1955 BSA A10 engine build

Went to watch those crazy beggars riding the wall of death when I was at the Rhinebeck N.Y. show/ swap meet a few years back....Side saddle - no hands on an old Indian Scout, swooping up and down the wall, while grabbing dollar bills out of peoples hands. Sometimes two people riding in the 'tub' at the same time. Incredible riding skills and a total disregard for ones life! You won't see me warming anything up in one of those!

Much more shiny than when you started. I was just wondering about a few things that I did not see in the thread above. First I was wondering what your valve-stem to guide clearance was, and second I was wondering what the clearance was between the timing-side crankshaft main journal and the timing-side main-bearing bushing?

Also were the valve-springs new or used, and if used what specification lets you know a good used valve from a bad one?

Thanks for your valuable time.

Lets see now...valve to guide clearance was actually a little tight...Nicholson's recommends 0.004" on new cast iron guides as they tend to tighten up with use and can result in the valve getting stuck in the guide (I know this for a fact from personal experience...twice). Now I have to admit that seems a little sloppy to me, I have found that if re-using cast iron guides that have been through several heat cycles, a clearance of 0.002" suits just fine and that is what I reamed these guides to. If you are using Phosphor Bronze guides, you can ream them to 0.002" right from new and be just fine. I think I mentioned in a previous post that the timing side main bearing clearance was found to be 0.002"...in the past I have set them closer, but after having a newly built A50 nip up on the owner (He had been riding it around for three weeks with no problems, but after idling in his driveway for 20 minutes, it nipped up...duhhh!), I like to have the extra thousandth clearance. I set the thrust clearance at 0.003". The valve springs are the original used ones, they weren't rusty and all were equal lengths...I've put dozens and dozens of these old Brits back on the road over the past 40 years or so and never had any problem reusing valve springs as long as they are rust free (rusty springs can break). Valves themselves...I look for pitting on the sealing face, wear on the stem where the rocker adjuster contacts it, malformation such as tuliping, good seating for the collets and worn/ scuffed valve stems. If they are worn, or cannot be reground to a smooth sealing face they get tossed into the junk bin. If the seats are pitted, they get a three angle re-cut, then valves and seats get lapped and checked with machinist's bluing to check for proper contact.

Today's progress, the transmission found to be in amazingly good condition...after being gutted and cleaned:

...And there is the transmission all back together. Shifting smoothly and no internal parts required replacement...this has got to be the least expensive engine/ drive train job I have ever done. The transmission sprocket was found to be almost as sharp as a circular saw blade and so a replacement is on the way, along with a new seal...the old one is still a snug fit on the sprocket, but the rubber has gone so hard that it would be foolish to consider reusing it. There is also a new kick lever on the way...the chrome is totally shot on this one, however I'll recommend he keep it as it would be perfect for a military restoration project.
So, that's about it for this thread. I have been helping him here and there on this restoration, last year I rebuilt the forks, replaced the rims and laced the front and rear wheels. As soon as he has the frame and tinware panted, I have a funny feeling that I will be helping him do the final assembly of the machine, if so I will continue the tale under the restoration section. Thanks for the encouragement along the way.

Bruce

I've done a couple of A50/A65 motors over the years.
Have a couple of early 50's A10 for crazy long time, they are still in storage (early ones were 'semi-unit' transmission bolted to crankcase)
You have service and parts manuals?

I restored an early plunger frame model last year.
PM sent.

Is that mag a K2F manual advance? It looks very similar to my mag, except for the HT lead pick up being at a 45* angle instead of a 90*. I converted mine to electronic ignition with a Thorspark and has been running great with that.

It's a K2F with auto advance. Has a vicious spark...works too good to consider switching to EI.

If I ever get around to doing my A10 I'm going to do the SRM end oil feed conversion. I think they still have the drawings for it on website?
Used to call in when they were in Penarth but when they moved to Aberyswyth it was a it too far to go (around 110 miles each way)

Due to neglect combined with shit and abuse that younger people tended to put these engines through way back when, the TS bushing has gotten a bad rap...as a result people tend to be a little shy about them. Its a very interesting conversion and has a proven track record (literally), but the std bushings will last a very, very long while with regular oil changes and 'normal' running...now on the other hand, if you plan on challenging any sort of LSR or hunting down and punishing Nortons at the local dragstrip, it would be well worth the cost.

I would DIY it.
Small amount of welding inside timing cover I would have to farm out but I can do all the machining.
The plunger A10 motors had smaller journals IIRC so that wouldn't be a good motor for LSR ;D

I like to do my own machining too, in fact I sometimes wonder how someone can manage do this sort of work without having access to some basic machine tools...but they do.
You really ought to drag the old A10 out of mothballs and get it on the road, they really are a very pleasant machine to ride, very smooth running (for a Brit twin) and they pull like a Massey Ferguson tractor...plus when properly sorted/ maintained they are quite reliable.

I really should restore it, some of the chrome parts were re-plated in the early 1970's (my father worked at a chrome plant at that time)
He gave it to me sometime in late 80's but I always had a bunch of bikes to work on or fix up.so it kept moving further and further back in shed (40'x25' two story)

Back to motor porn ;D

goldy said:

It's a K2F with auto advance. Has a vicious spark...works too good to consider switching to EI.

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My mag was burnt up and only firing on 1 cylinder. It was easier and more productive to convert mine to EI.

Tune-A-Fish said:

Back to motor porn ;D

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Dammit man, don't post that when I am at work. Going to have to find a quite spot to sit down now.

Grab a rag...some porn for you Brodie. Highjacking my own tread...I know.
This is what I'm working on now...

Bet that went BANG!

From one extreme to another...the A10 engine may have been the least expensive engine job I have ever done, but after ordering a shit load of parts this morning, this one may wind up to be the most expensive...although it may not hold that title for long, as there is another Norton engine waiting in the wings that is even worse off than this one.