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I have no idea how the petcock on my 94/750 is supposed to function. When it is on the PRI (right) positon, fuel comes out of both lines when unhooked from the carbs. When the petcock is on RES (left) or ON (bottom) no fuel comes out of tank. Oddly enough my bike runs the same no matter which setting I put it on. Is there something wrong???
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"Do not look to deeply into anything I say, I'm a very shallow person." -
NO, that is the correct operation.
PRI stands for PRIME and it means allow fuel to flow unrestricted. This setting is only used temporarily, and is intended for refilling the carb float bowls when they are empty, such as after draining them to work on the bike or after you've had an accident. 60 seconds should refill the carb bowls from dead empty.
From: http://www.katriders.com/forums/viewtopic.php?t=25794
PS - I have the petcock rebuild kits in stock if you need to rebuild your petcock, but it doesn't sound like you do.Originally posted by The CyberPoetLet's see if I can make this petcock thing make more sense for you.
Behind the pick-up screens (green in my pictures) are two tubes, one short (the reserve/prime tube) and one tall (the standard ON tube).
The petcock acts as a three position switch comprising two pick-ups and two fuel passages.
In position "ON", the system selects the taller fuel pick-up tube, and routes it through a passage that only gets opened by engine vacuum pulling a rubber diaphram open (the rubber diaphram is normally held closed by a weak spring).
In the position "RES", the system selects the shorter fuel pick-up tube, and routes it through the same passage with the vacuum diaphram.
In the position "PRIME", the system selects the shorter fuel pick-up and shunts the fuel through a straight pipe that by-passes the vacuum diaphram.
The engine doesn't produce sufficient vacuum to open up the diaphram until the engine is turning at least 500 RPM or so. This vacuum is created by the intake valves to the cylinder opening while the piston is moving downwards, which causes the air to be sucked through the carb (which is also where the vacuum pick-up is located). When the engine isn't spinning, there is no vacuum in the line to the petcock; as the starter turns the engine, it produces low levels of vacuum, and once it fires (sucessfully catching), the vacuum levels climb.
Since the carbs normally had fuel when you shut the bike down, there is normally no immediate need for additional fuel flow at start-up, unless the fuel in the carbs has been evaporated or emptied somehow. Thus, the fact that the petcock is in the ON or RES position when you start is normally irrelevant because there's enough reserve in the carbs. Once the engine starts, fuel will start flowing through the petcock and refilling the carbs as their levels drop. In cases where the carbs are empty or low on fuel for whatever reason, it makes sense to use the PRI (Prime) setting to flow fuel to the carbs to refill them before trying to start, then to switch back to the ON or RES position.
Cheers,
=-= The CyberPoet -
it A OK, everything is working the way it shouldComment
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So should I keep the petcock switched to "ON" when I am riding as well as parked?"Do not look to deeply into anything I say, I'm a very shallow person."Comment
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Yes (unless you are too low on fuel, in which case switch to RES and seek a gas station to fill it up).Originally posted by chatty katty
KNOW THIS:
almost all tank rust is a result of air-space in the fuel tank permitting condensation, which then falls to the bottom of the tank and rusts the metal there. Topping off the bike just before returning home for the day each time you ride any significant distance is a good way to help prevent this annoying and time-consuming (to repair) problem. Tank rust can mean a week stripping/etching/sealing the tank, plus multiple carb tear-downs to clean out all the rust sediment.
PRI (prime) should only be used for 60 seconds or under. Although correctly operating float bowls should keep the carbs from flooding fuel into the engine and/or airbox with the bike upright, keeping it out of prime is easier than tempting fate.
If don't do a pre-ride check, start doing one (it may save your life one day, such as tipping you off to a flat tire before your first turn). Make a glance at the petcock position part of that pre-ride check (mostly because kids and child-like others tend to fiddle with knobs).
Cheers,
=-= The CyberPoetComment
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Thanks for the info!"Do not look to deeply into anything I say, I'm a very shallow person."Comment
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hi, i'm a new rider. just bought a 94 600 kat, i accidentally left the petcock in the prime position for the last few days thinking the valve was only an on/off valve..could this cause my bike to miss out when given throttle? it idles fine, but now whenever i try to give it any more than about 1/4 throttle it misses badly. help?Comment
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is there a diagram of where each position is? my bike dosnt have any indiacators on it, and idk if its the same as other makesComment
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