B&S Opposed Twin Rebuild Guidance Needed

8363 Views 56 Replies 13 Participants Last post by larrybl, Sep 11, 2015

RustyGuy

Discussion Starter · Jul 13, 2015

I started another thread about my rebuild of a B&S opposed twin horizontal engine (model 422437), but wanted to start this new thread because I'm now on a second 422437 engine and wanted to separate out the two.

History: acquired a free 917 CM 18HP GT that died in the field on the PO. The tractor is in great shape and I was hoping for a simple fix. No luck on that as the engine (Engine #1) had thrown a piston rod and the shrapnel took out the casted valve guide. Pulled it apart and scrapped the block, so I now have lots of parts. Enter Engine #2, also a B&S 422437, I pulled off a junked GT but that tested out with 75/90 compression.

Engine #2 Rebuild: Got the second engine running with some fresh oil and starter fluid, ran it a bit to wake it up (been sitting for two years) and then tested compression on cooled engine at 95/115. Pulled the heads to inspect valve seats and cylinder, with mixed results. Not much carbon, but one cylinder wall is pretty pitted, but the other side is clean. I've not gotten to the valve seats yet, but on first inspection they look decent, though one valve stem is also pitted. I'm probably looking at doing the valves and re-ringing this engine.

Questions:
1) Considering the pitting in the one cylinder, is a rebuild worth the time and money? I'm guessing it's going to require a bore job, meaning new pistons and more $$. Possible to do just a hone and ring job? I know, I should probably spec the cylinders, but I don't have that tool.

2) Engine 1 had a tri-circuit strator with a single lead and 10A AC that gets split into 5A DC- for lights and 5A DC+ for charging, but engine 2 has a dual circuit strator with two leads with 5A AC for lights and 3A DC for charging. What is the best way to proceed?

3) Can I use the valves from engine 1 for the valve job in engine 2. I still need to spec the valves and seats, but it would be good to know how interchangeable the valves are. I know one valve stem on engine 2 is pretty worn. I'd obviously reseat the valves, regardless of where they came from.

Thanks for any guidance.
Rusty

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RoyM

· #2 · Jul 13, 2015

If you can't clean up the cylinder with a deglazing hone you need to rebore. I believe .020 is the only oversize piston currently available from Briggs. I do suggest tearing it down, make up your parts list then check with a supplier for cost and availability, OEM parts for those engines are drying up.
The valves are interchangeable. If the seat turns in the block when lapping stake it in three places with a center punch then peen the aluminum block material over the circumference, they had a bad habit of working loose. Use the tri circuit alternator for simplicity.

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Walt 2002

· #3 · Jul 14, 2015

I would say that cylinder needs rebored and of course you will want to do both. I suggest Maple Grove Distributing for parts, they are or were not on the net. I suspect the cost is going to be more than practical unless it has sentimental value.

I can send you a Service Manual for your engine IF you like, address below, put in proper format and remind me engine model number and what you want.

Walt Conner
wconner5at frontier dot com

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suspicionofignorance

· #4 · Jul 14, 2015

If eng 2 has 95 and 115 psi....Why bother with a rebuild ? Your prior owner was using the tractor on only ONE cylinder...and got bye...
Can you pop off the flywheels easy enuf ?...if so, just swap alternators, as someone posted in orig thread..

crawler

· #5 · Jul 14, 2015

Walt 2002 said:
I suspect the cost is going to be more than practical unless it has sentimental value.

That was my first thought. That's a lot of money and work put into a Breaks & Scatters on a craftsman, IMHO.

larrybl

· #6 · Jul 14, 2015

RustyGuy said:
I started another thread about my rebuild of a B&S opposed twin horizontal engine (model 422437), but wanted to start this new thread because I'm now on a second 422437 engine and wanted to separate out the two.

History: acquired a free 917 CM 18HP GT that died in the field on the PO. The tractor is in great shape and I was hoping for a simple fix. No luck on that as the engine (Engine #1) had thrown a piston rod and the shrapnel took out the casted valve guide. Pulled it apart and scrapped the block, so I now have lots of parts. Enter Engine #2, also a B&S 422437, I pulled off a junked GT but that tested out with 75/90 compression.

Engine #2 Rebuild: Got the second engine running with some fresh oil and starter fluid, ran it a bit to wake it up (been sitting for two years) and then tested compression on cooled engine at 95/115. Pulled the heads to inspect valve seats and cylinder, with mixed results. Not much carbon, but one cylinder wall is pretty pitted, but the other side is clean. I've not gotten to the valve seats yet, but on first inspection they look decent, though one valve stem is also pitted. I'm probably looking at doing the valves and re-ringing this engine.

Questions:
1) Considering the pitting in the one cylinder, is a rebuild worth the time and money? I'm guessing it's going to require a bore job, meaning new pistons and more $$. Possible to do just a hone and ring job? I know, I should probably spec the cylinders, but I don't have that tool.

Have a machine shop do the boreing, $70-100

2) Engine 1 had a tri-circuit strator with a single lead and 10A AC that gets split into 5A DC- for lights and 5A DC+ for charging, but engine 2 has a dual circuit strator with two leads with 5A AC for lights and 3A DC for charging. What is the best way to proceed?

Swap the stator for the correct one to use on the machine that the engine is going in.

3) Can I use the valves from engine 1 for the valve job in engine 2. I still need to spec the valves and seats, but it would be good to know how interchangeable the valves are. I know one valve stem on engine 2 is pretty worn. I'd obviously reseat the valves, regardless of where they came from.

NO, these valves can only be adjusted by grinding the valve stems. You need to mark them as to which cylander they came out of.

Thanks for any guidance.
Rusty

You might want to look this thread over.
http://www.mytractorforum.com/44-sm...114-second-18hp-b-s-rebuild-org-hulk-eng.html

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RustyGuy

Discussion Starter · #7 · Jul 14, 2015

I'm thinking of just putting it back together as is and running it till it quits. It has enough compression to run awhile. I suspect that if I continue with the tear down I'm going to find lots of other i$$ues with the internals. Oversize pistons are about $70 for this model, and I'm assuming that's each, so times 2 plus machine work costs, plus valves...It would be $500 before I see this thing running (some of that in new tools which is always worth the excuse). Already have about $200 in with rebuild kits, gaskets, and tools.

Questions:
1) With the heads off, anything I should do before closing it up? Maybe reseat the valves and check clearance? I should be able to do that without a full tear down, if I find away to flush the lapping compound out.

2) I have to pull the bottom pan because it's leaking. Any quick diagnostics I can do to assess the crank and rod connections?

Thanks,
Rusty

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RustyGuy

Discussion Starter · #8 · Jul 14, 2015

Hi larrybl - yes, I read your project thread. Inspiring.

larrybl

· #9 · Jul 14, 2015

RustyGuy said:
Hi larrybl - yes, I read your project thread. Inspiring.

Thanks, hope it answered some of your questions.

RustyGuy

Discussion Starter · #10 · Jul 17, 2015

Still struggling with the flywheel. I left it under pressure while I'm traveling for a few days in hopes it creeps. I'm reluctant to take a sledge to it, not so much because of possible damage to the flywheel as I have a spare, but because of possible damage the impact might have downstream on the bearings and races. We'll see when I return.

Still debating doing the rebuild. Leaning towards just doing valve adjustment and putting it back together. It should run a little while before I need to do full rebuild. With my compression reading of 95/115 within the recommended 25% (can't seem to locate that online reference again) I think it should run awhile. I have just begun reading up on leak-down testing and was thinking I could modify my compression gauge with a T to provide input for compressed air. B&S seems to favor the leak-down test over compression. I'll need to locate acceptable readings for my engine. Any advice on doing leak-down testing would be appreciated as this is a new test concept to me.

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RustyGuy

Discussion Starter · #11 · Jul 17, 2015

Here's where I'm at. Shrouding all painted, but engine still under production. At least it will look good for awhile and oil leaks will be easy to spot.

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Walt 2002

· #12 · Jul 17, 2015

I don't believe in beating flywheels off, B&S has a simple inexpensive puller, I made my own which I have used for years.

Walt Conner

larrybl

· #13 · Jul 17, 2015

Not hitting the flywheel. Tighten the puller till it warps, leave the impact socket on the puller. Whack the impact socket HARD! (This is only for those stubborn flywheel's). Out of the umpteen I have done, only one required this abuse.

Kbeitz

· #14 · Jul 17, 2015

.......................

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gardentractornut

· #15 · Jul 17, 2015

Kbeitz said:
.......................

That's how I do 'em

RustyGuy

Discussion Starter · #16 · Jul 22, 2015

Got the flywheel off. Left it under pressure - the harmonic puller was bowing and bending in all directions it was so tight - came back after six days and nothing! So switched back to the B&S puller (which I was using all along, but had rounded out the stock bolts and had to replace with harder steel), "gently" whacked the puller housing over the flywheel nut and then the two bolts tying the puller into the flywheel and pop!, off it came. Whew, glad that out of the way.

Decided to pull the pistons to get a better look at the cylinders. The pistons and rings, connecting rods, and bearings all look good. The crankshaft was a bit rusted, making me think this engine sat in water for some time, which also may have left the "marks" in the one cylinder wall. The pictures show the rust on the crank, and then after I cleaned it off and pulled the pistons. I also tried to get a good shot of the cylinder wall that has "rivulet" type marks like water was running down it for eons and left a water channel. There was a small patch of corrosion on one of the journals, but not bad. I'm thinking I can reuse the piston rods, bearings, and crank.

Next step is to take the block to the local machine shop to see if it needs a bore, or just a good honing. I suspect it will need boring. Looks like I'm in for the long haul...

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larrybl

· #17 · Jul 23, 2015

Doesn't look too bad, similar to one of mine that had water in it. You might get by with a good hone.

RustyGuy

Discussion Starter · #18 · Jul 24, 2015

Got the valves out. 3 of 4 look good. One intake valve definitely needs work - grooved seat and valve lip and lots of carbon on the back side indicating leaking during firing. Opened the crank case and pulled crank and cam, both look good but I'm swapping out the cam shaft with the one from the first engine as it looks a bit better. Took block to machine shop and they said they are going to try honing cylinders first to see how it cleans up, but most likely will need to be bored. Also looking at probably having to replace the one valve seat. Pulling a replacement valve from first engine (nice to have a spare parts engine). The other valves are in good shape and should clean up with a little lapping. Did a water test before removing valves and the one bad intake valve dripped steadily, the two exhaust valves held tight, and the other intake valve seeped a bit. Getting expensive. If it weren't for the fun factor and hands-on training experience it would definitely not be at all worth the expense. ?

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larrybl

· #19 · Jul 25, 2015

The valves are adjusted by grounding the stems. If using "used" valves It is best if you can keep the same valve in the same cylinder. I learned this the hard way.... Mixed the valves up

Troubleshooting

After swapping the valves around to get into spec.

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RustyGuy

Discussion Starter · #20 · Jul 28, 2015

Cylinders bored at .030 over. Found decent price for oversized Pistons at GooseGear. Not the easiest site to search unless you know your part numbers. Also ordered complete gasket kit. Still need to order valve seals and crank oil seals. Valve seats can be lapped and don't need new seats, saving on machinist costs. Once I get block back from machine shop I can start assembly. I'm anticipating having to adjust valve clearance, as lapping should make them a little tighter. I understand the procedure but would love to see a video on it. I don't have a bench grinder, but do have a file and dremmel motor. Any advice?

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