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The Shop
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?
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.
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.
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.
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 ???
Any insight ?
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.
Pit Row
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