The current engine is B&S 259707. Sorry, I forgot to post it in the OP.

Bolt pattern must be the same.
I notice in the spec's, that it says-
Wiring Code:
Gray is kill wire
Black is 12 volts to ignition switch
Red is charging wire

I take that to infer that the engine has a carb fuel solenoid (Black wire) that will need 12V to start/run, but must be able to be switched off so the battery doesn't run down when stopped.

One thing to keep in mind is that a modern OHV engine will have a much better (flatter) torque curve throughout it's operating range then an "old" flat head. A "new" 11HP Honda will outperform an "old" 11HP Briggs AND use less fuel.

Your price appears pretty good though!

thanks for the help, Bill. If bolt pattern is so critical, then why do these engine manufacturers not post them everywhere like wheel bolt patterns (4.5x5 or somesuch)? I'd hate to pay freight on an engine only to find I need to drill new holes.

The engine supplier should be able to tell you if it has the correct bolt pattern.

You;ll have to ask the engine manufacturer why they don't post them "everywhere". Maybe anti littering laws?

An ordinary 12.5 hp Briggs engine will do everything you need to do, so you don't have to buy some exotic engine! Or, a Tecumseh! As long as you do the regular maintenance on an engine, they will do the job!
Yeah, i guess the hypnotic effect of bragging rights when you install an engine made in Japan, can make the ordinary home country built engine seem mediocre, but the USA built engines have held up right well for many years!
I either give away those Honda mowers, or take them to the lawn in the sky. (The scrap yard) I have a Honda engine that has been ignored for several years in my driveway, and it's next in line for a ride to the scrap yard. Don't know if its any good--don't care, either.

So Rusty, what do you think of the Briggs Vanguard?

I for One like any engine that is FREE or low priced, if it's riceburner all the better. Now, with that said that don't mean I going to give extra just for that. If you shop around you can find anything way cheaper that retail especially at the 400% dealer mark up!?! Did I say that?????

To Bill Kapaun: If it runs and doesn't rap, i install it! I'm not well versed on engine makes or models. I deal mostly in old faithful B&S and Tecumseh enginesa, and if they can be made to run--well--they are then installed in anything i need to use, or sell.
If not usable, off they go to the scrap yard!
Rusty

old ya say,mine is a 1972 that I found at a yard sale for $10 with blown engine,I replaced the old 8 hp briggs with
a 12 hp briggs I/C ,gave it a good paint job,new seat,and have been using it without a problem 14 year's later..their bulletproof........

A few years ago, i found part of an old Cub Cadet setting out for the garbage man. So, being that the owner had been installed in a nursing home, and his off-spring didn't have the sense to keep it, i scarfed it up and took it home.
The engine was a Briggs 12 h.p., in need of some restitution. So, i gave it a shot of ether, with some new gas in the tank/carb, and it started! WOW!!
Well, needing an engine in a free Simplicity Broadmoor tractor, i installed it in that, and have been using it ever since!
About 4 years ago, a man gave me a vertical Tecumseh 10 h.p. commercial engine, said it was good. It is! I use it in my smaller Snapper Hi-vac rider.
Engines are as good as proper care can make them! If you do a wipe of the dip-stick, then dip it and pull it out again, you'll get the proper oil level when you check it. Some folks don't seem to understand that engine oil will stay high on the stick after running it, and next time they check it before starting the engine, --yep--lots of oil on the stick---WRONG----without a wipe off, thats when the low oil bugaboo gets ya! That congealed oil will stay on the dip-stick for weeks, if ya don't run it!

Ar you still thinking of installing the Honda GXV390?I'm doing the same swap now.The Honda will bolt up,with a couple of changes. There is a bracket that bolts thru the deck on the left side,the nuts are on the top with the bolt shanks up,this keeps the engine from lying down.I turned the bolts over and that works better,if I did it again I would countersink the holes and use c'sunk screws.The Honda has blind bolt holes at the front mount holes,this makes for a hard time installing the bolts along with the belt guide and aligning and starting the bolts.I would get a couple of 5/16-24 studs,screw them into the engine holes then the nuts and guide would be much easier.The muffler fouls against the right push bar,I spaced it out about 1/2 in with washers,do both sides so it sits level when on end

To be on the safe side, i installed fuel shut-off valves on all of my gravity feed engines. And i use those valves! I'm always getting 50 feet from the garage when they shut off, because i forgot to open the valve, but thats much cheaper than a replacement engine. I had one engine on a RER that went BANG! and that was because it didn't have a shutoff valve on it!
I'm always looking for good used Briggs and Tecumseh engines for use in a tractor or RER. Folks give me their old machine, and i try to resurrect it, either for my use, or for sale!

My personal choice for a re-power would be a Kohler CV14s. Most small engines in this size range have the same crankshaft size and the same bolt pattern. With the Kohler they usually have a re-inforcing plate under the engine. Large washers at each mounting hole *probably* would do the job. The Kohler will have meteric threads into the sump. Kohler CV12.5, CV14, CV15 would all work.

Second choice would be a 14 - 15 hp B&S OHV. Both the Kohler and the OHV B&S will have different exhaust arrangement than the 12.5 hp B&S original engine.

I don't know anything about Honda.

Walt Conner

THE SWAP IS DONE!been mowing for a month,the Honda is quieter,smoother easier starting and uses less gas than the 9hp Briggs.Acouple of guys have PMed me about the swap,so I thought I'd post some more info.My Snapper is a WM280921 model 2001.I've never owned an older RER,so I cant answer a lot of questions about them.One of the best sources of info is one of the large Snapper parts vendors,they have exploded views and parts listings of all models.Snapper built some mowers with the Honda GXV 390 AND 340 engines.The Models 281123HVE AND 331323HVE,The parts manual(on the vendors or Snappers web site) shows the electric schematic,electrical parts,and all Honda specific parts.The Honda throttle cable is 11 in.longer than the Briggs,and the arm on the engine moves up and down instead if side to side on the Briggs.I bought a new one but a mower shop might make you one.I routed the cable up and over the tank using the depression next to rhe gas cap.I also had to use the lower hole on the engine arm for the wire.

The Honda GXV 390 and 340 are commercial rated engines,there are many different models,built in at least 4 countries.There are Propane burning models with stellite valves,110 volt starters,and a filter on the cooling air inlet.They are found on mowers,generators, floor buffers,pumps,and other apps.The engines have two balance shafts,which are supported in roller bearings,and the crankshaft is also roller bearing at both ends.The aluminum rod runs directly on the steel crankshaft,they have oil pumps but only to spray oil on the top crankshaft bearing,all other,lube is splash,some have oil filters some don't,they can have recoil or electric starters,or both,a gas tank or not.They list for $750 or so I saw an 11hp 340 with recoil only sell on e-bay for $380 plus shipping so keep your eyes open.My engine is a GXV 390A1 det3 It's built in the USA and has both starters and a filter and tank I used the Snapper tank. I paid about $450 for it on e-bay,the 340's seem to be mostly built in Japan with the 390's built in Japan USA, Thailand and China.As I said in an earlier post the Honda's have blind holes(5/16-24)on the front of the engine(next to the seat)the rear holes are open with bolt and nut.A belt guide uses these holes also and if you try to use a bolt in the front holes it is hard to manuver the bolt,washer, bolt guide and start the bolt.I pulled the engine back off to adjust the drive plate and installed studs before re-installing the engine.The studs were about 1 inch on each end which is about the depth of the blind holes,I used loc-tite on the studs and used two plain nuts tightened together to tighten the studs in the holes,then used lock nuts on assembly. I ruined my original drive plate trying to remove it,I made a puller using a 1&1/8 -12 x2inch bolt,well greased,holding the shank of the plate with a pipe wrench and a large crescent wrench on the bolt head,this pulls the plate away from the engine,to pull the plate toward the engine,thread ,a 7/16x20 bole into the end of the crankshaft and put a large heavy washer on the plate, hold the shank of th plate with a pipe wrench

Well done! It's very satisfying to me to re-power worthy lawn equipment (or most anything) like a riding mower or rototiller and give it new life for many more years, with minimum coin expended.

toDC3: did you know that the round flat plate screws onto the adapter on the crank-shaft, and the adapter is held tight onto the crankshaft by 2 allen screws! loosen them and the whole thing comes off! And, hammering on a web of the plate allows it to spin off of the adapter!

Rusty:You're describing an earlier drive disc,the later ones(not sure which series changed)are a one piece steel design.Snapper no longer shows them as available,and interchange with the later type.However I have seen a few NOS on e-bay.The later type is threaded internally in the disc area to 1&1/8 x 12 thread. Snapper sells a puller that screws into this thread for $60,I made my rig for $6 with a new bolt,it's an odd size and I couldn't find a used one.I think the set screws(allen)are 3/16 and I found a 6 in. long "T"handle wrench in my tool box which will fit through one of the holes in the rear of the mower and tighten or remove these much easier than trying to use a short allen or an allen socket.Another tip: my engine had the oil filter which is very close to the wires and brake/clutch cable,coming through the deck,the stock Honda filter sticks beyond the filter adapter and makes less rooom,on the advice of a friend who is a Honda nut(bikes cars & lawnmowers) I bought a ST7317 filter at Walmart for $3 that screws on the stud ok and seals on the base ok,gives about 1/2 in. more clearance

Thanks dc3mech, for that info. I probably won't live long enough, or stay in the business much longer, but it is good to know or learn anything i can for the future! I'm well past my 84th. birthday, and looking forward to some more years, but ya never can tell! Going to a bluegrass weekend tomorrow, down in Richeyville, PA., on Rt. 40, a celebration of the old National Road, which was first built to make travel between the east and Ohio, way back in the "olden days", as my grandmaw used to say!
The drive down is probably 60 miles or so. some wag asked if i was taking a team of horses and a cart. I told him "No, i'm driving my self!" And, if i hadn't sold my motorcycle a couple years ago, i'd probably be taking it! Sheesh!