Really battered 66 thunderbolt rebuild.

[Bigmac]

Have a really battered Thunderbolt looks like its been kept out in the rain for many years will try my best to bring the old girl back to life.

Few questions for the group appreciate any help or advice

1. Oil leaks I know these bikes have a habit of leaking oil are there any resources on how to prevent this?

2. Disc brake conversion? Had a bad crash on a CBR a few years ago would prefer to avoid repetition of that.

3. Any other general performance and maintenance tips for the rebuild would be really appreciated, my first time in one of these engines looks simple enough, but I heard they are full of "character"

Trying to avoid high costs, the missus still thinks I plan to sell it.

[DAVE BRADY]

Hello Bigmac,

Welcome to BSA ownership and the Forum. 
1) They do not have to leak.  2) Brake improvements are possible.  3) Lots of tips but the full answers to your questions would take a very long time to complete so I would suggest that you get a workshop manual and a parts book.  Study them.  Then look on youtube were you will find some very good A65 rebuild videos.  Watch all of them.
Then have good look at what you have and what needs doing.  Any specific problems can be addressed on this Forum and better still join the BSAOC and attend your nearest Branch for more personal and hands on assistance if needed.
Please post some photos of what you have.  This will help with any replies to your questions and good luck with your project.

Dave.

[Bigmac]

Thanks Dave

I have the manual and have watched plenty of videos (especially the four part SRM A65 rebuild) but these are the main items I couldn't find anything about. Especially the oil and brakes.

[DAVE BRADY]

Hi Bigmac,

1) I suppose that the main thing to reduce/prevent leaks is good and very clean joint faces.  Flat and without gouges to help get a good seal.  Good quality gaskets and a sealant.  I prefer Hylomar on one side of the gasket and high melting point grease rubbed into the other side.  This means that if necessary the joint can be undone and the gasket stays in tact.  If the engine is good there should be nothing more than a bit of mist out of the engine breather but some prefer to fit a tube to take this to the rear chain or to the back of the bike.  Obviously all seals are replaced during a rebuild but on the main gearbox bearing use a sealed bearing with the one seal removed and the open side fitted towards the gears.  This with a new seal keeps the oil in. 
Care when fitting the head and correct torquing after cleaning the threads will help eliminate any weeps from the head gasket especially at the front where the rocker box oil drain holes are.  'O' rings can be fitted in the holes in the gasket to help with sealing.

2) What brake does your bike have?  The half width hub can be quite good if set up properly and new linings can be fitted and machines to fit the drum.  The later TLS brake is very good but may need a bit of modification to the forks.  Other options would mean moving away from BSA parts ie Triumph or Japanese front end.

3)Too much to cover here but I have watched the youtube rebuilds by Angus Campbell and Paul Henshaw and find them to be quite comprehensive.  The main thing is to take your time and re-check every thing.  Try to find the best parts possible from the likes of SRM.  Ask questions as you go.  No matter how simple they may seem ask as all the answers will be useful.

They certainly do have character and each rebuild results in a different bike to some extent and in terms of performance, unless you want something special, stick to standard but build it well.  Run it in properly and it will last for ever.

Dave.

[berniej]

Read this while thinking about my current A50 rebuild and oil leaks.

On two previous bikes (A65 and A50) I've had oil leak problems at the flat union where the flow and return pipe assembly is joined to the crankcase. The design of this never seemd that brilliant to me and I was wondering if it would be a fairly simple matter to tap the casing and fit threaded unions that would then connect direct to the flexible hoses?

Not sure if there's enough meat in the casings or clearance to the frame though.

Cheers,
Bernie

[DAVE BRADY]

Hi Bernie,

This can be a problematic joint.  On both of my A65s there always seems to be a film of oil here but no specific leak.  As you say there is not much room for threaded fittings.  All I can suggest is always renew the 'O' rings and ensure that the oil pipes run slack to prevent any push/pull on the union.   

Dave.

[Bigmac]

Thanks Dave some brilliant tips very useful appreciate it. Never heard of hylomar but will check it out.

  Right now only have an original rear wheel with the drum brake so for the front am totally open to options as I have to buy a wheel anyway. I heard the disc and drum works well? Maybe worth getting a later model wheel off a rocket or something?

[DAVE BRADY]

Hi,

Hylomar was developed by Rolls Royce so it must be good.  If you get the Aero Hylomar that is better but a bit more expensive.  As you need a complete front end the TLS one from the late '60s would be a good option and I would say a good as a disc when set up properly. For a disc front end you would be looking at Triumph as BSA never fitted a disc as standard even to the powerful and heavy Rocket 3.

Dave.

[Bigmac]

Thanks again Dave, your amazing, guess I had better get on ebay and order up!

Bernie - let us know if you get the oil leak fixed, maybe some learnings for me to take into account on my end, I have lot of scrubbing, rebalancing and cleaning before I get to the point of putting the cases back on

[Dibble]

Hi Bigmac-it wasn't long ago i was in a familiar situation embarking on the long road of restoration. I took on a 67 Hornet which found its way back home from the States in a thousand pieces,or thereabouts! Daunting to say the least. The advice you've had sofar is spot on. That's exactly what I've come to expect on this forum and indeed the bsaoc too. Your in good hands so enjoy your project and fear not your not on your own!  Dave

[chaz]

My recent completion of a Triumph T100 bobber used TLS front set up, but the forks were T140 with single disc bracket on left side. I could have cut the bracket off but decided to keep it incase I decided to retro fit a hydraulic brake instead. an option but as wheels were good left standard apart from the TLS which was half way house.