Nimbus
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Location: Mission , BC Canada
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« on: January 19, 2023, 01:18:48 PM » |
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Help. Can someone explain the cause and cure for the crankcase get filled with gas.
Looked at club files and did not find an answer.
I have had my ’92 FJ since 2007 and some 100,000 km. winter storage in my heated garage and monthly battery charge and Startup. The bike is well maintained, new float needle and seats (twice) float height meticulously adjusted. Yet went to start it and soon had gas and oil flowing out of the crank vent. Crank vent with a KN filter as I am running Pod filters. Sadly this is the 3 or 4th time it has done this, once year or so. How does so much fuel get into crank. I have a new fuel pump, but it happened as well with the original.
Do I install a shutoff solenoid at tank? But is the fuel pump itself not blocking flow, I mean it holds prime even after weeks not started.
I am reaching out to my fellow FJ friends as I am at a loss for a fix.
Thanks
Henning AKA - Nimbus
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92 FJ1200
1953 Nimbus
1988 Honda VFR 400R
2018 Montesa 4rt
2003 Suzuki SV650S
1968 Honda CL450
1976 Honda CB400F
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RPM - Robert
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« Reply #1 on: January 19, 2023, 02:35:50 PM » |
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1) Your fuel pump is no good. It shouldn't let fuel continue to flow when not on.
2) Float needle tips should be sealing and not letting fuel by or your floats are stuck or out of adjustment. They shouldn't be letting fuel by.
3) Needle seat o-rings are bad and are letting fuel by.
1 Is guaranteed.
2 & 3 could be either or; or both.
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Urx
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Location: Edinburgh
Posts: 99
1990 uk 3CV in black(blue) and gold, 32k miles
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« Reply #2 on: January 19, 2023, 03:17:04 PM » |
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That was my thought
Fuel is passing through the fuel pump an overflowing a carb or carbs and draining into the lower casings
If the fuel pump is not an original yamaha one then you need to look there as action #1 and likely replace with one that does actually lockoff the flow.
After that is sorted one or more carbs are leaking gravity fed fuel into your engine
The carbs should show which is / are leaking with some bench testing
A cup under each carb should show which one(s) need attention
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Still running original chain and sprockets from new (scotoilers really work)
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Nimbus
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« Reply #3 on: January 19, 2023, 04:57:23 PM » |
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Carbs I will say GOOD, ok fuel pump and it was slated as a FJ replacement. Looks like I need a RPM order placed.  Thanks |
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92 FJ1200
1953 Nimbus
1988 Honda VFR 400R
2018 Montesa 4rt
2003 Suzuki SV650S
1968 Honda CL450
1976 Honda CB400F
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red
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« Reply #4 on: January 19, 2023, 05:56:13 PM » |
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Carbs I will say GOOD, ok fuel pump and it was slated as a FJ replacement. Looks like I need a RPM order placed. Thanks Nimbus, Sorry, but no. The fuel pump should block fuel flow when off. The carbs (floats) should block fuel flow, even if the fuel pump does not. The carbs may be fine in every way for driving, but a leaking needle-and-seat/O-ring seal will still allow gasoline to flow into the crankcase. Replacing those few parts at the floats will be all you need, there, although a new fuel pump is also needed. I believe RPM can supply just what you need. |
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Cheers,
Red
P.S. Life is too short, and health is too valuable, to ride on cheap parade-duty tires.
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Nimbus
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« Reply #5 on: January 19, 2023, 07:14:58 PM » |
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 Carbs I will say GOOD, ok fuel pump and it was slated as a FJ replacement. Looks like I need a RPM order placed. Thanks Nimbus, Sorry, but no. The fuel pump should block fuel flow when off. The carbs (floats) should block fuel flow, even if the fuel pump does not. The carbs may be fine in every way for driving, but a leaking needle-and-seat/O-ring seal will still allow gasoline to flow into the crankcase. Replacing those few parts at the floats will be all you need, there, although a new fuel pump is also needed. I believe RPM can supply just what you need.
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Logged
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92 FJ1200
1953 Nimbus
1988 Honda VFR 400R
2018 Montesa 4rt
2003 Suzuki SV650S
1968 Honda CL450
1976 Honda CB400F
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twood1972
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Life long motor head.
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« Reply #6 on: January 19, 2023, 08:37:52 PM » |
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Needle seat o-rings for sure.
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TIMOTHY
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RPM - Robert
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« Reply #7 on: January 19, 2023, 09:50:34 PM » |
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Red is correct. Two fail safes.
One fuel pump should stop flow, it is not, so it has failed.
Two the float needles/float should stop it. Again something here has failed, be it float needles or needle seat o-rings.
If one fails two should still stop fuel flow while off. Since it is not the second fail safe needs to be addressed. Ideally both should be fixed but at minimum carb internals need looking at.
We do have everything in stock including new Yamaha fuel pumps.
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Nimbus
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« Reply #8 on: February 01, 2023, 12:56:22 PM » |
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Well she is back running, sounding awesome. Replaced fuel pump, ultrasonic carbs, new o-rings and the seat/needles replaced. I feel confident that will the last of that issue. Thanks to FJ friends and of course RPM.
Henning
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92 FJ1200
1953 Nimbus
1988 Honda VFR 400R
2018 Montesa 4rt
2003 Suzuki SV650S
1968 Honda CL450
1976 Honda CB400F
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