Crankshaft Remeza LB75 — Part No. R 21131007

Remeza LB75 Compressor: Technical Profile

The LB75 is a two-cylinder industrial Remeza compressor with belt drive for continuous production use. Crankshaft R 21131007 is engineered for the loads of this configuration — two crankpins for two cylinders, synchronising intake and discharge strokes.

The Role of the Crankshaft in LB75 Operation

The crankshaft is the foundation of the two-cylinder crank mechanism. Its functions:

1. Receives torque from the V-belt drive pulley
2. Converts rotation into reciprocating piston motion via the connecting rods
3. Synchronises the strokes of both cylinders — typically offset by 180° for even loading
4. Runs on main bearings in the crankcase, which carry the radial loads

With correct lubrication, crankshaft service life matches that of the whole compressor. Premature failure always has a specific operational cause.

Technical Specifications of Crankshaft R 21131007

💡 Before ordering: cross-reference part R 21131007 against your LB75 compressor serial number. Different production series may have constructive differences. Confirm with an Acvatron SRL engineer: +373 22 503-580.

Causes of LB75 Crankshaft Wear

Oil starvation Insufficient oil level or overdue oil changes — the primary cause of crankpin and main journal seizure. Seizure is irreversible: the crankshaft must be replaced.

Hydraulic shock Liquid in a cylinder (condensate from failed drain, oil from overfilled crankcase) causes sudden impact load on the connecting rod. Journal cracking or fracture is possible.

Fatigue wear under overload Running at 100% load without pauses or above rated pressure accumulates fatigue cracks in the shaft body.

Abrasive wear Oil contamination with metal swarf or dust (failed filtration) destroys journal and bearing surfaces.

Pulley imbalance Drive pulley imbalance creates alternating loads on the main journals and accelerates their wear.

Loose connecting rod cap bolts Under-torqued con-rod cap bolts lead to bearing shell rotation and journal seizure under vibration.

Signs of Crankshaft Failure: Pre-Disassembly Diagnosis

• Metallic knock in the crankcase, varying with speed — bearing wear or shell rotation
• Excessive vibration with correctly tensioned belts
• Oil pressure drop at normal oil level — journal clearances exceed tolerance
• Metal swarf in the oil at drain — journal surface seizure
• Visible cracks on the shaft body during visual inspection after crankcase removal

⚠️ Critical: crankcase knock is a signal for immediate shutdown. Continued operation leads to connecting rod failure, crankcase fracture, and total unit loss.

Crankshaft Replacement Procedure for Remeza LB75

1. Preparation

Isolate the compressor from power, bleed pressure to zero, drain all oil. Confirm the unit has cooled.

2. Remove the drive pulley and belts

Remove the V-belts, undo the pulley nut, extract the pulley using a puller — no hammering.

3. Disassemble the compressor block

Remove the cylinder heads, valve blocks, and cylinders. Extract the pistons with connecting rods.

4. Remove the crankcase cover and crankshaft

Undo the crankcase cover, extract crankshaft R 21131007. Inspect the main bearing housings.

5. Inspection

Measure journal diameters with a micrometer. If seizure, out-of-round, or dimensions outside tolerance — replacement is mandatory.

6. Install the new crankshaft

Fit new main bearing shells, lubricate journals with fresh oil, install the crankshaft. Bearing cap torque — per Remeza documentation.

7. Reassembly and run-in

Reassemble with new gaskets. Fill with fresh compressor oil. First 30 minutes unloaded — monitor oil pressure and head temperature.

Associated Parts for LB75 Major Overhaul

Replacing the crankshaft without simultaneously replacing the bearing shells is a mistake. A new shaft with worn shells will knock again within 200–300 hours.

Check availability: +373 22 503-580.

Genuine vs Alternative: Why R 21131007 Matters

Expert Opinion

“The LB75 is a popular workhorse in small workshops and car service centres. When the crankshaft comes in, the cause is almost always the same — oil starvation: either the level wasn’t checked, or the oil wasn’t changed for years. The first thing I do in an LB75 overhaul is flush the oil passages of the crankshaft and crankcase — there’s often sludge that will destroy the new shaft immediately. Second — I always replace all the bearing shells, even if they look fine visually: with a new shaft at 0.02–0.04 mm tolerance, a worn shell at 0.06 mm will knock on a cold start. Third — find and fix the cause: fit an oil level alarm, set up timely oil changes by the hour meter.”

Vitaly Boluchevsky, Chief Engineer at Acvatron SRL, 15 years in the industry

FAQ

❓ What is the difference between crankshaft R 21131007 (LB75) and R 21131009 (LT100)? R 21131007 is for the two-cylinder LB75 (5.5 kW, ≈480 l/min) and has 2 crankpins. R 21131009 is for the three-cylinder LT100 (7.5 kW, ≈650 l/min) and has 3 crankpins. The parts are completely different in geometry and are not interchangeable.

❓ Is R 21131007 compatible with Remeza LB50 or LB40? No. Part R 21131007 is listed in the catalogue for the LB75 specifically. The LB50 and LB40 use crankshafts with different geometry and different part numbers. Confirm against your serial number with an Acvatron SRL engineer.

❓ Can the crankshaft be reground rather than replaced? For minor wear (up to 0.05–0.08 mm) without seizure or cracks, and where undersize shells are available — yes. For the LB75 in Moldovan conditions, fitting a new genuine R 21131007 is generally more practical: the cost of regrinding plus shipping is comparable to the price of a new part, and a reground shaft has a shorter service life.

❓ What should be checked before installing the new crankshaft? Mandatory: measure the main bearing housings in the crankcase; check the crankcase for cracks; blow out the oil passages; confirm no metal swarf remains in the oil lines.