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pw50 compression

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Hi guys. My brother gave me a PW50 that he had in his garage for awhile never running. It needs alot TLC and will most likely have more questions in the future as I bring this bike back to life . At first it did not have any spark but someone had plugged the wrong wires into the connectors. So I fixed that and now I spark, but would not fire. Tried some satrting fluid but still no luck. I tested the compresson and it is reading 90 psi which seems very low (I do not have manual). I poured some oil in the cylinder to see if the compression raises. After that my compression was reading 160psi. I tried to start it after that and the bike did fire and run off the satrting fluid I had in the cylinder. After that, when the oil was all burned off, it would not fire again. I would assume, at a minimum, it will need new rings, but what should good compression be on a fresh engine? All my compression readingwere with the throttle wide open. Sorry for the long post.

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Have you cleaned the carb? Before you go messing with anything else, I'd give the carb a good cleaning. While you have the carb off, check the reeds under the intake. I can't say what the compression should be, but it's possible to have decent compression on a compression gauge and still not fire even on ether if the reeds are in bad shape. Had that happen to me in the past.

Also, try starting it in the RUN position instead of START, be careful though, it'll take off on you if you give it gas when you start it in RUN instead of START.

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I am just trying to figure out if i should put any money into the bike. The bike has been taken apart and left apart for atleast 5yrs. The carb is missing the needle and it needs new throttle cable. Just looking to see if it is going to be worth my time/money to repair. Mostly little odds and ends but would like to know what teh compression should be so that I can start putting together costs to see if it is worth it

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Well, used PW50s typically go for at least $500 even in bad shape, where a used PW80 might fetch $400 in pretty decent shape.

Other people have said their PW80 makes 80 PSI on a new top end and there have been reports they've run on as little as 10 PSI. PWs are typically low compression bikes.

I'd buy a whole carb off ebay, clean it and install it. Depending on which odds and ends you need, the PW80 stash I have may include them, or may not. Feel free to PM me a list.

Definitely check that your reeds are sealing though, that was a frustrating experience for me as everything checked out, compression, spark, fuel.. fixed the reeds (turned them upside down for the short term) RAN!

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i would pull the top end and do a piston and rings at a minimum. hone the cylinder if its not too bad. check all clearances and put back to gether.

you can find lots of parts on ebay for cheap. you are not looking at more than a $100 to get it running.

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Thanks for the offer on parts. I do not know when i will get a chance to work on the bike as I have been working some crazy hours lately and been workingh out of state also. I will PM you about parts when I figure out what the bike still needs but it probably will not be anytime in the near future. On another note, the bike does not roll very easily. There seems to be quite abit of drag in teh rear end? I have not had a chance to check it out, but any ideas?

Well, used PW50s typically go for at least $500 even in bad shape, where a used PW80 might fetch $400 in pretty decent shape.

Other people have said their PW80 makes 80 PSI on a new top end and there have been reports they've run on as little as 10 PSI. PWs are typically low compression bikes.

I'd buy a whole carb off ebay, clean it and install it. Depending on which odds and ends you need, the PW80 stash I have may include them, or may not. Feel free to PM me a list.

Definitely check that your reeds are sealing though, that was a frustrating experience for me as everything checked out, compression, spark, fuel.. fixed the reeds (turned them upside down for the short term) RAN!

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The PW50 is always "in gear", so there will be some drag as the rear wheel turns all the transmission gears and part of the clutch. There may be some drag in the clutch as well since it hasn't been run in a while and the PW50 (not the 80) use a dry drum-type centrifugal clutch it may have a little bit of rust on the inside. Nothing to worry about and will clean itself once you have it running.

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Finally had some spare time to look into this bike further. The cylinder is scored pretty badly (my guess was oil injection stopped working). Not worth my time and money to fix it. Will most likely throw it on craigslist for parts. Thanks for all that responded

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