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Carbs sending fuel into filter not cylinder 27 Mar 2020 10:22 #821904

  • Bluerider
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There is spark. the plug smells of fuel. Did the old school thumb over the plug hole and spun the motor over feels like the other cylinders. Going to go through with feeler gauges at a later date. Thank you

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Carbs sending fuel into filter not cylinder 27 Mar 2020 11:04 #821905

  • Mikaw
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Swap the #3 plug into another known running cylinder and see if the problem follows the plug. If it does it’s a bad plug. If not the the plug is fouled. If plug fire in known good cylinder, possibly plug wire, try swapping out plug wire. These are cheep ways of test items
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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Carbs sending fuel into filter not cylinder 29 Mar 2020 09:38 #822118

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The plugs have been moved around soo much I have no idea what one was the original. But the problem always stays at cyl 3. But did check the valve clearances. But I think this just opens another can of worms. The thinnest feeler I have is a .03. and I have 4 that are tighter than that. And 3 that are over the .1. and 1 is within spec at .06. I am working mm. But the bike starts and fires up just fine then the cyl 3 carb starts to leak. This is becoming such a PITA.

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Carbs sending fuel into filter not cylinder 29 Mar 2020 13:51 #822132

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The bike will start fine with those clearances, just won't run as well as it could. The valves with < 0.03mm clearance could be always open (almost certainly will be when the engine warms up). This may cause airflow back through the carbs on the compression and exhaust strokes. If it's enough airflow it will pull fuel out through the jets (on the compression stroke there will already be fuel mixed in with the air). This air and fuel will then end up in the air box/filter.

Is the intake valve on cylinder 3 one of the ones with no clearance?
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Last edit: by calum. Reason: Corrected logical error

Carbs sending fuel into filter not cylinder 29 Mar 2020 13:53 #822133

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You mentioned you swapped the plugs. Did you switch plug wires? Unfortunately any mechanical item can be a can of worms in and of itself. Take a deep breath and understand there are no shortcuts. These bikes are easy to work on, meaning physically things come aparts simply without a lot of stress. Basically once the tank is off you’ve done most of the hard work. Sounds like you should start at page one on the general maintenance engine adjustment section of a FSM. Testing and checking timing, valve lash, float levels and such. Can’t start in the middle and have good results

I’ll send you a like link to a FSM,
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
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Last edit: by Mikaw.

Carbs sending fuel into filter not cylinder 29 Mar 2020 13:55 #822135

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1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
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Carbs sending fuel into filter not cylinder 29 Mar 2020 17:01 #822149

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It currently has a 270a in it on the intake side and that puts it under .03. And a 220a in the exhaust putting that one over .1.

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Carbs sending fuel into filter not cylinder 29 Mar 2020 17:09 #822150

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I have it thanks. And deff not starting in the middle.

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Carbs sending fuel into filter not cylinder 29 Mar 2020 17:20 #822152

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Quick test may be to swap the shims. You'll probably have too much clearance on the intake side (which should hopefully solve the problem as the valve will definitely be closed on the compression stroke and won't open too early on the exhaust stroke). The reduced clearance on the exhaust side may cause some smoke out of the exhaust but should be OK if you're just testing.
If swapping the shims solve the problem then start measuring and order some new ones ;)

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Carbs sending fuel into filter not cylinder 29 Mar 2020 17:27 #822153

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You need to get your valve clearances right before looking at anything else. Otherwise you're just wasting time and energy. If you know you have some tight valves then why not fix them?
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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Carbs sending fuel into filter not cylinder 29 Mar 2020 18:09 #822155

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calum wrote: Quick test may be to swap the shims.
If swapping the shims solve the problem then start measuring and order some new ones ;)


In order to “swap” shims you need at lease one extra. Do not rotate the engine without a shim in the bucket. Bad bad!

Please listen to the members here. All systems need to be operating correctly in order to get a good running machine. Fuel, spark, and compression. The only way to do that is to take the time and do it.
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
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Carbs sending fuel into filter not cylinder 30 Mar 2020 02:10 #822174

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Mikaw wrote:
In order to “swap” shims you need at lease one extra..


Not if you pull both cams. But I agree, the clearances need to be sorted. If it was me though, I'd be too curious (impatient?) and would want to find out if this was the problem while waiting for the shims to arrive.
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