Crankshaft Thrust Washers, Bearing Shells and Liners — End Float and Undersizes

Crankshaft thrust washers are the only thing stopping the crank moving lengthways in the block, and they are the part most often overlooked in a rebuild. They are supplied in standard and oversize thicknesses precisely because that end float has to be set, not assumed. Get it wrong and the symptoms are dramatic: on a manual vehicle the crank walks every time the clutch is pressed, and the damage runs through the thrust faces into the block. This article covers thrust washers, main and camshaft bearings, how end float is measured and set, and how undersize shells are numbered.

Crankshaft thrust washer သည် crank ကို ရှေ့နောက် မရွေ့စေရန် ထိန်းသည်။ End float ကို တိုင်းတာ၍ သတ်မှတ်ရမည် — ခန့်မှန်း၍ မရပါ။

1. What Thrust Washers Do and Why They Fail
Thrust Washer ၏ လုပ်ဆောင်ချက်နှင့် ပျက်စီးရခြင်း

A crankshaft is pushed forwards every time the clutch is released and rearwards on a torque converter under load. Two thrust washers, usually at the centre main, take that force. They are thin and they run on a small area, so anything that removes their oil film wears them quickly.

• Riding the clutch. Continuous pressure loads the thrust face constantly — the most common cause on a manual vehicle.
• Holding the vehicle on the clutch on a hill instead of using the brake.
• Low oil pressure or dirty oil, which removes the film the washer depends on.
• A dragging or misaligned clutch release that keeps load on the crank.
• Wrong end float at assembly, which either binds or lets the crank hammer.
• A failed torque converter on an automatic, ballooning under pressure and pushing the crank forward.

2. Measuring and Setting End Float
End Float တိုင်းတာခြင်း

• Use a dial gauge on the crank nose, and lever the crank fully one way, zero the gauge, then lever it fully the other way.
• A feeler gauge at the thrust face is the alternative where a dial gauge cannot be fitted.
• Typical figures sit in the region of 0.05–0.30 mm, but the engine specification is the only figure that counts — do not work from a general range.
• Too little float binds the crank as the engine warms and expands.
• Too much float lets the crank hammer the washers and quickly destroys them.
• Measure with the main bearing caps torqued to final specification, not finger tight.

Dial gauge ဖြင့် တိုင်းပါ။ အင်ဂျင်အလိုက် သတ်မှတ်ချက်ကိုသာ လိုက်နာပါ — ယေဘုယျ ကိန်းဂဏန်း မသုံးပါနှင့်။

3. Standard and Oversize Thrust Washers
Standard နှင့် Oversize Thrust Washer

Order thrust washers after the crank has been inspected and machined, never before. The thickness needed depends on what the machine shop found.

4. Main and Big End Shells — How Undersizes Are Numbered
Shell Undersize နံပါတ်များ

When a crankshaft journal is reground it becomes smaller, so the shell must become thicker to keep the same oil clearance. Undersize is quoted as the amount removed from the journal.

5. Camshaft Bearings and Cylinder Liners
Camshaft Bearing နှင့် Cylinder Liner

• Camshaft bearings are fitted with a purpose-made driver, aligned so the oil holes line up exactly. A bearing fitted a few degrees out blocks the feed and destroys the cam.
• Check camshaft end float as well — it is set by a thrust plate on most overhead-valve engines.
• Cylinder liners come as dry or wet types. A wet liner is sealed against coolant by O-rings at its base and its protrusion above the deck must be measured and set with shims.
• Liner protrusion is critical. Too little and the head gasket will not clamp the liner; too much and the liner is crushed. Measure every liner.
• Dry liners are an interference fit and are pressed in, then bored and honed to final size in place.
• Never mix used liners between bores. Each one has bedded into its own position.

Wet liner ၏ အမြင့် (protrusion) ကို တိုင်းတာ၍ shim ဖြင့် ချိန်ပါ။ Camshaft bearing ၏ ဆီပေါက် တည့်နေရမည်။

6. Fitting — Cleanliness Decides the Outcome
တပ်ဆင်ခြင်း — သန့်ရှင်းမှုက အဓိက

• A rebuilt engine fails on dirt more often than on parts. Wash the block with hot soapy water and brushes, then dry and oil it immediately.
• Clean every oil gallery with a rifle brush, including the plugged ends.
• Fit shells dry into clean housings — oil behind a shell stops it seating and transferring heat. Oil the running face only.
• Do not file or scrape a shell to adjust clearance. Measure with plastigauge and select the correct size.
• Check the thrust washer oil grooves face the crank — fitted backwards, they carry no oil at all.
• Torque main caps in sequence and in stages, then turn the crank by hand and confirm it is free before going further.

Block ကို ရေနွေးနှင့် သန့်ရှင်းပါ။ Shell နောက်ကွယ်တွင် ဆီ မလိမ်းပါနှင့်။ Thrust washer ၏ ဆီကြောင်းများ crank ဘက် လှည့်ရမည်။

7. How to Order from Win Auto Parts
Win Auto Parts မှ မှာယူနည်း

Win Auto Parts stocks crankshaft thrust washer sets, main and big end shells, camshaft bearings and cylinder liners for the engines common in Myanmar.

• Call 09 5105768 with the engine code and the machine shop figures.
• For shells, give the undersize the crank was ground to. For thrust washers, give the measured end float.
• Order after machining, not before — the sizes depend on what was found.
• Or email support@winautoparts.com with the machine shop report.
• Or browse the engine range at winautoparts.com.

Engine code နှင့် စက်ရုံမှ တိုင်းတာချက်များဖြင့် 09 5105768 သို့ ဆက်သွယ်ပါ။ စက်ဖြင့် ပြင်ဆင်ပြီးမှ မှာယူပါ။

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ဆက်စပ်ဆောင်းပါးများ

• Pistons and Piston Pins — Sizing, Pin Types and Fitting
• Head Gaskets and Engine Gasket Sets — Grades, Bolts and Fitting
• Measuring the Bore and Choosing Oversize Rings
• Fitting a Bearing Without Damaging It
• Why Bearings Fail — Diagnosis Guide