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Author Topic: How to cure an airlock?  (Read 1774 times)

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Offline lordmoonpie

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How to cure an airlock?
« on: April 11, 2010, 07:09:31 AM »
Lovely sunny day for a change and time to run the bikes up. The 750 decided to drop onto two cylinders. Checking the fuelling and the plugs were dry - culprit, an air lock in the fuel filter, keeping it as empty as you like. I flicked the pipe, tuned the fuel on and off, opened the petrol tank and still no fuel. So, what's the smart way to get rid of an air lock in the filter? Oh I tried a different filter too - same thing!! To say this is frustrating is an understatement - I'm so mad I'm gonna connect up the battery on the ducati and go scare some tourists! ???
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1994 Ducati 888 SP5
1951 Ducati 50cc Cucciolo
1981 Yamaha XV750 SE

Offline mystic_1

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Re: How to cure an airlock?
« Reply #1 on: April 11, 2010, 07:22:49 AM »
Tank full?  That'll give you a tad more hydrostatic head.  Set petcock to reserve if you have it, opening is lower in tank.

How are your lines routed?  All downhill?

mystic_1
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Offline raymond10078

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Re: How to cure an airlock?
« Reply #2 on: April 11, 2010, 07:25:49 AM »
Air in the filter is not necessary bad.  I've had bikes with filters that run with a "pocket" of air all the time - because a portion of the filter is higher than the adjacent line (air had no where to go).

If you open one of the carb drain screws, does the fuel still flow?

If you dropped two cylinders - I'd first suspect points/ignition.  Were the two cylinders 1-4, or 2-3?  If so, look into your ignition.
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1978 CB750A (upgrading very, very slowly)

Past bikes - Honda: SL350, CX650C, CB900C, CB1000C, CM450A; Kawasaki: several 1972 750 H2's; Suzuki: TC90J.

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Offline lordmoonpie

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Re: How to cure an airlock?
« Reply #3 on: April 11, 2010, 11:27:23 AM »
Tank is very low Mystic so I could help by fillign her up a bit. Petcock is at reserve and seems full flowing. Cylinders that dropped out were 3 and 4 - served by the same petrol pipe, 1 and 2 share one that seemed OK. I checked the battery too and it's very low (I'm running a self generating ignition but it's hopeless for starting so has to have battery until warm), so with a new battery coming tomorrow for my solo starter, I will wait to try that out next weekend....maybe the air in the filter is a red herring as you said kandrtech?
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1994 Ducati 888 SP5
1951 Ducati 50cc Cucciolo
1981 Yamaha XV750 SE

Offline lordmoonpie

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Re: How to cure an airlock?
« Reply #4 on: April 12, 2010, 02:08:18 PM »
Unbelievable! Petcock in the off position for 24 hours and went in the garage tonight....both fuel filters full to the brim with motion lotion. I seem to have found an anomaly in the laws of physics - where's Sam when you need someone to explain the weird and wonderful  ;D
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1994 Ducati 888 SP5
1951 Ducati 50cc Cucciolo
1981 Yamaha XV750 SE
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