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Joined: Jan 05, 2009 Posts: 622 Location: Michigan
Posted: Fri May 01, 2009 5:13 pm Post subject: an easy petcock question, bet someone knows
Ladies and Gentlemen may I so humbly ask a "dang stupid question" I just picked up that really pretty 79 XS650 a week or so ago, even came with a repair manual that doesn't have the answer to this question, but rest assured the owners manual you get when you buy the bike new had it. On all the bikes I've had so far, the petcocks have all been the same, Off, On, Reserve. This one is of course a vacuum petcock, which my Harley has, but it has an "Off" position. So, the question is, what position should it be in when sitting for a day or more? I don't want raw fuel in the oil, or to wreck the engine because of it, I am guessing here, the way the petcock on the 650 is marked is Pri, On, Res. so I think Prime to start, then On to go and Reserve if I forget to watch the clock, other than the vacuum, what assures it is "off"? The tank was low when I ran it the other day for the first time and had to shift to reserve to get it going again, so I put it to the on position because it had run out, figured that would be safe till I found out, so if any of you folks have the answer or explanation, I'd appreciatte it......thanks, Blue
nope no manual shut-off, just hope your float needle valves don't leak, yes PRIME is starting with dry carbs (flows fuel without engine vacuum), ON regular running and RESERVE is for those CRS days...... I have seen a article about switching the internals in those petcocks to make them into manuals, Pri becomes off, run is run and reserve is reserve, however I think you needed to have two (one on each side and swap parts acrossed) don't think re-build kits are availible either.... However mikesXS does sell replacement manual valves (make sure of year and all that)
Joined: Oct 24, 2008 Posts: 68 Location: prescott valley az 86314
Posted: Fri May 22, 2009 3:00 am Post subject:
sorry for the late reply.
the cv (constant velocity) system on my xj 700n works flawlessly.
however, since the bike is new to you,next time your tank is low on fuel take it off,drain it and pull the petcock
and make sure the "tower" fuel filter is good and secure.
if it comes off in the tank ( and they do-i know!)the fuel will drain into your crankcase.
no fun especialy on a ride.
i definately prefer the res-on-pri set-up to the old one.
Joined: May 07, 2009 Posts: 18 Location: East Central Iowa
Posted: Sun Jun 21, 2009 8:39 pm Post subject: yamaha vacuum petcocks
Mike's XS sells manual petcocks that are a swap-out replacement for the yamaha vacuum petcocks. My advice is to get some now.
You really only have two options with Yamaha vacuum petcocks. One is to replace them with manual petcocks. The other is to CONVERT them to manual petcocks. You can't leave them in place simply because they don't work properly. Sooner or later -- most likely sooner -- you'll be off somewhere on your own and you'll try to start your bike. When you try to start your bike, it won't start because it's flooded so badly that the plugs are gas-fouled. You will either replace the plugs (if you brought spares) or you will haul the bike home. Then you'll rebuild those vacuum petcocks. Then the same thing will happen again.
Get rid of the vacuum petcocks if you want to be happy with your XS650.
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