Yamaha PW50 Issues | GTAMotorcycle.com

Yamaha PW50 Issues

oioioi

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Hey guys,
I picked up a 2001 PW50 in great condition for a good price.
According to the PO, it was working fine but once it died (this past Saturday) it now has not spark.

I have not had a chance to troubleshoot anything as I just picked it up today.

However,
Any chance anyone has any spare parts for this beast. Specifically ignition coil or stator or CDI box.

I am more less looking to borrow for testing purposes to figure what the problem with mine would be or possibly work out a deal.

I Am willing to travel within reason.
 
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Wiring diagram shows it has a diode located above the cylinder head.
Diodes have a relatively high failure rate and can be meter tested super easy, might be a good place to start.

2001_pw50_wiring.gif
 
Thank you for the input so far.
I'll try to get on it this weekend.
Good thing is that my neighbor 3 houses down has one as well so I can maybe borrow parts off of his.

BTW.
Wish me luck. The last one I tried to buy I asked for permission before the purchase. This time I am trying the approach of asking for forgiveness after the purchase. ;)
(Wife thinks the 24V electric dirt bike is enough for my son)
 
I was able to get on this little project today.

I started off by checking some grounding and the kill/start switch. All good.
While I was trying to unplug the cables to connect new CDI box I either disconnected another able or it was already disconnected and I just helped it come apart.
I reconnected it, check the spark plug and I HAVE a spark.
I was able to start the engine.

HOWEVER,
It is not running perfectly well. It boggs down a little and it takes a little longer than it should to really wind up.

I asked my neighbor who has one of these bikes and is very familiar with motorcycles/engines to help me look at it. He actually brought his PW50 over. His bike is running perfectly.

Mine does have an aftermarket air filter (which I will be replacing). If we take the air filter off completely it runs perfect. Winds up completely and sounds healthy.
We tried his air filter and sound a little better than mine but still boggy at times.
We took off the carb (which also seems to be aftermarket) and cleaned it out completely. Reassembled and same problem.
We even took off his carb from him bike and his air filter and same issue. It is boggy a little.
We checked the choke, although a little sticky, its not really the cause of this.

I also tried a new CDI box and no real difference in the way it is running.

He is more stumped than I am about this.
I do have new fuel in it and a brand new spark plug.

Any other suggestions from you guys?
I have new fuel in i
 
That's a helpful neighbour to have. My first thought was your carb is not jetted properly but his didnt work great either. Any leaks in intake path where it could be sucking air?

I am assuming test was in neutral? Any chance your clutch adjustment may be off and your bike is fighting the clutch as it tries to rev up?
 
Good neighbor indeed. He said he use to visit this forum back in his racing days.

I will check your suggestions, hopefully today

Another fellow in the FB PW50 group suggested checking for compression. I will stop at PA and grab a compression tester.
 
You even switched out the entire carburetor and the problem persists?
Then yes to compression test, your motor must be lacking intake vacuum.
Does it have reed valves? Check your reed valve.
 
Yes. Switched the entire carb.
His bike runs like a professional dirt bike .

Luckily a piston kit is only $20.
 
Is it smoking a lot (sucking gearbox oil), or perhaps sucking air from behind the crank seal on the magneto side ?
If you have a way to pressurize the crankcase you can tell pretty quickly if there is a bottom end issue.
 
lol wait until you see how much they want for Boyesen reeds for that bike.
 
Is it smoking a lot (sucking gearbox oil), or perhaps sucking air from behind the crank seal on the magneto side ?
If you have a way to pressurize the crankcase you can tell pretty quickly if there is a bottom end issue.
I wouldn't say it's smoking anymore than it should/normal.

lol wait until you see how much they want for Boyesen reeds for that bike.


Just took a look. Not impressed.
 
I wouldn't say it's smoking anymore than it should/normal.
...
Just took a look. Not impressed.
You can buy a whole OEM assembly for less then 20 bucks or just 2 pieces of special plastic for more then 54 bucks plus. :unsure:

Pull the reed cage and hold it up to sun, if you can see any gaps where the reeds should close you found a problem. The steel finger plates that limit the reed valve travel can usually be bent back a little more to increase flow and that is a common modification when you fit fibre reeds in place of the steel ones. If the neighbour has already done that modification your scoot will never perform as well.
 
Checked the compression
Getting between 110 and 120 psi.
From my research that should be a good amount.
 

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As open as she will get.
 
So back at it,
Compression is good.
I was advised to check the exhaust as it might be plugged. I look into it and it looks good. However I tried the entire exhaust with silencer from the neighbours bike. During this I found that mine is missing a copper seal/gasket at the connection of the cylinder head. This would explain the oily/gunky buildup on the outside of the head/engine casing.
Once I installed his exhaust (with the gasket) bike ran, but it was smoking badly with blue smoke.

It is burning oil.
I'm thinking that the crankshaft seal is either bad or the oil pump is not mixing the correct amount of oil.
 
I assume you’re letting the bike fully warm up.

You could pull the oil line off the carb, block off the opening and run premix in the tank. If the symptoms don’t change, suspect the crank seal. The oil line will still spit oil so make sure to have a container on hand.

Btw, is the oil pump set to spec?

Is the crankcase oil level correct?


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Crank seals are cheap and easy to do on little 2smokes, I’d change them.
 

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