fuel tap mod
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Please can you post items for sale or wanted in the correct For Sale section. Items / bikes for sale here will be removed without warning. Reasons for this are in the FAQ. Thanks
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Neosophist
- Moderators
- Posts: 8172
- Joined: Fri Jul 04, 2008 1:01 pm
- Bike owned: CBR954
Re: fuel tap mod
The standard fuel tap has a rubber diaphram that is opened by vaccum from the engine, this means that even with the fuel tap set to on / reserve unless the engine is running to create a vaccum, the tap won't be open so no fuel will flow.
It's a Honda safety type feature.
If you crash the bike and the engine shuts off but it's on it's side for example, with a conventional tap, this gives the potential for the carbs to overflow and fuel to keep flowing until your tank is empty, creating a dangerous load of petrol all over the hot bike and road.
With the Honda tap, if the engine stops, the fuel flow shuts off and prevents this.
The slight downside to this was found on the HRC racebikes.
With full WOT on long straights the rubber diaphram that opens actually inhiibits a bit of fuel flow allowing the carbs to run out.
Don't forget the HRC spec bikes use a lot bigger jets and are more thirsty than road-going counterparts.
The HRC mod just removes the diaphram so the tap is always on.
This means should you crash, or the carbs not seal and shut off, fuel will leak until the tank is empty.
PS: I've never had fuel starvation at full WOT on a road-going bike, the only time I felt like it was running out of fuel it turned out to be the vaccum hose, it was weakend and collapsing in on itself under the high vaccum of WOT and shutting the fuel off until I backed off.
I can run my bike at WOT until the tank is empty without fuel flow issue, it's running 115/118 jets.
It's a Honda safety type feature.
If you crash the bike and the engine shuts off but it's on it's side for example, with a conventional tap, this gives the potential for the carbs to overflow and fuel to keep flowing until your tank is empty, creating a dangerous load of petrol all over the hot bike and road.
With the Honda tap, if the engine stops, the fuel flow shuts off and prevents this.
The slight downside to this was found on the HRC racebikes.
With full WOT on long straights the rubber diaphram that opens actually inhiibits a bit of fuel flow allowing the carbs to run out.
Don't forget the HRC spec bikes use a lot bigger jets and are more thirsty than road-going counterparts.
The HRC mod just removes the diaphram so the tap is always on.
This means should you crash, or the carbs not seal and shut off, fuel will leak until the tank is empty.
PS: I've never had fuel starvation at full WOT on a road-going bike, the only time I felt like it was running out of fuel it turned out to be the vaccum hose, it was weakend and collapsing in on itself under the high vaccum of WOT and shutting the fuel off until I backed off.
I can run my bike at WOT until the tank is empty without fuel flow issue, it's running 115/118 jets.
xivlia wrote:i dont go fast on this bike so really do not need a rear brake.. /
vic-vtrvfr wrote:Ask xivlia for help, he's tackled just about every problem u could think of...
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ColinP
- Settled in member
- Posts: 24
- Joined: Sun Aug 21, 2011 12:25 pm
- Bike owned: NC30
- Location: Arrochar, Argyll
Re: fuel tap mod
I done the fuel tap mod about a year ago and had no problem until now, last week i was going up the motorway and it started bogging down and running on 3 cylinders, i pulled in and the engine died, left it a few mins started it up and off i go again back up to motorway speed and more, soon after down to 3 cylinders again 
if i keep the bike under 60mph it will run all day go above this and im down to 3 cylinders sometimes 2 within a short time, im sure its the fuel tap mod thats at fault after a bit of researching on here and what neosophist says above, need to get a repair kit and put it back to standard...
if i keep the bike under 60mph it will run all day go above this and im down to 3 cylinders sometimes 2 within a short time, im sure its the fuel tap mod thats at fault after a bit of researching on here and what neosophist says above, need to get a repair kit and put it back to standard...