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Message started by TheSnakeLady on 06/15/13 at 18:54:51

Title: Bike will only run on prime
Post by TheSnakeLady on 06/15/13 at 18:54:51

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 ? :-?

Title: Re: Bike will only run on prime
Post by bobert_FSO on 06/15/13 at 21:03:37

Well, you know what our answer is going to be. If it runs on prime, it ain't the carb.

The stock petcock must be complete junk. I believe it is the #1 issue with these bikes, especially older ones.

Granted it did take 11 years for mine to crap out. The diaphram got stiff and would shut off in low-vacuum conditions, especially at highway speeds into headwinds and in cold weather.

Title: Re: Bike will only run on prime
Post by Steve H on 06/16/13 at 13:54:11

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.

Title: Re: Bike will only run on prime
Post by justin_o_guy2 on 06/16/13 at 14:48:44

Pull fuel line off carb. Point it into a jug. Turn to "ON" position.

Apply vacuum to hose. A syringe stuffed into the hose so that it doesnt leak will do fine. PUll on the syringe plunger. IF the hose isnt leaking at the petcock end or where the syringe is stuffed in it, or, somewhere down its length, the plunger should pull a short ways & get hard to pull & stay RIGHT like that & fuel should flow. IF it pulls away & doesnt get hard, the petcock is a wreck..

Title: Re: Bike will only run on prime
Post by busterboy on 06/16/13 at 18:22:34

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

Title: Re: Bike will only run on prime
Post by BobR on 06/18/13 at 19:24:05

I think I got the same problem, 1986. Is it dangerous to ride it on prime?

Title: Re: Bike will only run on prime
Post by oldNslow on 06/18/13 at 19:34:22

5A777A4A180 wrote:

I think I got the same problem, 1986. Is it dangerous to ride it on prime?

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

Title: Re: Bike will only run on prime
Post by BobR on 06/18/13 at 20:07:34

and should I turn it to ON when I park it, to be safe? I think I'll be getting a Raptor. Can't wait to see how much the local dealer charges.

Title: Re: Bike will only run on prime
Post by jcstokes on 06/18/13 at 21:16:37

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

Title: Re: Bike will only run on prime
Post by BobR on 06/19/13 at 12:26:15

The website says Raptor 660 part # 5LP-24500-01 I have a 1986. Fit???

Title: Re: Bike will only run on prime
Post by Dave on 06/20/13 at 06:25:41

220F0232600 wrote:

The website says Raptor 660 part # 5LP-24500-01 I have a 1986. Fit???

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

Title: Re: Bike will only run on prime
Post by strathken on 12/20/14 at 03:24:40

8-)i am scottish..and therefore known for being tight with our cash..so, let me say the bike will run fine on prime..just remember to fill tank every 100 miles.

Title: Re: Bike will only run on prime
Post by Dave on 12/20/14 at 04:10:28

41464053465A59575C320 wrote:

8-)i am scottish..and therefore known for being tight with our cash..so, let me say the bike will run fine on prime..just remember to fill tank every 100 miles.

Title: Re: Bike will only run on prime
Post by oldNslow on 12/20/14 at 05:16:59

A raptor costs about 25 bucks. That's three tanks of gas where I live. What are you waiting for ?

Title: Re: Bike will only run on prime
Post by Art Webb on 12/20/14 at 10:06:28

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

Title: Re: Bike will only run on prime
Post by strathken on 12/20/14 at 13:43:38

i should have mentioned in my earlier post that i completely removed the vacuum hose and blocked off both ends so that there is no chance of fuel getting into the engine oil.

Title: Re: Bike will only run on prime
Post by justin_o_guy2 on 12/20/14 at 14:16:23

Well, I have to say, that is an interesting concept, but, the gas isn't strictly prohibited from going down into the oil that way. If the carb float doesn't shut off, then, well,

Title: Re: Bike will only run on prime
Post by Art Webb on 12/20/14 at 21:33:02

65626477627E7D7378160 wrote:

i should have mentioned in my earlier post that i completely removed the vacuum hose and blocked off both ends so that there is no chance of fuel getting into the engine oil.

That do make it a little safer, I just figured I'd do it right, once, and not have to worry about it

Title: Re: Bike will only run on prime
Post by HAPPYDAN on 12/26/14 at 11:45:48

1B202D3A2B273C3A2129243B480 wrote:

[quote author=41464053465A59575C320 link=1371347692/0#11 date=1419074680] 8-)i am scottish..and therefore known for being tight with our cash..so, let me say the bike will run fine on prime..just remember to fill tank every 100 miles.

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.[/quote]

Listen and heed this sage advice - save yourself the unnecessary grief and embarassment. The stock petcock is crap. My 2012 did the same thing after 1000 miles. New ones are no better. Get the Yamaha Raptor 660 petcock. Easiest, most effective mod I've made. Plug the vacuum port on the carb, too.