Here is my situation:
I have the Raptor petcock installed.  As a habit when I park the bike, I turn the petcock to OFF position.  When I come back to the bike, whether it is a few hours later or a few days later, it takes a couple of good cranking sessions to start up.  Not a huge deal, but it gives me a scare.  

There have been a few times where I park the bike and have left the petcock in the ON position.  When I do that, the bike usually sits for a short period of time, (less than 1 hour). Under these conditions the bike will start right up with no effort.  It is unclear if the ease of starting is due to the engine being warm or fuel being readily available.

My question is, could this be due to a vacuum leak somewhere? (My guess would be carburetor)  Don't know if this is how it works, but maybe the leftover gasoline in the carb. bowl evaporates, and the system takes a bit of cranking in order to prime itself, thus giving me a longer starting process.

Should I always just leave my petcock in the ON position even if it sits for a 4-5 days between rides?

I am trying to get a better understanding of the whole carburetor/fuel delivery system.

Thanks.

I can't say for sure what is happening. I believe it is evaporating. I always forget to turn my Raptor off. It sat for a few days while on vacation and was fine.

Could you have a kink in the fuel line, so that fuel flow from the Raptor is restricted?

I'm also wondering if your carb bowl float height is set so low, that the bowl quickly depleats through evaporation on a hot day. Can't say that is the problem, but could be. However that wouldn't explain the delay in starting. I'd flip the Raptor petcock on first, then mount the bike, give a little time for fuel to flow.

I'd be tempted also to pull off the fuel line from the carb, just to see how quickly it drains into a container. If it dribbles out, there is something else going on.

Perhaps the Raptor rubber disk seal is improperly installed or slipped?

Just speculating, but I am sure the answer is out there.

Mine does the same, I have a feelin the gas in bowl evaporates and the churning of the engine to get her running after sitting takes a few turns to pull some fuel through. Leaving the petty on a few minutes before a ride helps but still takes me a few chugs if its been more than a day.

Savage 1987 wrote on 07/09/12 at 13:19:22:


Crankcase oil, or air box... or both...
.. depends on parking angle...

If this is the problem,... a vacuum petcock would prevent it...
Unfortunately,.. it would also prevent you from finding out about it... because the leak would only happen while you rode...

That would suck... in a figurative sense... ...
Blissful ignorance of such a problem is not good for your engine...
Better that the Raptor let's you know... ...

justin_o_guy2 wrote on 07/09/12 at 13:27:49:

JOG... not if it's a slow leak over a couple of days, and the Raptor is off...

Serowbot wrote on 07/09/12 at 13:29:51:




Ima no argue wid a you on a carb a questione,,
You wanna talk abouta the Fed,, Now Ima gonna argue,,

I'm old, but even so, the way I read it, there is something ammis w/ Sero's original post.

Maybe I'll go read it again. I have been known to mis read stuff.

Edit.......
I read it again,......
there is only one way for the bowl to drain of gas, it either evaporates, which will take days, or the bowl itself.....or its drain is leaking. It would have nothing to do w/ the "float needle" leaking.