125 Running Issue

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125 Running Issue

Postby dfmonroe » Mon Aug 23, 2021 11:06 am

My 1952 125 starts on first or second kick but will not continue to run it is unresponsive to the throttle. I am sure it is getting gas nd it appears to be back-firing, if that is possible with a 2 stroke. I am assuming the timing needs to be set, does anyone have a method that does not involve removing the engine and setting the timing on the bench? Are there any other possibilities for these symptoms other that mistimed?
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Re: 125 Running Issue

Postby hennesse » Tue Aug 24, 2021 10:07 am

Tell us a little about your bike. Did you recently get it and this is first time you have tried to start it? Have you owned it for years and suddenly this summer it won't run? Have you disassembled the engine or any parts of it? After it starts, how long does it run?

Factory timing marks on circuit breaker plate and crankcase aligned or very close? I've never had to set the timing on one of these bikes - except after an engine rebuild. Once set, the timing stays put for decades. Points in good shape and set to .020? Points need to be checked and set fairly regularly. Have you replaced the condenser?

Gas/oil mix 25:1 and recently purchased/mixed? Disconnect the gas line and let it run until it fills a small jar. Sometimes the filter on the petcock gets dirty and only lets a trickle through - after awhile it's enough to start the bike, but not continue running. Blow through the vent hole in the gas cap - is it clogged?
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Re: 125 Running Issue

Postby dfmonroe » Tue Aug 24, 2021 10:52 am

Bike is new to me, did not run when purchased in several baskets. Put new rings, points, condenser, coil, spark plug, rebuilt carb, new brushes on generator, new clutch plates. Points gapped @ .020 plug gapped at .025.
Motor starts on first or second kick, will run for maybe 30 seconds. Carb is getting gas but engine does not respond to the throttle ( it does not increase in RPMs as the throttle opens ) the throttle is functioning properly. If it is possible for a 2 cycle motor to backfire, this one sounds like it backfires.
At times it runs long enough to drive a couple of blocks, but has no power or throttle response. New gas and proper oil mixture. Have let gas cap off suspecting venting issue with no change. I can't readily identify the timing marks on the breaker plate or crank, will check that out.
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Re: 125 Running Issue

Postby Mutt » Tue Aug 24, 2021 11:01 am

did ya change the crank seals? If ya didnt, ya might do a leak down test and see which seal is leaking. Usually the left seal
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Re: 125 Running Issue

Postby hennesse » Wed Aug 25, 2021 5:05 pm

Mutt,

Who sells the seals?

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Re: 125 Running Issue

Postby Mutt » Wed Aug 25, 2021 5:32 pm

I sell new seals. Email me pigstye13@aol.com
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