1968 BSA Thunderbolt 650cc - going home, or NOT (part 1)

1968 BSA Thunderbolt 650cc - going home, or NOT (part 1)
Just when you think it’s safe to return a motorcycle to it’s owner..
Applying the final steps to Tim’s BSA before returning it and it won’t start. There’s a decent spark at each plug but both are bone dry, suggesting that fuel isn’t getting through to the cylinder heads. I’m assuming that one of the jets or passages is blocked from the bike being stood for several months.
Removed the carburetor and find another little issue with the manifold being a little warped. This shouldn’t affect the starting but could have explained a little rough running. So straightened the manifold out by rubbing down with glass paper and then thoroughly cleaned the carb, jets and other passages and used compressed air to clean everything out.
Just looking over the bike to refit the carb, I notice that the stator wires are in bad shape. I knew that they were brittle but they seemed okay when wiring the bike. One bullet had already come off, possibly while removing the carb or the air filter. The other stator wire simply broke when I twisted it.
So the next job will be to remove the stator and replace / solder the stator wires and refit them to the bike.
*Buy me a coffee? ☕ 😉*
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[@ronthompson9555]

Carb flange truing, I find that putting the carb body in a flat jawed vise like a milling machine vise and gently squeezing the flange & body back to true. This does two things. It flattens the flange some and more so you can true up the slide bore so the slide no longer binds. You don't want a stuck slide riding. Then sand the flange to true. When reinstalling you need to be careful not to use ANY soft gaskets or you will re warp the carb body. I usually add the phenolic plates to insulate the carb some and thin gaskets on the head side and just the O-ring on the carb side.

[@TheMightyGarage]

Thanks very much Ron, this is excellent advice. Best wishes, Mike

[@Thomasuki267]

Do you make the phenolic plates or is there a source of reaady-made ones? I just got my hybrid BSA ('67 Thunderbolt engine, 68 Royal Star 500 chassis) running this weekend. I rebuilt the carb, but I have a monobloc, not a concentric. It was burning oil when I put it away in 2013 becase the gas taps rusted off, I cleaned and de-rusted the tank, re-fitted fresh taps, new gas lines with an in-line filter and last fall put a bunch of combustion chamber cleaner in both cylinders. A whole lot of grime came out in the sump screen, cleaned it all up, put it back on being careful to tighten evenly, put gas and oil and the 10-15 year old battery in, cleaned the main electrical terminals (coils, Zener diode) and it fired up very easily, and no longer burns oild so a ring must have been stuck and now loosened up without a tear-down. I find with the carb flange you just should not over-tighten it, it comes with lock washers, tighten to snug and check regularly and it should not warp any of the carb body. Now I need to go over all lubrication points, new tires, check the brakes, find the fault in the horn circuit, fix up the lever clamps, clean everything up and polish a lot, and I want to fit a kill switch for safety. These things handle so nicely and the ergos are really comfortable. Hoping to get out on it a fair bit this summer. Cheers

[@A65Bill]

Plywood makes an excellent heat shield for the carb. Have you checked the passages within the carb body for humming? Please check the angle of the front brake drum operating lever. It should not be at 90 degrees until applied

[@townsey5612]

You will never be bored with a British bike in your garage.

[@TheMightyGarage]

So true!!!

[@stevenleek1254]

or, with no work

[@debbiegreen5963]

mister roger's garage. love the presentation

[@TheMightyGarage]

Hehe, thank you Debbie 😉 You are always welcome in this neighborhood 😉

[@celiaansell4860]

Oh what joy to see this bike I used to ride all the time can't go wrong with vintage bikes

[@tubadude905]

That was awesome Mike...took me back to when I had a BSA Starfire (my L plate bike) and '69 Rocket 3 - squeezing those Amal carbs off, tearing them apart and cleaning everything up. I really enjoy watching you work om these bikes. Time has changed - those English 650s used to be really big bikes when I was a youngster!

[@johnorchard9164]

Don’t put copper slip on spark plugs even the smallest smear will work down to the tip and go black and short out have learned this the hard way. Happy days

[@TheMightyGarage]

Thank John, I don't do this anymore. Cheers, Mike

[@hogtied12]

Awesome years i was 18 then, love British bikes had a load of 'em spent alot of time working on them enjoyed every minute. Unfortunately they are out of my price range now

[@TheMightyGarage]

Thanks a lot for your note. I'm glad that you like the videos and they bring back some nice memories. Best wishes, Mike

[@Wooley689]

Wish I lived near you, I could spend hours learning and tinkering with those British bikes. Oh, and about one job leading to another, I coined and often say "every solution causes another problem" I think I should make T-shirts that read that. It comes from years of doing things with engines and what have you only to find the simple fix always leads to something else.

[@TheMightyGarage]

Haha, so true Wooley. Have a great weekend. Mike

[@BilgemasterBill]

Bit late to the party--just been binge-watching your stuff on and off all day and evening, commencing with your superb and extensive 'Norton Atlas Project - Shep' series, for which I cannot thank you enough. As far as this BSA's Amal carb, unless I'm mistaken it seems to have one of those craptastic original white plastic float needles. They're too light to do the job properly, and because they cause all sorts of mysterious fuel delivery issues, most have long since been replaced with the heavier and better brass viton-tipped ones. In fact, it's pretty rare to even see the plastic needles still in use. As for the flange, I usually give the rubber O-ring a very light smear of RTV Red silicone gasket goo, and that seems to keep her from wheezing.

[@TheMightyGarage]

Hi Bill, thanks a lot for your note. I appreciate your advice. Best wishes, Mike

[@caahacky]

I'm looking forward to the follow-up.

[@CravingClassics]

Love those year bsa s

[@ymtmr60]

Wah like this bike

[@Thomasuki267]

Your wet sumping problem is likely the little ball valve in the oil uptake pipe, if it gets grime stuck to it or the spring sticks it will wet sump. Also, next time you have a complete tear-down (which is of course inevitable; in fact it's part of the factory maintenance schedule) make sure you find and clean the grime trap in the crank. Silly way to have a grime trap, but that's why the Japanese took over, much better engineering and design. But not as much character. Cheers!

[@TheMightyGarage]

Thanks very much Thomas! Cheers, Mike

[@A65Bill]

Drain down can't be via the pick up nrv, that can only drain the return pipe. There can be a little leakage past the gears in the oil pump, but the most likely cause is the ball valve behind the oil pump needs reseating. And yes, clean the sludge trap & fit an external oil filter in the return to the tank.

[@bigred8438]

what I don't quite understand is why some models from various years with the same size tank have daylight between them and the rocker cover. Mine sits quite low so that the rocker cover is obscured and it is difficult to find a path for threading the high tension leads behind the petcocks. I am going to check the rubber mounts to see if the correct one are on it.

[@kevinjohnson2764]

Great video. I bought a 68 Royal Star October 2016. I will be following gyour vids to help me. I m pretty handy and have a few old Brit bikes, and have done quite a bit of work on them but any extra learning is always good. I rebuilt the kickstarter and put in a Wassel ignition. New Wipac dimmer and horn switch. It has a kill button on it but haven't figured out how to wire it up with the wassel yet. Any ideas?I also have a billet sump plate the original has had 3 of the 4 bolts removed (probably stripped) and screws put in. I think I will need to get a shop to drill the holes and helicoil it for new bolts to mount the plate. Starts okay but I think next winter I will completely overhaul fuel system including relining tank. Have you adjusted the clutch on these bikes? I followed the MMM Nicholson book instructions and I think its too tight now. But cable adjuster is at max if I leave the center screw adjuster slightly slack and tighten the nut.

[@bigred8438]

The cable tidy at the top of the right fork leg, is that something you made or bought? and it is only for the choke and brake I gather!? What Amal Concentric did they run of these '68 models?

[@keithhall4883]

Hi Mike, Good to see you found the problem why no gas is being sucked into the engine the air-lead on the carb, I had a bad running problem on my old 650 Bonnie!! that was down to air leaks on the carbs too. Is the inlet port part covered by a gasket under the heat gasket or something or is it the camera angle ?

[@TheMightyGarage]

Hi, thanks for pointing that out about the inlet port gasket. I just had a close look and everything seems good. The gasket isn't blocking any part of the port and it butts up against the metal manifold so no other obstructions thankfully. The manifold sure is quite deep so it will need a good suck to pull gas/petrol all the way into the cylinders, so hopefully the warping and cleaning of the carb will help. Cheers.

[@bigred8438]

Can bikes this age run on unleaded gas or does a lead substitute have to be added with each tankful?

[@TheMightyGarage]

Hi, yes, they run very well on unleaded gas. A lot of guys try to run non-ethanol fuel and higher octane fuel, but they seem to cope very well.

[@RyanChelberg]

Hi there, I have a question for you about a BSA... I bought a 69 Lightning and am in the process of restoring it, I have hit a snag that I can not figure out... when I try and hook up the battery it instantly blows the 17 amp glass fuse that is in line with the positive terminal, I have checked all over the bike for a short and cant find anything... any help would be greatly appreciated because I am at my wits end...

[@TheMightyGarage]

Ryan Chelberg Hi Ryan Thanks for your note. Yes, it definitely sounds like a short but I will ask all my friends who have A65s and get to you ASAP. Cheers, Mike

[@TheMightyGarage]

Hi again Ryan. here's a reply from one of my pals: My first guess is that a negative got hooked to the frame somewhere. It can get confusing with the positive being the grounding wire. Not knowing your machine, some one could have started to make it a negative ground unit but didn’t switch the whole thing over. Isolate your different systems at the battery if you can and check them one at a time. Hopefully You will find the short quickly.

[@RyanChelberg]

Thanks I'll look into that!

[@TheMightyGarage]

Ryan Chelberg hello again Ryan, and here’s another reply from another friend: Your fuse should be in-line with the negative battery terminal as your system should be a positive ground system.

[@TheMightyGarage]

Ryan Chelberg hi Ryan. Here’s another reply: The first question I would ask is whether the ignition switch is on or off when the battery is connected and the fuse blows. If the switch is off, the short should be in the immediate vicinity of the battery, since none (or very little - consult the wiring diagram) of the other wiring should be activated. If the switch is on, I would first experiment with a larger fuse. I can’t find anything in the BSA electrical specs or wiring diagram that specifies fuse size, but my 71 Triumph calls for a single 35 amp fuse. After that, if the fuse is blowing with the ignition switch on, I would try to isolate parts of the electrical system by disconnecting grounding wires (typically red), to try to locate the portion of the system with the short.

[@dereksmith5019]

1968 BSA 650 models all had a twin leading shoe front brake , what happened to this bike ?

[@TheMightyGarage]

I returned it to its owner. It's still here in Portland, looking sad at the back of his garage!

[@lesmontgomery6498]

Some of the a65,s had porous lntake manlfolds. A couple of coats of paint would fix them

[@TheMightyGarage]

Thank you Les, cheers, Mike

[@marquee6]

So it was not passing gas...?😂

[@TheDevonblacksmith]

Float hight?, it sounds strange listening to someone talking American with an English accent.