Briggs & Stratton 5s - Where to start restoring?

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New member
My son and I just purchased a B&S Model 5s (type 700041 - sn 318034) to get started in the hobby (photos in link below). I also ordered a B&S repair manual last evening.

We are at best "green" in the area of engine restoration. This is our 1st engine.

All of the parts appear to be present on the engine and there are no cracks or broken pieces. I was amazed the muffler, breather & gas tank seem to be physically sound and not dented. The engine was sitting outside and I found the gas tank was about half full of water.. but still physically sound and not rusted through (amazing to me).

I don't know if the piston is froze or not as this is where my questions begin. Being so green, I was afraid that if I attempted to turn the flywheel, it would score or damage the cylinder etc since it was out in the weather. Better safe than sorry.

We've put Liquid Wrench on most of the threads in anticipation we would have to remove them. We've not removed the plug to see what it looks like inside.


What do we do next in the process?

Do you always completely remove everything & start rebuilding from there for such an "outdoor" found engine?

Again, we are GREEN greenhorns.

Thank you in advance for ANY & ALL advice you can give us.

David Thomas
Bryant, Arkansas

The other rust in my life:

Doug Kimball

I'd drain oil out of crankcase & check for water. then remove spark plug & also check and/or drain any accumulation of water. In any event I'd pour in a couple of ounces of Marvel Mystery Oil into sparkplug opening & roll it over. Don't force anything too hard. If it appears stuck let oil soak for a while. You could also use automatic transmission fluid.

Mike in NC

David, Your engine was made in Oct. 1950. You can do as Doug said and put some oil in the sparkplug hole. If you turn it over some, even with out oil in the plug hole, it should not hurt anything. Just be easy on it if it is tight at all, it could be a stuck valve as well as the piston. Brake fluid and diesel fuel work also. Here is a pic of our 5S. This is as found on a Eclipse reel mower.

Briggs & Stratton Information

Briggs & Stratton 5S Serial Number List

Neale Behm

New member
You have chosen a great piece for a first time restoration. The 5S is a nearly indestructable engine as evidenced by the large number of them still around. This also means you can find most any part without paying a premium price.
The biggest tip I can offer on the 5S is... THE FLYWHEEL NUT HAS LEFT HAND THREADS!!!
We'll be happy to give you all the advice you can stand if you just keep us updated on your progress.

Leonard Keifer

Neale is correct, the 5S is a great little engine to start on. Once you get it running you're HOOKED!! I know, that's how my son and I got hooked.

There are a lot of good books available on repairing small air cooled gas engines. A couple of the best on basics are by Paul Dempsey: How to Repair Briggs & Stratton Engines and Small Gas Engine Repair. Look for them on or at your local book store.

Peter Ruffle

New member
Welcome!! You have picked a great first engine to tackle. Mine was a Briggs 6S. Take it slow and ask lots of questions. Chances are someone has been there before and will be more than willing to share tips, tricks and how to info along the way. How far you take it apart will depend on how easily things break loose and how detailed you wish to take your restoration. Remember you can always go back and redo at a later date. I find I want to hear it run before I go whole hog in stripping it down to paint and reassemble, but that is just me. As others have said, get the spark plug out and something into the cyl to get things loosened up. Then check for spark. That may help you decide how far to take things apart.


New member
My first engine was a 5s. I am rather fond of the 2"bore briggs engines. I have 2 5 s engines, one runs a compressor, the other a pump. I also have a WM, an N, and (it's a different block, but still 2") an Briggs A. Mine was also sitting out exposed and would only turn over anout a quarter turn. I needed a new gas tank (only $20 from a B&S dealer) and just about everything else that an engine could need other than piston, crank and connecting rod. There are pics of mine on my website.

Just click on the engines link and you should be all set.

The simple Serf


A 5s Briggs is a very good starter engine, me and my dad use to have one, and to let the truth be known, they seem to be the perfect combination in parts to make an engine and i have been able to get them to idle the lowest and smoothest of all Briggs & stratton engines....with juuuust the right adjustments, they run smooth as a sowing machine,..the vacu-jet carbs they have seems to be part of the percision running they seem to offer....just an opinion but from the experience i have had from briggs engines, expecially the model 5s and 6s Briggs, they will be and continue to be the #1 small engine in my book, for the number one reason is that you can fix them and they dont put up a fuss as you do so and after you do so,...tuff lil suckers too!, see how long they lasted and continue to last through the years! :cool:


New member
Part of the fun is taking it apart to inspect everything. The antique B&S book has a list of steps to overhaul. Make drawings of the governor linkage before you take it apart. Clean the sump of all old oil. Best to get the flywheel off to inspect the points and condenser, also instructive to go over the ignition system anyway. Remove the head is necessary to clean out the old carbon and check valve seating.

Leonard Keifer

I would add that you should not only inspect the points but either file and reset them or replace them. Without decent points you can never get a decent spark.

You may also need to reset the magneto air gap. Very easy to do: Turn the flywheel so the magnet isn't under the arms of the mag. Loosen the 4 little screws that hold the armature on, place an ordinaly playing card between the armature and the flywheel and roll the flywheel around until the magnet pulls the armature down. Retighten the screws.

All of this should, of course, wait until you get the pisotn and or valves freed up. If you can rock the flywheel any, in my experience the piston isn't your problem. More often than not there's a stuck exhaust vlave.

Here we go (no one has emntioned this benefit before): Time to buy NEW tools!! You'll need a small valve spring compressor tool so you can get the spring retainer pin out. If you remove the piston you'll also eventually need a small ring compressor to reinsert the piston.

Hope we aren't overwhelming you with info. YOu can tell how enthusiastic we are to "infect" new folks with old iron fever. Beware, there's no known cure!

Happy restoration.

If you run into problems check around in your area, there may be a small engine repairman who'd be willing to help you out. You can also check around for an engine club in the are; we're everywhere! 4H, FFA, and local tech schools are also places to look for classes and project books.

Mike S

New member
When you take the flywheel nut off DO NOT try to keep it from turning by holding the flywheel fins! The flywheel is aluminum and the fins will bust off. This will take it out of balance and the engine will vibrate.

Mike in NC

One easy way to get the flywheel nut off is to remove the sparkplug, and put some clothes line down through the sparkplug hole in to the cylinder. Put as much in as is needed so that the piston stops before it gets to TDC (Top Dead Center). And as someone already said, the flywheel nut is LEFT HAND THREAD!. Also you can use the same methed when puting the flywheel nut back on.

Mike S

New member
I usually get a wedge shaped piece of wood and jam it under the pulley on the pto side. Of course to do this the engine needs to be bolted down to something. Just be careful when you jam the wedge in so you don't bend the end of the crankshaft.

Bill Sherlock

I find the use of an impact wrench is handiest for removing flywheel nuts. Don't even have to hang onto the flywheel in a lot of cases. Just make sure that you have the correct rotation so you don't land up tightening the nut instead of loosening it. If the nut doesn't move after a couple of raps, best investigate further before any damage is done.


Tom Schaech

I have to agree with what everyone else has said. The little cast iron Briggs engines are nearly indestructible! We have a 5S, mounted on a Montgomery Ward reel mower that is on its 3rd generation in our family as the yard machine.

I've been working with Briggs engines for over 30 years and have quite a collection!

I'm glad to assist you in any way you need...feel free to email me!


Tom Schaech
Vintage Briggs and Stratton Collector
Bel Air, MD :D

Neale Behm

New member
Good thing you sent those pics...another No-No is soldering the sparkplug wire on the magneto coil. The wire is usually tinned and then twisted securely onto the coil lug. Soldering it to the lug is taking a huge chance of melting internal insulation on the coil and ruining it.


The only thing I can think of that hasn't already been said, and might keep you from pulling your hair out later is that its a good idea to replace the plug wire while you have the shroud off. I've seen them fire through the insulation that's touching the head or shroud, and won't get any to the spark plug. There are very few parts still available new... mostly gaskets and such. Briggs and Stratton does have "Antique" Microfiche cards which will help with part numbers, but those should be in your manual. Good luck and have fun!

P.S. I need a carb and tank for a 5s.


New member
Thank you everyone who has responded with your advice & support. These have been wonderfull.

The left hand tread would have been a killer.. in hind sight, this makes since.. but I'm sure it wouldn't have crossed my mind till it was too late :(

The clothes line rope down the spark plug hole tip to remove the flywheel. Had to stop and think about this one for a minute (I'm slow :) )... then it dawned on me how it works. Blocking the pulley would work .. except I don't have a pulley... will need one of those sooner or later. If I only had an impact wrench... that seems like a winner... but I've only got a 2gal 100psi compressor. One of these days.. maybe.. at this point I don't want to break the bank.

On the coil (or is it magneto) spark wire that seems to be soldered in the middle of the wire wrappings ... that was as I bought it... looking at some on e-bay that are older.. I see the plug wire is not solder there. Sorta scared of removing the wire & soldering on a new one... as I don't want to screw up what might work.

I'm guesssing my engine may have been rebuilt... since the coil is different, the carb & breather may be from a newer parts (so I'm told) and there is some overspray black paint on the plug and its wire.

Tools.. yes... it dawned on this old man (deer in headlights) that some tools would be needed... more $$$... but it is better than paying lots of $$$ to my
former shrink :) This is a topic for later discussion also.. as I'll need advice on who, what, when & where on these too... and are there any "get by" tools I can make or conjure up. The flywheel puller & socket (big 'un) ... on a 5s to you need one of those big bar type pullers (fin teeth in the middle & handles on either end) or will on of those bolt type tools work. The big socket.. what do you do for 1 of these?

The photos posted are very helpfull. I see where my gas tank mount is offset & the breather is not an oil bath type as on a OEM 5s... must have been added later. The older plug pattern colored wire looks really nice.


1. The piston is stuck for sure. Last night I put some Marvel Mystery Oil in the plug hole (rocked it around to get good coveraged) and now we are waiting for a couple of days. Hard to when you got a 16year old that is chomping at the bits... this project IS bringing us closer together :). The wife said he got home from school last night & went to work liquid wrenching the parts & cleanup... without even getting a snack.. was there when I got home.

2. With the help of liquid wrench.. followed by the better PB Blaster (LW didn't work).. we got the drain plug off.. with some work. The bad news is that what drained out was a opaque oilly liquid... I guess water & oil. Only about 1/8 cup. Doesn't sound good... at least it was not rusty looking.

QUESTIONS ============================================

1. The plug on it is a Champion CJ8. Is the what I should buy as a replacement ... or ?

2. Looking down the spark plug hole.. I see a step down (ledge) to the cylinder head rather than an unobstructed view. What is this ledge?
The cylinder seems to be in at the top.

3. In making a starter rope.. how long should it be?

Have to close & go to work. I'm sure I didn't cover everones tips & advise... please forgive me... they WILL be used as this site & this message thread is now my reference book.

More later.... Keep the advice comming.

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