Ok, I know what you're all gonna say, time to upgrade petcock.   But I need you guys to tell me anyway.  So, I only rode once last year (20 miles round trip to get it inspected), I love to ride but I was broke and working two jobs to get by.  Replaced the battery first thing this year cause it wouldn't hold any charge.  First time out, 7.5 miles into ride, bike dies, have to run on prime to get home.   Replace torn vacuum line and tear down and completely clean the carb.  Take bike out for 25-30 mile ride, runs great!  Bike sits for 2 1/2 weeks (completely rotten weather including several tornado warnings which is unusual in upstate NY).  Take bike out today to get it inspected, stalls twice before I turn around, again have to run on prime to get more than 2 miles.  Seems to run fine on prime.  Notice oil seems a little too full, do an oil change.  Oil seems to smell a little like gas, otherwise fine, not black or burned smelling and no metal shavings.  Also replace spark plug with exact replacement and gap it to .033.  Bike starts very hard, which I guess isn't unusual considering the fresh oil and spark plug.  Let the bike idle with full choke and petcock on "on".  Bike dies suddenly after about a minute.  Bike will not start, have to do prime (again) and full choke to get it to start, let bike idle like that for several minutes, seems to run well, bike warms up and I turn the petcock to on agian, and take the choke down very slowly.  Bike idles for several more minutes just fine.  I start to turn bike around (not even in gear so no throttle), bike begins idling "funny" with little backfires and begins to stall, I give it some gas, and it "chokes", acts like it's starving for fuel.  Turn petcock to prime, runs fine, ride bike to garage and turn petcock to on.  There she sits.  I've actually been trying to sell the bike to move up to a C50 but I can't sell it if I don't trust it.  

So, what are your thoughts? Petcock or carb or ?

I vote petcock.  It runs on prime, that's a sure sign it ain't opening the fuel flow when the engine is running.

Mine took 25 years to die but it did.  They all will sooner or later.

Mine did the same thing, I replaced with the raptor and have had no issues since,

BobR wrote on 06/18/13 at 19:24:05:


No. but on Prime you've got no reserve. If you run out of gas you're walking.

You can get Raptors on EBAY but you must check you get the right outlet size

BobR wrote on 06/19/13 at 12:26:15:

All gas tanks, all years.......all the time.

strathken wrote on 12/20/14 at 03:24:40:


The petcock is most likely failing as a result of the diaphragm going bad, and eventually the diaphragm is going to decompose enough to let fuel flow down the vacuum line and into the intake port.  When that happens the fuel leaks past the rings and goes down into the crankcase and dilutes the oil.

Several times a year on this forum we have folks posting about the smoke coming from the exhaust, the air filter and filter box being soaked with fuel, and the bike bogging down and not running right.  The end result is the petcock has failed and filled the crankcase up with gasoline.

False economy, you're risking a 500 dollar engine for want of a 25 dollar petty
we mechanics call that 'spending a dollar to save a dime'
that phrase also applied to buying cheap crappy parts that fail quickly instead of quality stuff
I'm a Scott, to, and I'm not that cheap