PW 50 wont start!

racer369
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631
Joined
4/1/2008
Location
MO US
10/31/2018 12:58pm
Didn't read all of this. BUT did you know there is a fuel filter inline inside of fuel petcock? Its on tank side. Remove it and fuel will flow!
11/25/2018 11:57am
I can throw a rock and hit the Howard Franklin bridge.
Nice. Im near brooksville. Im having same issue as 2 stroke did. Got the crank seal on order hoping it fixes it. If not im lost...
Nice. Im near brooksville. Im having same issue as 2 stroke did. Got the crank seal on order hoping it fixes it. If not im lost. You work on these on the side?
I can try to help you if you don't have any luck. I am off work all next week.
So finally had a chance to work on it. I put crank seal in and it runs but wouldnt idle. So i put a new carb on it and it runs and idles but has barely any power.
11/25/2018 12:13pm
So finally had a chance to work on it. I put crank seal in and it runs but wouldnt idle. So i put a new carb...
So finally had a chance to work on it. I put crank seal in and it runs but wouldnt idle. So i put a new carb on it and it runs and idles but has barely any power.
How old is this bike ?

The Shop

RJC3PO
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30
Joined
6/7/2018
Location
Oceanside, CA US
2/4/2019 10:52pm Edited Date/Time 2/5/2019 7:08am
Hugely helpful read. Thank you for all the info. I picked up an 09 and already have a 90s PW. To the older PW we have done the Chinese 60 top end on and a China carb. it worked well until it was run without oil in the resivour. I haven't pulled that one apart yet but we just kicked it through the seizing and ran it for the rest of the weekend. It ran surprisingly well but not like it did before.

I just picked up the 09 and it was not running. I could get it to pop on starting fluid but as soon as the charge was burned it would die. I checked the plug and it was bone dry. I then cleaned the carb by soaking it overnight and blowing out all the passages with compressed air. Reassembled and it was much of the same. I could however to get it to start with one or two kicks with my hand over the air intake to the carb. I could then milk the throttle to keep it running but it doesn't rev up with opening the throttle it kinda bogs with more throttle.

With a compression test and the throttle wide open I can only get a reading of 60psi. Super low, so I pulled the head and can't get a .002 past the rings? The cylinder and the Piston look good from what I could see. Pretty sure they are OEM. I also swapped out the reeds but the originals looked to be in really good condition.

I then pulled the flywheel and stator to take a look at the crank seal. There was a very small amount of oil. It almost looked like assembly lube but the residue was both clear and black, kinda separate. Can you guys opin on whether this is the issue?




dkurtd
Posts
901
Joined
4/15/2018
Location
TN US
2/5/2019 8:37am
Not sure I follow your method of checking piston clearance, so you are trying to stick a feeler gauge past the rings? If you have already removed the head and will need a head gasket why don't you go ahead and pull the cylinder (cost of a base gasket) and check the piston to cylinder clearance either by measuring with micrometers or a feeler gauge on the skirt of the piston to cylinder. With such a small bore I wouldn't want more then .002's clearance.

As for the seal, it very much looks like it is leaking. With only 60lbs of compression the engine doesn't create a vacuum to suck the fuel mixture in.

Replace the seal, buy a head and base gasket and provided the piston/cylinder clearance is good I say buy a set of rings and put it back together. If you wanted to spend a little extra then go ahead and put a piston in it for good measure.
RJC3PO
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30
Joined
6/7/2018
Location
Oceanside, CA US
2/5/2019 9:44am
Thank you for the response. Parts are on order and I'll post the results.
2/5/2019 4:58pm Edited Date/Time 2/5/2019 5:07pm
RJC3PO wrote:
Thank you for the response. Parts are on order and I'll post the results.
Was there any sign of a head or base gasket leak ? Had an old Suzuki LT50 and put a China top end on it. The head they sent was far from square. With six psi of air into the intake with the intake and exhaust port plugged, a hit of soapy water at the head gasket turned into a bubble bath.

I chased my ass for a minute on that one, as it ran good before I pulled it apart. Put the OEM head on it and it fired right off.

Crank seal, ignition swap, a few back fires and 3-5 seconds run time, then quit. Finally stuck a gauge in the hole, low compression. About 60-70 lbs if I recall.

Someone dropped a PW by one day, said it did not run good, but had a new top end. And only three of the four head nuts were on it. Of course, no air filter to finish the job right.

RJC3PO
Posts
30
Joined
6/7/2018
Location
Oceanside, CA US
2/6/2019 12:26pm
Hi Project Racer,

Thank you for the insight. Of the two PWs I am working on, the 2009 still has the stock barrel and piston. I did not see any signs of leaking around the head or base gasket. Once I put the new crank seal in I will follow your advice and use soapy water to detect anything around the head and base of the cylinder upon startup.

I purchased an older PW about four years ago and it had much of the same as you have described. No air filter, cables barely pulled through the sleeves, only ran on choke. We got it into running condition with and it was perfect for our eldest to learn to ride. It has, over the years, been beaten in the desert and at the track by my kids and countless other friend's kids. Many of the kids had peppy ktm's sitting on their stands and preferred the PW. The dollar to smile ratio on these little bikes is unmatched.
7/4/2020 4:16am
Interesting topic , but no clear solution.......
I thought I was the only one with this exact problem as the original topic starter,
It's heart breaking when a 5 year old can't ride his bike and I'm a bloody good mechanic.

same symptoms after rebuild, pre rebuild bike ran and idled good but hard to cold start..

put old head, cylinder , piston back on with a slight improvement..
Cut exhaust and removed packing and inner pipe so the box actually works as a expansion chamber.
Some improvement bike starts easy now
won't idle
Dies like fuel disappears or the devil is in it
Fluctuates when throttle held steady open
Old carby and new carby swapping runs exactly the same
Idle screw fully screwed in

Preasure tested crank seals and it holds 7psi for hours


Then today I find when I unscrew the carby bowl drain I get a constant flow of fuel but with air bubbles... how can air bubbles come out the drain on the bottom of fuel bowl ???
7/4/2020 4:20am
Did 2stroke 153 ever solve the issue ? Or did he burn the pw50 on a bulldozed heap of wood and go buy a new bike ?

Any insight ?
7/4/2020 4:27pm
Last year I bought a '94 PW50 for my 4yo grandson. It was pretty well thrashed and I paid too much given the condition, but who doesn't love a project, right?

New top end, crank seals, QA part carb, air filter, front forks, complete plastic kit and graphics. It has been running pretty good until it decides it won't. I thought we had seized it on a hot day at the pee wee track when it quit running. I assumed the oil pump failed, but the top end looked great and was well lubed.

At the end of the day it was the petcock filter plugged full of crap and there were two sheet metal screws loose in the tank floating around. With good gas flow it's running great.
7/4/2020 5:35pm
Yeah cleaned the petcock filter , thought that was the issue as it was half blocked, put it back on only to find no change.
10/16/2020 2:50pm
Burn my pw wrote:
Did 2stroke 153 ever solve the issue ? Or did he burn the pw50 on a bulldozed heap of wood and go buy a new bike...
Did 2stroke 153 ever solve the issue ? Or did he burn the pw50 on a bulldozed heap of wood and go buy a new bike ?

Any insight ?
I'm dying to know after reading this whole thread - I've got two PW50's I'm about to start overhauling...

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