Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board Firebird Scrambler - Working to finish up

Looked back at my old messages and it's been a damned YEAR since I last made progress on putting the top end back on this bike. It needs to be up and running for the TSMR, and time's flying.

In the meantime, I did install a new Indian-made rear fender (seems to be good metal and chrome, proper rolled edges, had to "mill" some of the mounting holes to make it all line up but that might be a combination of the fender and the bike), a chainguard that I bought years ago from Alex, and a few other bits and pieces.

Now I'm working with a brand new set of .020" over pistons and rings and a swap-meet cylinder that's been bored and honed and measures .020" over.

The ring gaps are .011", which is in the .008 - .012" range for new rings in the book. The new wrist pins are a proper heat-piston-to-fit clearance in the pistons, and a play-free slide fit in the conrods. I'm measuring-twice-cutting-once on the piston-to-bore clearance. The pistons are, of course, oval, to allow for differential expansion across the small-end bosses. I measured bores and pistons and calculated tonight till I got buggy-eyed, so I'm going to hold off until tomorrow before fitting everything - want to make sure I don't seize the thing up.

Sent off several cables from this bike and my C15S project to Barnett, including the levers that I'm using, so that they can make up matching ones. Going back and reading up on what kind of dual-sport tires that Semper Gumby uses on his Firebird - the K70's I've been using wear out very quickly and aren't all that great on either road or dirt, despite the fact that they've been my go-to Brit tire since 1973.

Actually putting in some quality shop time between this and the C15 ... and I need to get stuck back into the TSMR Norton, which goofed on me about 200 miles after the rebuild, right when I'd done the third head retorque .... It really helps when I keep the shop clean and organized and all the tools put away. It's amazing how fast that will get away from you if you don't keep after the cleaning and organizing.

Lannis

Funny how hard it is to get back into the mood on a stalled project sometimes. It seems like once you touch it, the feeling comes back pretty quick! Sounds like You’re on a roll ! 🛠 🏍

Measure twice, cut once, they say, and now I'm convinced that the pistons, rings, and cylinders are compatible and will have the right piston-cylinder clearance and ring gap when running. The tappets are smooth and tight in the bores, the cam follower surfaces smooth and unworn after all these years, and a little grease will hold them in the bores without the little C-clips while I'm lowering the cylinder down.

Checking with the panel one more time .... 2023 wisdom is still "bores and rings clean and dry for initial installation"? Always feels funny to me to assemble moving engine parts with no engine assembly lube, but I do understand about "breaking in" the rings to the bores. Don't want it burning oil until it's worn out .... !

Lannis

Ok, here we go.
I myself lightly oil the bores, I do not oil the rings, and I do smear some oil on each piston skirt. If you do it this way and then after assembly rotate the engine a few turns before you put the head on, you will see a small ring of oil near the top of the bore. That is the left overs. The rings get just enough lube and scrape the rest toward the top of the cylinder.

This is what I do these days. I oil the skirts but not the rings. Otherwise you end up with metal to metal contact until oil has found its way up the bore.

I started off building my motors like this, the first bantam I did was liberally oiled and it ran really well. I can’t say it never smoked… it was a bantam.

I later fitted them dry, I ended up with full thrust faces (not scratches) on the pistons and in some cases they wanted to nip up.

Your oil control ring will scrape off most the oil till it’s bedded in, I also don’t think there’s such thing as a quick break in.

Lannis,
Is that the motor I worked on many years ago? It should still be running!!!I I used assembly lube about everywhere there was metal to metal contact. Somewhere out in the shop I have the rebuild specs on that motor if it's the same one. I did my A65 motor about the same time as yours and it is on its second owner after me and still running great. The new owner emails me from time to time with "How to" questions.

Pretty soon you will be up in age where I am now. I only have the B-50 left, the others have gone on down the road.

Mr Mike

Same motor, Mike. Bottom end is still good, but it developed a "piston slap" that was annoying and getting worse. Ring gaps were .028" and up, and bore clearance too high. It probably had 20,000 miles on your/Ed V's top end so that's still pretty good.....

Lannis

What Ive done on a couple of bored barrels because i JUST CANT reassemble it with no oil ... its a blockage for me. When i got out of my business i had some cutting oil ( used on automatic lathes etc as coolant) ,, it is designed to keep the machine flooded with oil but give a good cooling medium for the tooling.

So i used a fairly liberal amount of that in the old school fashion, seems to work well ... smokes like a train for 5 seconds then calms down as the bikes oil supply takes over. I dont recon it will prevent breaking in as it is a cutting oil .. and it makes me feel better. At least i dont visualize dry rings taking thousands of mile of life off the pistons/rings/bores with a dry start .

I do it "pretty dry." Usually I am doing this after a rebore or honing, so the cylinder gets washed pretty thoroughly. Then, because its rare that I am immediately ready to install, I oil the cylinder so nothing rusts. When it is time to install, I wipe out the cylinder, but I don't wash it again. So there is still some residual oil. I just put a dab of oil on the front thrust face of the piston and thats it. Nothing on the rings. I have never had any problems, except once on a mid-90s Ducati. I was helping a pal re-ring his 750. He is old-school and wanted to slather everything in oil. I told him that is not the current thinking, so we did it "dry." A ring broke as we were putting the cylinder on. He attributed it to putting it on dry and then said the Ducati handbook said to oil everything up. I attributed it to the lack of proper ring compressors. We were using hose clamps and I think one wasn't tight enough.

Hey, are the Shocks going to work on the C-15?

Ed from NJ

OK, since others have admitted their process, I will join the parade. I oil the crap out of everything, turn the crank over a couple of times, and wipe out the excess at the top before head goes back on. And by the way, that might be days or weeks later. In the meantime, the oil is protecting exposed parts. I do this to avoid fouling the plugs at the very beginning. Not sure how I have gotten away with it, but no oil burners here.
Oh, and all of that information about speeds and push it hard at the beginning…..?? Again, fools luck, I guess. 🤪 🛠

Hey, are the Shocks going to work on the C-15?

Ed from NJ[/quote]

Ed - Yup!

[quote=edunham]


The bottom bushing on the shock was a 3/8", which is usual on BSA singles early and late. On this "competition" frame, the bottom bushing is 1/2", and mounts to a stud made into the swingarm. I tried drilling out the 3/8" ID to 1/2" on a drill press, but that was never going to work - the rubber is just too wobbly. So I found a pair of NOS 1/2" bottom bushings, pressed out the old ones, pressed in the new ones, and for the cost of your generosity, shipping, and a couple of bushings, I've got a lovely new pair of Shocks .....

Lannis

my issue with the assemble dry then ring the tripe out of it brigade ( unless u have bored it to "racing clearances" ) is that u cant possibly NOT decrease the miles u can expect from a fresh bore and pistons.

The question is, then, by how much? Like, every time your engine turns, your ignition points cam turns and wears down the rubbing block. So no matter how well you set your points and dwell, it's all wrong, and getting worse every second, every second that your engine runs ....

Lannis

No-one ever suggested you "assemble it dry and thrash it"
A wipe of oil in the well honed bore and a brisk ride of the bike
is basically all they got at the factory. Testers never babied the engines,
to bed them in they must have the rings loaded or you just glaze the bores.

assemble dry and trash it has been suggested OFTEN on this site ... not saying on this thread but that does seem to be a line of thinking

There seems to be a slight misunderstanding.

I've used this example before but here it is again. A piston aircraft engine break-in is 1 full hour at low altitude and wide open throttle. This is to seat the rings. Obviously, nobody is going to do that to an old BSA; they aren't designed for continuous WOT, but it illustrates the point that rings NEED high cylinder pressure to properly seat.

I know that I follow a procedure that could be called "dry and thrash" but the rings are the ONLY part that is assembled "dry". The rings then get what little oil they need from the lightly oiled cylinder bore. Everything else in the engine gets some type of assembly lube.

As far as "thrashing", I don't baby a relatively modern street engine to break it in. It gets ridden briskly with occasional third to half throttle roll-ons or mid range pulls through the first 3 gears and then I back right off and just cruise to let things cool. Then after a few miles I do it again! I do NO sustained hard up hill pulls or sustained high revs. The first few rides are fairly short so the engine can cool down completely and any small problems dealt with. You need the cylinder pressure to seat the rings but it's also important to keep the heat down.

If your overhaul clearances and tuning are good, this kind of break-in works just fine.

I put top ends together “dry”. Been doing this for a very long time. I learned it from a former Triumph dealer who built some fast Triumph flat track and drag bikes.

Ronnie Jones of Stark Triumph built his top ends dry. Carefully hone and clean everything. He claimed they got enough oil from your fingers during assembly to be ok.

And his break in procedure was special too. Didn’t matter if it was a street engine or race engine, he would pull the bike out of the shop, start the engine and let it warm up and make sure oil was circulating. About 1/2 mile or so from his shop was a small tavern, once he could feel heat in the cylinder, he started from a dead stop and pinned it through the gears to the tavern. Turn around in the parking lot and repeat the process back to his parking lot. Roll the bike inside, put it on the lift and check it over. After it was cool, retorque the head and it was good to go.

He built some of the most reliable race motors of the era around here. And reliable street motors.

I have never been able to bring myself to use his break in procedure, but I don’t baby them

"Dry" as I understand it means the slightest smear of oil on the bores and on the thrust faces of the piston.
Nothing on the rings or the piston non thrust faces.
When we were racing in the 60s we would very often arrive at the track with a motor that had finished rebuilding at midnight the night before.
Break in was two laps riding hard but not 110%, then change the oil and ready to race.
Never had a seizure or smoke!

Upon mature reflection and consideration of all of the experience presented here, I decided to go basically this way. No oil on the rings, a very slight smear on the bores.

Annealed the new head gasket this morning .... on a gas stove with an infrared thermometer to make sure that every point on the gasket reached 450 - 600 degF, now to buff off the oxides and combustion ash and roll along ....

Lannis

Glad to hear the Shocks are going to work out! I heat copper head gaskets till they are cherry red on the stove. They are nice and soft then.

Ed from NJ

Lannis,
I do not over lube anything but everything gets a light smear except the rings. One of the changes I had on my bike were small drillings in the rod to squirt more oil up into the bore. I read about this but of course you never really get to see if it helps once the engine is assembled. The materials in those days are not what they are today. I had piston slap in one of my b44's after about ten thousand. It ran good but the noise drove me crazy so I rebored. I always would send pistons with the cylinder on rebore jobs to make sure they it comes out on the lower end of the tolerance range and hopefully a longer life span

Mr Mike.

Sorry about the hijack but, Nicholsons recommends .0025" clearance on a street ridden B44 as being invariable the way to go. But a B44 that is raced or ridden hard should get the .0035" clearance. My current B44EA engined bike has .0035" and it is noisy unless I am riding it hard, then it quiets down. Other B44's I've had in years past were bored to .0025" clearance and were much quieter, and I never had one seize on me.

There is a Service sheet on the drilling, can’t remember the size but it’s pretty darn small. The set of rods I fitted into the Thunderbolt didn’t have them (aftermarket rods) so I marked it all out and drilled it though and cleaned it up. When I primed the pump and the crank (with the cylinders off) oil would clearly weir from the hole, so I can imagine it will be quite a jet of oil when the engine is running.

So this is pretty embarassing, considering the number of times I've taken heads on and off of A65s. As far as I know, I always take off the heads before I take the engine out of the frame, and I think I did it with this one, but ....

I've got the engine back in the frame, pistons in, cylinder block on and torqued down, and head ready to go on ...

... and it won't go on. There's no way that the front center valve cover stud will clear the top frame tube so that the head will slip down over the head studs. I swore that's the way it came off, but maybe not. I have two other heads on the shelf, and neither one of them has the front center valve cover stud in place.

I'm not positive that the head I got back from the rebuilder is the same head that came off the bike, as I told him to just give me a good rebuilt Firebird head back, so the one I sent may not have had the stud on it.

At any rate, I'm sure I've never pulled a stud out to install a head .... so

(1) Am I missing a trick and '69 A65 cylinder head will install with all six studs in place if you hold your mouth right and say the right words? Fay and I puzzled over it for an hour today, and no way.

(2) Do folks pull that stud, and just use a bolt for the front and rear valve cover fastenings instead of a stud? I tried pulling this one with two nuts, but it's going to have to be destructively removed, it's not coming out that way.

I can't believe I don't already know this. I have 4 different BSA A65 shop manuals, and none of them say anything about it ....

Lannis

I know virtually nothing about BSA twins, but …. (and this is not knowing much about the actual circumstances) if the stud won’t come out with the double nut method, then it might just want to snap off when you use another method. Maybe worth trying some localized heat and give the double nut another try? There were a couple of occasions where I wish I had followed my own advice about using heat.