T140 crank balance factors

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Tigernut

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I have a TSS crank which I will be using in a T140 engine I'm building. TSS cranks were balanced to 69%, whereas T140 cranks were balanced at 74%. I have no idea why Triumph decided to use 69% for the TSS, when it went in exactly the same frame (if anybody understands why this was, I'd be very interested to know).

I am told by an expert Triumph twin engine builder that 80% is pretty much the best balance factor to go for. So I have three to choose from! If anybody has knowledge about this, and would be willing to share, I'd be very grateful Thanks in advance....
 
I can’t offer any advice here. But I do know the TSS balance factor worked, mine was the smoothest Triumph twin I’d ever ridden at the time. The fastest too!

They have lighter pistons, a stiffer crank, and a higher rev potential, I’d guess this was all factored in.

There’s no such thing as the ‘perfect’ balance factor, it depends on the frame being used, the rev range at which you want it to be smoothest, and many other factors. I’d find a balancer that knows Triumphs and comes highly recommended, and tell him where you want it to be smoothest, and hope for the best!
 
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Yes, what Fast Eddie says...If you ride a dozen T140's ,they all vibrate differently...And a smooth Triumph is relative to other Triumphs because none of them smooth by modern standards. And more power usually means more vibration, something to consider.
I would think a TSS crank is an excellent starting point...
 
My instict is to go with the 69% balance factor that Triumph decided on, if the TSS frame and engine mountings were the same as the T140? I wondered whether the TSS had any frame mods, or AV engine mounts? If not, I can't think of any reason not to go for 69%.

It will be using standard 8.6:1 pistons - even if these are heavier than the TSS pistons, would this give any reason to change the balance factor?

I wish I knew a TSS expert in the UK I could give a ring about this!
 
I see you asked the question on Brit Bike and a poster with supposed experience claims the TSS crank has designs differences that will be a problem...Have you looked into that?
 
Tigernut said:
My instict is to go with the 69% balance factor that Triumph decided on, if the TSS frame and engine mountings were the same as the T140? I wondered whether the TSS had any frame mods, or AV engine mounts? If not, I can't think of any reason not to go for 69%.
Click to expand...

There is no difference between T140 and TSS frames. AV frames were, of course, a different ball game but not relevant.

Personally, I’d be inclined to give the 69% factor a go too...
 
I've built a couple of 750 motors for other people & had the cranks dynamically balanced to the factory 74%. Both were nice to ride according to the owners. My own 750 Tiger is so nice that I left the crank alone when I stripped the engine to replace the failing T.S. main, so I think the factory knew what they were doing but sadly did not always apply it. Also, I recently rebuilt a Harris Bonneville which has the TSS crank but the big ends are ground to a smaller diameter to suit the T140 rods. Have you taken this into account?

Martyn.
 
My two cents worth Tigernut has the best single piece of a TSS engine "the crank" my good mate had a TSS for many years and during these years that bike sent may long nights up on my work bench rebuilding and tinkering with that dam engine, we un-fondly referred to that Meriden Acronym as Thousands Spent Stupidly.

I did actually put a TSS crank into a set of T140 cases with a Weslake 8 valve kit up top. I run this ridged mounted in wide line feather bed, balance factor unknown but yes it vibrated but didn't really worry me as it was a race bike. Engine went for a few years and then sold engine to a bloke for a road bike I lost touch with it there after. I then fitted a complete 750 180deg Nourish Westlake parallel twin pre unit arrangement to the featherbed, this was a good set up and probably the most Vib free parallel twin I have raced.

From what I have heard yes the std balance factor of the TSS engines was pretty good but I would like to here from any one who rode a TSS long enough or far enough to really draw comparison against a same year 750 Bonni :-)
 
I did about 15,000 - 20,000 miles on a TSS inc thrashing, touring and commuting. Definitely the smoothest standard Triumph twin I’ve ever ridden and good grief did it rev! I was younger and stupider then, I would rev the poor thing past the digits on the tacho in pursuit of my Japanese mounted mates.

Its the ultimate ‘what cudda been‘ engine. The Weslake / NRE stuff is truly excellent. Triumph suffered from some bad suppliers, some bad quality control, and some unexplainable design changes whereby Brian Jones changed aspects of the Weslake design for no apparent reason. Had they got it right, and done it 5 years earlier, it would have been a true game changer for them.

I had a few minor niggles, like a dropped valve and two cracked heads. Eventually I split the cases in half. But it’s all character right? Probably wudda dropped a liner too had I not fitted the excellent Gilardoni nickasil barrels. It also had NRE rocker shafts, valves, guides, head gasket arrangement etc quite early on in my stewardship. And the powder coating...I stripped mine off very early on, it was SO thick in places, between the fins etc, it was like an insulating jacket and must have led to them running really hot.

Until it split the cases it had never been stripped below the barrels, it had over 30,000 hard miles on it by then. The big ends didn’t even need grinding (paper filter kit in the OIF). I took it off the road and went through it thoroughly, even fitting bronze skulls in the head. A forum member (perhaps ex member now who got fed up with some of the BS) and his friend bought it off me as an unfinished project and completed it to a very fine example.
 
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<Had they got it right, and done it 5 years earlier>

Same could have been said about the Trident, sadly.
 
I have a Harris Bonneville T140, and so it has the TSS crank but with the smaller big end journals as Martyn said. It was a none runner when I bought it and so as I was rebuilding the engine, sent it to Basset Down for balancing. They drilled it a lot, so much so that it looked like a piece of swiss cheese and said that they had balanced it to 80%, even though I specified a lower figure, possibly 72%-75% but can't be absolutely sure now.

The results are that the engine is quite smooth up to 5,000rpm, but after that, it vibrates quite badly through the frame / seat area and is not nice at all. With hindsight, I wish that I'd left it as it was, seen what it was like and then if I was unhappy with it, despite it being a bit of work, going back in then and changing the balance factor based on good advice, which is what you are trying to do now.

Somebody that I know that has one of these, has told me that his Harris Bonny is smoother than his Moto Guzzi V twin, which is surprising to me having owned 2 x Guzzis which were very smooth at all revs.

I am led to believe that the TSS crankshaft is heavier, although I don't know absolutely if this is correct, but this probably has something to do with the different balance factor? So my advice (for what it's worth.....not much :D ) would be either to leave it as it is and try it, or consider having it balanced to the 69% factor with the rods and pistons that you are using. Does it have the TSS large journals and TSS rods?
 
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Reggie said:
I have a Harris Bonneville T140, and so it has the TSS crank but with the smaller big end journals as Martyn said. It was a none runner when I bought it and so as I was rebuilding the engine, sent it to Basset Down for balancing. They drilled it a lot, so much so that it looked like a piece of swiss cheese and said that they had balanced it to 80%, even though I specified a lower figure, possibly 72%-75% but can't be absolutely sure now.

The results are that the engine is quite smooth up to 5,000rpm, but after that, it vibrates quite badly through the frame / seat area and is not nice at all. With hindsight, I wish that I'd left it as it was, seen what it was like and then if I was unhappy with it, despite it being a bit of work, going back in then and changing the balance factor based on good advice, which is what you are trying to do now.

Somebody that I know that has one of these, has told me that his Harris Bonny is smoother than his Moto Guzzi V twin, which is surprising to me having owned 2 x Guzzis which were very smooth at all revs.

I am led to believe that the TSS crankshaft is heavier, although I don't know absolutely if this is correct, but this probably has something to do with the different balance factor? So my advice (for what it's worth.....not much :D ) would be either to leave it as it is and try it, or consider having it balanced to the 69% factor with the rods and pistons that you are using. Does it have the TSS large journals and TSS rods?
Click to expand...

It has the large journals, being a TSS crank, not a Harris Bonnie crank. Steve Campbell is making me a set of rods, which will be compatible with the T140 top end. I have decided to g with the 69% balance factor, now that I know a little more about the bikes (I had wondered whether the TSS had slightly modified frames, but it seems they were identical)
 
Fast Eddie said:
I did about 15,000 - 20,000 miles on a TSS inc thrashing, touring and commuting. Definitely the smoothest standard Triumph twin I’ve ever ridden and good grief did it rev! I was younger and stupider then, I would rev the poor thing past the digits on the tacho in pursuit of my Japanese mounted mates.

Its the ultimate ‘what cudda been‘ engine. The Weslake / NRE stuff is truly excellent. Triumph suffered from some bad suppliers, some bad quality control, and some unexplainable design changes whereby Brian Jones changed aspects of the Weslake design for no apparent reason. Had they got it right, and done it 5 years earlier, it would have been a true game changer for them.

I had a few minor niggles, like a dropped valve and two cracked heads. Eventually I split the cases in half. But it’s all character right? Probably wudda dropped a liner too had I not fitted the excellent Gilardoni nickasil barrels. It also had NRE rocker shafts, valves, guides, head gasket arrangement etc quite early on in my stewardship. And the powder coating...I stripped mine off very early on, it was SO thick in places, between the fins etc, it was like an insulating jacket and must have led to them running really hot.

Until it split the cases it had never been stripped below the barrels, it had over 30,000 hard miles on it by then. The big ends didn’t even need grinding (paper filter kit in the OIF). I took it off the road and went through it thoroughly, even fitting bronze skulls in the head. A forum member (perhaps ex member now who got fed up with some of the BS) and his friend bought it off me as an unfinished project and completed it to a very fine example.
Click to expand...
Not that a TSS isn't the best of the bunch but a dropped valve and two cracked heads is far from minor issues, LOL.
I bought a well used T140D a few years ago...some friends rode it and called the Triumph Mr Smoothie. A lot less vibration than others especially over 4500 rpm.
The next year I split the cases and rebuilt the engine with a few performance tricks. Other than making sure the new pistons were as close to weight as the old ones, no balancing work done.
The now has noticeably more power but it still a smooth runner for a Triumph. Running the 750 up to 7000 in the gears ,it does feel like it's not thrashing the engine to an untimely end......Riding my 96 900 Monster in comparison is a whole different sort of non intrusive vibration...
 
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Reggie said:
It was a none runner when I bought it and so as I was rebuilding the engine, sent it to Basset Down for balancing. They drilled it a lot, so much so that it looked like a piece of swiss cheese and said that they had balanced it to 80%, even though I specified a lower figure, possibly 72%-75% but can't be absolutely sure now.
Click to expand...

Basset had an experienced balancer who knew British twins and they had an excellent reputation, he left and set up his own outfit. Basset for a period of time then had no experienced Brit twin balancer, do not know even if they have one now but during the time after the experienced balancer left results were dire, Paul Goff was one who ended you in your position with his A10 as documented on his site.
 
What’s the name of the ex Basset Down bloke and / or his company Kommando ?

I used Basset down for years and was seriously impressed with them. Reggie is being kind above as it was I who recommended he go there... DOH!

I had my Commando crank done by a chap called Paul Gardias in Witney. Tony Smith put me on to Paul and he seemed to do a very good job.

I used to have cranks rebalanced as a matter of course, no matter what. These days, if it’s good beforehand, I’m more inclined to leave it be...
 
The bloke I dealt with at Basset Down was called Phil. I was very happy with the cranks he did for me.
 
Fast Eddie said:
I used Basset down for years and was seriously impressed with them. Reggie is being kind above as it was I who recommended he go there... DOH!
Click to expand...
Nigel, don't beat yourself up. I asked the question on the forum, "should I or shouldn't I," and I had used Basset Down prior to this and was very pleased with the results they did on a Guzzi crank I'd sent them, so anticipated the same positive result.

I don't know if I ever told you this Nigel but prior to sending the crank I'd been in touch with Rockerbox in Farnham about another matter, and they told me of a recent destruction done to one of their T140 crankshafts by B.D. i.e. swiss cheese and vibration and so what did I do? I still sent my crankshaft to B.D. What sort of an idiot am I? Answer.....a big one.
 
Tigernut said:
My instict is to go with the 69% balance factor that Triumph decided on, if the TSS frame and engine mountings were the same as the T140? I wondered whether the TSS had any frame mods, or AV engine mounts? If not, I can't think of any reason not to go for 69%.

It will be using standard 8.6:1 pistons - even if these are heavier than the TSS pistons, would this give any reason to change the balance factor?

I wish I knew a TSS expert in the UK I could give a ring about this!
Click to expand...
The balance factor depends on the RPM you use the most. For continually revving above 5,000 RPM, I would use the 80% balance factor. For commuting I would use standard.
 
Fast Eddie said:
What’s the name of the ex Basset Down bloke and / or his company Kommando ?
Click to expand...

I have the info somewhere but it's of no use as he no longer operates independently.

Found it, he moved to

J&J Engineering
Unit 5
Unicorn Business Centre
Chiseldon
Swindon
SN4 0HT

But left there too, no idea where he went too.
 
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