1952 Triumph Thunderbird 650cc
This of course then became an addiction and I acquired a 1952 650cc Triumph Thunderbird which looked complete, but in fact the guy I bought it from had obviously dismantled the engine, discovered problems and reassembled with only one piston and con rod.
I magnamiously decided no point in challenging him, and subsequently completed a full and total dismantling and began a rebuild.
HISTORY OF DEFECTS ENCOUNTERED DURING RESTORATION of TRIUMPH THUNDERBIRD
It is of interest to highlight the issues that I encountered during the rebuild, and these are addressed in no particular order below;
Upon dismantling I found the cup was jammed in the pressure tube body, I elected to replace both components, it is important to ensure that assembled forks are of identical length overall.
It was a challenge compressing the spring on reassembly, I made a compression jig to allow cap nut to be fitted. See photos below;
Frame was undercoated then final enamel coat applied
TELESCOPIC FORKS REPLACEMENT TO FRAME
This is where my jig to compress springs was invaluable, refilled forks with oil (125mm) difficult to start cap nut with fine thread, established best method was with a 38mm socket, now on to wheel replacement.
I found with current bike stands very unstable decided to place lifting lugs in workshop ceiling and tie off much more stable and safe.
Modified as below which allows for unimpeded access
Section of rear guard installed together with bike stand needed to make a jig to expand spring;
Upon dismantling it was obvious that the gear operating quadrant was worn, a replacement was purchased, and installed after all gears were checked
With gearbox installed in frame I was not happy with gear selection and decided to dismantle again I established that there were no rollers for the gear control cam plate will try to source.
Sourced another gear box as I was not happy withe gear selector plate. Dismantled and decided to use the gear selector plate from the second gear box
Assembled OK requires a degree of dexterity
No problem with special tools replaced one plate
To separate the gear box from the fixed frame, I experienced great difficulty in removing the Clutch Hub, during the attempt I mangled the special tool, mangled home made puller, used lots of gas to heat and in desperation eventually cut clutch hub with grinder, I was able to purchase a replacement.
With the gearbox and clutch separated, you are able to remove the primary chain case cover, which then allows easy access to engine, the cylinder head was removed and to my horror it exposed the damaged cylinder block, I was able to source another block
Union Jack motorcycles who specialises in Triumph’s. was a very good source for all of the replacement of damaged components
Difficulty was experienced in sourcing another con-rod, but eventually located Crankshaft Rebuilds Blackburn Victoria, who replaced both con rods with a generic type and fitted slipper bearings instead of white metal.
Crankshaft was rebalanced with crankshaft journals machined and cylinder bores honed a first class job and very helpful.
Important to mark con rod and crankshaft to ensure con rod matches crankshaft journal.
The modifications from white metal to fitting of slipper bearings on the crankshaft journals resulted in the final dimensions as follows;
Original specification for 6T
Big End 1.4360 inches
Modified 1.408 inches
Con Rod internal diameter with slipper bearings 1.409 inches
Gudgeon pin hole 0.688 inches
Gudgeon pin 0.687 inches
Bore Diameter 2.7953 in ches
Modified 2.806 inches
Purchased Pistons 2.803 inches
Removed old crank shaft bearings with hydraulic press replaced with the following
KSM bearings made by Minamiguchi Seiko Co Ltd
RMS8-2RS ball bearing OD 2.5 inches ID 1 inch width 3/4 inch
RMS9-2Rs ball bearing OD 213/16 inch ID 11/8 inch width 13/16 inch
There are three issues that have not been raised before;
- Crankcase scavenger pipe damaged with a section missing
- Crankcase oil filter and plate missing
- Crankcase breather valve missing which is incorporated in inlet camshaft.
See photo of damaged crankcase scavenger pipe 8mm diameter steel which has been severely damaged with the bottom section missing. Experiencing difficulty sourcing replacement.
Needs to be formed to fit crankcase filter.
Whilst searching for these components which are difficult to source I made a bracket to assist in engine reassembly
Finally located engine scavenger pipe and crankshaft breather valve and can start assembly.
As a matter of interest I was able to locate two but in one case had to take half a crankcase which is available to anyone
Commenced reassembly crankshaft breather fits in the inlet camshaft
Attached mounting plates for frame
Timing of Engine and Magneto
The timing and replacement of the camshaft and crankcase breather requires a complete understanding of the four stroke cycle, also it is necessary to have the correct tools for reinstalling timing gears
The photos below show the engine with timing gears in place also assembled valve tappets assembly
Purchased triumph valve tappet spanner as it is difficult to access nuts for adjustment customised ring spanner to facilitate easier access.
All complete all I need is assistance to place in frame
With help from my son engine is now in frame
Moved bike to elevating work stand which will be much easier when motor is being installed
With engine in place commenced re assembly of clutch no problems see photos
With the removal of the voltage regulator, dynamo and magnet,o inspection revealed it would be necessary to refurbish all of these components. A search of the web located Antique Auto Electrics Kangaroo Flat Bendigo, who were very obliging and professional.
Magneto was rewound, poles re-magnetised, cleaned, fitted new brushes and bench tested. Dynamo had the common armature skimmed undercut and polished.
Regulator was refurbished and then bench tested with dynamo.
Was able to source an original cloth wiring loom, now the hard part begins will require small delicate fingers; installed instruments and horn. Decided rather than have wiring loom hanging loose will proceed with installation of gearbox and defer wiring until all components are in place.
Started the wiring of nacelle but prior to that drew a wiring diagram which has enabled the wiring to proceed see diagram and the slow progress
Completed wiring was able to locate a cloth wiring loom lots of patience required to action as per diagram
With wiring complete it is now possible to replace tank, first the tank was dressed see finished product
Then controls were fitted, battery holder, seat, oil reservoir, carburettor and new hosing
All that is remaining is control for air mixture on AMAL carburettor, repaired exhaust’s and lock for toolbox this proved difficult but located a Dzus lock as it is called the USA
However I have taken photos with bike at this stage
Replaced throttle and choke cables
All I am waiting on now is returned of exhaust system and choke lever from chrome plater
Exhausts received and installed.
Started bike OK but trouble with oil relief valve we believed purchased new replacement also changed oil pump,
problem still exists with pressure indicator showing no pressure
Examination revealed that crankshaft bush on timing gear casing worn to such extent 20 thous
Had timing gear casing machined to accommodate a modified seal see photo
Timing chain cover replaced after timing, ensured that crank case breather connected to oil tank
Kicked over and started runs well