Friday, June 3, 2011


GrandPaul posted this on one of the Brit Bike forums. I thought I might want to be able to find it again later:

First of all, you really ought to have both a workshop manual AND a parts book on hand before starting in. It helps to open the engine section of the shop manual and read it through while keeping the parts book handy for visual reference of all the parts and fasteners. I typically make a copy of the appropriate section and take it out in the shop on a clipboard; having the total "Kim the CD Man" BritBike library, I can simply look up the proper page and print it out.

In very general terms you should proceed methodically through the dismantling stage with several empty boxes and bins on hand to set the various parts into as you go. There are umpteen ways to categorize your parts, depending on how you intend to process them; perhaps one box for the engine covers to go to polish, one bin for all hardware to be replated or replaced, one box for the bigger bits that will go to the machinist. Some folks like to put all hardware in separate Ziploc bags with the associated bit that it holds on, others use egg cartons; whatever.

TAKE LOTS OF PICTURES AS YOU GO! It helps to remember how it came apart, and what fasteners go where.

First, pull the engine from the chassis "by the book". Some engines require major component removal first, such as carburetor, transmission, etc., before the actual "power unit" can be removed.

It's a good idea to remove the carb(s) first anyway, and set it/them aside for overhaul.

Remove outer engine covers and set aside for refurbishing and/or polishing.

Remove rocker section and/or head, and inspect for obvious valve-related issues such as loose guides and/or any retaining hardware adrift. Proper, accurate measurement of valve stem-to-guide wear, face & seat wear, and head surface flatness is required.

Remove the cylinders & pistons, pushrods, cam followers, etc. Inspect for piston, ring & cylinder condition and wear compared to spec; check cam follower faces for flat spots and any visual damage such as flaking of hardened surfaces or obvious overheating discoloration. Check pushrods for end wear or damage, and general straightness (roll on a glass plate and look for wobble).

Remove alternator stator and draw out electrical wires carefully, inspect for possible interference wear from rotor contact. Remove and inspect alternator rotor, shaft keyway & woodruff key for wear or damage. Check stator studs for damage caused by primary chain looseness.

Remove clutch springs or diaphragm and check for correct free height or deflection. Remove all plates and check for surface wear and engagement tooth integrity. Remove main shaft retainer hardware and draw off remaining clutch subcomponents, inspect grooves for notching and primary system teeth for wear and/or damage.

Typically, you must draw off the primary crankshaft sprocket and clutch basket together, as the primary chain cannot be slipped off in place. Check primary chain for excess wear and/or any damaged rollers. In the case of BSA & Triumph, take care not to lose any of the tiny barrel roller bearings behind the clutch basket; they yearn to be free!

On Triumph & BSA, remove sprocket access door, sprocket retaining nut & sprocket. Inspect sprocket teeth for wear and/or damage. Typically the sprocket teeth will be slightly fish-hooked, often some teeth are chipped, and in extreme cases, there will be virtually no teeth remaining.

Remove ignition trigger system and remove timing side cover; inspect both. Remove oil pump and timing gears, inspect for wear and/or damage to plungers, rotors & gear teeth. Check mating shaft keyways & woodruff keys for wear or damage.

Remove transmission outer cover and check shifter mechanism for excess wear or damage, check kickstart mechanism also. Remove any fasteners required to allow removal of inner cover and further disassembly of transmission, remove inner cover. Draw out gear cluster taking care to photograph the placement of each gear and fork, for ease of re-installation. In the case of Triumph, be sure not to lose the tiny rollers that belong on each shifting fork. Inspect each gear tooth on both sides for wear and/or damage, inspect the shifter camplate grooves & fork teeth also.

Remove all hardware holding the main crankcase halves together including the two screws inside the cylinder spigot opening on Triumph & others.

Carefully split the cases using any handy tips in your shop manual and remove the crankshaft and cam(s). Inspect cam lobes for wear or damage, and measure bushings or bearings for tolerance spec. Remove connecting rods from crankshaft and visually inspect for damage and excessive wear at journals and underneath big end shells on rod & cap.

If you do not have good quality precision measuring tools such as calipers, inside and outside micrometers, etc., you’ll have to rely on a trusted machinist to verify wear tolerance on AT LEAST the following items:

Valves, guides & springs
Head flatness & valve seat wear
Pistons, rings & cylinders
Transmission main shaft run-out, shaft & bushing tolerance
Camshaft lobes & journals, bushing/bearing tolerance
Crankshaft journals
Connecting rod big end roundness & bearing tolerance
Con rod small end condition & bushing tolerance
Crankshaft main bearing tolerance

Typically you’ll need the following parts:
Complete gasket set w/ head gasket & O-rings
Oil seals (all)
Miscellaneous rubber bits such as alternator wiring seal
Carb overhaul kit including Viton-tipped float needle (or replacement carburetion system)
Valves & guides, seals & clips if applicable (may be oversized depending on head bore condition)
Pistons, rings & gudgeon pins with clips (may be oversized depending on cylinder condition)
Alternator rotor key, clutch center key, crankshaft pinion key
Alternator locktab washer, clutch locktab washer, kickstart gear locktab washer, sprocket locktab washer
Primary chain & adjuster slipper (or replacement belt drive system)
Clutch friction plates
Miscellaneous fibre washers not included in gasket set
Drive sprocket (investigate any desired final drive gearing change before ordering)
Ignition points (or replacement ignition system)
Shifter & kickstart rubbers
Transmission bearings & bushings, thrust washers
Camshaft bushings or bearings
Connecting rod big-end bearing set (may be UNDERsized if crank journals are re-ground and/or OVERsized if rods are excessively out-of-round or worn)
Con rod small end bushings (may be oversized if rods are worn)
Con rod bolts and nuts as required (some manufacturers recommend replacement every time)
Crankshaft bolts & nuts as required
Crankshaft sludge tube & sludge trap plug (allen head type are preferred)

Take your time, and HAVE AT IT!

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