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General Category => Yamaha FJ1100 / FJ1200 Running Problems => Topic started by: 81Delorean on May 20, 2025, 11:13:48 AM

Title: Carb Vent Tubes
Post by: 81Delorean on May 20, 2025, 11:13:48 AM
Quick question, the two white "T" fitting vent tubes between #1/2 and #3/#4, do they need a hose coming down off of them? Or are they ok to run with no hose ran anywhere? They weren't on mine when I took the carbs apart (along with another piece, thanks RPM for sending me one). I'm ready to put it back on the bike, just want to make sure first. Thanks in advance
Title: Re: Carb Vent Tubes
Post by: FJmonkey on May 20, 2025, 01:05:42 PM
I think the vent hose(s) is routed down so it drains to the street. 
Title: Re: Carb Vent Tubes
Post by: Chainlube on May 23, 2025, 10:38:29 AM
Quote from: 81Delorean on May 20, 2025, 11:13:48 AMQuick question, the two white "T" fitting vent tubes between #1/2 and #3/#4, do they need a hose coming down off of them? Or are they ok to run with no hose ran anywhere? They weren't on mine when I took the carbs apart (along with another piece, thanks RPM for sending me one). I'm ready to put it back on the bike, just want to make sure first. Thanks in advance

Just a note...  When I worked at Vance & Hines (when they were roadracers), I installed tons of Dynojet Kits and exhaust systems for street riders.  Every kit wanted those hoses removed and the T fittings pointed down.
Title: Re: Carb Vent Tubes
Post by: FJmonkey on May 23, 2025, 11:46:20 AM
Quote from: Chainlube on May 23, 2025, 10:38:29 AMJust a note...  When I worked at Vance & Hines (when they were roadracers), I installed tons of Dynojet Kits and exhaust systems for street riders.  Every kit wanted those hoses removed and the T fittings pointed down.

Did they tell you the reason for removing the hose? Did they find an issue with the hoses or routing? Just curious.
Title: Re: Carb Vent Tubes
Post by: Chainlube on May 23, 2025, 12:29:04 PM
Quote from: FJmonkey on May 23, 2025, 11:46:20 AM
Quote from: Chainlube on May 23, 2025, 10:38:29 AMJust a note...  When I worked at Vance & Hines (when they were roadracers), I installed tons of Dynojet Kits and exhaust systems for street riders.  Every kit wanted those hoses removed and the T fittings pointed down.

Did they tell you the reason for removing the hose? Did they find an issue with the hoses or routing? Just curious.

No reason was given, but I would guess it is to prevent reduced venting flow due to hose collapse from heat.
Title: Re: Carb Vent Tubes
Post by: Pat Conlon on May 23, 2025, 01:10:19 PM
With today's ethanol laced fuel, stuck floats and debris in the float needle seats are a common occurrence.

Yes, the oem vent hoses are thin walled rubber, but changing them out to heavier wall high pressure fuel injection hose will mean that those vent hoses will never collapse or pinch off.

I want that free flowing fuel on the ground, not on the top of my engine case.

Ask me how I know....