1975 25hp Troubles

This topic has 9 replies, 5 voices, and was last updated 8 years, 11 months ago by benchrascal.

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May 16, 2015 at 7:56 pm #1506
chris-p
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I had posted about a ’75 25hp Johnson I was working on for a friend that was lean sneezing like crazy.

I had thought I had it licked, but it continued after trying all the usual tricks.

Figured it had to be the upper crank seal, so pulled flywheel today and found this.

Always the motors that you offer to look at for friends that end up getting you in trouble!

I do still think the top crank seal is shot, the mag plate is pretty dirty, the flywheel I can replace, but that crank is missing big chunks! Pretty sure it is scrap.

EDIT: The crank damage is hard to see in the shadows, but look above the Phillips screw holding the coil on.
May 16, 2015 at 10:44 pm #16146
Mumbles
Participant
Ouch!

The guy who worked on your motor might be the same guy who worked on one of mine.
May 16, 2015 at 11:05 pm #16150
fleetwin
Participant
US Member - 2 Years
YIPES! Looks like someone used an air chisel to remove the flywheel. I’m surprised the key wasn’t sheared
May 16, 2015 at 11:18 pm #16156
legendre
Participant
quote fleetwin:

YIPES! Looks like someone used an air chisel to remove the flywheel. I’m surprised the key wasn’t sheared

Yah, well the key went missing one time, you know, and so we had to make one out of a nail.. 🙄

@OP – I also see a lot of oil film on & around the points. That’s no good, in and of itself.. clean that up.
May 17, 2015 at 3:02 am #16176
chris-p
Participant
Yeah, I know. Hence the original reason I pulled the flywheel. To change the upper crank seal. See post #1 😉

Mumbs, did you fill it or use it ?
May 17, 2015 at 7:25 am #16191
Mumbles
Participant
quote Chris_P:

Mumbs, did you fill it or use it ?

That crank came out of a ’55 Big Twin on which the flywheel had been cut off with a torch. I replaced it when I rebuilt the powerhead.
May 17, 2015 at 12:21 pm #16206
chris-p
Participant
Is there a way to fill this gouge? I have never had to before. If it were my motor it would get a rebuild, but its not mine.
May 17, 2015 at 4:08 pm #16223
fleetwin
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US Member - 2 Years
I’m thinking a good used/reasonably priced crank won’t be hard to find.
You post that this is a 1975 25hp, yet the pictures show universal mag ignition, these engines used low tension ignition in 1975. So, be sure to confirm the year of your engine before looking for another crank.
Your flywheel tapers may be damaged/distorted by that lousy crank as well.
May 18, 2015 at 10:33 pm #16382
chris-p
Participant
quote fleetwin:

I’m thinking a good used/reasonably priced crank won’t be hard to find.
You post that this is a 1975 25hp, yet the pictures show universal mag ignition, these engines used low tension ignition in 1975. So, be sure to confirm the year of your engine before looking for another crank.
Your flywheel tapers may be damaged/distorted by that lousy crank as well.

Thanks Don.

Yeah, I believe this is a transported powerhead from an earlier version. I haven’t verified exactly what year yet, have to dig deeper. Someone blew her up in the past and transplanted this on.

Has anyone ever filled a gouge before while on motor, then used compound to lap the tapers?
May 19, 2015 at 5:21 am #16414
benchrascal
Participant
A local machine shop used to use something like a machinable weld and built up old shafts like that but….. that was before machine shops stated charging $120 an hour .Now I would just stick an ad for a pre 1975 powerhead on this site and transplant those pretty coils etc, and away you go .
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