Petcock with off position?

[MrZig]

yes...center to center...it's hard to measure without proper tools so if it looks like it's anywhere in that area within a couple mm then it's golden. Odds are it's the same, but I don't want to guess.

Okay it looks like it's a 44mm. Plus it has '440' imprinted on the top of it. Whether or not that means 44mm I don't know, but I'm going to take the chance and buy the 250 petcock. If it doesn't work, well then I can return it at a 20% restocking fee so it's not the end of the world.

 

[Matchless]

Rather replace your petcock with the original that has the vacuum shut off. It is a very good design regardless of what some people say. If it is in good condition you never have to worry about it leaking or fuel getting into your sump.

Just think about it, a manual petcock is OK if you are never, never, ever going to forget to switch it to "ON" when pulling away and that you or anyone else is never, never, never, ever going to leave it "ON" after parking the bike.

It is unfortunately expensive, but finally your decision.
Just my 2 cents worth.

 

[MrZig]

Well here's the plan, I'm going to buy the OEM petcock for $96 and if it breaks on me again I'll switch to the 250 petcock.

I bought this bike for cheap so dumping a little money into it doesn't bother me.

 

[jpaul]

Try here for the petcock. They list it at $70.

http://http://www.worldofcycles.com/catalog.asp

I've gotten good service from them.

 

[makenzie71]

That's your call...the OEM petcock is a good piece, I just hate vacuum hoses and I hate not having an off position...I also hate spending money so I was faced with using a free RMX piece or spending $50 to rebuild mine or $100 to get a new one. A new one should last longer than you'll realistically have the bike.

 

[Agemax]

The original taps will last......31 years. Sorry, just guessing yours is the orginal fitment but they do last a long, long time.

Other taps that'll fit with an on position? In the UK the I'm pretty sure that a TS250 will fit but couldn't swear on it - might be too tall - and the US could be different anyway.

The problem with fuel leaking in to the crankcase is that the crankcase fills up with fuel, you spin the motor over and get a hydraulic lock and bend and bust something.

its impossible to get a hydraulic lock up in the crankcases, thats why engine breathers are fitted. you can only get a hydraulic lock up from in between the pistons and the head as there is no escape for the fluid on the compression stroke.even if the breather was blocked, it would clear the blockage or blow a seal before it bends anything metal!

as for the petcock, a trick on a gs1000 is to grind off the little lug at the top of the petcock, then you can turn the lever up to the 12 0'clock position and it gives you a true "fuel off" position. depending on which model it is you may have to shorten the lever slightly to avoid hitting the tank.
not sure if this mod would work on your model though.......

 

[MrZig]

That's your call...the OEM petcock is a good piece, I just hate vacuum hoses and I hate not having an off position...I also hate spending money so I was faced with using a free RMX piece or spending $50 to rebuild mine or $100 to get a new one. A new one should last longer than you'll realistically have the bike.

Well I would use the 250 one if it was free, too. unfortunately every site I see has it listed between 50-60 dollars, so itd be around 70 here.

As far as that $70 one posted above, I bet it would come to more than $100 once you figure shipping & currency.

 

[hampshirehog]

its impossible to get a hydraulic lock up in the crankcases, thats why engine breathers are fitted. you can only get a hydraulic lock up from in between the pistons and the head as there is no escape for the fluid on the compression stroke.even if the breather was blocked, it would clear the blockage or blow a seal before it bends anything metal!

You're right of course. It's when the crankcases get full and the fuel gets on top of the pistons that it happens. I've only ever seen it once years ago - on a Fiat 500 (the tiny original one) fitted with (or more accurately on top of) a Jag V12 motor. I kid you not, it was an exhibit at a custom car show; the guy who owned it was obviously an engineering nut as a) he'd built the thing in the first place and b) once it had gone pop he beautifully cut the motor in half to show the damage.

 

[MrZig]

I talked to a local mechanic and he's going to try and repair my petcock for cheap. He said he has a repair kit - anyone have any luck with 'em?

 

[tkent02]

I talked to a local mechanic and he's going to try and repair my petcock for cheap. He said he has a repair kit - anyone have any luck with 'em?

On some models they work perfectly, on others they don't fit at all.
Give it a shot and post your results for the rest of us.

They are really simple D I Y repairs, it's just a matter of if the parts fit or not.

 

[MrZig]

"Can it hydrolock the engine?"

I found out today that the answer to this is yes, yes it can. Warmed up my oil before a change by zipping around a parking lot, then I ran it into the shop. Found that gas was dripping out of the airbox drain at a steady rate, and it was also leaking in between the left-side carb and airbox.

So I changed the oil, refilled it and went to start the bike. Turned over once and stopped, just like that. Oh ****, I knew exactly what happend. I took the tank off and took both spark plugs out then pushed the start button.A crapload of fuel sprayed out of the left cylinder. WAY more than is needed to run an engine. After it stopped spraying out, I put the plugs back in and it started up and ran like a champ. Luckily the other piston didn't fire and cause it to blow the engine.

So I'm going to tear the carbs apart and fix that petcock asap.

Lesson learned: don't **** around when you know you have a bad petcock!

 

[MrZig]

Okay I got a 'new' petcock. It's from another bike in the suzuki line, not sure what from. But it fits the bolt pattern & flange perfectly.

Under the ON/RES settings it doesn't leak, and in PRI it flows. Nice.

Only thing is if I have fuel in the tank, with it selected to ON or RES, and I shake the tank, a little bit of fuel will dribble out then quit. Is this normal? My best guess is the shaking is overcoming the diaphram spring and opening the valve until you stop shaking. Seems like it would do the same thing on a brand new valve.

If anyone can identify the new petcock/tap, that would be great:

 

[MrZig]

Son of a bitch, this one leaks too. I've had it with vacuum fuel taps, its time for that manual one.

 

[MrZig]

The only thing about the RMX250 fuel tap (this one: http://www.bikebandit.com/suzuki-motorcycle-rmx250v-1997-fuel-cock/o/m6665sch266626) is that the pipe is really tall and it will hit the top of my fuel tank. I suppose I could cut it, but then the filter is worthless.

 

[MrZig]

Okay I ended up ordering a fuel tap from a Yamaha WR400F. Part #2GU-24500-02

It might fit, it might not. I'm going to give it a shot. It's only $42 Canadian, and it has ON/RES/OFF positions. I'll let everyone know if it fits.

 

[makenzie71]

Zig I've got a couple Yamaha's in the shop and none have 44mm patterns like the GS. Did you search for the flange dimensions?

 

[MrZig]

Zig I've got a couple Yamaha's in the shop and none have 44mm patterns like the GS. Did you search for the flange dimensions?

No, couldn't find any information, however I did find this:

http://www.thumpertalk.com/forum/archive/index.php/t-451280.html

The guy mentions the part number I found, and at the bottom of the page another guy says "FWIW, my 1990 RMX-250 petcock appears it will bolt up no problemo. It has a reserve tube for sure. 44300-05D00"

That's the part number you used on your 750. The flange looks the same from what I can tell on exploded views, but there's only one way to tell and that's by ordering it.

I'm getting it through a local dealer so if it doesn't work, I can return it for a 20% restocking fee.

Edit: And the guys are putting the yamaha one on a Suzuki DRZ400S.

 

[CodyLHen]

I wanted to pass on a useful tip I found. My petcock did thing where if you shake the tank it leaks. I bought a rebuild kit and it made it worse. I almost gave up hope but I replaced the #61 o ring on the plunger with a #36 I believe. I also found a longer spring at the hardware store. I cut it down a little to make it fit. I lubed up the rubber parts and re-assembled. Works perfect. My guess is over the years the gas wears the plunger hole larger. You may need to use a different o-ring. Possibly the same size but thicker. It kinda depends on your selection at the hardware store.

 

[makenzie71]

Ok for anyone else interested...had an issue with my RMX piece: no screen (yeah sorted that out ziggy). It was letting too much debris from my crappy tank into my filter and plugging everything up. So, I went to modifying my stock piece to be an on/off/reserve non-vac operated piece.

You need: 1/8 hole punch/drift punch/empty .22 cal casing/you'll figure it out, #2 phillips screw driver, 5mm alan wrench (unless you're one of those fools who left the phillips screws in your petcock), 1.5" square piece of high density card (like from a steno-pad or cereal box), a fuel resistant sealer like RTV silicon, a 2-part clay epoxy like Pro-Poxy or Mega-Stik, a new 11mm X 16mm X 2.5mm O-Ring (applicable to 1981 GS750E), a new rubber gasket for the petcock base.

First, remove the petcock and remove the screen tower.

Then disassemble the petcock.

Remove the rubber diaphram and spring from the vacuum side. Throw both away.

Pick-up on the side-clips holding the selector knob in place. Pull the selector out of the petcock. Remove the small spring behind the selector. Remove the old o-ring from the selector. Insert the selector back into the petcock and use it to turn the valve inside the petcock housing. Pull the selector back out and turn the petcock over so the valve will fall out of the housing.

Thoroughly clean the selector, valve, and petcock housing (especially on the vacuum side where the gasket probably solidified and fused to the aluminum).

Break out the clay epoxy. Mix a small portion and press it into the vac port from the inside of the vac side cover. Mix another small portion and use it to plug the smaller hole on the valve (use an apropriate size drill bit or alan wrench, inserted through the larger hole, to offer resistance on the inside of the valve so that the epoxy will expand and form a proper plug). Press the valve back into the petcock housing to level off the epoxy, then remove the valve. Let epoxy on both parts set for 20 minutes.

Place vacuum side cover the cardboard and trace it using a pen, then cut out the outline. Use whatever you have to cut a 1/8"~ish hole to punch out the four corners of the new gasket. Leave center intact, and make sure that a perimeter stays intact. Lay a light film of fuel resistent sealer on both sides of the new gasket then reassemble the cover.

Place the valve back in the petcock housing.

Put the new o-ring on the selector and slip the snap-clamp thingy over the lever. Insert the spring into the valve, then push the slector into the housing. Press the snap-clamp thingy into place.

Let the whole assembly set over night. Then put the screen tower back into the housing, and resinstall the petcock.

You will now have no vacuum operation. Place a plug over the vac ports on the petcock and carburetor/intake manifold.

"On" and "res" are still the same. "Prime" is now "off".

Something to keep in mind, though, is that I had to go through three petcocks before I got enough good parts to make the whole thing work. The valve inside is plastic and wears easily. If your valve is not in good shape, it will leak.

 

[MrZig]

Okay so the Yamaha didn't fit, it was 34mm instead of 44mm. However, it was the cheapest and thus I thought about getting a piece of scrap alumunium and making an adapter.

Here is the adapter:

And here is the tap in the adapter:

You'll notice the flange over hangs the mounting hole. This is because the flange was too long and it hit the mounting bolt, but with it recessed like that I have just enough clearence for it to all fit. The two big holes in the center are for the fuel tubes. It shouldn't leak any fuel at all, either, but we'll see.

This block was also needed to clear the valve-knob from hitting the tank. When all mounted up it looks great. Not sure if I want to paint the adapter or not..