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Howard Inough
Howard Inough
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Okay, I am having a bit of trouble.

I bought a 1967 BSA Thunderbolt, recently rebuilt. It takes in the neighbor of 50 kicks to get the bike to turn over, but once it does, it runs like a top. I had been assuming it was because it needs to be broken in, it is cold outside, and I have not gotten the right 'feel' for the bike, yet.

However, we finally thought to check the battery to see what was going on, where it gets particularly confusing/weird/I want a beer.

We pulled the battery and checked the charge, saying it was at ~11.3. Since this is supposed to still be the 6-volt Lucas system, I was a bit confused. Then we put it back on the bike, turned the key to the 'on' position, and checked the voltage again, this time it was coming in at around 4 volts. When we turn the key to the 'off' position, it jumps back to around 11 volts.

Given the difficulty to get the bike to turn over and the weird battery issues, is it possible that the mechanic who rebuilt it put a 12-volt battery in a 6-volt system? The battery says nothing more than Motobatt (which seems to be a poorly-reviewed battery, and, oddly enough not even a new battery. Cheap bastard.)

For some reason, no matter how many beers my dad, brother, and I drank, we couldn't figure it out. Any advice/thoughts/beer brand suggestions?

















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Your '67 Tbolt should be a 12v system. That being said the battery fully charged shoulb be 12v or hair bit more. Does the bike have its original point ign setup or has it been converted to electronic?


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Hi,

Originally Posted by SBredberg
Since this is supposed to still be the 6-volt Lucas system,

Are you sure it is still 6V? Even if it started out like that, it's relatively easy to convert - Lucas supplied the same RM19 alternator throughout most of the 1960's, it's simply a matter of connecting the Green/Yellow alternator cable to the same side of the rectifier as the Green/Black, bolting a Zener diode to something and connecting it between the rectifier output and battery +ve (assuming no-one has tried to convert the bike to 'negative ground' sick ), and changing the bulbs and battery. Have you checked any bulbs to see if they're 6V or 12V and whether they still work?

Originally Posted by SBredberg
put it back on the bike, turned the key to the 'on' position, and checked the voltage again, this time it was coming in at around 4 volts. When we turn the key to the 'off' position, it jumps back to around 11 volts.

But that could just be a dud 12V battery?

Originally Posted by SBredberg
When we turn the key to the 'off' position, it jumps back to around 11 volts.
is it possible that the mechanic who rebuilt it put a 12-volt battery in a 6-volt system? The battery says nothing more than MotoBatt

The only 6V Motobatt I can find on their site is the MBT6N6 and, apart from the 12V MB2.5U, is the only one with cables attached.

Originally Posted by SBredberg
which seems to be a poorly-reviewed battery,

Digressing slightly, can you post any links, I've only seen good reviews of 'em?

Hth.

Regards,

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The 1967 Thunderbolt is a 12 volt bike. Nothing surer.

The bike is running because the charging system seems to be working ok. What is not at all correct is the battery.

Those symptoms are exactly what you would expect from a 'expired' battery.
Given that the bike starts and runs I think it all sounds great. You will find it start with just a couple of kicks with a fresh battery.

You may need to check the Zener is working and keeping the voltage down to 14 volts or so. A failed Zener could be responsible for killing the present battery.

Are you sure the bike is a 1967 Thunderbolt ? Many owners discover their bike is something else..


Why, Y, Dash Y..



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Okay, I appreciate the advice. I think where I got confused was that I was initially told that it was a 1965 Thunderbolt, when it was, in fact, a 1967. In that time, they switched it to a 12 volt system.

I grabbed another 12 volt battery that I know is in pretty good shape and it was easier to start, but still pretty rough.

Perplexed, we started looking at the carburetor and the shop manual and realized that while the bike came with a choke, it was not actually on the bike. Can I find a replacement to add it or do I need to replace the entire carb?



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A choke ?

I have never used one on my twins. I do remember brand new Bonnevilles with working choke slides fitted. I really don't know if any of my current fleet still have slides fitted. If they do I most certainly never use them.

Most AMAL style carbs will have a 'tickler' button which you just depress and it opens the float needle valve to flood the carb bowl. As soon as fuel comes onto your finger you can give it a swift kick and it should light up.

If the bike has been rebuilt it should be a good runner. First you need to sort out what you have.
Is it really a 1967 Thunderbolt ?
It is pointless reading books if you are going to get the wrong impressions etc. it happens far too many times, guys buy a bike and it turns out to be something else.

A 1967 book will work for a 1967 bike, - it may not be so helpful if the bike is something else.
If you were told it was a 1965 what now makes it a 1967 ?
Do you have some pics so we can see what you are dealing with ?

You don't want to be kicking a bike so much that you end up damaging other items. For those that try and start bikes on a stand it will only be a matter of time before the stand gives out.





Why, Y, Dash Y..



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Here's the bike:

[Linked Image]


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Is there by chance a "Y" at the end of the serial numbers, engine and frame?
Looks like it might be a 1970 from that photo.

I've run a single AMAL without a choke for years, at cooler temperatures than you're at. Here's my starting process.

- gas tap open,
- in neutral, not on center or side stands,
- hold tickle button down until gas appears,
- ignition on,
- open throttle about an eighth of a turn,
- kick, should start,
- you may have to blip the throttle a bit before it will idle with no throttle.


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No, it ends in a "T."


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Is there a "Y" in there anywhere?

I can't really see how this bike gets mistaken for a 1967 without one.
Is it matching numbers, are the engine and frame the same?

edit Just checked out your other thread, no need to overly worry about your brakes. As long as they're working properly, the ones you have are fine.

[Linked Image]


Last edited by Two Alpha; 02/03/14 12:47 am.

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Ditto, I see much 1970 model here.

I can't see anything 1965 and there is not much there to suggest it could be a 1967 either. Both engine and frame/cycle parts are screaming out 1970 to me.

I think it may well be Y bike of 1970.
It has a Concentric carb and given the starting symptoms I have to guess it still has 6CA points.

Thanks for posting the pic, - all viewing here can see exactly what we are dealing with now so we soon manage to get you up and running.

It worries me a little that someone can do an engine rebuild on a 1970 engine and not realise what year bike they are working on.
That is why I thought we should all see the bike here first..

I am pretty sure Steve is about to discover he owns a 1970 Thunderbolt. It seems to happen to someone about every two months here.


Why, Y, Dash Y..



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Whatever,
I happen to LIKE the paint scheme of this machine!
It isn't black!

The front brake hub looks small to me though...

Have LOTS of fun riding this bike!

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I like the styling also and the front brake did catch my eye.
It is possible the brake could be the smaller 7" tls variant.
I think a few guys here would have a method of telling from a pic.

I am sure Steve will have fun riding it. He may not find the 50 kicks trying to start it each time so enjoyable.

There is a big difference between fault finding on a 1965 model twin and a 1970 model. I shudder when I think of someone using a 1967 parts book on a 1970 bike.



Why, Y, Dash Y..



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Very nice indeed, and shouldn't take much to get it starting and running right.


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I'm sorry if this sounds like a tired refrain, but why do we experienced advisors keep forgetting the most BASIC rules of British motorcycle get-it-running?

Compression - Ignition - Fuel in that order.

1. What are the compression readings on each cylinder, throttle open. What are the valve clearances? A bike with low compression or a tight valve will start hard and seemingly run OK.

2. Is the ignition timed right? Point gaps are ….. _____? And keep in mind that a 12V battery that reads 12V at rest is as dead as Stonewall Jackson’s horse. Use a load-tested battery on that thing. Even with a dead battery, it MIGHT start and run just on the alternator. Mine will.

3. Fuel – If a BSA starts and runs OK with no choke in this weather, then the pilot circuit and mid-range are WAY too rich …..
I know we always want to think that a “rebuilt” bike is just perfect in all these respects, but if that bike doesn’t start on one or two kicks, then ONE OF THE ABOVE is screwed up ….
Good Luck!

Lannis


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This is what I am finding, regarding the bike's numbers.

[Linked Image]

[Linked Image]


Once the bike gets going,it is a dream to ride, it's just such a beast to turn over.


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Well, I was initially told by the mechanic (Perry of Perry's Motorcycle and Sidecar in Ft. Worth, Texas) that it was a 1965. However, on the receipt he wrote out "1967," something I did not notice until I got home. At this point, I am completely confused.



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At least it's crystal clear matching numbers.

1970.



Last edited by GrandPaul; 02/03/14 12:42 pm.

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Originally Posted by SBredberg
Well, I was initially told by the mechanic (Perry of Perry's Motorcycle and Sidecar in Ft. Worth, Texas) that it was a 1965. However, on the receipt he wrote out "1967," something I did not notice until I got home. At this point, I am completely confused.

One things for sure, the mechanic was confused.

As long as he wasn't cursing about parts not fitting, you're probably ok, the bike looks great.

As Lannis has mentioned above, these bikes should start first or second kick.
If not, there's probably some minor work to be done.
Make sure the battery is good for starters.

Thanks for posting the pictures, removes all doubt about what the bike is. As you can see from the chart posted above, it's an early 1970 model, off the production line in August of 1969.

You might be able to find the shop manual online, the DVD linked to on the upper left hand corner of this page is a good way to go, it covers any BSA you'll ever own.
Here's a shortcut to it.


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Hi,

To add to the previous two posts, I dunno what Perry had been smoking the night before, but he was definitely confused; grin there is no way on God's green earth that number's anything but 1970.

. "A65T" is the model code for a Thunderbolt.

. "JD" is the date code;-

.. "D" is the code for 1970, but it's the 'season', 'model year', 'automotive year', etc. not the calendar year .

.. "J" is August, but these letters ran from A (January) to X (December) (obviously missing out some of the more-forgable ones like F, I, L, O, etc. smile ).

Thing with "'season', 'model year', 'automotive year', etc." is BSA (including Triumph) didn't start 'em in January. Internet legend has it that a new one started after the end of the factory summer holiday shutdown (although examining actual original documents doesn't really support this whistle ); however, you can usually reckon on a new "'season', etc." starting sometime around July/August/September of the previous calendar year ...

Helpfully, also at the beginning of each "'season', etc.", at least Small Heath also re-started the number count from 'something-101' (before '69 - 101, '69 - 11101, '70-on 00101).

So, 'cos your bike's number is relatively low compared to a year's total production, you can reckon on it being a '70-season bike built in calendar August 1969. :bigt

Hth.

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Yep, all good posts and now Steve knows exactly what bike he has bought.
We can all see the condition of it and can now help him work through the starting issues.

I think we should include technique into the checklist Lannis provided also.
I remember reading a post here about someone trying to start a bike and it transpired he wasn't even turning it over, - the clutch was slipping.

Lannis had compression as top of the list. You would hope that the clutch problem was identified at this stage of the fault-finding.


I have to doubt the mechanic, or the interpretation of what he said. We can see the confusion over the bike.... perhaps we need to consider the battery comments.

I think any number of readers here would have that bike running sweetly after just a few minutes. Troubleshooting is so natural when you have the bike in front of you but so is starting and riding technique. What is natural for us may not necessarily be so with someone new to the game.

I went for a drive with one of the Chinese flatmates the other day as she was concerned about driving in a different country. She was doing a good job and I had made a mental note of just 3 or 4 basic defensive driving issues she should be aware of. It was only after some km that I realised something else was different. The car wasn't cruising so smoothly at times...

When I looked down at her feet it was apparent she was riding the brake, using both feet in an automatic. The right foot was doing the going, the left was constantly on the brake adding 'speed control' as well. It must have been confusing for the cars following her with the brake lights coming on all the time.

Anyway, just a reminder that it is often a case of the obvious being overlooked.
Age of fuel for example in this case.

I know of one brand new bike, a 1972 Bonneville, that was ridden for many miles with the choke on.
I helped assemble the bike out of the crate at the dealers. Some weeks later the new owner was describing to me how the bike went so much better when he advanced the ignition !!

A year or so later another owner of the same bike turned up on my doorstep with the bike running poorly. All he had done was wash it some days earlier.
It turned out the choke cables had been disconnected and the slides pulled up and held by tightly bending the cables back upon themselves. Plastic insulation tape was used to hold everything in place.
well the tape aged and the water loosened the cables so that the slides dropped back down. Here was the poor bike getting around once again on full choke.
For all that it never seemed to harm the engine, it was still running well years later.


Why, Y, Dash Y..



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That's a nice looking bike, and I'm finding this story very interesting. Perhaps one of you BSA serial number experts can explain this to me. I recently looked at a 1970 Thunderbolt that a friend was thinking of selling. I took a bunch of pictures, including one of the serial number. The pad and the stamped numbers look just like in SBredberg's pictures above. The number, however, is JD115XX A65T (last two digits obscured by me). That puts these two bikes more than 10,400 units apart, yet they have the same date code. Is that possible? If so, I wonder why BSA went out of business. They must have been chunking the bikes out like popcorn!

Ray


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Hi Ray,

Originally Posted by TR6Ray
1970 Thunderbolt
The number, however, is JD115XX A65T
That puts these two bikes more than 10,400 units apart, yet they have the same date code. Is that possible?

Pending the arrival of an "expert", grin I'd suggest that one was built in calendar August 1970 ...? Fwiw, this isn't unusual on Triumphs either.

Hth.

Regards,

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As you possibly know. Bsa were supposed to be part of the NVT co-op considering bsa basicly owned the T part of that you can only pin it down to 2 things

1) the bsa name wasn't a big seller anymore - they didn't break speak records like triumph did! Ok they were far far ( grin ) better bikes and handled much better but out of the box they were slower. Possibly more reliable though laughing

2) Jap bikes were innovative. Well not that bsa hadn't already tried OHC but they didn't push it enough to make it work. They didn't see the future and they didn't give the funding. Japanese took over with their big ideas and short term plan. No one ever predicted that crazy people would be restoring bikes 30+ years from when they were made or regardless of which origin.

However like a Brunel bridge, after all this time the Brit bikes survive much better wink


Now let’s all have a beer beerchug

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71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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I am not sure BSA were supposed to be a part of NVT, BSA had stopped building their range at the time but the factory may have still been used for the triples production. I can remember the collapse and it seemed like a year or so after BSA had gone and we were left wondering what was going to happen next.
I think Stuart and Two Alpha will have a pretty good grasp of the sequence of events.

The 1969 Twin numbering started at 11101, I think I said 10101 the other day. Regardless they started at a very high number and all 'normal' 1969 models had the five digits starting with the 1 or 2. I think they got into the 23,000 series by the end of the season.
If all allocated numbers were used that would be about 12,000 normal bikes and possibly 1,000 or so Y bikes.

If we consider the 1970 season then the numbering that year started at 00101, or similar. All the normal twins had the 5 digits with and starting with 0 or 1.
It may have even been 01101. Edit, answered by John in a following post.

Anyway we can now see what Stuart was saying.
01148 is a very early number, and undoubtedly made in August 1969 as the start of the 1970 models. We can see from the pics that it is all 1970.

Ray's example is 115XX.
We can see that it would be Aug 1970 of the 1970 season.
It would appear they made about 11,000 normal twins that year plus about another 1,000 Y bikes.

Very similar numbers to 1969 and of course by now the sales were starting to fall.

I think I can remember Stuart saying that the Triumph model season for 1970 was a little longer and with similarities to these examples. The OIF bikes would have to have been getting ready for production by Aug 1970 but we all know that it was not an easy transition.

John or someone will correct my S/N but I know I am close to the mark. Interesting having examples of a similar date code, one at the start of the season and another at the very end of the pre-OIF production.

Last edited by Kevin (NZ).; 02/03/14 7:05 pm.

Why, Y, Dash Y..



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