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Spanners for T140 Bonneville Special 1979

4K views 27 replies 10 participants last post by  Boggie 
#1 ·
Hi,

It seems I have to do some work on the upper end of the engine during the coming winter. I have an oil leak at the front base, and also a small leak at the head gasket.

Could someone please specify the spanners needed for the cylinder base nuts and the top bolts? For the hex nuts at the base I have the correct spanner, but for the torx(?) nuts I do not have spanners that fit.

The clearances between the base nuts and cylinder block are very small, so maybe there is some specially made tools I can buy somewhere?

Any hints or help are very welcome.

Helge Walle
Norway.
 
#3 ·
A standard a-f "American" set is fine
Americans often use "whitworth " to describe any British nut but actually whitworth is a screw thread and few if any threads are whitworth

What will be useful is a cylinder base nut spanner

https://www.feked.com/triumph-cylinder-base-nut-spanner-7-16-x-1-2-af.html

But some grinding will make a normal one fit

Plus a head tool
https://www.feked.com/stainless-steel-cylinder-head-torque-tool-triumph.html

You can get by with taking an inch or so off a standard L shaped hex key to use as an adaptor - or find a bolt that will fit the socket head, add some nuts to it to create a hexagonal slug

If you do remove the head then look at the washers on the head. Replace them with the larger ones used elsewhere on the head, a decent supplier should provide those washers when you order the smaller ones by part number. Examine the seat of the washer and dress any crush damage. The original was too small and recessed into the cylinder head.

Buy new pushrod seals - I always buy more than I need because postage for one set or ten is about the same.
 
#5 ·
If you are doing the base gasket, change the O rings on the tappet blocks which requires removing the blocks from the barrels. You will need the two pronged tool that is hit with a hammer. Do not try and remove the blocks without one or it might shatter.
Base nuts, use a half inch AF ring spanner and grind it around the edge until it will sit over the nuts. A top quality spanner needed as it will have thin sides after grinding. I use Britool or Bedford. Gedore,Gordon, King Dick,Williams makes will also suit.
 
#6 ·
Interesring read!

I have the same job on my winter list, under the heading "Make Engine Oil Tight". E.G. Leaks from the cylinder base and rear pushrod tube.

I have a set of thin-walled cranked ring spanners that will undo the base nuts but how do you torque them down again afterwards? I cannot see a socket and torque wrench getting access, even with a UJ.

Cheers,
Ian
 
#8 ·
I have a set of thin-walled cranked ring spanners that will undo the base nuts but how do you torque them down again afterwards? I cannot see a socket and torque wrench getting access, even with a UJ.
I've been wondering about this too. You could possibly practice on other similarly sized nuts on the bike with the torque wrench and get a feel for how far you'd have to tighten the same nut with the thin walled spanner to achieve the correct torque? Then transfer it to the base nuts, it would be approximate but you'd be able to achieve even tightening.

Or something like this if you can find the imperial size.

https://www.dirtbikexpress.co.uk/product/motion_pro_torque_spanner_adapter
 
#7 ·
https://www.norbar.com/en-gb/Home/Torque-Wrench-Extension-Calculator

Assuming you have a torque wrench, the above pic shows the use of an extension spanner that fits the nuts.

Admittedly it only shows a perfect situation where the bits fit in a precisely straight line. This is not important.

What is important to know the radius from force applied (on the handle)in a straight line to the bolt, and the corresponding distance from the same point on the handle to the torque wrench centre. All that is important ia relative radii, as long as the connection isn't bent beyond 30 deg.

As you have a spanner for the nuts, presumably it has an opening at the other end. Some nuts and a bolt can fit that, which can fit a socket into a torque wrench maybe? Just throwing thoughts out.

I'm sure there's a way.
 
#10 ·
I have rebuilt a number of engines over the years and always go by the book, wherever possible. I like the idea of the extensions and that torque calculator is great too, thanks both!

I fear that the previous builder tightened the nuts by feel and this is why it leaks and I found some of the nuts had worked loose. I can't blame the PO though, he was one of the throw money at it brigade, and paid a renown tuning company to build the engine. I prefer to do these things myself, so I know it is done right. ?
 
#12 ·
Picked up a set of imperial Crow's Feet at the Great Dorset Steam Fair today! What a great event! Over 140 classic bikes on show and many hundreds of steam engines too! Got a great video of all the bikes (well, all that would start) going out into the parade arena. I would upload it here but there is a non-specific warning on large files in the forum T&Cs...
 

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#13 ·
Hei Helge,
I would not worry so much about the torque settings on the nuts, thousands of Triumphs are oil tight with just hand tightening.
There are several other things that can lead to oil leaks at the base;
The condition of the studs are important, the inner 4 larger studs have blind holes, it is important that the studs bottom out on the crankcase, you should see at least 1/2 a turn of clear thread sticking up above the crankcase face. If there is not, then there is not enough thread on the stud. If the stud jambs on the top thread all of the load is on that point near the surface, this could pull the metal up making a ridge that the barrel will sit on instead of being flat on the crankcases.
If you look at the 4 smaller studs, you will see the ones that have their holes drilled all of the way through the crankcase. There is no way for these to bottom out, so they need to be inserted carefully and not very tight. If they are tightened hard, the metal around them will be pulled up. They need to be fixed with ‘loctite’ to hold them in place and also to seal the threads. If you don’t do this oil will work it’s way up the threads and cause an annoying leak. Once loctite is used on the stud, the nut can be tightened normally to pull the barrels down.
If the crankcase face has already been distorted around the studs, removing the studs and carefully countersinking the holes can recover the face without resorting to having them milled.

The dreaded Triumph crankcase step might be causing your leaks.
At some point in Meriden history, Triumph decided that instead of bolting the crankcases together and machining the crankcase face as one unit, they could machine the left and right halves separately and when the bolted them together they would be perfectly matched. I don’t know how they got the idea that they could achieve this on 50-60 year old worn out machinery, but they thought they could.
Sometimes they are flat (lucky) and sometimes there is a 5 -20 thou step between the left and right sides (leaky).
Repair is not easy as you need to set a mill up, measuring from a mandrel placed between the main bearings to rectify this properly.

As Rambo has pointed out, the tappet block seals after 40 years will be brittle and need replacing, this is often overlooked.
You need the special tool and you need to measure carefully that the tappet block is square to the barrel, you will only be able to twist it when you are knocking it in, it will not turn when it is static. Failure to get the tappet block square means the valve timing will be unbalanced between the two cylinders.

Good quality O rings for the pushrod tubes are needed, a variety of thicknesses is useful to help get the correct pressure on them.

I might have made it sound a bit daunting, but it is not really.

As for torque settings, just tighten evenly by hand, run the bike, let it cool down and check again.

Regards
Peg.
 
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#16 ·
Quote StuartMac

"Yes and no. Actually you torque with the torque wrench at 90 degrees to the "extension", then there isn't actually any extension to the leverage. Or slightly less than 90 degrees if you want to be really precise ... assuming you've had your torque wrench calibrated ..."

Good info. Where do you get your torque wrenches calibrated? I've got 3 that have never been calibrated since birth as far as I know. So where do I go?

Thanks
 
#17 ·
Thank you all for the useful comments. I bought the 1979 T140 Bonneville Special in april. The engine ran ok on the road when I revved it up, but was rough on idle, later located to the balancing pipe between intakes having fallen off at some stage.

I have not yet found the source of the leak from the cylinder base area. It may come from the cylinder base to crankcase joint, or maybe from the lower end of the front pushrod tube.

My Bonnie needs a lot of care. Most of the time I have worked on it so far has been focused on sorting out the electrics. However I have now turned my attention to the engine. I am thinking of using degreaser to dry out the front area of the cylinder base, start the engine, and then try to see where the oil seeps out. If I am lucky it is only the bottom seal on the pushrod tube causing the leak. Wishful thinking.

But I also want to prepare for more work, hence my question on tools for the cylinder base nuts. I have now ordered this, and also the allen bit for the central head bolts.

I have a couple of torque wrenches for small and bigger torques. What I have done to check their calibration is:
- Lock a suitable bolt in a vice.
- Choose a torque setting on the wrench.
- Put the wrench onto the bolt, and put a fishing scale onto the handle, at 90 degrees angle.
- Measure the distance between the socket/bolt center and the location of the fishing scale hook.
- Read the scale when the wrench clicks.
- Use the calculation of power x arm to compare the setting of the wrench to the scale reading.

The fishing scale can be tested for accuracy with some known weight. On another note I have also used the scale as a torque wrench by hooking it directly onto a spanner and tighten to a scale reading that was calculated in advance.
 
#18 ·
Hi Peg,

If/when I get to the point where the cylinder block needs to be removed, I will check all the details you provided.

As for using a torque wrench, this is a habit to me because I do not trust the feeling of my grip very much. I have read an article showing that using a torque wrench has some possible flaws, possibly making a good mechanic's hand better. This is connected to the friction in the threads varying by lubricated/not lubricated/type of lubrication, friction between the nut and the base etc.
 
#19 ·
I heard that too but the guys where I get by torque wrenches calibrated told me the difference in negligible as the force acting upon the mating faces far outweighs/overcomes any difference in thread friction.

The reason I asked them the question was that in a number or critical applications (e.g. big ends and main bearings) I clean the threads and nuts with carb cleaner to ensure they are grease-free then apply Loctite 286 Red. I was concerned that this effectively lubricates the thread (at least until the 286 is set) and wondered if I should apply a compensation to torque settings. Chap I spoke to said not to worry (felt like I had asked a stupid question ?
 
#21 ·
Hi Helge,

It seems I have to do some work on the upper end of the engine during the coming winter. I have an oil leak at the front base,
Normally, I would not dissuade anyone who wanted to "go by the book" and/or acquire yet more shiny tools and gadgets, being a long-time sufferer of Magpie Syndrome myself. However, in pursuit of the perfectly-set cylinder base nut, several points are being missed by the theoreticians:-

. Triumph cylinder base nuts were never designed to be torqued. When Edward Turner designed the Speed Twin, no-one had a torque wrench. Twenty-five or thirty years later, many commercial workshops did not have a torque wrench, never mind owners working in their sheds and garages. When the last of the Speed Twin's direct descendants was produced around fifty years later, a torque wrench might have become a common tool for home mechanics but no-one had changed those descendants' cylinder base fastening ...

. The earliest Triumph twin parts book I can find is 1946. Even then, the twins' cylinder base nuts were 3/8" small-hex., because Turner had not left enough space between the base studs and the cylinder bore for there to be standard-hex. nuts, a common spanner/wrench to tighten and loosen the nuts and enough cylinder material to support the bore. Small-hex. nuts for original British Standard threads were an off-the-shelf item for Meriden's fastener suppliers and Meriden made use of them in several places on all models; the 12-point nuts were only used after the change to Unified threads because small-hex. UNF nuts were not an off-the-shelf item, but 12-point UNF nuts were.

. To a great extent, the torque on a cylinder base nut is irrelevant, as long the nuts (and studs) are not so loose that increasing cylinder compression causes a gap between the cylinder block and the crankcase. The reason for an oil leak between crankcase and cylinder block is either gasket failure or the gasket cannot seal the gap between crankcase and cylinder block at that point.

. Tightening a fastener to prevent a leak between two components is only of use if the two surfaces are parallel to each other and perpendicular to the fastener's axis. On a Triumph, it is not wise to assume these things instead of actually checking them ...

Hope this helps.

Regards,
 
#24 ·
Understood, I didn't realise you got others to build your engines. However, torque wrenches have been around in various forms since at least the steam age, perhaps earlier and surely you would agree there is no more accurate way of torquing fasteners than a properly calibrated torque wrench?! Common sense and experience should always prevail in rare instances where published torque values are incorrect....
 
#25 ·
Yes, common sense and experience are very important tools in my opinion. Experience, however, comes at a price sometimes.
Luckily I found this great forum, and got help to find the spanner and Allen bit I need to avoid rounding off the nuts and bolt heads in question. And as a bonus I got lots of information on other pitfalls and torqueing.

After reading the interesting discussion taking place in this thread, I can't leave the forum for more than a few hours before I must come back looking for interesting information in this, and other threads.
 
#27 ·
I got my cheapish 'Daniel Forge' brand torque wrench calibrated twice in 30 years, I gave up after the first 10 years because it came back as almost spot on both times [last calibration sheet was 19.995 at 20ft/lb, gotta be happy with that]. The guy doing the calibration was actually impressed because he didn't think it would be that good given the price I paid. It is a reversible ratchet 'click' to set unit, probably Taiwanese.

I have never used a torque wrench on the general nuts and bolts including base nuts, its just not worth it. I do use mine on the head, gearbox sprocket and kickstart, clutch centre, engine conrods, sprocket and timing pinions etc etc
Everyone I know and have worked with do the same. But do whatever works for you.
 
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