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Hello everybody,

Reading here in the forum has helped me a lot, now it's time to ask a question:

I'm disassembling an old riding mower to restore it - first and foremost is the engine.

It is a Briggs "Boxer" (opposed twin) and exactly the air baffle, in which the numbers for model, type and code should be stamped is missing.
I hope now with the assembled professionals here, due to the characteristics of the engine, to narrow down its identity.

* The model so far: 4xy7z7
4 - 40ci at least, it's the boxer
x - this is really only 0 or 2 in question, I think
y - basic design series unknown
7 - vertical with FloJet without wind govenor
z - have not yet opened the crankcase, do not know which bearing is installed, at least no external oil filter
7 - electric starter with alternator

* It seems to be the oldest carburettor in this series, with adjusting screws for both high and low speeds. It's not the Nikki_6.

* It is probably the earliest fuel pump installed, with the body made of beige plastic and sitting on the right side, not the front.

* The intake bridge seems to be of the oldest type, upper and lower halves can be split lengthwise.

* On the inside of the flywheel (all steel including the fins) there is a cast mark 'GI 76' - if this should indicate the time of the casting, it would be before the first pre-series boxer ...

I will gladly share more details or take pictures. Here in Germany, this engine is extremely rare, so I can't ask anyone here.

Many thanks for your help,
greeting
Franz

Put up a pic of it...

Thanks for your quick reply.

A pic of what precisely???

Franz

The engine, the carb, anything.

The starter.

GMG_2 said:

Hello everybody,

Reading here in the forum has helped me a lot, now it's time to ask a question:

I'm disassembling an old riding mower to restore it - first and foremost is the engine.

It is a Briggs "Boxer" (opposed twin) and exactly the air baffle, in which the numbers for model, type and code should be stamped is missing.
I hope now with the assembled professionals here, due to the characteristics of the engine, to narrow down its identity.

* The model so far: 4xy7z7
4 - 40ci at least, it's the boxer
x - this is really only 0 or 2 in question, I think
y - basic design series unknown
7 - vertical with FloJet without wind govenor
z - have not yet opened the crankcase, do not know which bearing is installed, at least no external oil filter
7 - electric starter with alternator

* It seems to be the oldest carburettor in this series, with adjusting screws for both high and low speeds. It's not the Nikki_6.

* It is probably the earliest fuel pump installed, with the body made of beige plastic and sitting on the right side, not the front.

* The intake bridge seems to be of the oldest type, upper and lower halves can be split lengthwise.

* On the inside of the flywheel (all steel including the fins) there is a cast mark 'GI 76' - if this should indicate the time of the casting, it would be before the first pre-series boxer ...

I will gladly share more details or take pictures. Here in Germany, this engine is extremely rare, so I can't ask anyone here.

Many thanks for your help,
greeting
Franz

Click to expand...

40

Assuming you description of the engine is correct, I can send you a Service Manual IF you like. Address below, put in proper format and remind me the, well I usually say engine model number, but since you don't know, the description of the engine or overall photograph and what you want.

Walt Conner
wconner5 at frontier dot com

wilco - just shortly outside to make the pictures - be back soon.

Franz

Ok,

back inside and threw some pictures in two PDF's:

The pic of the starter wouldn't help much as the seller changed it for an aftermarket starter, as well as for the ignition-coil.

Please be specific if I should make some more detailed photos - thanks.

Greets
Franz

Looks a lot like this model..

https://www.partstree.com/parts/bri...rtical-engine/carburetor-assembly-manifold_3/

Service Manual sent from my desk top computer, hope you got it. As Fish said, probably model 401707 but not that critical on that engine for most things. Will use the same rings as 28 series "L" head, early 28 series OHV and 42 series opposed. Difference between 40 & 42 series opposed is piston stroke as far as displacement is concerned. Many parts interchange.

Walt Conner

@ Walt: thank you, Sir!
Interestingly I couldn't find out the stroke of the 40 and the 42 in the manual.
So I went out in the dark and measured a stroke of 55mm - together with the bore that gives abt. 658ccm - which makes it a 40, no doubt.

Cylinder reminded me very much of the 28 and it seems I wasn't wrong.
The head on the other hand reminds me from the inside of the 25.

@ Fish: so I'm going to go with 401707, thanks a lot!

Type should be below 0500 because of the lid for points and condensor - althought it's a magnetron on the engine.

Possible problems:

- the 393301 Carburetor Overhaul Kit (which sets the engine to pre 79031900, is that right?) is not available - can I use an aftermarket kit like this https://www.ebay.de/itm/Vergaser-Re...tor-B-S-16HP-18HP-393301-394034-/120995029011 hence it has gaskets for different versions in it?

- as one can see in the pics, one of the two hose couplings of the fuel-pump-body is broken. Someone in the past "fixed" it with a piece of brass-hose which looks quiet odd and presumably isn't airtight.
The old beige/white body 280197 isn't available anymore - will the successor in black be an 1-to-1 substitute?

- are there any other problems I will possibly run into with that old babe?

Thank you all,
have a good week,

Franz

Hi Fish!

-

Fish said:

https://www.milfordpower.com/280197-Genuine-Briggs-Stratton-Fuel-Pump-Body-p/280197.htm

Click to expand...

found him already ... but: "This item must be picked up in our store."


-

Fish said:

https://www.ebay.com/itm/Briggs-Stratton-691896-Fuel-Pump-Body-Replaces-280197-691896-/400477096584

Click to expand...

... but: "Does not ship to Germany"

-

The question was NOT where I can buy it, the question was about 691896 "will the successor in black be an 1-to-1 substitute?"

Thank you,

Franz
.

Take a pic of both sides of it, and compare it to the ones on e-bay.
The one ad says that it replaces that part number.

The partstree site says that it replaces that part number...

"The old beige/white body 280197 isn't available anymore - will the successor in black be an 1-to-1 substitute?"

Yes, provided it has 3 screws in body rather than 4.

I thought the Service Manual had bore and stroke specs. IF it is a 40 series and that old it may be aluminum bore, hope not.

Walt Conner

)

@ Fish: You are right. I was mistaken there, before your link to partstree I looked up parts elsewhere and this wasn't quite clear as it seems to be now. Thank you.

Tinkerer200 said:

"The old beige/white body 280197 isn't available anymore - will the successor in black be an 1-to-1 substitute?"

Yes, provided it has 3 screws in body rather than 4.

Click to expand...

Good to know, thanks.
As I said, it's not the Nikki_6 and all the Walbros had three screws, right?
Pic Boxer_CarbPump_3Screw.jpg attached.

Tinkerer200 said:

I thought the Service Manual had bore and stroke specs. IF it is a 40 series and that old it may be aluminum bore, hope not.

Click to expand...

I thought so as well, but the manual just says "Bore (All) 3.4365” – 3.4375” (87.28 – 87.31 mm)". A number for stroke is nowhere given ...

As for the material of the bore: I fear for the the worst.

- Attached pic Boxer_CylBore_r.jpg shows the cylinder track, which has a gray color, looks like coated and seems in good condition.
- The sealing surface does not look like a cast iron sleeve in it ... what would you say, aluminum or iron?

That would be really bad, since the cylinders are not removable, so you can not just shrink a sleeve into it ...

In your country, the supply of replacement engines is good, you would just change the engine ... but what do I do if I want to keep this old engine running?

Many Thanks,
greeting
Franz

It is a side valve engine so you can get it sleeved without any problems as the head will hold a top hat sleeve in place.
Weather it is economically viable to do so is a different matter.
Lots of companies in the EU doing sleeves for motorcycle engines , usually about 100 Euro + fitting.

Hi Bert,

thanks for your reply and Goodday down there!

Lets put economical viability to one side for the moment, shall we? )

I've done it to Guzzi cylinders a few times to get a bigger bore e.g. 850-to-1000ccm, even to OHV engines with pushrods - no problem, you are right and the price is just a little bit too optimistic nowadays in this country.

Where I see the biggest problem is the sheer hugeness of of this motor-block: due to the fact that the cylinders are not detachable you have always this vast piece of metal cyl_1-block-cyl_2.
I can't measure right now but that must be as long as 80-90cm -> 800-900mm -> about 3' -> 35", almost as if you would try to do a BMW-Twin without detaching the cylinders first.

I don't know someone I can think of right now with a machine big enough to put an engine that size in it to do this job ... must be someone who rebuilds ship engines, but then this bore and the tolerances are perhabs a bit tight ... will research ... )

Thanks mate,
have a nice evening,
greets

Franz
.

A magnet will quickly tell if bore is aluminum or cast iron sleeved. IF aluminum you might be lucky and cylinder bore be OK but at that age, odds are not good. I realize your problem but my experience rebuilding that old an aluminum bore engine have not been good.

Walt Conner

Good morning, Walt!

Magnet says: no attraction at all! - funny how sometimes the simplest things fail to spring to mind, tststsss ;o)

Right hand cylinder bore looks quite nice, will see other side later today.

Perhaps I'll be lucky for a while, because we found tons of reasons why this engine wasn't able to run for quite some time:
- the man we bought it from, how can I say this, he was not in the workgroup that invented the deep dish, if you understand
- - the magnetron was mounted the wrong way and he was wondering why he didn't get spark
- - he told us about his last mowing which ended with misfirings and we found a destroyed sparkplugthread with a loose plug in it - which I fixed today
- - the sparkplugs in it had way too low a heat value which must have led to glow-ignition
- - half of the interior of the fuelpump was missing
- - and on and on it goes

Every screw we loosen a new surprise - stuff for endless joy. I think that this engine wasn't running much in the last dozens of years, should be pretty much life left in it I hope
Measurments will show.

Thank you all,
greets

Franz
.

GMG_2 said:

Hi Bert,

thanks for your reply and Goodday down there!

Lets put economical viability to one side for the moment, shall we? )

I've done it to Guzzi cylinders a few times to get a bigger bore e.g. 850-to-1000ccm, even to OHV engines with pushrods - no problem, you are right and the price is just a little bit too optimistic nowadays in this country.

Where I see the biggest problem is the sheer hugeness of of this motor-block: due to the fact that the cylinders are not detachable you have always this vast piece of metal cyl_1-block-cyl_2.
I can't measure right now but that must be as long as 80-90cm -> 800-900mm -> about 3' -> 35", almost as if you would try to do a BMW-Twin without detaching the cylinders first.

I don't know someone I can think of right now with a machine big enough to put an engine that size in it to do this job ... must be someone who rebuilds ship engines, but then this bore and the tolerances are perhabs a bit tight ... will research ... )

Thanks mate,
have a nice evening,
greets

Franz
.

Click to expand...

Most industrial vertical mills will have a knee with better than a metre of travel .
Although it would be better mounted flat on a horizontal mill as there is more area to clamp down on to and tables always travel true to the cutter where as knees can be a bit wonky
You would only do the nearest cylinder to avoid excessive spindle length then flip the engine to do the other side.
Lots of set up not much machining.
The trick to machining is to find an old shop with lots of machines where the owner runs it and works as a one or two man shop.
Real engineers like a challenge because that is what engineering is all about, overcoming a challenge.
So you ask if he can do it , explain it is a non commercial hobby job and you are in no hurry for him to do it.
This is what I do here and it works well until they close down.

Now it is never cheap, but again I have never been charged what the actual cost was as machine shops charge around $ 200 /hr down here, job on to job off and there would be around 6 hours in doing your engine.

GMG_2 said:

Good morning, Walt!

Magnet says: no attraction at all! - funny how sometimes the simplest things fail to spring to mind, tststsss ;o)

Right hand cylinder bore looks quite nice, will see other side later today.

Perhaps I'll be lucky for a while, because we found tons of reasons why this engine wasn't able to run for quite some time:
- the man we bought it from, how can I say this, he was not in the workgroup that invented the deep dish, if you understand
- - the magnetron was mounted the wrong way and he was wondering why he didn't get spark
- - he told us about his last mowing which ended with misfirings and we found a destroyed sparkplugthread with a loose plug in it - which I fixed today
- - the sparkplugs in it had way too low a heat value which must have led to glow-ignition
- - half of the interior of the fuelpump was missing
- - and on and on it goes

Every screw we loosen a new surprise - stuff for endless joy. I think that this engine wasn't running much in the last dozens of years, should be pretty much life left in it I hope
Measurments will show.

Thank you all,
greets

Franz
.

Click to expand...

If the bore is alloy then the mobs who do bores on two strokes are worth looking at.
They bore off all of the old hardfacing then machine the cylinders reapply the hard facing by either plating or flame spraying then hone to size.
Again, not unexpensive but doable.

Hello Bert,

Thank you very much for your comments, I completely agree with you as to the type of workshop that will most likely suit me.
While reading your lines I was almost able to smell the workshop - hopefully not all of those I knew gave up due to their age.
We will see.

Yesterday we opened the left cylinder and found it's track not as good as on the other side.
After replacing the spark plug threads, installing spark plugs of the correct value and tightening the cap screws with the correct torque, we were able to get the engine running a bit with "open outdoor gasification". ;o)

Over night some parts arrived, we'll be able to redo the carb and some intake-gaskets today and see (hear!) how it'll run ...

Let's see how it will continue with this project - I know anyway that I will pay much better attention to the quality of the initial model at the next boxer or B & S in general, e.g. cast iron sleeve vs aluminum etc.

Information about this are always very welcome! I'm not that experienced as to what B & S engine model to look for and which one to better leave ...

Many Thanks,
greeting

Franz

Hello everybody.

If it is of interest what happened next:

- We got the engine running after reworking the carburettor and planting a new ignition coil

- Since the part 222859 has not yet been delivered, we have no proper air filter and therefore waived longer running and a test under load

- a problem now is that apparently too much fuel is sucked in (and burned?) and we have the impression that the new oil (about 15 minutes running time) starts to smell like gasoline. An experienced agricultural machine mechanic, however, said that it smells more like oil that has not been changed for years, and that it will continue to do so for several oil changes ...

- The track of the left cylinder (# 2) is significantly worse than that of the right, the grooves are unacceptable
- - interesting is that the left cylinder is also the one whose air baffle is missing (which is why I had no number and have started this thread in the first place), which could be a sign of how important the originally intended forced ventilation is for cooling!

- We wanted to know how dimensionally sound these aluminum cylinders still are, without disassembling the whole engine. To do this, we rotated each piston to bottom dead center and measured the space above it, in three elevations in two directions each ... I know that this is not the right way to really diagnose the health of the engine

- While the absolute cylinder bore is only slightly above the maximum setpoint (# 1: ok, # 2: + 0.01mm / + 0.0004 "), out-of-roundness is up to twice the allowed value
- - a revision of the whole engine seems so unavoidable, whether this is worth it is questionable

Whatever we do, we do not want to make the entire mower's restoration project dependent on a later decision on this engine (401707) and will receive a replacement engine (422777) in about a weeks time.
This does not fit into the era of the mower, but keeps it going.

I have a certain affection for the boxer engine and specially for sidevalves (e.g. BSA M20), but for future projects where strength and reliability are important, I have to make friends with younger alternatives.

Therefore, I have opened a new thread that is about the B & S V-Twin engines, of which I still know very little, but which are available here in Germany on the second-hand market in a larger range and newer than the boxer.

Should I be imprecise somewhere, please ask.

Thank you for reading and every tip,
to all a nice weekend,
greetings
Franz