Air leaking into fuel system?
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stevenmc87
- Brass Member

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- Joined: Thu Jan 08, 2015 2:16 am
- Location: Cincinnati
Re: Air leaking into fuel system?
Update, So I pulled the old fuel filter and a decent amount of junk came out of it and it looked pretty old. I cut into it to see the actual filter and while it was dirty I don’t think it was to the point of restricting the flow to significantly. I replaced the filter and the line leading into the pump with a clear one. Took the bike out for a ride and seemed to improve a good amount, for a while at least. then once bike got warm the issue persisted. Next step is run the bike with a stand alone fuel tank and see if I’m still not getting a consistent flow into and out of the pump. The flow check on the pump seems like a decent amount of work in lieu of just replacing the unit entirely. You guys have decent luck with the 50ish buck ones on eBay?
1978 burgundy and gold gl1000
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gltriker
- Honored Life Member

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- Joined: Fri Sep 24, 2010 9:11 pm
Greg Foresi likened a rusty fuel tank to an upstream from carburetors sewage plant
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There have many many reports of newly, completely cleaned and "professionally" rebuilt GL1000 carburetors that have been reinstalled onto bikes with rusty internally contaminated fuel tanks. Big mistake...
Although a new fuel filter may have been installed, rust fines will sneak through the fuel filtering element and slowly but surely obstruct a very fine filtering element attached to the inlet side of the float valve seat in each one of the 4 carburetor bodies.
RE: a thorough fuel tank cleaning
"And your carbs will thank you. They no longer live down stream from a sewage plant." -gregforesi
Yes, a repeat session of total disassembly and cleaning of all fuel passages, again, from the inlet fuel hose barb fitting into each of the 4 carburetor float bowls. The job doesn't end there, though.
You've seen photographs witnessing where the contamination can further disrupt how well your engine will operate.
stevenmc87 wrote: ↑Mon Aug 11, 2025 5:25 pm Hey guys just got this amazing 78 wing and road it home 120 miles and it performed flawlessly. That is until the last 2 miles or so it started dying at stop lights and at very low speeds.
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The carbs have been professionally rebuilt and synthesized. The fuel pump has been “overhauled ” says the guy I got it from.
Double trouble evident there-stevenstevenmc87 wrote: ↑Wed Aug 13, 2025 9:08 pm Update, So I pulled the old fuel filter and decent amount of junkcame out of it and it looked pretty old. I cut into it to see the actual filter and while it was dirty, I don’t think it was to the point of restricting the flow too significantly.
There have many many reports of newly, completely cleaned and "professionally" rebuilt GL1000 carburetors that have been reinstalled onto bikes with rusty internally contaminated fuel tanks. Big mistake...
Although a new fuel filter may have been installed, rust fines will sneak through the fuel filtering element and slowly but surely obstruct a very fine filtering element attached to the inlet side of the float valve seat in each one of the 4 carburetor bodies.
RE: a thorough fuel tank cleaning
"And your carbs will thank you. They no longer live down stream from a sewage plant." -gregforesi
Yes, a repeat session of total disassembly and cleaning of all fuel passages, again, from the inlet fuel hose barb fitting into each of the 4 carburetor float bowls. The job doesn't end there, though.
You've seen photographs witnessing where the contamination can further disrupt how well your engine will operate.
Last edited by gltriker on Tue Sep 09, 2025 10:52 pm, edited 7 times in total.
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redglbx
- Platinum Member

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- Location: NW Indiana,
Re: Air leaking into fuel system?
Steven, have you by chance checked that the screws on top of the “rebuilt” pump are actually tight ? Don’t get crazy on them because you don’t want to strip them but they should be tight. This is a good place to pull air in.
Red 1976 oe owner
1976 LTD restored
1980 CBX , in the que, to fix the ignorant heavy handed owner
1981 CBX
1977 CB750 K7
2014 FJR OE owner, sold
1980 GL1100
1984 GL1200 naked
1969 CL350, in the que
1976 LTD restored
1980 CBX , in the que, to fix the ignorant heavy handed owner
1981 CBX
1977 CB750 K7
2014 FJR OE owner, sold
1980 GL1100
1984 GL1200 naked
1969 CL350, in the que
- pidjones
- SUPER BIKER!!!!

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Re: Air leaking into fuel system?
You might try switching the petcock to "reserve". I've seen the main line (well, and the reserve line, too) get plugged.
"Love 'em all.... let God sort 'em out!"
Ex 2006 GL1800 - the Black Pearl SOLD! to make room for:
2021 Can-Am Spyder RT Limited Dark Chalk Metallic
1975 Red GL1000 project - ex Pistol Pete project
1972 Triumph T150V Trident rescue - finished and FOR SALE!
1976 Yamaha RD400c
1978 GL1000 with '75 engine - the Hunley
Ex 1978 GL1000
Ex 1979 GL1000
Ex '79 CB750F rat bike
Ex '86 SEi
Ex '77 GL1000
Ex '76 RD400
Ex '72 Penton 125 set up for flat track
Ex '73 RD250
Ex '68 TR6C - chopped
Ex 2006 GL1800 - the Black Pearl SOLD! to make room for:
2021 Can-Am Spyder RT Limited Dark Chalk Metallic
1975 Red GL1000 project - ex Pistol Pete project
1972 Triumph T150V Trident rescue - finished and FOR SALE!
1976 Yamaha RD400c
1978 GL1000 with '75 engine - the Hunley
Ex 1978 GL1000
Ex 1979 GL1000
Ex '79 CB750F rat bike
Ex '86 SEi
Ex '77 GL1000
Ex '76 RD400
Ex '72 Penton 125 set up for flat track
Ex '73 RD250
Ex '68 TR6C - chopped
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redglbx
- Platinum Member

- Posts: 1682
- Joined: Tue Jun 02, 2020 8:39 am
- Location: NW Indiana,
Re: Air leaking into fuel system?
Steven, one thing that just came to mind is you might remove the gas cap and run it to see whether or not you still get the bubbles, if they go away then you probably have a plugged or slightly plugged vent in the cap, just a thought
Note,, re-reading all this I see that Ritalz had already addressed this potential problem & his suggestion to use a remote tank is a good one ! Let us know how you do.
Note,, re-reading all this I see that Ritalz had already addressed this potential problem & his suggestion to use a remote tank is a good one ! Let us know how you do.
Red 1976 oe owner
1976 LTD restored
1980 CBX , in the que, to fix the ignorant heavy handed owner
1981 CBX
1977 CB750 K7
2014 FJR OE owner, sold
1980 GL1100
1984 GL1200 naked
1969 CL350, in the que
1976 LTD restored
1980 CBX , in the que, to fix the ignorant heavy handed owner
1981 CBX
1977 CB750 K7
2014 FJR OE owner, sold
1980 GL1100
1984 GL1200 naked
1969 CL350, in the que

