PW50 No Power :(

[Eric B]

My son's PW50 acts like it has no power when the bike is under a load. If
he is sitting on it going down hill the bike works fine. If he is going
on
a flat or uphill, the motor does not rev-up. If I run the bike on a stand
with the rear wheel off the ground the bike seams to run fine (no load).
Throttle response is fine etc when not under a load. I have cleaned the
air cleaner, the silencer and replaced the spark plug.
Thanks for your help and wisdom!
Brad

You take the spacer out of the exhaust?

Eric

[Tiago Rocha]

seems that you need a top end job!
check the compression!

[James]

You didn't say so, but I'll assume this is a problem that didn't used
to be there.

First, look for water/moisture because this is exactly how these
little bike act when they get wet. While it sounds like it should have
had time to dry out, check anyway because this is free. Take off the
ignition cover, pull any connectors apart and blow them out gently
with compressed air, etc. Let it sit there opened up for a few
minutes, hook it back up and then try it.

Second, if that doesn't work, pull the connector that hooks to the
Start/Run/Stop switch and see if the problem goes away. The bike will
start without it. If it runs OK, you need a new switch (or just keep
it unhooked).

Third, if that doesn't work, take off the carb and clean it. These
little carbs get clogged easily, but I doubt that's your problem.

Fourth, if that doesn't work, change the rings because it's a cheap
and easy job.

Fifth, if that doesn't work, look at the clutch. If I remember right,
it's kind of a bitch to get to because I think you have to drop the
engine partially out of the frame, but it might need new
pads/springs/something.

James
00CR250

My son's PW50 acts like it has no power when the bike is under a load. If
he is sitting on it going down hill the bike works fine. If he is going on
a flat or uphill, the motor does not rev-up. If I run the bike on a stand
with the rear wheel off the ground the bike seams to run fine (no load).
Throttle response is fine etc when not under a load. I have cleaned the air
cleaner, the silencer and replaced the spark plug.
Thanks for your help and wisdom!
Brad

[Jim Hall]

My son's PW50 acts like it has no power when the bike is under a load. If
he is sitting on it going down hill the bike works fine. If he is going on
a flat or uphill, the motor does not rev-up. If I run the bike on a stand
with the rear wheel off the ground the bike seams to run fine (no load).
Throttle response is fine etc when not under a load. I have cleaned the air
cleaner, the silencer and replaced the spark plug.
Thanks for your help and wisdom!

I had an intermittent power problem that took me a day to find on my
son's old PW. Turned out that there was water in the carb float bowl.

Your issue may be more low-compression related.

Jim Hall
520 EXC and others
turning Money into Noise...

[Jay C]

My son's PW50 acts like it has no power when the bike is under a load. If
he is sitting on it going down hill the bike works fine. If he is going

on

a flat or uphill, the motor does not rev-up. If I run the bike on a stand
with the rear wheel off the ground the bike seams to run fine (no load).
Throttle response is fine etc when not under a load. I have cleaned the

air

cleaner, the silencer and replaced the spark plug.

You need to take the restrictor out of the exhaust.

Jay

[James]

These are centrifugal clutches. What can happen is a spring breaks and
there is less tension holding the pads back. Then they engage the
basket before the bike revs far enough into it's torque curve to pull
a load. It would still free-rev, but it wouldn't pull a kid up a hill
unless given a decent run.

This is why Insane Nazi Dad Assholes adjust there children's Senior 50
clutches to kick in at about 6,500 RPM, so there will be plenty of
instant power to shoot junior over the triple. Not that there's
anything wrong with that.

James
00CR250

Doesnt really
sound like the clutch to me, as you said it wont rev up under power. If it
was the clutch it would rev, but wouldnt go.

[Brad Saunders]

Thanks for all of the advice so far. Here is my report from last night. I
will cover in this note what I have tried so far based on everyone's
suggestions.

Exhaust restrictor - I was sure that it had been removed already (I bought
this bike used). However, just to be sure I removed the pipe and checked.
The restrictor washer has been removed. Although there was a bit a carbon
build up that I removed. After doing so, I tried the bike and this did help
some, but it is not back to where is was.

Electrical connectors - These were all dry near as I could tell.

Stop/Run/Start switch - it was not apparent to me exactly how to remove
this. I was looking around the switch its self. After rereading the post
this morning, James had said a connector, so I guess I should have been
looking under the seat where all the connectors are. James could you
clarify?

Carb - I did drain the float bowl (in case there was water in there).
Otherwise I have not touched the carb yet.

Brakes - The brakes are adjusted correctly.

Clutch - Haven't looked here yet, mainly since it is such a pain and I
didn't have the time.

Compression - The compression is 40lbs. I just bought the compression gauge
yesterday and it is a little bit suspect. I tried it on my lawn mower and
it read 70lbs. I shoot some air from my compressor which had a tank
pressure of 70lbs and it only read 50lbs. I am going to take it back since
it looks like it is 20 or so lbs off. BTW, what should the compression be?
I couldn't find anything in the manuals.

Thanks for all the help so far.

Brad

My son's PW50 acts like it has no power when the bike is under a load. If
he is sitting on it going down hill the bike works fine. If he is going

on

a flat or uphill, the motor does not rev-up. If I run the bike on a stand
with the rear wheel off the ground the bike seams to run fine (no load).
Throttle response is fine etc when not under a load. I have cleaned the

air

cleaner, the silencer and replaced the spark plug.
Thanks for your help and wisdom!
Brad

[Jim Hall]

Post by Brad Saunders
Compression - The compression is 40lbs. I just bought the compression gauge
yesterday and it is a little bit suspect. I tried it on my lawn mower and
it read 70lbs. I shoot some air from my compressor which had a tank
pressure of 70lbs and it only read 50lbs. I am going to take it back since
it looks like it is 20 or so lbs off. BTW, what should the compression be?
I couldn't find anything in the manuals.

Bingo.

Check the compression with the throttle open. I'd hate to guess
exactly what it should be, but likely well over 100. Most bikes are
in the 150 and up range.

Jim Hall
520 EXC and others
turning Money into Noise...

[Brad Saunders]

I didn't do it with the throttle wide open. I will redo it.

Brad

Post by Jim Hall

Post by Brad Saunders
Compression - The compression is 40lbs. I just bought the compression gauge
yesterday and it is a little bit suspect. I tried it on my lawn mower and
it read 70lbs. I shoot some air from my compressor which had a tank
pressure of 70lbs and it only read 50lbs. I am going to take it back since
it looks like it is 20 or so lbs off. BTW, what should the compression be?
I couldn't find anything in the manuals.

Bingo.
Check the compression with the throttle open. I'd hate to guess
exactly what it should be, but likely well over 100. Most bikes are
in the 150 and up range.
Jim Hall
520 EXC and others
turning Money into Noise...

[Ralph Furley]

The top end is a piece of cake on this bike

Post by Brad Saunders
I didn't do it with the throttle wide open. I will redo it.
Brad

Post by Jim Hall

Post by Brad Saunders
Compression - The compression is 40lbs. I just bought the compression

gauge

Post by Jim Hall

Post by Brad Saunders
yesterday and it is a little bit suspect. I tried it on my lawn mower

and

Post by Jim Hall

Post by Brad Saunders
it read 70lbs. I shoot some air from my compressor which had a tank
pressure of 70lbs and it only read 50lbs. I am going to take it back

since

Post by Jim Hall

Post by Brad Saunders
it looks like it is 20 or so lbs off. BTW, what should the compression

be?

Post by Jim Hall

Post by Brad Saunders
I couldn't find anything in the manuals.

Bingo.
Check the compression with the throttle open. I'd hate to guess
exactly what it should be, but likely well over 100. Most bikes are
in the 150 and up range.
Jim Hall
520 EXC and others
turning Money into Noise...

[James]

Post by Brad Saunders
James could you
clarify?

Just follow the wire from the switch until you come to a fat
connector. I think it's down by the steering stem area or under the
gas tank.

For more, go here:

http://www.yamahaoftroy.com

Click on the OEM parts finder icon/button.

Click on the "Dirt Bikes" link for Yamaha.

Select pretty much any year.

Click on the PW50.

Click on "ELECTRICAL_1".

It's #10. I think.

James
00CR250

[Brad Saunders]

I cleaned out the carbon from the exhaust pipe and that has seamed to do the
trick. My son rode the bike this weekend and gave me the big thumbs-up. He
said it is back to where it was.

Thanks for all of the help!

Brad

Post by James

Post by Brad Saunders
James could you
clarify?

Just follow the wire from the switch until you come to a fat
connector. I think it's down by the steering stem area or under the
gas tank.
http://www.yamahaoftroy.com
Click on the OEM parts finder icon/button.
Click on the "Dirt Bikes" link for Yamaha.
Select pretty much any year.
Click on the PW50.
Click on "ELECTRICAL_1".
It's #10. I think.
James
00CR250

[john]

spray in some oven cleaner or barbeque cleaner
in the exhaust pipe. toss it into your propane grill
for 20 minutes on high
then thread an old frayed brake cable into the muffler
attach the cable to a drill & give it a whirl.
sand & repaint the exhaust with that high
temp barbeque paint.


"Brad Saunders" <no

I agree with the top end. I am waiting for the parts to come in. Also, I
don't have a torch, but my buddy does. We are going to get together to
finish cleaning the carbon out. The pipe is so small for such a long
distance and the bike is older,so I am sure that it really needs a good
cleaning.
Brad

Post by Brad Saunders
I cleaned out the carbon from the exhaust pipe and that has seamed to do

the

Post by Brad Saunders
trick. My son rode the bike this weekend and gave me the big thumbs-up.

He

Post by Brad Saunders
said it is back to where it was.
Thanks for all of the help!
Brad

Glad its running better. But with your compression reading, I am sure
you still need a top end. Order a piston kit and throw it in, it
should only take about an hour if youve never done one, and it will
cost around 45-50 bucks. Dont forget the gasket. I would be willing
to bet theres a LOT of power lost as it is.
And Im not sure how you cleaned the exhaust pipe, but I used to do
mine with a oxy/acetlyline torch. You can actually just make a good
hot fire and throw it in there for a while. Then repaint of course.
Rich

[Eric B]

I agree with the top end. I am waiting for the parts to come in. Also, I
don't have a torch, but my buddy does. We are going to get together to
finish cleaning the carbon out. The pipe is so small for such a long
distance and the bike is older,so I am sure that it really needs a good
cleaning.
Brad

Do what I do, wait 'til the wife is out of the house. Preheat your oven to
about 450, soak the pipe in oven cleaner, pop it in the oven for a while.
Then take it outside and pressure wash it, it'll be like a brand new pipe.

Eric

[Young]

Post by Brad Saunders
Exhaust restrictor - I was sure that it had been removed already (I bought
this bike used). However, just to be sure I removed the pipe and checked.
The restrictor washer has been removed. Although there was a bit a carbon
build up that I removed. After doing so, I tried the bike and this did help
some, but it is not back to where is was.

I just bought one of these little bikes for my son and I have been following
this thread to learn how to service this little critter. Where would one
find the restrictor washer and how would you remove it. Thanks for the
information.

Scott

[Wudsracer]

Post by Young

Post by Brad Saunders
Exhaust restrictor - I was sure that it had been removed already (I bought
this bike used). However, just to be sure I removed the pipe and checked.
The restrictor washer has been removed. Although there was a bit a carbon
build up that I removed. After doing so, I tried the bike and this did

help

Post by Brad Saunders
some, but it is not back to where is was.

I just bought one of these little bikes for my son and I have been following
this thread to learn how to service this little critter. Where would one
find the restrictor washer and how would you remove it. Thanks for the
information.
Scott

Remove the exhaust pipe, and you will find the washer just inside the
pipe, where it connects to the cylinder. It pulls out easily.


Wudsracer
'99 Gas Gas EC 274
Team LAGNAF
SMACKOVER Racing
www.smackovermotorsports.com

"We Only Ride on Days That End in Y"

[Young]

thanks

Post by Wudsracer

Post by Young

Post by Brad Saunders
Exhaust restrictor - I was sure that it had been removed already (I bought
this bike used). However, just to be sure I removed the pipe and checked.
The restrictor washer has been removed. Although there was a bit a carbon
build up that I removed. After doing so, I tried the bike and this did

help

Post by Brad Saunders
some, but it is not back to where is was.

I just bought one of these little bikes for my son and I have been following
this thread to learn how to service this little critter. Where would one
find the restrictor washer and how would you remove it. Thanks for the
information.
Scott

Remove the exhaust pipe, and you will find the washer just inside the
pipe, where it connects to the cylinder. It pulls out easily.
Wudsracer
'99 Gas Gas EC 274
Team LAGNAF
SMACKOVER Racing
www.smackovermotorsports.com
"We Only Ride on Days That End in Y"