A Hypothetical . . .

[IanDMacDonald]

What would happen if one petcock stopped working and only two of the cylinders ran? What would happen to the other two cylinders? too hot and burn.a hole in the piston?

[natemoen]

Don't know and since I connected all 4 it will never be an issue for me!

[IanDMacDonald]

I've been thinking about doing exactly that to prevent that from happening.

[crazy steve]

The cylinders that are getting fuel would be the ones that could be damaged. But you'd notice the power loss before anything happened....

[natemoen]

I mounted a pipe on the bottom of the bowls with 2 T's to connect them to the carbs and on each end there is an elbow to connect to the petcocks.

Most of the time I only turn one petcock on. It is only if I hit reserve when I turn the other on.

[GLoweVA]

What would happen if one petcock stopped working and only two of the cylinders ran? What would happen to the other two cylinders? too hot and burn.a hole in the piston?

Agreed that you would notice the power loss, but what if you HAD to limp it home on 2 cylinders?
You'd melt some holes in the 2 pistons that stayed running. Don't ask me how I know.
My failure wasn't a petcock, but the head gasket, thus 2 of my cylinders lost.
I had about 15 miles to get home and the fastest I got was about 35mph.

Oh, thinking back, 4years ago, when the pickup coil wire went bad on my G and I limped it home, that's when I burnt my first hole in one of those.

Next time, I call the wife and have her bring the truck.

[CRXSi90]

How did the 4-6-8 v8 engines work then?

[CRXSi90]

Oh, and Greg/BA80 claims to have done exactly this in the LOST rally thread. Apparently it worked for 5 miles for him...
http://www.xs11.com/forum/showpost.p...3&postcount=79

[GLoweVA]

I suppose as long as you didn't push the engine too hard then the remaining cylinders (be it 2 or 4) could provide enough power to keep the engine speed up without over doing it on the ones that were firing.
Then again on the fuel injected computer controlled engines, the o2sensors and such should keep the fuel mix not too lean and therfore not to hot.

[sparkfly88]

On the way back from Ohio...

In North Carolina, as we were getting fuel, the vac line for my rightside petcock popped off.

I got on the highway and it lost ALL power, it sounded very airy, like an aircompressor, not an engine at all...I thought something blew up...lol.


I gimped to the next exit at like 30mph with it throttled up.

Shut the engine off, found the vac line, coughed and belched then fired right up!

[Rasputin]

I pretty much agree with Steve on this one. The two that have no fuel will not produce any unwarranted heat due to not firing. The oil and all that will stay in play so no big deal.
I think (and may be wrong) that the two cylinders still running the bike will require extra fuel to try to maintain life. That alone will cool the engine a bit as well as enrichen the two working cylinders.
You would absolutely know there was a power loss at any speed and then figure it out pretty quickly after that. Your ride will be ruined until the fuel is corrected.

[CRXSi90]

So just to hypothetically push this a little further.........

I believe GLoweVA's actual experience, but I follow the hypothetical explanations. Was the piston holing possibly due to the jetting? I'm thinking something along the lines of that the jetting was too lean for high load situations. The jetting was okay for intermittent bursts, and the heat developed could dissipate into the piston fast enough. Typically you can only stay on the throttle so long before you find a corner and have to slow down! If there were a sustained high load situation (pulling trailer in 100mph headwind), then the same holed piston problem might have occurred on all 4!

I'm just asking with curiosity and interest and trying to learn; no bad intentions here.

[GLoweVA]

I believe GLoweVA's actual experience, but I follow the hypothetical explanations. Was the piston holing possibly due to the jetting? I'm thinking something along the lines of that the jetting was too lean for high load situations. The jetting was okay for intermittent bursts, and the heat developed could dissipate into the piston fast enough. Typically you can only stay on the throttle so long before you find a corner and have to slow down! If there were a sustained high load situation (pulling trailer in 100mph headwind), then the same holed piston problem might have occurred on all 4!

I'm just asking with curiosity and interest and trying to learn; no bad intentions here.

In my case I rode the bike home and trying to accellerate on 2 vice 4 is hard to do.
Just getting off the line at a stop light was hard. I pushed the bike hard on those 2 running cylinders and they got too hot. I was at times WOT just to maintain speed at 40 mph so I wouldn't get run over by the cars.
Stock jetting, so they shouldn't have been too lean in the first place, just pushing them that hard and that long did them in.

I also agree that the theory should work too and maybe in a different set of circumstances mine might not have done that. In my case it was 2 and 4 that went bad.
If it were a fuel flow issue (like wht this thread started out as) then it would be a 1&2 or 3&4 pair and maybe that would change how the engine developes power.

[MPittma100]

Hole in Piston

I am having trouble figuring out how the two cylinders that burned the pistons overheated enough to do that?

MP

[DGXSER]

I too am puzzled how the two getting fuel will get damaged. To some degree these engines are almost four independent engines. I get there is a lot of work to be done. But unless your going WOT on those two AND getting the high revs, not sure I see it.