A guy could, in this case, since it’s a hobby bike and not a competition machine, take a small, cleanup cut in the cylinders, then sleeve them for A7 pistons. A7s came with early and late bores of 62 and 66 mm vs. the 70 of the A10. This would restore the strength of the barrels at the expense of cubic capacity. $0.02😉
A guy would need to look at rod length and pin height to be sure, since the A7 stroke is shorter for both bores. With a shop like yours, work-arounds can be found, is my guess.
From what I can gather, the early engines had an 82 mm stroke. The A10 is 84. It may be possible to use the stock A10 crank and rods by shimming or decking the block by 40 thousandths, depending on the pin height.
Great repair. I like the use of dye penetrant. But the method you are using is the colour contrast red liquid penetrant method which requires white light at a minimum of 500lux for inspection. UV light is used for fluorescent penetrant...the green stuff. Only saying because I'm tig welder and NDT weld inspector. Post machining / honing dye pen inspection is a good idea. All the best.
Thanks for watching and commenting. The penetrant I use is red for visible light testing, and the pink stuff I used there was for UV, it's old though, I had it when I was in my twenties 🤔
A very interesting watch mate, I can imagine the frustration when more cracks started appearing. A lot of things are worth a shot with these old bikes, given your care and consideration I think this is one of them!
Thanks for watching Will, good job we do what we do us purveyors of olde shite and detritus or none of this wonderful engineering, motorcycle, and automotive history would have survived.
Hi Ade, I'm like you, not the best at TIG. So when i get something to do that's past my skill level at TIG, I prep it as much as possible and pop over to the welding shop. One of the guys there does it in the evening before heading home and it works out quite cheap and i know that it's going to work well. Re A7 thick flange barrels. They are like hen's teeth. BSA made some for their A7ss racers in the USA in 1964. Part Number 671310. They were never available to anybody else. Been looking for 20 years. 😒 Keep the vids coming there good and it's nice to see A7 and A10 engineering work done.
The US racing rules in the 50's and 60's allowed 500 cc overhead valve singles and twins and 750 cc sidevalve engines. This was to favor the Harley-Davidson "KR" V-twin engines which, by virtue of their torque characteristics, were very good in the US-style "flat track" (dirt track) races at the time. Thus, there was lots of "hot stuff" for the 500 cc British twins at the time which was considered superfluous in other markets. Too bad, because there was some good gear going.
Hi Ade, I have had some barrels repaired in a similar manner, we drilled the end of the cracks and then welded up using some special cast iron repair rods , not sure what composition exactly. We grooved the outside of the spigot and only welded outside, the bores were then taken out to +40. I didnt hear anything about additional cracking but a lot of heat was put in before welding up. I wouldn't trust the fix in a Rocket spec engine but we will see how it gets on. Pictures on request! Excellent video - thank you.
Extremely well done in my opinion. I have no experience of tig brazing let alone tig brazing cast iron, before you even get to the vagaries caused by that crack position. It is a pleasure to watch you work. Although I don't work on motorcycles (as you know well, my brother does) I learn a huge amount from you about general technique. I think this film you have put up today is going to become reference material for anyone doing similar. As you also know, Dean could not tig the fins on the bantam cylinder, he ended up mig welding them. Tig kept cracking on cooling, starting immediately on the post gas phase. Much like you saw. I have got a reel of mig brazing wire (bronze of some sort I think). Do you think mig would have worked better on your application - leaving aside the access issues? I would value your opinion on that and I know Dean would too. Great video as always. I am very grateful to see you posting again. You are in Staffs aren't you? I am in Derbyshire currently, visiting my daughter!
Thanks for your thoughts Carl, I didn't even know mig brazing wire was available, but never looked tbh, I'll look into that one. I'm on the Derbyshire border actually but it depends which end of the county you are? Burton on Trent, if you're close call in 😉
@@AGEngineering You are more than welcome for the comments. I am no expert, but I have tried a little bit of mig brazing and my gut feeling is the heat input is not as intense as with tig. I may well be completely wrong on that score. Thank you very much for your kind invitation, I will get your details from Dean and drop you a text message to arrange something if that is OK with you?
I had a an A65 engine blow to pieces in the early 1980's. The gudgeon pin tore the skirt off the bottom of one barrel. The engineer I took it to said don't worry I'll remove them both, the re-sleeve will be ok on its own. But that was a shorter stroking engine than the A10, so who knows perhaps you could dispense with that lower section of both cylinders, and forget about doing any welding.
Thanks for sharing your story. That would have been my preferred way of fixing, but it would leave less than 1/8" wall thickness on the remaining barrel, so even that is risky.
Great video Ade. We learn a lot from your adventures into the trickier end of restoration. I wonder if BSA increased to wall thickness of the cylinders when they introduced the thick flange barrel? I believe that the thin ones cracked regularly, ofen above the flange.
I'll try and find a thick flange barrel to measure, it would have made sense to, maybe thick flange barrels would then be what the liners are aimed at, great thought, many thanks 👍🏼
Ade, great video. I don't think it's bad at all because you stop drilled it and normalised the stresses before brazing. As you say, not the highest stressed part of the barrel and out of the ring land. Worth a go I think and very interesting to watch. If your new barrel needs a fin welding back on, I can recommend a video that shows you how not to do it! Best wishes, Dean.
Ayup Ade, I'm just imagining the noises that were coming from the repair, bet you were waiting for the twang! Looks like internal casting stresses eventually pinged open, maybe like you say when it has been over bored, it looked very springy.
Ade, looking at standard cylinder liners for the BSA A10 barrels from Westwood are part no. L2148 - 69.99mm x 73.08mm x 149.23mm and part no. L5470 - 70.0mm x 73.5mm x 177.8mm. I measured the OD of the spigots on my barrels as 78mm. Westwood makes a liner part no. WCL 13DFL - 69.0mm X 79.0mm X 228.6mm. Using that liner would it be possible to machine it to 73 or 73.5mm and leaving the 79mm OD x the length A10 spigot to form a new spigot. Then bore the barrel to suit the liner, machining off the damage spigot flush with the flange or slightly counterbored. Finally, installing the liner from the bottom, cosmetically restoring the spigot. Whether this would work mechanically, I am not sure?
May I suggest heating the cylinder in an over first then using an oxy-acetylene torch, brass braze the crack with flux covered brass rod. This always works well for me.
Is it not possible to machine the split area down to the flange and machine a bespoke stepped sleeve and shrink it in to bring it back to nominal size?
Hello Ade. Why do we prat around with these old bikes? Although there might be a problem with distortion I think that I would have gas bronzed it to get a more even heating around the crack. But as long as it works alternative methods are purely academic.
I tend to agree, with a better set up, oxy acetylene and good pre heat with slow cooling might be better but I've never had great success with thin cast iron, been okay with motor mounts, manifold lug etc.
