And yet another T120...

Triton Thrasher said:

The chokes will almost certainly fix your cold starting, but they're just such a bloody contraption to buy and fit.

And then they shut themselves at high speed!

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EXACTLY !!

That’s why I said “I’m resigned to it” ie I would prefer to avoid fitting them.

Fast Eddie said:

You omitted to finish the Bonneville story Dave, did you fit chokes to it? Did they resolve the starting issues?

I’m reigned to the fact now, so next job is to fit chokes.

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Ah, yes, good question Nigel, and I can't answer that yet definitively until I get the poor old thing together! My rebuild has been pretty slow - delays, awkward repairs, not enough time, etc. The bottom end and gearbox are together. I was thinking of posting a rebuild thread but not the usual, instead highlighting the awkward, fiddly jobs I encountered.

In the meantime, I found this on Youtube:

A very nicely presented '67, running sweetly in the South of France. Now that is a place to ride bikes.

Don’t think about it Dave, post it! That would be a very interesting thread...

I raced against unit-construction Triumph 650s back in the 60s. They were fast and handled superbly.

daveh said:

Ah, yes, good question Nigel, and I can't answer that yet definitively until I get the poor old thing together! My rebuild has been pretty slow - delays, awkward repairs, not enough time, etc. The bottom end and gearbox are together. I was thinking of posting a rebuild thread but not the usual, instead highlighting the awkward, fiddly jobs I encountered.

In the meantime, I found this on Youtube:

A very nicely presented '67, running sweetly in the South of France. Now that is a place to ride bikes.

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That is certainly a lovely running machine on some spectacular roads. Am I the only person that finds the rider a bit reckless at times? Man. He must have ESP the way he cut around some of those vehicles. He may risk his life, but damn it.....the bike..... (kidding)

Britfan60 said:

Am I the only person that finds the rider a bit reckless at times?

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No, I wasn't impressed either. How many Bonneville's do you suppose have disappeared over the last 50 years from being horsed around like that.

Blimey guys...

It’s a motorbike not the Mona Lisa !

Guy has a nice bike and was enjoying it, s’what they’re for innit?

And I’m sure some things looked worse than they were due to camera angles etc.

Yeah, but smooth is best.

The fish-eye lens definitely distorts things. I didn't see anything dangerous, not even close.

I love riding my '67 (although it's been a while); you just have to embed the operating envelope into your brain before you engage 1st gear, and BRAKE ACCORDINGLY! SLS front brake and half-width MUST be accounted for.

Very interesting thread Eddie, and very nice bonnie, only just found it in a Norton forum!

I have a v original 68 I repatriated 10 or so years ago, and am in the throes of a similar-ish mild "pep up" hence my interest; Mine is v v original (ok, resprayed, but very nicely) so I didn't want to mess with it externally. I thought I'd share my thoughts and approach compared to your build? None of this is criticism, just compare and contrast stuff.

My own recipe is:-

Megacycle cams - dialled in - hugely impressive on my much-modded T140, albeit a hotter grind than the 510-05 mild ones in the '68 which was really more about known quality rather than performance, after some issues with other makes.

Dynamic balancing - reckon you were lucky without doing that, I recently recommisioned and rode an "as per factory" two owner T140 which is horrible above 60mph, so admittedly clearly a bad one!! My own T140 with other pertinent mods as well is as smooth as my commando at least up to 80. It was never as bad as that 2 owner T140 (they were built on the same day in 1975!) but balancing made a huuuge difference. The '68 pre-rebuild was somewhere in between, and definitely not as comfortable at a 70-something cruise as the t140 is. Which leads neatly into'..

Gearing up - not as far as I went on the t140 as that has very detonation-resilient Nikasil barrels, but find standard gearing still too busy. From memory I am at 20 teeth on the '68. It's a light bike and I am 12 and a half stone, it's a one up bike, all part of the equation I think?

I too was going to go the 5 speed route as the 4 speed is pleasant but a bit crunchy in 1st and 2nd, but ended up using the cluster I had got for it in my recently acquired Rocket Three. I figured (correctly I think, based on the results in that bike) the triples need a 5 speed more than any of the twins? Nowhere near the need to keep a Triumph twin on the boil as the triples.

Big bore- I went for an Aerco kit as I personally dislike the Morgo barrel shape? I had detonation issues wih this until I rejetted but I strongly believe a 750 can be as smooth as a 650, given a decently balanced crank, and sensible compression. I.e. nowhere near what you can get away with on a commando with it's much better combustion chamber. My hot rod t140 actually runs quite low (static) compression due to the low domed Asso pistons in the Gilardoni barrels, but is fast, sweet and smooth, helped I guess by the better ring sealing the nikasil affords? It will wipe the floor with my (admittedy singe carbed) 850 commando.

Belt drive - I had a Hayward kit for about 10 years on the T140 - run in oil which you are not really supposed to? No problems but after 10 years it started to shed teeth which is fair enough I reckon. Put in a new "red" belt and started to run it dry (I was experimenting with reed valve breathers so wanted a dry primary for this) - supposedly improved oil resistance with the red belts?? Whole belt stripped to the reinforcing wires inside a 1000 miles, a right mess. For an almost exact recreation of mine see Sump online magazine! Could have been lack of cooling from the oil, who knows?

http://sumpmagazine.com/classic-bike-workshop/triumph-t140-primary-belt-failure.htm.

I'm not trying to open a can of worms discussion wise, or divert this thread, as I'm aware belt drives can be divisive things! Once I abandoned it and went back to the triplex primary (in oil of course), I became aware of two things however?.

1/ I stopped worrying about a belt failure in the middle of nowhere and plans to carry a spare belt and necessary tools - which would have negated any weight savings!

2/ I couldn't actually tell the difference vibration wise or anything else (effective flywheel weight for example) before and after, except possibly a little bit more noise from the primary chain tensioner? Possibly.

You mentioned you weren't sure about the P&P seat? I cant post pics here but the totally original seat on my 68 looks v similar, albeit mine had the mid-season addition of a grab rail bolted to the pan, hence pan is bent up at the rear as everyone used that grabrail as a lift handle for the centre stand :0(
Cover should be plain vinyl not basketweave, but pretty sure that doesn't bother you or you wanted basketweave? P&P should have known though if you didn't?

I like schmozzles but those Camembert (as the French call them ;o) ) air cleaners are one of those lovely iconic pieces on a 60s Triumph that I would personally always have to leave on. I love the view of them from above when riding! A bit like the GT handgrips on most britbikes, or the "Z" plates on a commando, or the...I guess everyone has a different "do not mess with" list!!

I don't think my '68 will ever be the long distance tool my T140 undoubtedly is (4000 miles last summer) as that would entail too much money and/or other more noticable mods, but I do agree the Triumphs are lithe and wieldy in a way that not even a Commando can offer, by way of compensation!


Anyway, please excuse stream of conciousness and enjoy it, it's very nice!

Oh, and would love it if you DID dyno it! I estimate my t140 with some nice headwork, better flowing Mikunis, hotter cams and that low compression is around 50? But it's 50 lbs lighter than the commando, heh heh.

Dave

wavey_davey said:

I too was going to go the 5 speed route as the 4 speed is pleasant but a bit crunchy in 1st and 2nd, but ended up using the cluster I had got for it in my recently acquired Rocket Three. I figured (correctly I think, based on the results in that bike) the triples need a 5 speed more than any of the twins? Nowhere near the need to keep a Triumph twin on the boil as the triples.

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T120/140 use a different mainshaft from the T150/160...

grandpaul said:

T120/140 use a different mainshaft from the T150/160...

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Yes I know, thanks Grandpaul. There's a handy list of parts for the 5 speed version in the 1972 BSA parts book. I think there were a few other bits that weren't interchangable like gearlever quadrant shaft etc? Phil Pick, a long-standing Triples guru does a nice tutorial on the conversion available through TR3OC website and probably elsewhere?

Great post Dave, thanks.

Yes belts are a strange one aren’t they? Stories of unexplained failure etc.

FWIW, I ran a dry red Hayward belt on a 84rwhp 8 valve Triumph twin racer without issue.

With my current one, a dry primary is not possible. But, removing the pin that locates the primary chain adjuster rod leaves a large drain hole very low down. So I figure my primary is being lubricated by little more than mist, rather than the belt dragging oil with it. I’m aware of the alledaged issue of oil twixt belt and pulley causing the effective diameter of the pulley to increase and cause failure. I’m hopeful that my set up allows some lube, but not enough for that.

Time will tell I guess.

BTW, the 5 speed box is a delight on this engine. Highly recommended.

5 speed box a winner then Nigel ,good stuff. As for the boy on the video and his riding style, I thought it was just a guy riding with confidence. Couldn't see anything wrong !

wavey_davey said:

I like schmozzles but those Camembert (as the French call them ;o) ) air cleaners are one of those lovely iconic pieces on a 60s Triumph that I would personally always have to leave on. I love the view of them from above when riding! A bit like the GT handgrips on most britbikes, or the "Z" plates on a commando...

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Dave, I am just less respectful than you! I took the air cleaners off of the Bonnie, I took the Z plates off of the Commando, and I take GT handgrips off of most of my Brit bikes (tho they’re still on the Bonnie, for the time being)...!

Belts are excellent and will last a long time without any adjustment. I have never had to adjust belts in service on my G50 and that gets thrashed regularly.

Because the Triumph clutch drum runs on open rollers rather than a sealed ball race, they have to be kept lubricated. Racers tend to run their primary cases dry only because they take their clutches apart regularly. Therefore, I think it's best to run them wet and then you can virtually fit and forget for many thousands of miles. Tony Hayward belts will run wet or dry. I had a long chat with him last week (not related to belts) and he told me he sources the more expensive and well-made belts because experience has told him that the cheaper stuff doesn't last.

Edit: Of course unit twins' belts can't be adjusted. My mind was on pre-unit...

Re the Bonnie Youtube vid, I think it's great to see a Bonnie used as was intended by the factory

(The same guy also posted a vid of his '68 Bonnie being ridden off-road, jumping off crests, etc).

daveh said:

Re the Bonnie Youtube vid, I think it's great to see a Bonnie used as was intended by the factory

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Indeed, big respect from me too!

daveh said:

Belts are excellent and will last a long time without any adjustment. I have never had to adjust belts in service on my G50 and that gets thrashed regularly.

Because the Triumph clutch drum runs on open rollers rather than a sealed ball race, they have to be kept lubricated. Racers tend to run their primary cases dry only because they take their clutches apart regularly. Therefore, I think it's best to run them wet and then you can virtually fit and forget for many thousands of miles. Tony Hayward belts will run wet or dry. I had a long chat with him last week (not related to belts) and he told me he sources the more expensive and well-made belts because experience has told him that the cheaper stuff doesn't last.

Edit: Of course unit twins' belts can't be adjusted. My mind was on pre-unit...

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I just knew that someone would comment that I am wrong to distrust my belt primary, sigh... Yes, of course there are many who run them and have ZERO issues, just as there are SOME who definitely have problems, as did I and as did the other T140 in the link I posted (theirs was wet I think?), both from Hayward btw. I ran it in oil for 10 years and it had started to break down, fair enough. I ran it dry (with greased clutch rollers) for less than a year and the results were horrible. YES I spoke to Tony Hayward first (nobody has a SHORT conversation with him ;o) ) and he gave me the same story about wet or dry. I see why Commando riders use them to prevent primary leaks, but still not sure what they "fix" in a road going unit Triumph, was my ultimate conclusion? Weight saving? Mine saved about 2-3 lbs? Why would I go there again??
p.s. My ex-racing Harley has belt final drive, and I love it, but then I hate exposed chains on modern bikes!

Please, really don't want to turn this into yet another belt primary thread, so let's agree to differ?

Fast Eddie said:

Indeed, big respect from me too!

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This is my favourite you tube footage of a sixties triumph twin, good camerawork and, extremely rare on youtube motorbike vids, good sound.



This one is a bit "hipster" and self-conciously cool (and the bike is a bit of a bitsa, but that's fine), but nicely done (professional video).



Dave