Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board Restoring (to a point) my '68 BSA Spitfire Mk4

@MarkB mentioned the front stud in the rocker box. That came out with the nut and is in my the bin with those parts. Threads look good (phew!)

I recently ordered hardware from British Tools & Fasteners and thought their prices were fair. They're in Lyons NY so may be pretty local to you.

Alternatively, whenever I order from CBS (site sponsor) I throw some random needed hardware into the order. Free shipping FTW.

There might only be one thread on the bike which is Whitworth or supposed to be (one of the cylinder head studs should be whit in the head and BSF at the nut end). The rest should be BSF or CEI (aka BSCY)

Might sound like I’m being picky but if you buy “Whitworth” bolts which won’t be cheap you’ll be wondering why they don’t fit anything and why the heads are bigger than the shank.

Maybe I need to be educated. I bought Whitworth wrenches and sockets so I had the right tools for the bolt heads and nuts on this bike. I understand that there is also BSF and BSW and those are fine and wide(?) threads. I also understood that Whitworth sizes were measured across the flats of the hex component, rather than shaft diameter. Beyond that, I guess I'm not sure what I'm facing here. :-)

David, sounds as if a bit of thread/fastener education is needed here if you don't mind me saying so.
You can try the internet of course but British Tools and Fasteners are in northern NYS--their website is pretty good and they are helpful.
HTH

You are correct, Whitworth bolts are measured at 1 flat of the hex, however every other bolt in the world is measure from the unthreaded part of the shank, it just so happens that a BS (be it BSF, BSC (british standard coarse) CEI/BSCY) all have a same head size as Whitworth, although you will see on a decent set of spanners that a 1/4W will also say 5/16BS next to the 1/4W stamping. many dont however and it doesn't mean the tools are bad, just they are probably newer tools and the maker hasnt given all the info. By the time the bikes done you'll be selecting the correct spanner blindfolded.

So are Whitworth bolts.


The width of a flat on a Whitworth bolt head is the same as the shank diameter.

BS uses heads one Whitworth size smaller than a Whitworth bolt.

Latest: https://www.youtube.com/watch?v=25VhCyRkQY8

I also order some silencers, clamps and brackets: https://www.armoursltd.co.uk/product/silencer-bsa-a50-a65/

Cool! If you have those down pipes de-chromed you can weld the dents up, snd them back and you’ll never know they were dented. Obviously have them chromed again.


That cylinder head will look sweet vapour blasted also. Keep up the good work!

I set up an elevated work surface in the garage and organized the parts I have off. cleaned up the air cleaners and ordered new filter elements (the foam was falling apart). Should I use new foam around the original cores or is a paper element just fine? I've ordered paper elements and AMAL Concentric rebuild kits from CBS.
I also should have looked at the factory workshop manual I have sooner. Some questions were answered there! I'll definitely work through that in any further work I do.

Paper filters work great unless you are subject to a lot of rain? Soon as they get wet they are ruined. I used to buy K and N TB100 filters, they squash into the pancake housing a little but work great and last a lifetime.

Ready to get the head of next!
https://www.youtube.com/watch?v=S9Au80QbjbU

Nice vid.
Barrel base flange nuts, not unusual to find slack, after a rebuild they take time to settle in , mine need nipping up at 500 and 1000 miles after being disturbed.

Carb bodies, strip bare and soak in vinegar/ coca cola/ rhubarb juice ( whatever is most convenient), to loosen up oxides and crud. Order #78 drills to clean pilot jets.

Head steady , needs to be removed to lift head.

Chrome on cases, worth trying a wire wheel to remove old chrome, you might get lucky.Polish to finish off.

End float, with the sump plate removed and a clock gauge on the crank end ,try prying the flywheel with a tyre iron , right and left, correct endfloat is 1.5 to 3 thousands of an inch.

Carb slides, twistgrip and cables, remove and bag, label slides for right and left.

The lack of percebtible end float is good, a badly worn thrust washer will allow the crank to audibly clunk when push pulled.

Before attempting to remove the inner timing chest make sure the two hidden lower screws are out, and the tacho drive spindle is removed.
Hing in there

Thanks, Gavin. I'll get after some of those things you listed. Got the head off and here's a look:
https://www.youtube.com/watch?v=idOjpie3RIk&list=PLT-TfyGi33jabaHsVdDWFrrAMvz7J9hYP&index=7

And the cylinders are off as well: https://www.youtube.com/watch?v=ZLZ...HsVdDWFrrAMvz7J9hYP&index=9&t=0s

a bit of play in the big ends. I hope the journals are in good shape and I'll just need new bearing shells. I'll find out once I get the crank out!

Great videos!

At +.020” it’s most likely to be its first rebore, pistons are sometimes found like 30 thou. But more commonly they are in 20 thou increments. It looks like you have 9:1’s fitted. They would have originally been 10.5:1 is really what makes the spitfire a spitfire and not a lightning. Poor gasoline won’t help though however if you do find a set of 10.5:1’s then removing the sharp corners of the pistons will eliminate any pinging (also known as radius-ing)

A decent bore gauge is expensive, micrometers would be a better companion you can then compare wear of the pistons if any and then using a feeler gauge get a rough measurement of wear on the bore, more gap front to back then at the sides. Expect to see anything up to about .006” with a feeler gauge. If there’s more then start thinking of a rebore, but if I’m doubt have someone who does this professionally do the check. If they are getting the work for a home or a rebore they may do this for free.

It’s common to fit washers to parts on the bike but after seeing some very good unrestored examples there are a lot of washers lacking from the bikes, whether it be engine or cycle parts, in many cases it helps the nuts from coming loose by biting into the surface, at expense of ruing the finish. If you choose to use washers, I use stainless flat washers. Don’t use spring washers on anything that requires a torque setting. Barrel nuts (for pre70 bikes) at 20-22 ft pound. This is easier done with the motor out of the bike,

Keep up the great work!

Please, wrap the con rods in rags/ bubble wrap. cardboard, anything to stop them rattling off the case mouth. I was wincing.
And plug the open case mouth, when you find stuff in the bottom its good to know if it was there all the time , dont let bits fall in.
Also make sure you cannot turn the motor over with the pistons exposed, they can catch on the case lip studs and break.

Pistons look pretty fresh.

Piston side to side is normal, to free the stuck rings heat the piston crown with a small flame, douse with a wet cloth, repeat until rings pop out.
The wrist pins/ gudgeon pins in the pistons will push free after the outer circlips are removed and the pistons are warmed up.
Big end side to side rock is fairly normal , its up and down that really matters, there is always some side to side.

The motor looks like its done very few miles since its last build up, looking at the carbon.
Head gasket on the drive side looks like it was passing.

i suspect this motor top end was refreshed , then the rebuilder failed to follow up with retorqueing the head and barrel flange as it settled down.

The timing side bore with the stuck rings, has corrosion witness marks, these might clean up with a hone.

before stripping the head pour some alchohol in each port and look for leakage around the respective valves.

A simple valve spring compressor can be made with a G clamp and a ~ two inch piece of tube that is just under the top collar diameter with a cutout to allow access to the keepers.

all you need to estimate bore wear is a piston ring , piston and feeler gauges.
Insert the bare ring , not fitted to piston into the unworn lower bore , use the piston to square it up, measure the ring end gap with the feeler gauges.

Do the same thing with the same ring about one inch down from the top of the bore, this is the point of max wear, the bigger the difference in the ring end gap the more worn the bore. If its about 5 thou or less then I would be happy , more than that you may need better measuring instruments to be sure you need a rebore.

Not in '68. Pistons were the same as Lighting by then. Carbs and bodywork were all that was left of the Spitfire by then.


I do this by feel, as only a wrench fits in most of the nuts. No washers used.



I recently picked this one up from Amazon:
8MILELAKE Valve Spring Compressor Automotive Repair Tool

It's only $18 and is a bit flimsy but you're only doing 4 valves

Great progress.

One weird thing to keep in mind regarding the early 932 carbs: the very early ones had a removable pilot jet screwed into the bottom of the carb bodies. Later ones have a pressed-in pilot bush inside the body. Finally, the new premiere carbs have a removable screwed-in jet accessible outside the bowl.

What's weird is that, after the change to the pressed-in bush, AMAL did not change the threaded hole in the body so it's actually possible to have both in place. If the carb bodies aren't original, it's possible whoever replaced them wasn't aware of the change and moved the jet from the old carbs to the new unnecessarily.

There's also a change in jet holder, needle jet, and needle that took place around '69. I've got a bulletin on that I can dig up if you'd like. When ordering new parts, you'll need to know what you're looking at to ensure you don't mismatch parts.

Lastly, ethanol fuel does a number of fiberglass tanks and will clog up the pilot jet/bush. Get a different tank and/or get it lined by someone who really knows what they're doing. I also recommend the premiere carbs because of the ease in clearing the pilot jet as well as the addition of anodized slides and better floats.

Marc

I was unsure about the pistons for 68’ but thanks for the clarification.

Worth noting that in 68 all Concentrics were 2 stroke carbs. So apart from the pilot jet they also had the wrong needle jet, spray tube, jet holder, and needle. You might also have float bowls without the drain plug. (Just noticed as already pointed out by Marc)

As Mark says the jetting changed by 69’. The above also changed too however the spitfire never received those jetting changes as they stopped production with the 932s mounted to A65’s after 68’. Also if you ordered a brand new set of AMAL’s premier or otherwise, they would come jetted as per 2 stroke spec.

The good news is, if you compare the jetting of the time to the lightning then the only change I remember was using a 107 needle jet. By 69 the Lightning’s leaned off at every point, the 2.5 slide went to a 3, the middle clip position for the needle was now in clip 1 (highest clip position- lowering the needle, but it’s also a different needle than 68 and the main jet went to 180 from 190.

You could order 932’s jetted as per a Lightning but with a 107 needle jet also. That way you can find out what the bike actually wants, plus it will run and pull more cleanly than if it had the 68 jetting still.

After reading the note about the pistons, I compared to the original pistons that came along with the bike (it has a box of curious spares, maybe I'll do a video, going through that!).
I compared the distance from the gudgeon pin to the dome and the shape of the top of the pistons... AFAIK, they seemed to be the same in those respects. I also was going through the owner's manual the other day, specifically looking for how the Spitfires were different from the other bikes and the 32mm carbs were the one thing I found. Where the cams any different?

Cams are the same as A65 L. Big carbs , alloy rims and different fuel tanks are the main
differences between Spitfires and Lightnings. other details like side panel badges and control levers are maybe not so significant.
According to R Bacon only the MKII had 10.5 to one pistons and GP carbs, MKIII and MkIV were 10:1.
All 650 twins had the "Spitfire" cam after 1968.

You are much better off with lower compression pistons taking into consideration current gas quality and less vibes from the engine.
It looks like somebody refreshed a top end, but made some mistakes doing it, not re torquing it and using too fine hone what caused primary side cylinder to get glazed and let oil pass to the combustion chamber. This is why you have so much oil around a head gasket, shiny cylinder on primary side and no carbon on it's piston.
These pistons look to me like original BSA pistons, if this is true they are much better quality than Hepolite and much lighter from current Taiwanese pistons, in short very worth using in your bike if clearances between them and bores are still good.
I hope your top end didn't do too many miles and needs just much rougher hone, new piston rings and that's it.
A big question is quality of the valves / guides and their seats, but I hope those were refreshed as well.
Big and clearances don't look too bad, I'd just change shells to new ones and check them with plastigage.
After cleaning grease trap in a crank it is important to install proper oil filter on a return oil line - this will make your engine much more robust in a long run.

I assume I'm looking for a hone similar to this: https://www.grainger.com/product/WE...Search-_-IDPPLARECS&cm_vc=IDPPLARECS
What is the proper grit to make the proper crosshatch I'd like to see?
I've remove the piston rings carefully. The oil ring for #1 broke but the other 2 seem in good shape. The upper rings on the #2 piston have some corrosion and is likely why they were stuck. Can I clean those up, or just buy a whole set of rings and be done with it?

I wouldn't mess with the old rings. You want a new set of Hastings rings to mate up with the cylinder wall, otherwise you'll chase your tail trying to get a good seal.

The ball hones are ok but getting the crosshatch pattern takes a steady hand. I think you want a coarser grit than what you linked. Mine were done between 150 and 180 grit.

I imagined doing something like what's done on this Jag engine near the beginning of this video: https://www.youtube.com/watch?v=DCU1lWPYlPQ
He seems to get good results.