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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Something needs explaining /cgi-bin/YaBB.pl?num=1405531051 Message started by bmwnunkie on 07/16/14 at 10:17:31 |
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Title: Something needs explaining Post by bmwnunkie on 07/16/14 at 10:17:31 Sorry to be immensely stupid. I have changed the standard petcock for a raptor petcock as per recommendations. What I can't figure out is if the original petcock ( and fuel system ) used a vacuum pipe to operate why should replacing it with a raptor petcock( without any vacuum pipe ) be ok also? Can anyone explain the mechanics behind it please? I ask as my old machine runs as rough as a badger backside and I am tempted to put a genuine petcock on. :( |
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Title: Re: Something needs explaining Post by jman on 07/16/14 at 10:19:24 Did you cap off the vacuum port on the right side of the carburetor when you swapped to the Raptor petcock? Switching to the Raptor petcock is the same as running the factory petcock in the "Prime" position. My wife's bike runs significantly better with a constant fuel flow, regulated by the float needle, than it does with the vacuum activated fuel flow, due to a bad petcock. Also, the Raptor petcock is only about $26 from Bikebandit.com, whereas the only place I've found an OEM petcock was on MRCycles.com for about 3 times the Raptor's price. |
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Title: Re: Something needs explaining Post by verslagen1 on 07/16/14 at 10:57:15 changing from the stock petcock to the raptorcock is changing from an automatic to manual. Stock petcock uses vacuum to turn it on while the engine is running. you sometime have to turn it to prime to fill the carburetor prior to starting. The stock petcock can be flakey at times and after a few years... flakey all the time. Flakey as in 'shuts off by itself'. Now replacing it may or may not solve your particular issue. But it does remove it from the possibilities. |
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Title: Re: Something needs explaining Post by oldNslow on 07/16/14 at 11:41:26 Quote:
A petcock is nothing more than a valve that lets fuel run run from the tank into the carb. The raptor is manual. Turned to either ON or RESERVE it lets fuel flow. Turned OFF it shuts of the fuel, just like turning off a faucet. The OEM petcock requires engine vacuum from a port on the carb- to pull on a rubber diaphragm built into in the petcock to open the fuel passage when the lever is either in the FUEL or RESERVE position. That's the reason for the vaccum line from the petcock to the carb. There is only vacuum applied to the diaphragm when the engine is running. When the engine is not running the petcock shuts itself off. The only reason for the extra complication is so that you don't have to remember to turn the fuel OFF like you would with a manual valve like the Raptor. When the stock petcock lever is turned to PRIME, the fuel passage is always open however. In that position the valve cannot be shut off. When you install a Raptor you need to plug the vacuum port on the carb. If your bike is not running right with a Raptor, and you have that port on the carb plugged, switching back to a stock petcock is not going to fix anything. A properly operating stock petcock and a raptor do exactly the same thing; they let the gas run from the tank into the carb. That's all. The stock unit is known to malfunction and cause problems sometimes. That's why people switch to the Raptor. If the stock petcock is not malfunctioning a Raptor isn't going to change anything except that the Raptor won't shut off automatically when the bike is turned off. You have to turn the lever to OFF by hand. |
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Title: Re: Something needs explaining Post by Serowbot on 07/16/14 at 13:03:09 Simply said,.. both petcocks are gravity feed.... the stock one requires vacuum to open the flow passage... it doesn't use vacuum to draw fuel, just to open the passage... The Raptor is just eliminating that added complication... Be sure to block that vacuum tap on the carb... else you have a big ol' air leak... |
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