October 2012

I first became acquainted with this Bonneville at a BSA club run in October 2010, but it had not required my attention until two years later.

Initially this was to cure a problem with the front disc brake, and ended up involving the replacement of most parts thereof.

Later in 2016 the bike came back for more work. The brief was to give it an oil change and clean the filters, but upon removing the crankcase filter several lumps fell out. Tends to be a little disconcerting. One lump proved to be the head of a bolt from the crankshaft flywheel, which was not too worrying, but another looked to be a piece of cylinder liner, which was.

I stripped the top end and found that the errant bolt head had shot off at great speed and knocked a sizeable lump out of the lower reaches of one cylinder liner. It seemed that an entire strip and rebuild was in order, and as twins are not my forte the lump was handed to our favourite twin builder for his attention, and duly returned looking like a new one.

My engine crane proves invaluable at such times, as it allows easy manoeuvering into the frame when working alone, such that one does not risk damaging the paintwork.

Once the engine is safely installed it is just a matter of putting all the bits back on, but of course this also means all the bits have to be cleaned up, and any repairs to sub-assemblies are carried out at this time.

With reassembly complete there is the first run and attendant tuning required, then a few brief rides and more checking of tensions and clearances. All went well, and a few oil changes were made in quick succession to ensure the best possible filtration had been achieved.

After a brief period of use a problem appeared with the primary chain tensioner. It had been repaired and modified prior to the engine rebuild, but the repair had now failed and it was decided to revert to a standard setup. Fortunately it did not involve more than disassembly of the primary drive, and the process was completely successful.

The bike now has more than 1000 miles since the rebuild and is performing in fine style. Only requirement of late was a brief carb tune as a couple of adjuster screws had failed to remain where they should have.

A very nice example of the T140 in original form.