Had carb issues that turned out to be petcock   2 (2.8%)
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Only 2,......out of 70 ?? This wadnt sposed to happen !

I'd bet OF is sorry he ever started this poll !.......probably going off the deep end about now !

 
Routy,

Let's look at the numbers together and Charon can watch carefully to make sure I don't overstate what they say.

A sub-set of this week's readers comprise the poll sample, these are the readers who come to RSD regularly.   This generally does not include all the Cafe people nor does it include all the Politics/Religion people.  Well heck, nothing else does either, so let's just say we are short term polling the tech heads and be satisfied we understand our sampling well enough.

Understanding these sampling limits, we will have to accept the people responding to the poll as a representative sample of the tech heads (time period "now").

We have done the same tech head sampling in poll form once before, so you can try to say "then" and "now" as far as the results, with a little salt thrown on it because the questions were a little different.

And all you can judge really is if people are responding at a different RATE or RATIO of "problems" to "no problems" than they did before.

What did I learn from that first poll that was unexpected?   SOOOO many more newer bikes were having petcock issues than I had expected back then.  There HAD to be a reason for this .....

This partially fueled the new though that really came out of the vac suction tests on my failed petcock, that low intake vac leads to low fuel delivery and WE MIGHT BE DOING IT TO OURSELVES BY TAKING OUT THE STOCK FAIRLY RESTRICTIVE AIR FILTER SYSTEM (lowering system vac levels across the board) while also asking for more gas volume to fuel a higher hp engine.  This is logical enough, I think.

So, in this second poll I carefully noted the upswing in people reporting "lack of gas" at various stages -- while being surprised at the fairly large number having to use their wrist to keep the bike going at stop lights (which is relatively new to my thinking).

Conclusions?   Overall ratio of vac problems to no vac problems is increasing.  Why?  Maybe age creeping up on the bikes, maybe more people trying to get that last 10 hp out of the engine, more likely a combo of both items and some other, not yet considered causes.

Now, as to your point about "carb problems" really being petcock only being two (2) this time -- I take that as a positive comment on the fact we make all "carb issues newbies" do the Serowbot test first right off the bat now --- and we correctly identify the petcock issue before they even start taking their carbs apart.


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Problems to no problems is about 50%-50% now  .... it is increasing some from one year to the next


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Raptorization still makes the bad stuff stop COMPLETELY.   There is no "common incidence" of downside float bowl leakage getting gas into the sump as was initially feared -- we are still eagerly looking forward to the very first verified non-preexisting float needle leaker bike and we are pretty sure eventually it will arrive, given enough time.

Surprisingly my stock petcock doesn't leak either.When better petcocks are built Suzuki will built them.

Routy wrote on 08/26/12 at 06:51:34:

Wonder how many had petcock issues that turned out to be carb... ...
Not many, I bet... ...

I was looking through a book I have about the Nebraska Tractor Test lab in Lincoln, NE. It lists results of tractor tests from the inception of the lab up through 1984. It includes gasoline, propane, "tractor fuel" and diesel tractors. The part of interest is a large table of economy figures, telling how many horsepower-hours are produced per gallon of fuel. There are over 400 gasoline tests, and as best I could tell (besides a few outliers) the results ranged from roughly 8 to just over 13 horsepower-hours per gallon. My unscientific method of choosing the mean was to go to the middle of the list, where I found about 11 horsepower-hours per gallon to be pretty common. These measurements are made with the tractor at full power pulling a load, so might be reflective of a motorcycle engine running wide open. If we relate this to the Savage/S40, and generously grant it 33 horsepower, it burns three gallons of fuel per hour, max. If we claim to have gotten another 11 horsepower with performance mods, it makes 44 total and burns four gallons per hour, max. Now, someone needs to measure the fuel flow for the standard petcock and the Raptor. I may get a chance to try it with the standard petcock, but don't hold your breath waiting (you might turn blue).

The point I am trying to make is that we need to get some real numbers instead of anecdotal data. The Raptor does not depend on engine vacuum for operation, so it should be easy to measure fuel flow. Take the fuel line off the carburetor, run it into a calibrated measuring device such as a kitchen measuring cup, and time how long it takes to flow a measured amount such as a quart or even a pint. Convert that to gallons per hour. Even better would be to run a full two gallons, which would allow for differences between a full tank and a mostly-empty one.

The factory petcock would be a little more difficult, although it could be measured in PRIME just like with the Raptor. Measuring in ON or REServe would require that vacuum be applied, easy enough with a large syringe or maybe even a turkey baster. But to really characterize it would require a vacuum source and a vacuum gauge, to see just how much vacuum is required to initiate fuel flow and whether fuel flow is proportional to the amount of vacuum applied. Not difficult to do, but tedious.

 
Joe F,

Please tell us about what happened.

How did you manage to give a lick to the Raptor petcock since it is well recessed behind the curve of the tank?   Or did you hit it?

Or maybe you need to explain where the gas was coming from and all the rest of the circumstances (like which side was the bike laying on, etc).

Curious minds want to know .....

If the pulsing vacuum is a problem with the stock petcock, why could you not insert a restriction into the line that almost completely shuts down the vacuum?  That would still suck on the diaghram in the petcock to keep it open, yet it would dampen out the pulses.  They do this kind of thing in test equipment and aircraft instrumentation often.

Gyrobob wrote on 08/26/12 at 21:35:24:

That's a good idea.  Squeeze a round main jet into the vac line. 155 oughtta do it.  

One could take a running raptorized savage, hook up the vac line to another petcock and tank, and measure the flow rate at idle, 2-3000RPM, and 4-5000 RPM.  Then try it with the partially restricted vac line and see if the overall flow rate is any better.