1949 Firestone - Help me get it running!

nbarr7655

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May 23, 2017
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Hello guys! My dad has had an old Firestone boat motor sitting in the shed for years now and I finally grabbed it in hopes of getting it running. The motor DOES have compression so we are off on the right foot. I took the carb off and it looked pretty clean. Gas is moving through the line as well (although it's bad looking gas and I need to change it).

Right now when I try to start it I don't even get a choking start. The prop spins like normal, I can hear the piston moving but that's about it. I haven't checked for spark yet but could it be that? Should I just buy a new plug anyway? Is there somewhere else I need to look?

Thanks guys!

Model No: 133-8-486
Model/Serial/ID: 10-A-1
Year: 1949
 

fhhuber

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Definitely could be spark... so get that test done.

Check if you can feel it trying to pull air through the carb then make sure if its drawing fuel.

Make sure its got at least 90 psi compression.

Fuel/air mix, compression and spark (with proper timing). If you have those it will run.
 

F_R

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Actually, your motor is a 1948, made by Scott-Atwater. They are nice simple motors and run extremely well when right. It should have the WICO magneto with orange shellac coils, which are almost bullet proof. But you can just about bet the farm that the breaker points need cleaning. They always do after sitting that long.
 

nbarr7655

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Actually, your motor is a 1948, made by Scott-Atwater. They are nice simple motors and run extremely well when right. It should have the WICO magneto with orange shellac coils, which are almost bullet proof. But you can just about bet the farm that the breaker points need cleaning. They always do after sitting that long.


So I checked today and definitely have spark and some good compression. Now it's down to fuel I am guessing? I put the plug in and pulled the cord 3 or 4 times. After that I pulled the plug and didn't see much, if any, fuel on the end of it. I had the carb off yesterday and was looking and from what I could tell it looked fine? Attached to this post is a picture of a carb that I found on ebay that matches the one I have and took off and checked. Fuel is making its way through the line, so that's good.

s-l1600.jpg
 

Tech Tony

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Apr 30, 2016
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If you have any rubber hoses on it you should definitely change to new hoses.
 

nbarr7655

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Alright so I took things further apart today and found that fuel is making it through the carb but stopping right before where it would enter the chamber for the piston. I noticed that these motors implement a little flapper that I can only assume relies on back pressure to push the fuel through and then they close again? Attached are some pictures that I got. The first one is where the fuel makes it and then stops. The other two are just so people know what I am talking about.

tgqCtfN.jpg
 

brim_buster

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Looks like reed plate. The reeds might be sticking not allowing fuel to enter the chamber.
 

F_R

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Those "flappers" are called reed valves. Although there are other designs, the reed plate design was almost universal for many years and is still used today. They are opened by the difference between the pressure (partial vacuum) in the crankcase and atmospheric pressure on the outside. If you have good piston sealing (compression) and good crankcase sealing, you will have that pressure differential.
 

nbarr7655

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Those "flappers" are called reed valves. Although there are other designs, the reed plate design was almost universal for many years and is still used today. They are opened by the difference between the pressure (partial vacuum) in the crankcase and atmospheric pressure on the outside. If you have good piston sealing (compression) and good crankcase sealing, you will have that pressure differential.


Gotcha, thanks for the info. As far as I know, compression is good. If I plug the spark plug hole with my finger and give it a pull or even a couple turns, the pressure pushes my finger off.
 

F_R

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Then unless you have a major crankcase leak, you are barking up the wrong tree. It isn't a case of not pulling in air/fuel. (the suction is very weak--that is normal). Spin it over slowly with the spark plug out. Do you hear a "plop-plop" sound at the plug hole? That is a good sign that the crankcase sealing is ok.
 

nbarr7655

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Then unless you have a major crankcase leak, you are barking up the wrong tree. It isn't a case of not pulling in air/fuel. (the suction is very weak--that is normal). Spin it over slowly with the spark plug out. Do you hear a "plop-plop" sound at the plug hole? That is a good sign that the crankcase sealing is ok.


I do hear that sound and when giving it a good pull it makes the normal sound you would expect from an engine that was just pulled. However, I don't even get a hesitation of start.
 

fhhuber

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Reeds should spring closed when the engine is not running.
If they do not, then they won't seal properly for driving fuel-air mix into the combustion chamber. Also they can allow the crankcase to expel the fuel-air mix through the cab backward (which is a fire hazard)

Not really a good idea to be poking metal reeds with a screwdriver. Its easy to bend them so they don't close properly.
 

nbarr7655

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May 23, 2017
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Reeds should spring closed when the engine is not running.
If they do not, then they won't seal properly for driving fuel-air mix into the combustion chamber. Also they can allow the crankcase to expel the fuel-air mix through the cab backward (which is a fire hazard)

Not really a good idea to be poking metal reeds with a screwdriver. Its easy to bend them so they don't close properly.



Good news there is they still close properly. I actually got that plate off so I was able to look at the backside and everything was in good shape there.
 
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