and Ape pods, Dyna S and green coils, copper wires.
29MM smooth bores W/ 17.5 pilots, 0-6s and 117.5 main
16/42 gearing X ring chain and alum rear JT sprocket.

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Re: Popping or spitting out of carbs

21 Apr 2015 15:35
#669045
Yup. B)
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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  • Twilightoptics
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Re: Popping or spitting out of carbs

10 May 2015 17:41
#671432
Is there an online source for jets? I've got 102.5 mains that need a bump and no one seems to have anything local. Tempting me to get out the drill index.
1977 KZ650-B1

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  • Hamaya
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Re: Popping or spitting out of carbs

10 May 2015 19:26
#671453
Twilightoptics wrote: Is there an online source for jets? I've got 102.5 mains that need a bump and no one seems to have anything local. Tempting me to get out the drill index.

Jets R Us
1983 KZ550-M1 LTD Shaft

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  • Patton
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Re: Popping or spitting out of carbs

11 May 2015 01:57
#671482
ewolpert wrote: Hey guys. My 78 KZ650B is running, but has developed a new problem. When throttling up (or down) from about 1/6 throttle up (only under load or in gear) I get a popping, backfiring or "spitting" out of the carburetors. This was not happening and is new. Before you ask, I have pods but stock jets and I do not own an airbox. The valve clearance and timing have been checked and adjusted. I have no idea what the cause or solution to this particular problem is.

Would also double-check the intake valve clearances, as insufficient clearance can result in backfiring through the carb.

And assure proper ignition timing and functioning of the advancer unit.

Good fortune! :)
1973 Z1
KZ900 LTD

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