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Yamaha pw50 wont run. Please help

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So I have been riding for 16 yrs now & am passing it down to my 5 yr old son. I bought him a 2013 pw50 several weeks ago & he has put about 4-5 hrs on it so far. We have had a LOT of rain the past couple weeks & that hasn't let him ride, well I was going to take him 2morrow after work & I got his bike out to go over it incase there was something I might have missed b4 putting it up last time he rode. Then topped it off w/ fresh gas & went to start it. Took several kicks which was odd & once it finally started I switched the choke off & it died. I started it again & let it warm up a lil bit & this time left the choke on & switched it from "start" to "run" & it died again = like it was starving for fuel. I the pulled the air box checked air filter = clean as a whistle. Then took the carb off & took the jets out & blew em off w/ the air compressor & then blew air thru out the whole carb just incase there might have been something somewhere. Put it all back together & went to start it again which took even more kicks than b4. After getting it started it still dies when shutting off the choke but now when it's running on choke & I switch it from "start" to "run" it wants to go all by itself w/ out twisting the throttle. The throttle slide isn't stuck open cause I checked it b4 putting the airbox back on. I would call the dealer but they are closed on Mon. Was also thinking about buying replacement jets... Any info or tips from anyone? Thx in advance, Steve

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I cant imagine its the jets this early. Did you check the plug? They load up quick from being jetted rich. What happened to me after i got my sons running was that he wanted to start it to 'see if its still fixed' when we couldnt ride and ended up loading the plug. Just wipe it dry and spray a bit of carb cleaner in there, replace the plug and start it.

Ive also had to back the throttle stop screw out so you can clear it out once warmed up easier.

And maybe check the exhaust to see if that restrictor washer has crudded up. Im not sure how long it takes for that to happen.

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I cant imagine its the jets this early. Did you check the plug? They load up quick from being jetted rich. What happened to me after i got my sons running was that he wanted to start it to 'see if its still fixed' when we couldnt ride and ended up loading the plug. Just wipe it dry and spray a bit of carb cleaner in there, replace the plug and start it.

Ive also had to back the throttle stop screw out so you can clear it out once warmed up easier.

And maybe check the exhaust to see if that restrictor washer has crudded up. Im not sure how long it takes for that to happen.

+1 on the plug & throttle screw. I was laying in bed last night trying to think of what it could be & then realized I didn't even take the plug out to check it & didn't take the screw out to blow it all out. As far as restrictor washer, that was taken out the day we got it. Doesn't have enough power w/ it in & the whole screw taken off to ride in the grass so I pulled it & put the screw back in.

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These things are pretty indestructible. Mines a 99 with what looks like an original piston complete with deep carbon scores from the exhaust port and still starts before i bottom out the kick lever. The biggest thing was the rich jetting. Get the thing good and hot then open it up and itll run forever. If my son sits and lets it idle or more than a minute itll start to sputter. It happens quick. Im looking for a 67.5 main for less than $14 shipped to help, but for that price id rather kick it over a few times.

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Assuming it is oiled up: If you open up the muffler just a little with a drill and also bend parts of the core, then the rich stock main jetting works really well. Also if you want to properly clear it out, then unplug and remove the rev limiter. You see a redundant thing in addition to the CDI.

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I got it runnin now. Ended up bein the pilot jet. I was @ our local Yamaha dealer 2day cause my pops needed some stuff for his bike & when we were @ the counter they had this fuel treatment called Star Tron made by Star Brite. The manager of the store told me he uses it in EVERYTHING now & blah blah blah & I thought it was a sales pitch But boy is his stuff AMAZING. I soaked the jets in it for 15 min. Poured some inside the carb & put carb back together. Drained all the old gas out since it had Sea Foam in it & put fresh gas in w/ this mixed. Bike fired after a couple kicks. Spit & sputtered but finally cleared itself out. This stuff gets a +10 from me. No more Sea Foam.

Edited by stevekx500

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Glad to hear it. Ive been wanting to try startron after i used up my can of seafoam. Seafoam has always worked for me, but maybe ill grab a startron and see if im missing out!

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Steve, that's great about the pilot jet finding.

I still recommend anyone to de-restrict the muffler a little in any PW50. I mean just the muffler core. It easily unboltts and slides out the back. I did a little drilling and bending. It became a tiny bit louder, but it ran much better. Stock they are jetted too rich. I assume to avoid overheating if the cylinder fins get clogged with mud. With the more open muffler and also the rev limiter removed they rev out way cleaner and further. Plus it wont clog up again.

If you need to pressure wash it, then be careful around the choke knob on the handle bars. Water easily goes down it. I eventually removed our choke cable and screwed a stud into the carb, then used a sponge stuffed in the filter intake to cold start the bike. As a bonus this started much easier. I put the choke cable back on when I sold it to a friend - and then he went back to the sponge method as I had it.

Another good trick for less troubles is to properly seal the cable join where the throttle cable splits off to the oil pump cable. I wrapped ours in self amalgamating rubber tape. Then primed the inside of the cable with oil.

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Steve, that's great about the pilot jet finding.

I still recommend anyone to de-restrict the muffler a little in any PW50. I mean just the muffler core. It easily unboltts and slides out the back. I did a little drilling and bending. It became a tiny bit louder, but it ran much better. Stock they are jetted too rich. I assume to avoid overheating if the cylinder fins get clogged with mud. With the more open muffler and also the rev limiter removed they rev out way cleaner and further. Plus it wont clog up again.

If you need to pressure wash it, then be careful around the choke knob on the handle bars. Water easily goes down it. I eventually removed our choke cable and screwed a stud into the carb, then used a sponge stuffed in the filter intake to cold start the bike. As a bonus this started much easier. I put the choke cable back on when I sold it to a friend - and then he went back to the sponge method as I had it.

Another good trick for less troubles is to properly seal the cable join where the throttle cable splits off to the oil pump cable. I wrapped ours in self amalgamating rubber tape. Then primed the inside of the cable with oil.

I was talking to the salesman yesterday & he said he bought one a few months ago for his nephew & something Yamaha did w/ the 2013's carb is they put a brass plug on the outside face of the carb. He told me 2 CAREFULLY drill it out & that helps a LOT 2 lean it out = more airflow, cause that's what he did. Do you know anything about this little trick as well??? The more I read the more problems I find w/ these things. Now I am 2nd guessing myself on the purchase.

Also, Can you go into a lil bit more detail on what you did 2 the choke cable as far as removing it, stud in carb, "sponge" filter etc etc

Edited by stevekx500

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Be careful not to step in the bullshit. Pw's are not hard. In fact, they are stupid simple. They can run forever with little maintenance and because of that, people dont maintain them. Either that, or ppl try to modify them instantly upon getting them or as soon as their kid progresses a bit. These are not high performance machines. If making it lean is all you want, put smaller jets in. I wouldnt be drilling holes all over trying to improve air flow. If you think about it, the design has worked for two decades. Theres not much wrong with it.

Ill admit ive tweeked my sons quite a bit. And after some trouble, i found myself back to nearly stock and just jetting it like i jet my 250. Dont get frustrated, its a minibike :)

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Hey, The PW50 is a great bike! Be excited about it. Sorry to put doubts in your mind. It is the lowest maintenance bike I think anyone could own - with a few simple mods.

I would never drill an air opening to the outside of the carb. Unless it opened to the inside of the airbox. It'll suck in dirt that hole for sure. I still suggest you remove the muffler core and let it flow better and you're done. Leave the stock jetting alone. I did a little drilling and mostly I bent open the existing holes a little to line up better with the gas flow direction. Lots more power and lots less problems.

We used our PW50 often in damp conditions, so the advice I gave you about the choke cable removal and sealing the throttle cable, is all aimed at dealing with moisture, with zero problems, for years. You simply screw a short bolt into the carb where the choke went in there, to stop anything entering there, then remove the whole cable. The sponge would be kept tucked in behind the front number plate, then to cold start the bike I would hold it over the airbox intake to literally choke it, and it'd start easier than with the carb choke.

After a ride day I would pressure wash the PW50, spray the metal parts it with oil, and put it away for the next ride. Done. About 3 monthly, I would change the gear oil and air filter (ours was rarely used in dusty conditions). About yearly I would pull off the seat, clean and check things, install a new plug, and also repack the steering bearings. My boy (last to use it) would try jump it a lot so I ended up needing new stem bearings and forks. The bearings were cheap and aftermarket forks about $90 for a set. The motor and clutch just kept on going. I always used decent 2-stoke oil in the oil tank, and I never changed the oil pump ratio.

If you ride on soft ground or grass, then ditch the stock hard pack tires, and put some more agressive knobbies on there and the kid's confidence level goes through the roof. I put some D756s on ours years ago and never regretted it. When you're kid gets faster, remove the rev limiter box (it just unplugs), and away he goes.

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You simply screw a short bolt into the carb where the choke went in there, to stop anything entering there, then remove the whole cable. The sponge would be kept tucked in behind the front number plate, then to cold start the bike I would hold it over the airbox intake to literally choke it, and it'd start easier than with the carb choke.

Did you just use one of those white plastic (think they are nylon???) bolts 2 screw in the choke hole on the carb? Seems pretty simple & just one less thing than could go wrong.

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Did you just use one of those white plastic (think they are nylon???) bolts 2 screw in the choke hole on the carb? Seems pretty simple & just one less thing than could go wrong.

Yeah, I did use a white plastic bolt. Just because I had one and it seemed to seal real well. Funny you asked. :)

The whole need is mainly because we typically get a lot of summer rain here, so I like to pressure wash our bikes, and although I'm reasonably careful about the process, I found the PW50 choke cable could take water too easily and I was amazed how much crud ended up in the carb's choke circuit. Maybe some dirt got down into the bowl too, but my memory aint totally clear. I'm into preventative maint, and I loved that little PW50. I sold it to a friend and his little man loves it and rips on it. So good to see.

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Yeah, I did use a white plastic bolt. Just because I had one and it seemed to seal real well. Funny you asked. :)

The whole need is mainly because we typically get a lot of summer rain here, so I like to pressure wash our bikes, and although I'm reasonably careful about the process, I found the PW50 choke cable could take water too easily and I was amazed how much crud ended up in the carb's choke circuit. Maybe some dirt got down into the bowl too, but my memory aint totally clear. I'm into preventative maint, and I loved that little PW50. I sold it to a friend and his little man loves it and rips on it. So good to see.

Well I figured the nylon bolt would seal better than a metal bolt. Guess you could use a metal 1 as well & use some gasket sealer just incase. We get a lot of spring rains here as well. That's why it has been sitting cause it's been raining so much & when it's not raining he has "make up" games for baseball. He is 5 & LOVES it. He is still learning on it so far so I have the throttle limiter screw in it still. I started it yesterday evening after getting home from work & it was running fine w/ the choke off BUT when I would switch it to "run" & give it gas on the stand & I would let off the throttle it seemed like the throttle was sticking a lil bit cause it would above idle & keep wanting to "go". If that makes sense. Not much but enough for me to notice & also enough that I wouldn't put him on it incase he couldn't get it 2 stop so I am gonna pull the throttle slide out & sand it w/ SUPER FINE sandpaper & see if that helps.

Edited by stevekx500

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Not good. I've seen kids at our mini track get quite distressed with sticky throttles on PW50s. On older bikes it's usually rust or crud in the junction where the cable goes to the oil pump. On new bikes I guess it has to be a kink in the cable, or friction somewhere in the cable or throttle grip or carb slide. Or maybe your PW50 needs a little more slack adjusted into the inner throttle cable. Just so the slide can close that last little bit. Or else maybe the air screw is out a bit too far. Your clutch would be so new and thick that I guess it engages super low in the RPM range, making the problem seem worse. I've no idea if this stuff is the responsibility of the Yam factory or the dealer doing the delivery. Probably the dealer.

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I just purchased  '17 PW50 for my son the other day.  Same issue with not wanting to get off the line under its own power.  I removed the restrictor washer with no luck. Taking out the throttle limiter screw worked but the bike still barely moves with no rider. As the original poster described, it goes fine once moving.   Will be looking at the spark plug to determine jetting but not sure what else to do if that does not work.  Hope this works or there is an easy fix since the  dealer is almost 3 hrs away! 

Thanks for all the info here even if it was a couple years old :-)

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8 minutes ago, jakeroo7 said:

I just purchased  '17 PW50 for my son the other day.  Same issue with not wanting to get off the line under its own power.  I removed the restrictor washer with no luck. Taking out the throttle limiter screw worked but the bike still barely moves with no rider. As the original poster described, it goes fine once moving.   Will be looking at the spark plug to determine jetting but not sure what else to do if that does not work.  Hope this works or there is an easy fix since the  dealer is almost 3 hrs away! 

Thanks for all the info here even if it was a couple years old :-)

Pull the jets out of the carb and soak them in carb cleaner.  Your pilot jet may be clogged.

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Is this a bike with some hours of easy riding?

 

The pipe and silencer gets plugged up.

 

Try burning out and cleaning it

 

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