jeranb

Member
Aug 16, 2012
7
0
Recently bought my 5 yr old a pw50. It ran but never like it was supposed to. Constantly fouling plugs & it would barely idle. Guy I bought it from said he always had to clean the carb. My son was riding one day & went to turn around & it died. Took it home replaced plug & it started for about 30 secs then died. Wouldn't start again. Got tired of cleaning so I bought a new one. Put new carb & it fired right up. Had throttle slide 180 off so it was full throttle all the time. Fixed that issue & it hasn't started since. Put new plug again & noticed the plug wire was broke & cap would pull right off of wire. Bought new coil. Still won't start. New carb, new coil, new plug!!!! Is it the reeds??? Any help would be much appreciated!
 

_JOE_

~SPONSOR~
May 10, 2007
4,697
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Check for spark. Take an extra plug and put it in the cap. Lay the plug against the head (I don't recommend holding it with your hand) and kick it over. You should have a nice blue spark. How did the choke plunger and cable look when you changed the carb? We have an 03 that just had issues because of a frayed/rusty cable. The plunger bore was full of garbage and wouldn't close. It ran like ****. Got that all straightened out and the throttle started getting hard to turn. The oil injection pump has a cable operated aparatus that was full of mud and crap. That's under the plastic cover in front of the rear wheel. The throttle cable splits into two and run the slide and the pump wheel. With everything cleaned up and a new cable it runs like a champ. Ours responds well to airscrew adjustments too. You can make it smoother if you tune it a bit rich or snappier if you lean it out a bit.

Hope you find the problem to be something simple, let us know how you make out!
 

jeranb

Member
Aug 16, 2012
7
0
Thanks for the info!! Oil injection works just fine, got good spark. Made the mistake of holding it in my hand & got the crap shocked out of me. Right after I posted this I went to mess with it & it started after a few kicks. Ran like crap. I have a parts bike that I took the choke off & put it on this one. The original choke cable had no tension or play in it at all. This his tension & it seems to move up & down like its supposed to. The biggest thing that caughty eye was when I disconnected the oil line to make sure it was pumping oil as I twisted the throttle was that the bike kept smoking a LOT without any oil being pushed through the carb. I've read other places that the pipe could have carbon build up on it. This is an old bike. A 1987 so it wouldn't surprise me.
 

jeranb

Member
Aug 16, 2012
7
0
Thanks for the info!! Oil injection works just fine, got good spark. Made the mistake of holding it in my hand & got the crap shocked out of me. Right after I posted this I went to mess with it & it started after a few kicks. Ran like crap. I have a parts bike that I took the choke off & put it on this one. The original choke cable had no tension or play in it at all. This his tension & it seems to move up & down like its supposed to. The biggest thing that caughty eye was when I disconnected the oil line to make sure it was pumping oil as I twisted the throttle was that the bike kept smoking a LOT without any oil being pushed through the carb. I've read other places that the pipe could have carbon build up on it. This is an old bike. A 1987 so it wouldn't surprise me.
 

_JOE_

~SPONSOR~
May 10, 2007
4,697
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Excessive smoke is because it's too rich. Be it too much fuel, possibly because of the choke not closing, or too much oil, possibly because of the injection pump not closing fully when the throttle is closed. Ours had both of those problems. When you'd close the throttle the wheel on the pump wasn't returning all the way due to mud and rust in there. Ours was like a mosquito fogger at times. It would only start if you held the throttle open when it was hot. If I were you I'd take a close look at the choke plunger and cable, it should be very easy to flip the lever up at the bars and it should snap back down freely. Also pull the little plastic cover off the pump and make sure the wheel pulls the cable back when the throttle is close, if it doesn't move freely it can hang up and hold the pump open too far for the throttle position making the oil mix too rich.
 

jeranb

Member
Aug 16, 2012
7
0
If I let the bike sit awhile it will start but run like crap. Oil pump is working fine. The wheel goes all the way back like its supposed to. Leaning more towards the choke now. It doesn't move freely
Like it should. The cable is good & the spring is good. Not sure how the choke works. Looks like it just opens up & allows fuel to flow freely without pulling the throttle. Now the carb is dumpin fuel out of the hose on the bottom of the carb.
 

_JOE_

~SPONSOR~
May 10, 2007
4,697
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You said it was a new carb right? Sounds like you've got dirt getting in somewhere. Look at the airbox/filter. Also the tank. Make sure everything is squeaky clean. The choke plunger has a rubber end that seals up the passage when closed. If the plunger isn't returning all the way it won't seal off the passage allowing extra fuel to pass. Clean the plunger and it's bore in the carb and then use some rubber friendly lube on the o-ring to help things move and seal up properly.
 

jeranb

Member
Aug 16, 2012
7
0
Yes the carb is brand new. Looked at choke & there is no rubber seal anywhere to be found. Pulled the breather off & for to start but it's actually spitting gas out where the air intake is. So that's what it's got to be. Choke is staying open & flooding it. I will let y'all know what I get done. Does anyone know if there's a way to just bypass the choke for troubleshooting purposes??
 

_JOE_

~SPONSOR~
May 10, 2007
4,697
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I'm sorry, you're correct, there is no oring on the PW choke plunger. The bottom of the brass plunger is rubber and seals the passage off. There's a spring that pushes the plunger down into the carb. To rule out the cable holding it open you can just drop the plunger in without the cable attached and put the spring in on top of it. It probably wont start like that though unless it's really hot outside or you're way too rich on the pilot circuit.
 

jeranb

Member
Aug 16, 2012
7
0
Well I think I got it figured out. Let it sit for a day & it fired right up. Noticed oil was spitting out of the exhaust pipe. So I disconnected the oil line & it cleared up. Drained the gas & put 50:1 premix in it & it runs like a champ now. Not sure how to adjust the oiler but for now this will work until he outgrows it.
 

_JOE_

~SPONSOR~
May 10, 2007
4,697
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Many people disable the injection and run premix. 50:1 is probably a bit light on oil though....
 

jeranb

Member
Aug 16, 2012
7
0
Ya that's what I thought. But the local Yamaha shop said they premix all their 2 strokes at 50:1. I thought it was low myself, I'll keep adjusting the mixture & see how it does.
 
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