Smokstak Bulletin Board

Briggs & Stratton 5S
Where to start restoring?

My son and I just purchased a B&S Model 5S (Type 700041 - SN 318034) to get started in the hobby. I also ordered a B&S repair manual last evening. We are at best "green" in the area of engine restoration as 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. 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. Questions: What do we do next in the process? Do you always completely remove everything & start rebuilding from there, for such an "outdoor" found engine? Thank you in advance for ANY & ALL advice you can give us. -- David


I'd drain the oil out of the crankcase & check for water. Then remove the 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. -- Doug

Briggs & Stratton - photo by 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. -- Mike

You have chosen a great piece for a first time restoration. The 5S is a nearly indestructible 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 that 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. -- Neale

Neale is correct; the 5S is a great little engine to start on. Once you get it running you're HOOKED! I know because 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 the web or at your local book store. -- Leonard

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 come loose and how detailed you wish to take your restoration. Remember you can always go back and redo it at a later date. I find that 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 put something into the cylinder to get things loosened up. Then check for spark. That may help you decide how far to take things apart. -- Peter

My first engine was a 5s. I am rather fond of the 2" bore Briggs engines. I have two 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") and a Briggs A. Mine was also sitting out exposed and would only turn over about 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. -- Serf

A 5s Briggs is a very good starter engine, my dad and I used to have one, and to let the truth be known, they seem to be the perfect combination in parts to make an engine. I have been able to get them to idle the lowest and smoothest of all Briggs & Stratton engines, with just the right adjustments, they run smooth as a sewing machine. The vacu-jet carbs they have seem to be part of the precision running that they offer. It’s just my opinion, but from the experience I have had from Briggs engines, especially the model 5s and 6s Briggs, they will continue to be the #1 small engine in my book. The number one reason is that you can fix them and they don’t put up a fuss as you do so and after you do they are tough little suckers too! -- Skylar

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 and clean the sump of all old oil. It is best to get the flywheel off to inspect the points and condenser, and instructive to go over the ignition system anyway. Removing the head is necessary to clean out the old carbon and check the valve seating. – Bwegher

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 magneto. Loosen the 4 little screws that hold the armature on, place an ordinary 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 piston 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 valve. Here we go (no one has mentioned 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! 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 area; we're everywhere! 4H, FFA, and local tech schools are also places to look for classes and project books. -- Leonard

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 S.

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 method when putting the flywheel nut back on. – Mike

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. – Mike S.

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. – Bill

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

Dave, Good thing you sent those pictures...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. – Neale

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 it’s 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 has "Antique" microfiche cards which will help with part numbers, but those should be in your manual. Good luck and have fun! – ssimntih

Thank you everyone who has responded with your advice & support. These have been wonderful. The left hand tread would have been a killer, but in hind sight, this makes sense. 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. If I only had an impact wrench… that seems like a winner, but I've only got a 2 gallon 100 p.s.i. 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. I'm guessing that my engine may have been rebuilt, since the coil is different, the carb & breather may be newer parts (so I'm told) and there is some overspray black paint on the plug and its wire. It dawned on this old man that some tools would be needed... more $$$. This is a topic for later discussion also as I'll need advice on these too.


1. The piston is stuck for sure. Last night I put some Marvel Mystery Oil in the spark plug hole (rocked it around to get good coverage) and now we are waiting for a couple of days. Hard to when you got a 16 year old that is chomping at the bit. 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 and 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 an opaque oily liquid. I guess water & oil. Only about 1/8 cup, but at least it was not rusty looking. QUESTIONS: 1. The plug on it is a Champion CJ8. Is that what I should buy as a replacement? 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 everyone’s tips & advise... please forgive me... they WILL be used as this site & this message thread is now my reference book. – Dave

To get the flywheel off just put a piece of wood against the flywheel end of the crankshaft and hit the wood a couple of times with a hammer. That should knock it loose. You can use one or two large screwdrivers to pry up the valve springs and then pliers to pull the retainers out. I don't have a spring compressor and this is what I do. It is best a two person job, though; one with the screwdrivers and the other with the pliers. – Mike S. You don't need an expensive flywheel puller. There is a simple tool used for removing them, after removing nut just put tool over end of crankshaft and tap with hammer. It looks like a deep well socket that may be available at K-mart or Walmart stores. Cost a couple bucks. -- Dick

You can make do with screw drivers and such for everything but putting the piston back in. Small ring compressors aren't too expensive. If you have a JC Whitney catalog (or once you get one) there should still be a little section in the tools part of the catalog that lists small engine repair tools. Look around at some flea markets for used engine repair tools, you'd be surprised what you might find for a little bit of nothing. Another way to get the flywheel off (pullers not recommended, good way to split a stubborn flywheel) is to put the nut back on the crank until it is flush with the end of the crank, then place a piece of oak or a piece of brass or lead against the end of the crank and whack it with a hammer. If the flywheel is really stuck on you might have to have another person pry on the back with a large screwdriver while you whack the end of the crank. The key word on any restoration project is patience, nothing spoils your day more than getting impatient with a stuck piston and hitting too hard. I now have a Briggs FH piston as a paper weight because I got impatient and ended up knocking a big hole in it! Live and learn. – Leonard

Dad showed me how to remove a flywheel nut without having to clamp the wheel or use an impact wrench. Just put the correct size box-end wrench on the nut and give it a belt or two with a brass hammer. Dad also taught me to knock off Briggs flywheels and old Ford rear drums by removing the nut then screwing it back on backwards just 'til the end of the shaft is flush with the face of the nut. A couple of sharp raps with a brass hammer is usually all it takes for a Briggs, etc. The Fords sometimes took a rap from a sledge hammer. Nice thing about screwing the nut on backwards is that, if you accidentally put a ding on the nut or shaft, you can use the nut to chase the threads straight again. – Elden

Like many other Briggs & Stratton collectors my first engine was also a 5s. It was crank start and made in 1952 it is on a Firestone Reel Mower which was my grandfather’s. The exhaust valve of my engine was stuck straight up when I got it and it had been for a while, so I took it to a local machine shop and had the face of the valve cut as well as the seats cut and valve ground. I then bought a gasket set and then I cleaned the engine up and re-gasketed it. Elden is right you don't need a puller, all you need to do is spin the nut to the end of the shaft and bang on it with a ball peen or small sledge, also get a rubber mallet and tap around the flywheel itself. A few good taps should loosen it. Like others said don't try to stick a screw driver between the fins or try to pry against the mag plate both are soft metal and both will break, I learned this the hard way , way back when, but still flywheels are cheap for this model unlike F-series or a flywheel for a model P (which are like $ 200 each) Once you get this engine running, you will just want to find more to get running , it's a great hobby you will enjoy it for years to come, especially as a father son activity, I know I do, I got my father involved in restoring Fairbanks Morse farm engines and it a great way to spend time together. – Jonathan

Don't forget...a screw type radiator hose clamp works great for a ring compressor! -- Neale

Be careful prying on the back of the flywheel. The magneto plate behind it can easily be broken. Also I believe you asked about the piston being to the side. On these engines the spark plug is not directly above the piston. When looking down on the engine from the flywheel side the piston is on the right, exhaust valve on upper left, and intake valve on lower left. -- Mike S.

Many more pages and photos... CONTINUED

More Smokstak Articles

Visit the Smokstak Forums!

All use is subject to our TERMS OF SERVICE
SMOKSTAK® is a Registered Trade Mark
Copyright © 2000 - 2008 by Harry Matthews
P.O. Box 5612 - Sarasota, FL 34277