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skinny_9 View Drop Down
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    Posted: January/26/2006 at 3:04am
i have a old 70's? yahmaha trial 175 bike that i've had for years but have not rode it lately. in the end when it was still running we kept having to run hotter plugs to keep it going, and i think when i finally threw it in the barn because it would not start anymore or would run very little.

it is such an old bike i don't want to take it to a mechanic to get overcharged, and passed down to me don't want to junk.
does anyone know what to look for or maybe the problem could be, good with hands if knowing what to do.
i was thinking maybe electrical problem
suggestions appreciated thank you skinny_9
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donp View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote donp Quote  Post ReplyReply Direct Link To This Post Posted: January/26/2006 at 3:56am
first test compression. you must have 120 lbs or higher to run correctly if its a 2 stroke, 75 lbs or higher if its a 4 stroke. get a brand new spark plug of the correct type. then clean and regap your points (.014"-.016"). clean the entire fuel system from the gas cap vent on down thru the carb. make sure the air box and filter are clean and installed. make sure the exhaust system is clean and free flowing.
if it is a 4 stroke ohv, the timing chain and sprockets may be worn. to check the valve timing, they must both be closed and seated on the compression stroke, and will "dance" when piston comes to tdc on the opposite stroke. if you can roll the flywheel back and forth with out the cam moving, in other words there is slack in the chain, then the timing chain is worn as well as the sprockets.
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skinny_9 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote skinny_9 Quote  Post ReplyReply Direct Link To This Post Posted: January/26/2006 at 7:41am
thanks for the reply i will check those things but it is a 2 stroke that is oil injected no mixing.

i know the bike is old just want to get it going again just got the kid a kdx50 need something to tool around
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Post Options Post Options   Thanks (0) Thanks(0)   Quote donp Quote  Post ReplyReply Direct Link To This Post Posted: January/26/2006 at 7:56am
i'd premix a little oil, maybe 1-2%. oil injectors are not always fool proof and prone to failure. and you dont know that it has failed until the top end is shot. could explain your hard starting issue.
do a compression test, and if its low pull the exhaust header off, slowly roll the engine over by hand, and look closely at the piston sidewall. if you see scrape marks on the piston sidewall, its a good indicator of a failed or failing oil injector system.
plus with the header off, you will see if the exhaust port is plugged up with carbon or not. real common on a 2 stroke and can lead to the problems you have.
if you dont see scrapes, but compression is lower than 120 lbs, then you may just need to find new rings.
a bike that old is hard to find parts for, but they are out there.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote skinny_9 Quote  Post ReplyReply Direct Link To This Post Posted: January/30/2006 at 2:40am
donp
ok i worked on it all day yester. after a while i got it to start a few times for a moment, and also probably a minute or two once, but it only does it maybe 1 of 10-12 kicks, cannot get it to stay running to adjust carb.
When i had finally got it to start i had to screw in the idle screw all the way or close to it, other screw is either 1 1/4 out or real close whether it runs long enough.

cleaned carb,fuel lines, tank, air filter tube all hoses. going to get new plug today, couldn't find one yesterday.
only getting about 100 - 110# pressure piston seems to be scratched slightly but cyl. wall smooth as ice, family might have put new rings in years ago dad;s not sure if was this bike.
when you take spark plug out and kick it over gets good spark but i noticed that after maybe 3-4 kicks there is a slight pause with no spark not sure if that's normal.
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