1950s Big Twin

1stgenbird

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Aug 5, 2009
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397
I am going to check out a motor tomorrow and I'm told the numbers are 25920-19443. What year is this motor and is it electric start?
Thanks
 

1946Zephyr

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Oct 21, 2008
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Re: 1950s Big Twin

25920 would make it a 1955 Big Twin 25hp. Whether it has electric start or not, will depend on whether it's there, or someone has removed it. I believe this model number makes it a "Big Twin Electric" and those do come with electric start. Nice old motors. Take a compression test and make sure the numbers are as close to the same as possible. Anything over 100psi is favorable
 

1stgenbird

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Re: 1950s Big Twin

Thank you. My next question was going to be about what the compression should be but you answered it.

It's got a funky silver and blue paint job and hardware store numbers on the side but I can deal with that if it's otherwise in decent condition.
 

Bigkat650

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Re: 1950s Big Twin

Thank you. My next question was going to be about what the compression should be but you answered it.

It's got a funky silver and blue paint job and hardware store numbers on the side but I can deal with that if it's otherwise in decent condition.

100+ psi is certainly ideal, but I wouldn't be too scared if your compression is a little under 100psi in each cylinder, as long as they are withing 10% of each other--if the deal is right. I bought a 35hp big twin with 85 & 90psi... now that it's ran for a bit, the seals have expanded a bit and my psi is over 100 in each cylinder. I've heard people buying them with psi's as low as 65 (not recommended) and still being able to get them to run with minimal effort. But yes, higher psi is better.

With that being said, Zephyr is a much better authority on the subject then I am, he knows his classic OMC's better then just about anyone. I'm just saying if its a smoking deal, but psi is just a touch under 100--it doesn't have to be a deal breaker :)
 

1stgenbird

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Re: 1950s Big Twin

By the time I heard back from the seller about a time we could meet so I could buy it, someone else bought it.
 

1946Zephyr

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Re: 1950s Big Twin

Awwww damn it. Sorry guy. Keep and eye open. Another one will show up. I see them from time to time.

Thanks Bigkat. Yea, I love these oldies. All my collection consists of these old twin OMC's.
 

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