Started 40+ project backwards

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Mhops
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Joined: Tue Jul 12, 2022 11:58 pm
Location: Atlantic coast

Started 40+ project backwards

Post by Mhops »

Oof, new user
Typical dilemmas
Kindness appreciated, thanks

Off to a slow start on a 40+ reclamation that’s now seemingly gone into reverse. Bought some spares, plus a few we might need. While waiting patiently for post, sanded and cleaned tank, cleaned carb and though it spun freely, found dome nut appeared seized. Patient application of WD as well as PB Blaster.. still no nut removal.. Hmm. Parts arrived in post, tried new cord, spinning as expected, plus new plug but no start. Hmm, more penetrating oil and time, still no go. Patience ensued, more oil, tapped on a tightly fitting spanner against my hand held grip.

Finally! But with success, potential defeat rose her head: top half of shaft is missing teeth. A pal who’s worked on these before said it looked like somebody mangled trying to push start it and laughed when I asked if that wasn’t just for cars. Not funny I know. Looks like some nut was poxied on, yep, bargain no bargain. So:

Has anyone ever used a split pin to connect a dome nut on?

Or, do we need a new crankshaft?

If we do need one, what other parts should we replace while in there? Besides needing info on how to decode the timing angle and piston position… um is there a written or video primer for this experience?

What goes in the case itself? Miller Green gear oil work?

Many thanks
Journeyman
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Re: Started 40+ project backwards

Post by Journeyman »

Looks like you have a few problems, the crank shaft thread is 7/16 x 18 BSF if you can find the correct Die try restoring the thread. And then use a new flywheel nut.
Timing is set and there is no provision for altering it. A screw on the underside of the magneto plate locates in a dimple on the crankcase.

Oil for the gearbox is a strait SAE140 You will usually find it at agricultural dealers. Don’t know what Miller Green gear oil is but if it’s a 140 it will be suitable.
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Charles uk
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Re: Started 40+ project backwards

Post by Charles uk »

Can you post a picture of your crankshaft problem.
Make it idiot proof and someone will make a better idiot.
Mhops
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Joined: Tue Jul 12, 2022 11:58 pm
Location: Atlantic coast

Re: Started 40+ project backw

Post by Mhops »

Thanking you Journeyman and Charles UK.

Wonderful information re retapping the shaft, Thank You !! but it appears there’s no thread left under the poxy. What a dirty trick.

As to a photo, imagine drawing a tight black spiral line around a smooth metal rod by rotating it. That black line was formed by the grease remaining in the bottom of the pitch of the thread.. No v shaped mountains remain, the locations of former valleys only marked by the oily creeks left behind.

Recutting the thread with a die smaller than the factory specs die and replacing it with an appropriately sized dome nut and washer is an alternative I hadn’t considered, thanks for allowing me to be led that way.. Unfortunately the beef that’s left to cut into now is the diameter of the shaft at the bottom of the original thread. This means the final outcome would be shrinky dinked down a size.. Hmm, less nut diameter, less cover and wheel retaining capabilities.. Ok, I’m ordering a new crankshaft. It’s the time more than anything else, what with shipping to our hinterlands.

I am concerned about being able to properly document the orientation on the wheel and the piston position when I < attempt > to reinstall it all. I’ll
Do my best to document it and will send up a flare if I become lost. Hoping others are as kind to you as you’ve been to me.
Mhops
Posts: 11
Joined: Tue Jul 12, 2022 11:58 pm
Location: Atlantic coast

Re: Started 40+ project backwards

Post by Mhops »

PS

Miller’s is worth looking into.. they turned up when I was looking for clean alternatives.. while reviewing the other green engine oils you see on AmazOn

Of their product they offer:
“ Miller’s Vintage Green Gear Oil GL140 is a non-extreme pressure mineral based gear oil. These products are specifically formulated for vintage transmission systems. They contain inhibitors to prevent the formation of rust, to promote good oxidation resistance and encourage long life. “

Look up Millers Oils dot co dot uk to order direct. I don’t work for them or own any stock in the co.

: )
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Charles uk
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Re: Started 40+ project backwards

Post by Charles uk »

Seagull gear oil is SAE 140 that has the ability to form a fairly stable emulsion with any water that might leak into the gearbox & still retains most of it's lubricative properties in this mix.
Oils that do not emulsify tend to separate over time leaving the bottom half of the crown wheel basking in salt water!

John Williams is probably the cheapest source for a 40's crankshaft.

It's difficult to mess up the timing on a seagull the flywheel is keyed onto the crankshaft & the baseplate located by a screw going into a dimple, almost idiot proof!
Make it idiot proof and someone will make a better idiot.
Journeyman
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Re: Started 40+ project backwards

Post by Journeyman »

Just some information in case you decide to cut a new thread.
The core diameter of 7/16" BSF is 0.3663" and the outer diameter of 3/8" BSF is 0.3750 only 0.0087 dif which is well in tolerance. It would be very easy to get some Hex Bar the same size as the original Nut and drill and tap that for 3/8" and you would have a domed nut that looked original.
PS the Millers oil will be good.

Cheers, Dave.
Mhops
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Joined: Tue Jul 12, 2022 11:58 pm
Location: Atlantic coast

Re: Started 40+ project backwards

Post by Mhops »

AHHH Thanking you Dave!

This is the best and proper use of the forum… writing for those future users with similar questions… Bless you!
Mhops
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Joined: Tue Jul 12, 2022 11:58 pm
Location: Atlantic coast

Re: Started 40+ project backwards

Post by Mhops »

Thanking you too Charles, I’ve learned so much from your many posts, hoping others treat you as kindly!
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Charles uk
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Re: Started 40+ project backwards

Post by Charles uk »

Dave, Seagull crankshafts were made from forged EN 40 B steel which was nitride hardened before being finish ground, the thread & the keyway were machined before the nitride hardening.

7/16 BSF is a 18 TPI thread & 3/8 BSF is a 20 TPI thread, cutting a new 3/8 BSF might well be a difficult task in surface hardened steel, for an American who might not have access to a machine shop & easy access to BSF taps & dies & prove more expensive than buying a used 40 crankshaft & nut.
Make it idiot proof and someone will make a better idiot.
Journeyman
Posts: 137
Joined: Thu Aug 16, 2018 6:26 pm
Location: Pembrokeshire

Re: Started 40+ project backwards

Post by Journeyman »

Hi Charles,
As you surmise I have a full boat building workshop and everything you would expect to find after 60 odd years of work. My attitude if it’s broke fix it, the last thing we need is more gash to throw away. I would think the cranks where made in Villiers Street then taken somewhere for the cyanideing. It will be just case hardened to no great depth.

Cheers for now, Dave.
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