You can hear the starter motor turning the engine over, but there's no pop, no fire, nothing. This is the most reported issue on the V8 Pro's first start — and it's almost never the CDI. Check these first.

• Battery first: measure the voltage at the terminals while pressing the start button. It needs to stay above 11.5V while cranking — not just at rest. A battery showing 12V on the shelf can drop significantly under load, which is often enough to prevent a reliable spark.
• CDI ground wire: must connect to bare unpainted metal on the engine block. One customer had the same "no spark" issue four times — the wire was on an anodized surface the whole time.
• Hall sensor LED: slowly rotate the flywheel by hand and watch the LED. It should flash exactly 4 times per full rotation. If it stays solid and doesn't flash, that channel has failed.
• Quick CDI test: hold the main HV output wire 3–5mm from bare engine metal. Briefly touch the sensor wires together with tweezers. A visible spark = CDI is working fine. No spark = CDI may be faulty.

The indicator light flashes, the distributor produces high voltage, but when you check the plugs individually — nothing. The spark is being lost somewhere between the distributor and the cylinders.

• Firing order must be exactly 1 – 8 – 4 – 3 – 6 – 5 – 7 – 2. A single swapped wire throws the whole sequence off — the engine won't fire even if every other part is correct.
• The blue dot hole on the distributor rotor must line up with the black hole on the housing. If these are even slightly off, no cylinder gets spark at the right moment.
• Cut a short piece of clear silicone hose and use it to connect cylinder 1's distributor wire to its plug directly. Watch for a spark when you crank. If it sparks, the distributor is fine — go wire by wire on the others. If it doesn't spark, inspect the distributor cap contacts for carbon build-up or burns.

This one comes up regularly: the V8 Pro fires up, runs for a few seconds, then dies — and from that point on there's no spark no matter what you do. The Hall sensor indicator stays lit solid instead of flashing.

• When the Hall LED goes from flashing to constantly lit while the engine is running, the Hall sensor has failed mid-run. This cuts the ignition trigger signal and the engine stops firing immediately.
• Check the purple / indicator LED behaviour: it should always be flashing when the engine is running or when the flywheel is turning. A solid light = sensor failure.
• Before replacing the Hall sensor, rule out the battery — a voltage drop during running can also cause sudden spark loss. Monitor battery voltage while cranking; if it drops below 11V, the sensor may be fine and the battery is the problem.
• If the sensor has truly failed, contact Stirlingkit with your order number and a photo of the LED behaviour — we can confirm and get a replacement out quickly.

"The engine runs perfectly but there's blue smoke and oil spraying from the exhaust manifold" — this is one of the most common V8 Pro reports after first start. Usually the drip oiler rate is set too high, or the push rod / rocker lubrication is getting into the cylinders.

• Some blue smoke on the very first few runs is completely normal — oil residue from assembly burning off. If it clears after 1–2 tanks, no action needed.
• If blue smoke and oil spray persist after break-in, the oil supply rate is too high. Close down the drip rate adjustment and recheck after the next tank.
• Valve stem seals (new on the V8 Pro): if a seal wasn't clicked in fully during assembly, it can fall into the head and let oil past the valve guide. This causes heavy blue smoke from a specific cylinder. Removing the rocker cover on that side and inspecting the seals is the quickest diagnosis.
• Black smoke (not blue) means the fuel mixture is too rich — turn the main needle clockwise in 10° steps until the exhaust sounds clean.

If the engine sounds harsh and metallic, warms up quickly at idle, or loses power when you open the throttle — the fuel mixture likely needs to be a little richer. A simple needle adjustment usually sorts this out.

• Turn the main fuel needle counterclockwise in 10° steps. The sound should get smoother and deeper. Stop when the exhaust note is strong and even.
• Check the carburetor needle valve isn't fully closed or blocked — no needle adjustment will help if fuel can't enter the carb at all.
• Run your finger around the intake manifold base while the engine idles. An air leak here affects the mixture regardless of needle position — a change in idle tone when you press on a joint is a sign of a leak worth sealing.

• Idle speed screw on the carb: clockwise = faster, counterclockwise = slower. Small turns only — let it settle for a few seconds between each adjustment.
• If the screw doesn't help, the needle settings need fine-tuning. Altitude, temperature, and fuel brand all affect the right position — if you've moved locations or changed fuel, start from the baseline (main: 2.0 turns, auxiliary: 0.5 turns CCW) and work from there.
• Consistently lumpy idle: check valve clearance — 0.1mm. Too tight and the valves never fully seat, causing uneven compression and a rough, choppy idle sound.
• "One side of the V8 sounds rougher" — the two cylinder banks often need to be balanced separately. This is normal for a V8 configuration and takes some patience to dial in.

When you rotate the flywheel by hand on the V8 Pro, you should feel clear resistance as each piston compresses. If it spins freely with almost no push-back, compression is missing.

• On a new engine, low compression on the first few attempts is normal — give it 3–5 short start attempts before diagnosing a fault.
• Press each valve spring tip with a finger. If it doesn't return firmly, the spring has weakened or something is holding the valve open.
• Valve clearance must be 0.1mm. Too tight = valve can't fully close = compression escapes.
• After any disassembly, re-verify camshaft timing: D-axis flat face pointing straight up, exhaust valve of cylinder 1 just closing.

• Air in the fuel line: prime properly before starting — open throttle, block intake, rotate flywheel 3–5 times. Check for bubbles in the line.
• Overheating: confirm coolant is present and the vent is open. A closed vent causes pressure build-up and rapid overheating.
• Hall sensor: if the Hall LED goes from flashing to constantly lit while running, the sensor has failed mid-run. It should always flash, never be solid.
• Fuel starvation: check the fuel valve is fully open and the line isn't kinked.

Coolant seeping from the base of a cylinder means the bottom O-ring has failed — most often from pushing the throttle hard before break-in is complete.

• Remove the liner (push gently from below with a non-metallic tool).
• Replace the bottom O-ring (22×1mm OD). Upgrade to FKM fluorine rubber for a longer-lasting fix.
• Apply a bead of silicone sealant to the bottom groove before reinserting as extra protection.
• Clean the bore with WD-40 before reassembling — cast iron piston rings must be kept clean.

Almost always an assembly issue rather than a defective part.

• Add a clamp or zip tie to every hose joint — if you can pull the hose off with two fingers, it needs securing.
• Re-seat the intake manifold seal strip with quick-dry glue in the groove positions.
• The brass fitting needs thread sealant — remove, apply, reinstall if it's weeping.
• Check the coolant vent is open. A blocked vent pressurises the whole circuit.