Seafoam. 1 ounce per tankful. Can be had at Wallymart or most auto parts stores. Make sure there are no leaks in vacuum line to petcock. Also, you might want to search for Serowbot's petcock test, to make sure it is working right.

Yes I have heard about the petcock issue.  I will definitely test that.  I'll also pour some seafoam in the tank, since it can't hurt.

Thanks for the suggestions, I will get on it this weekend.

 Appreciate the help,

            -Hal

kingart3 wrote on 09/16/11 at 10:40:09:

I think Seafoam is used at 2oz per gal. I use a medicine cup from some cough syrup for a handy measure. Of course this cup is dedicated to Seafoam only.  

Routy wrote on 09/16/11 at 22:48:39:


I was having the exact same problem he is on and off for a week. I never had any high speed fuel starvation, only intermittent low rpm fuel issues. My idle was high enough, I had to put it waay too high for the bike to not try and cut out when the rpms dropped down for shifting or idling. I bypassed the vacuum and have never had that issue again. Didn't use any Seafoam, didn't take apart my carb.
*shrugs* Just my own personal experience with my bike showing the same issues his is.

 
Routy,

You are ignoring the "variable speed" nature of the vac petcock.   When input suction is low, fuel flow is low too.   The vac petcock isn't on/off at all, it reacts in a sliding scale from zero to full fuel flow according to the vacuum level it sees.  

There is nothing to say the vac petcock's rate of delivery just off idle to mid range is enough to keep the engine happy.   (probably depends on the diaghragm condition, air filter type, etc)

I would say that when the slide starts moving up, the needle comes into play and the main jet kicks in, the carburetor probably uses a ramp up in fuel used that isn't matched by any big increase in vacuum level (or big increase in the vac petcock's fuel delivery to the bowl).  

The slide just moved up because you got to the venturi point where the slide starts moving up and the main jet begins to ramp up its bigger fuel use at whatever that general input vacuum level/fuel delivery that happens to be.

Remember, there isn't any connection between vac petcock diaphragm and what it needs to raise up fully (certainly as it get older anyway) and the main slide diagphragm and what it needs to move the needle up (and ramp up the carb's fuel consumption).    

Enough of this out of sync and you get fuel starvation ...

BTW, expecting a newbie to tell you anything other than what he personally sees or knows about his one personal bike is probably futile -- and you should have rigged youself up a vac petcock to do the suction tests yourself by now so you would know this variable reaction stuff first hand already.

The good thing about the Raptor is that it is always on "full flow" and we know that full Raptor flow is very large compared to a vac petcock's total maximum possible flow through the diagphragm valve in the full open (full vacuum) position.

That's why wickers and high HP people like the  Raptor a lot.

   
A gummy intake vacuum damper valve (an entire new subsystem of the vac petcock that needs maintenance) -- if it were gummy what would that do to the "total response curve" of delivering fuel?

Would it decrease it?      


=============


Seriously, the more I learn about the vac petcock the more ways it shows that it can possibly not do what you want it to do when you need it to be doing it.

Now we need to be factoring intake vacuum pulse frequency and vacuum pulse strength vs fuel valve opening distance and duration just to get to fuel flow delivered .... then it becomes fuel delivered vs fuel required by the bowl to get to potential leaning/stalling.  

And it can happen at any point in the rolling open of the throttle, buffered only by the fuel sitting in the bowl at the time it starts to take place.

Please, tell me you are pulling my leg (pretty please .....)


I turned my old vac petcock into a little vac actuated musical instrument that sits on my desk and I play a new tune on it every time I go and learn something new about that vacsucker petcock.  

Now I need to go train me a woodpecker to suck on it at different RPM pulse ranges so I can compare what makes it out of the fuel tap according to how hard I squeeze the woodpecker's balls and how fast he inhales between screams as he speeds up and up and up .....



And now, now you are gonna make me take that vacsucker all apart looking for this new valve thingie that you gummied up and then removed as part of your ongoing vac petcock improvement program.

You is cruel, you is ....   all this work for getting new additional ongoing problems and a constant steam of troubles.

All I would make you do is bolt up a simple 2 screw manual petcock assembly you already know how to change out, then you wouldn't ever have to do anything except turn it on (assuming you wanted to keep turning it on and off that is -- most of us don't bother).  

No more problems, lots of gas whenever you needed it .....

No more F-whatevers sneaking up behind you and trying to mate with your motorcycle .....




   

That was a female Ford truck, right?

       

 
 
Aww, cut him a break -- he's on up on his meds right now and he's feeling OK.

Later on this afternoon when his meds wear off, then you can talk sense to him (but he'll be too grumpy to talk back to you).

We'll just try to keep him entertained and such during his convalescence.  If it means sacrificing a male woodpecker or two during testing, that's OK -- just don't go be telling the Feds about it.  

They will want to know why their woodpecker's cockaded is all red ....        They consider that a restricted activity -- according to their signs anyway.