Muncie/Neptune Master Twin Hard Starting

[wbeaton]

I’m having some trouble starting a Muncie/Neptune Master Twin 16 hp. It has a Tillotson MS47D carburetor. Would anyone have information on the correct initial carb settings? It has good spark and is getting fuel. I’m having trouble finding the right combination of settings to get it to start.

Wayne
Upper Canada Chapter

uccaomci.com

[The Boat House]

This Neptune is a bear to get started.
Shut it off and try to restart it.
You may get it going – you may not.
I had 2 complete magnetos but
one wasn’t any better than the other.
Never went out with it with out my
backup. Steve Wood has one and he
says his starts fine.
It looks cool though.

https://www.youtube.com/watch?v=-_rZ4zjYgn4

[wbeaton]

Well, that’s not encouraging. The best I’ve managed is some backfiring, which gets pretty exciting when you are directly attached to the flywheel with a rope.

On the plus side, I think I solved the mystery of what year the motor was manufactured. It appears that the MS47D was only used on the Master Twin in 1941. That would make this one of the last Master Twins produced, which may explain why there is no serial or model number stamped on the rope sheave.

Wayne
Upper Canada Chapter

uccaomci.com

[lyks2tinkr]

I also have a 1936 master twin, a nice original but it has also been a bear to find the right settings to get it started.
Is yours an opposed twin or an alternative firing?

I have been told they are strong runners.

[pm-t2]

in my limited experience with them, the Neptune singles and opposed twins were usually more reliable starters than the alternate-firing jobbies.

I’ve had a few of the Neptune/Muncie twins and they were all good for starting on the second pull. There was one that wasn’t, but it turned out to have the pistons in backwards.

With any Tillotson, normal range to start with on needle jet settings was usually 1 to 1 1/4 turns out from closed on high speed, maybe one turn on the low speed.

FWIW I usually try and fire motors on Gibbs penetrating oil fed through the crankcase prior to feeding them any gas. If they fire on the Gibbs, they’ll run on gas. If I can’t get anything out of them on the Gibbs, chances are it will be equally frustrating (or even more so) to get them to start on gas/oil mix.

Where is your timing advance set? I recall starting them with the handle more or less centred over the carburetor.

Backfire – sounds like combination of crankcase flooding (or excessively rich mixture) and incorrect timing of spark. Flywheel in correct orientation? Last incident that I recall of back-firing only led to discovery of sheared flywheel key.

Hope it helps.

Best,
PM T2

[wbeaton]

Thanks for all the responses. This one is an opposed twin. It looks the same as the late 30’s Master Twins. I had the advance set at about 5 o’clock when I had the backfiring. After I moved it to the 6 o’clock position the backfiring stopped and the flooding began. The throttle is set about halfway. Obviously, I’ve tried different choke settings. I regrouped this morning and managed to get the motor to fire on Seafoam (Gibbs isn’t available here) on the third or fourth pull. It ran for about 20 seconds and sounded pretty good. It died the moment I touched the throttle. I made a few more attempts to get it restarted on gas to no avail. I’m going away this weekend. I’ll try it again one night this week. I’d like to have it running for the Bellwood Lake Wet Meet on May 7.

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Attachments:

Wayne
Upper Canada Chapter

uccaomci.com

[Tom]

One thing to try, particularly with those Tillotson carbs is this: Turn off fuel, and rope the motor over with plugs removed and spark plug wires grounded. Do this until you are sure there is no fuel left in the motor. Reassemble plugs and wires. Set idle screw to one turn open main needle to 1 1/2. Open the gas petcock until the carb is full. You can tell this by looking at the float pin sticking up out of the back of the bowl area. When the pin starts to drop, shut off the gascock. Then try to start the motor. If it takes a while, occasionally open and close the fuel valve to keep fuel in the carb, but don’t leave it open when you see the float pin start to drop.

If this works, consider adjusting the float level so there isn’t so much fuel in the bowl when the float valve closes.

Tom

[david-bartlett]

I had one of those Master Twin’s once. I left it at my dad’s camp too long and he gave it to someone along with a Martin 60. That thing was heavy.

[lyks2tinkr]

Wbeaton: my master twin looks the same as yours. They are nice looking motors but as mentioned they are "gravitationally enhanced"

I have the same hard starting issues but I will try the things mentioned here to get it running. I’ve had this motor for a few years without a successful boat run.

[RICHARD A. WHITE]

Somewhere on one of my old phones we have video of that one running….. be darned if I can find it… I can check the setting of my 1938, which should be close…

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[Author]

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