Day 1: NPS Carlsbad Caverns Annual Engine Inspection + Rebuild
Incoming Work Order — National Park Service
Carlsbad Caverns National Park has dropped off a small Briggs & Stratton engine for its annual inspection and rebuild. Peak tourist season starts in two weeks. They need it back certified and ready.
Your job today: tear it down, document what you find, take measurements, put it back together, and decide whether it's fit to return to service.
Six engines. Six jobs. Each one keeps Carlsbad Caverns running. Check your Work Order card to find yours.
Powers the portable research station tracking 400,000 Mexican free-tailed bats. Federal wildlife data depends on this power source. Colony arrives in four weeks.
Drives circulation fans that prevent CO₂ buildup in the lower passages. When CO₂ rises above threshold, 300 feet of cave close to visitors.
Emergency lighting generator for the Big Room — 8.2 acres, 750 feet underground, 1,200 visitors at peak capacity. In a power failure, this is the only light.
Backup hydraulic power for the natural entrance elevator — 750-foot descent. If main power fails during a tour, this engine brings everyone back up.
Portable power for the cave search and rescue team. Powers communication arrays, medical devices, and lighting deep in the system. Was activated for a real rescue in 2019.
Powers environmental monitoring equipment used twice a year by NPS geologists. Stalactites that took 500,000 years to form can be damaged by conditions going undetected. Last active: October 2025.
Your Work Order card is on your table. It has your engine name, the NPS job description, and today's service requirements. Keep it visible all day — it's your reference.
You're about to take apart a 4-stroke internal combustion engine. Two minutes of context before you pick up a wrench.
Four strokes, one power cycle:
- Intake — piston pulls air + fuel mixture into the cylinder
- Compression — piston compresses the mixture
- Power — spark ignites it, expanding gas pushes the piston down
- Exhaust — piston pushes spent gases out
Today you'll hold every part responsible for that cycle in your hands.
- What is displacement and what does it measure? Find one real engine spec that includes it.
- What does horsepower actually mean — not the dictionary, a real explanation.
- Has anyone in your group ever had a car break down? What happened?
Nothing comes apart yet. Document the engine exactly as you received it. This is what modern shops call a Digital Vehicle Inspection — you photograph what you find, rate the condition, and send a report to the customer before any work begins.
Safety glasses on. Nitrile gloves on. Tarp flat on the table.
Assign three roles — you'll rotate these with every major phase today:
- The Tech — handles the tools, turns the fasteners
- The Inspector — examines each part as it comes off, calls out condition findings
- The Archivist — photographs, bags, logs on the Parts Manifest
With 4 students: The Inspector also writes the Padlet posts.
Before touching a fastener, spend 10 minutes observing. Use your packet's External Inspection section. For each item:
- Rate the condition: ✓ Good / ⚠ Attention / ✗ Service needed
- Write a brief note — what do you actually see?
- Photograph at least 3 findings
Check the oil dipstick. Pull the spark plug if it's accessible — what color is the tip?
Before any disassembly starts, post your group's external inspection report to Padlet. Format:
3–5 findings with photos (one photo minimum per finding)
Condition rating for each: ✓ / ⚠ / ✗
One sentence plain English: what you'd tell the customer about each finding
Your group's pre-diagnosis: what do you think happened to this engine?
This is exactly what a shop like Jiffy Lube or a dealership sends to a customer's phone before approving any work. You're doing the same job.
— Lunch Break — 12:30–1:00 pm —
Confirm all bags are labeled before you leave. Nothing loose on the table.
Time to open it up. Work through the engine outside-in, top-down. Every part that comes off gets logged on your Parts Manifest before the next fastener moves.
Two minutes. This is a horizontal-shaft B&S teardown pulled from a tiller — same family of engine as yours. You don't have to follow it exactly, but know the sequence before you start.
Official B&S disassembly technique reference if you want it: youtube.com/watch?v=h9mSlcV07UU
Rotate roles now. The Tech from Phase 1 becomes Inspector. Inspector becomes Archivist. Archivist becomes Tech.
Teardown sequence — External Components first:
- Air filter cover → element → base/adapter
- Fuel tank + lines (if present)
- Blower housing + recoil starter assembly
- Spark plug — examine the tip, record the condition
- Carburetor
- Ignition coil / armature
- Flywheel screen / guard (note: do not attempt to remove the flywheel)
- Governor linkage + springs — photograph before disturbing
Continue into the engine:
- Valve cover — some engines have rocker arms beneath it (OHV), some go straight to valves (side valve). Either is fine.
- Rocker arms + push rods if present
- Cylinder head bolts — remove in a crossing pattern, not one side to the other
- Cylinder head — lift straight up. Look at the combustion chamber.
- Head gasket — inspect condition
- Valves + springs — use the valve spring tool or improvise carefully
Rotate roles again before continuing.
- Crankcase cover / oil sump bolts → sump cover
- Connecting rod cap bolts → connecting rod cap
- Push the piston up and out through the top of the cylinder
- Examine piston rings — any gaps? Any scoring on the piston skirt?
- Crankshaft
- Camshaft — note the timing mark if visible
Your engine is now fully disassembled. Every bag on that tarp is a system. Everything you need to rebuild it is right there.
This is where the teardown becomes engineering. Take four measurements, record them in your packet, then calculate your engine's displacement.
- Spark plug gap — use the feeler gauge. Record in mm. What's the correct specified gap? Look it up.
- Bore diameter — calipers inside the cylinder, at the top. Record in mm.
- Stroke length — measure piston travel by hand or ruler. Record in mm.
Use the formula in your packet:
= 0.7854 × bore² × stroke
Result in mm³ → divide by 1,000 → cc (cm³)
A Honda Civic has about 1,500 cc. A V8 truck engine has about 5,700 cc. Where does your engine land?
If your result is between 100–500 cc — you're in the right range for a small engine like this one.
Cover the spark plug hole with your thumb. Rotate the flywheel by hand. You should feel pressure pushing your thumb off. Strong pressure = good rings and seals. No pressure = something is wrong. Record your result.
Reverse the teardown sequence. Bottom up, then top end, then external. The Parts Manifest is your reference — if a bag is still full, something isn't back in yet.
Rotate roles again before starting the rebuild. Every student should be working a different role than in the teardown.
- Crankshaft seated in the crankcase
- Camshaft — align timing marks if visible
- Piston rings — ring gaps should not be aligned with each other
- Piston + connecting rod back into the cylinder from the top
- Connecting rod cap — torque the bolts. Your packet has the torque reference.
- Crankcase cover — gasket in place, bolts snug in a crossing pattern
- Valves seated — tap gently, they should not rattle loose
- Valve springs installed
- Push rods seated in their guides (OHV engines)
- Head gasket placed — correct orientation, no folding
- Cylinder head lowered on
- Head bolts torqued in a crossing sequence — use the torque wrench. This is the most important fastener in the engine.
- Rocker arms set if applicable
- Valve cover installed
- Ignition coil / armature — gap set correctly (business card thickness if you don't have a feeler gauge)
- Carburetor mounted and linked
- Spark plug — gapped, hand-tight plus a quarter turn. Do not overtorque.
- Blower housing + recoil starter attached
- Air filter assembly reinstalled
- Fuel system reconnected
Before the engine leaves your shop, it needs to pass a final check. This is your sign-off — it means your team stands behind the work.
- All bags empty? If any bag still has parts, something is missing from the engine.
- Flywheel turns freely by hand?
- Compression felt at the spark plug hole?
- All external fasteners present and snug?
- Parts Manifest complete — every row filled in?
In your packet, make the call:
- APPROVED — engine is mechanically sound, return to Carlsbad Caverns
- CONDITIONAL — engine functions but we recommend additional service before use
- NOT APPROVED — found issues that need repair before return to service
Be honest. If something isn't right, the NPS needs to know. That engine runs in a cave 750 feet underground.
Final Padlet post for today. Include:
3 internal findings with photos (combustion chamber, piston, one other)
Your displacement measurement + calculated cc
Return-to-service decision with your reasoning
One thing that surprised your group when you opened the engine
You tore down a real engine, measured what's inside, and put it back together. Most people will never do that. Tomorrow morning you'll walk into NMJC's Automotive Center and you'll recognize things nobody around you will. That's what today was for.
What you did today is a real job. Here's what it looks like as a career — specifically in New Mexico.
- Entry-level tech, Hobbs NM: ~$20–21/hr ($43K/year)
- Experienced tech, NM average: ~$25–29/hr ($52–60K/year)
- With ASE certifications: $30–40/hr and up
- Oil field equipment mechanic (Hobbs area): $35–50/hr — Permian Basin demand is real
Tomorrow morning you're walking through New Mexico Junior College's automotive training program. That is a direct pipeline — NMJC's automotive program leads to ASE certification and employment. It's in Hobbs. You drove past it.
Come with the questions you wrote during today's teardown. The people in that building did what you did today, but for pay.
- Automotive Technician / Mechanic — what you did today, full-time. Path: ASE certification (NMJC gets you there), 2-year program or apprenticeship.
- Small Engine Repair Specialist — marine, outdoor power, generators. High demand in rural NM.
- Oil Field Equipment Mechanic — Permian Basin. Maintain engines on pump jacks, compressors, drilling rigs. Premium pay.
- EV Technician — fastest-growing segment. Dealerships can't hire these fast enough. Different skills from ICE but the diagnostic mindset is identical.
- Mechanical Engineer — designs the engine you took apart. 4-year degree. University of New Mexico, NMSU, NMT.
- Shop Owner / Service Manager — the business side. Every independent shop in Hobbs is owned by someone who started as a tech.
