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Thread: Triumph Twin twinshock trials bike.

  1. #1
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    Triumph Twin twinshock trials bike.

    Erm, no. But part of it soon will be........





    The background:
    Ever since i started competing in Classic Trials, (See http://www.ukgser.com/forums/showthr...-Tim-s-example) I have held the riders of old British bikes in some awe. Are they brave, skilled or crazy to pilot big lumps of iron around a trials course, when lighter and more nimble machinery is available? I must admit, watching them was great fun, and its better seeing some of the big old four strokes attacking sections instead of languishing in a museum. My favourites though were the big Ariels, and the Triumph twins.
    A couple of years ago I was offered a ride on a pre-unit Triumph 500 twin, in a Hardy frame, at one of our regular venues. So after the trial proper had finished, I gingerly took the bike out through 4 of the sections that were nearest to the car park. I had been able to 'clean' these quite easily on my Whitehawk, and manged to do the same on the twin, but it was very hard work! It seemed to be everything I expected the old bikes to be, heavy, ponderous, hard to turn, and in the 500's case, too powerful. I had arm pump, probably because the owner had told me how much it was worth, so had a death grip on the bars! I handed it back, thanfully undamaged, and decided the bigger bikes wern't for me.
    At the February 2016 Telford Classic Dirt Bike show, I came across this:



    Drayton are a renowned frame builders, mainly for Bantams, but have had sucess with other motors as well. Timolgra's C15 is in a Drayton frame. Now the colour wasn't exactly my cup of tea, but I thought the bike looked a good deal more compact than the one I rode. There was a for sale sticker on it, and spotting a familiar face manning the stand, I idly asked how much.
    Somewhat shocked, I dismissed any further musings in that direction! I did have a Pre 65 itch to scratch, so focussed my attention on looking for a decent C15 or Tiger Cub to dip my toe in the water, but not loose my shirt should it not be for me. Hence I became the owner of the Cub in the other thread.
    That Drayton Twin had been quite a talking point amongst the riders that I knew, and for each one that was shocked at the price, there would be one who could see how it had been arrived at. I hadn't realised that the bike was wearing just about the best of everything available, and the sums added up.
    Since then I have had chance to ride another twin, which was far more manouverable than the first. I asked the owner what he knew about the Drayton, and he replied that he and his father had spent considerable time trying to make his bike handle like it, with limited sucess!
    This itch was now starting to gnaw away at me, so this year's Telford show had me clutching my cheque book in anticipation. Sadly for me, a life changing illness had made Drayton's main man rethink his priorities. He would now only supply frames, not complete bikes. There were no 'customer' bikes for sale either, and none that they knew of. Crestfallen, I bought a couple of raffle tickets for the charity they were supporting, which was to win a frame kit, and wandered round the rest of the show.





    Telford is always a good place for catching up with people, some of whom I have known for years, and whose opinions I respect. By the time I left for home, I had half an idea in my head. On the Monday evening, a chance response to a facebook post, of all things, prompted a flood of messages and emails from various different people, the bottom line of which was "Stop pontificating and get on with it!" So I did.
    The frame kit is made to order, and take 4 to 6 weeks. With that on the go, I started the search for a suitable motor. I had been offered quite a few "boxes of bits", puporting to be a complete engine, or in some cases a complete bike, that had all been running when they were dismantled. I would much rather see one that was running now, and found one on ebay an hour away from me. This wasn't advertised particularly well, and only cropped up in my search term "3ta", as it was listed as a "Tribsa". It was registered, although SORNed, and had all the MOt's up to being taken off the road some 16 years ago. I had a brief conversation with the vendor, he said it ran, selected all gears, but smoked a bit. I put a bid on based on that, and a few days later became the proud owner!
    Collecting it that weekend, the vendor hadn't lied, but maybe his definition of 'a bit' and mine aren't quite the same! Still, nothing we can't fix.
    Mark
    Just when you've got this rat race licked, here come faster rats!

  2. #2
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    The purple & silver one is so cute! Keep the photos coming

    And what is the frame on the roadster? The tubes look so narrow.

  3. #3
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    I'd like to see this, when finished

    A mate has a trick C15 and he keeps saying 'have a go on it'..............but so far, I have resisted

    Maybe time for a rethink too, as (like Aqueduct) the Yorkshire Classic club put on some cracking Trials. over here
    JohnnyBoxer



    So many roads...........So little time......

  4. #4
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    Quote Originally Posted by markjackson View Post
    The purple & silver one is so cute! Keep the photos coming

    And what is the frame on the roadster? The tubes look so narrow.
    It definitely caught the eye! Apparently that is an original Triumph colour, mine won't be though.
    The "donor bike" for the motor was originally a BSA Barracuda, I'm reliably informed, modified to take the Triumph engine. There is a smattering of Suzuki parts on it too.
    Mark
    Just when you've got this rat race licked, here come faster rats!

  5. #5
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    These are nice..

    The Guzzi is my favourite though

    Attached Images Attached Images      
    JohnnyBoxer



    So many roads...........So little time......

  6. #6
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    At least the bike is a runner, and is in a rolling test bed of sorts, so I can get things sorted out before the new frame arrives.
    First things first, warm the engine and drop all the oils. There was some strange plumbing on the bike, which the vendor had said was from the previous owner making it look more like a high performance race bike. Emphasis on "look", he knew a lot of the bikes history and was quite certain there was more show than go to the modifications.



    The gearbox oil didn't look too bad, but the engine oil was like treacle. There are heated debates raging as we speak over "which oil?". I use the same oils as I use in all my other bikes, unless there is really good reason, so a couple of litres of Rock Oil Guardian 10-40 went in, and I ran it up again. There was a faint hope that the rings were just stuck, causing the smoke, and a couple of heat cycles might free them. It was supposedly stood for over 15 years! Needless to say, it still smoked, but at least it smelt better.



    Next I took the timing cover off to check the oil pump, and to see what the breather that had been added was doing. Nothing is the answer, there was a rawlplug jammed in it to block it up! I took the breather out and got the hole welded up.





    The primary drive side had quite a few jobs I needed to do for the new life the engine was going to get. Gear reduction and electric ignition were going to make it better as a trials bike. The primary and final drive sprockets were both due to go down a few teeth, 26 down to 16 on the primary, and 18 down to 14 on the gearbox. There are a few different ignition systems on the market, I opted for Electrex World after hearing good things about their ease of fitting. With all the parts ordered, I took off the side cover to see what I would find.



    One of the modifications carried out to later engines was to dispense with the rotary breather on the camshaft, and to take out the primary side crankcase seal, allowing the crankcase to breathe into the primary chaincase. Drill three small holes to let excess oil back into the crankcase, and vent the primary case to atmosphere. This explains the breather stuck in the chaincase filler plug. According to my triumph guru, reversing this mod wouldn't be detrimental to a lightly stressed trials application. Taking the clutch plates out I found there was an odd number of plates. This didn't seem normal, every other clutch I have know has had an even number of plain and friction plates. Must look into that. Pulling the old ignition rotor off allowed me to remove the clutch and primary gear, together with the duplex chain, as one. With the primary gear off it was a simple job to tap a new crankcase seal in, then put three small self tappers into the three holes.



    Taking off the inspection hatch at the back of the chaincase lets you remove the gearbox sprocket, and axchange it for the new one.



    Replacing the clutch housing allowed me to measure how much to shorten the duplex chain, before refitting it with a split link.



    With all that back together, it was time to fit the new ignition, which fell on with the minimum of fuss.



    The distributor and coils were dispensed with, and the new cdi and wiring added in just a few minutes. I carefully set the ignition timing, as per the instructions in the box, to 38 degrees before TDC, and pushed the bike outside to give it a try.



    I could barely turn it over on the kickstart! What had I done wrong?
    Mark
    Just when you've got this rat race licked, here come faster rats!

  7. #7
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    Changed the gearing ratio > kickstarter>via gearbox>primary chain clutch chain wheel>engine sprocket>engine crankshaft.

    What is the kickstarter like operating just the clutch chain wheel with the primary chain removed? Smooth? No. Gearbox jammed?

    With the primary chain still removed, turn the crank with a spanner on the lock nut. Remove 4 rocket box caps. 4 valves operating?

  8. #8
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    Quote Originally Posted by earthmover View Post
    ........I could barely turn it over on the kickstart! What had I done wrong?
    Mark
    Reducing the primary drive in respect of the engine has had the opposite effect in respect of the kickstart which works through the gearbox. You may need to rethink the primary ratio change.
    '83 BMW R100
    Yamaha S10
    '69 BMW R60 US

  9. #9
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    So, after stripping it down again to make sure everything was free, and that nothing could be binding when tightened up, I rebuilt it all. Same result. Can barely move the kickstart.
    Pulled the spark plugs and now I can move it, and there's a big fat spark at the plugs. Put them back in and same again, hardly turn it over. It's as though the compression has suddenly increased........
    There was a trial the next day, and I knew my Triumph mentor would be there. Fair play to him, he didn't laugh out loud when I told him of my predicament, simply smiled and asked if I'd thought about fitting a longer kickstart, made specially for trials engines with lowered primary gearing?
    Mark
    Just when you've got this rat race licked, here come faster rats!

  10. #10
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    Quote Originally Posted by earthmover View Post
    Fair play to him, he didn't laugh out loud when I told him of my predicament, simply smiled and asked if I'd thought about fitting a longer kickstart, made specially for trials engines with lowered primary gearing?
    Mark
    That would work too!
    '83 BMW R100
    Yamaha S10
    '69 BMW R60 US

  11. #11
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    This shows how the bike ran when I picked it up.



    "Smokes a little!"
    Mark
    Just when you've got this rat race licked, here come faster rats!

  12. #12
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    With the new kickstart fitted I was able to turn the engine over easily, and she fired up with very little fuss. With the timing set as per the instructions though, there was a distinct tendency to over-run when the throttle was closed. As yet I hadn't touched the carb or anything else (even though my spanners were twitching) having been advised to take one step at a time to ensure I didn't confuse the issue. Pre 65 patience, they call it. As the only thing I had changed that could cause it was the timing, I retarded it a bit, and it ran better. I retarded it quite a lot, and it ran perfectly, albeit hot. Now I was a lot closer to the figure I had been advised by other Twin trials riders, so this is now my benchmark setting for further "experimentation" once everything else is sorted.
    The distributor hole is now the crankcase breather, and the primary chaincase is sealed again. The gearing is lowered to trials spec, and everything runs well, but it still smokes like a chimney. I'm going to have to delve further.



    Stripping the exhaust pipes showed just how much soot and carbon was in there. Taking the cylinder head bolts off answered one question. Two of the bolts were chamfered nearly quarter of the way through their heads. This was to allow them to slide past the frame tube, so the head could be removed without taking the engine from the frame. I will be replacing those when the lump is in its new home.





    The rocker boxes were next, revealing an excess of silicone instead of gaskets. I use silicone myself, but sparingly. Not so the last person who had it apart!



    Carefully lifting the head off after taking out the push rods shows a very polished pair of bores.



    Ever so carefully persuading the barrel upwards, making sure the pistons dont flop onto the studs, and voila! More silicone!



    The rings weren't stuck, but the gaps were well beyond the limit, if they were the correct ones in the first place. The barrel was on its last overbore, but the piston clearance was within the limits.


    Carefully cleaning all the silicone off was a slow and laborious process, as was cleaning the carbon off the cylinder head, but I was convinced it would be worth it in the long run.
    The new rings slipped on, and then offered up in the barrel showed them to be good and tight. A light hone to break the glaze was all that would be needed before refitting. My initial thought, that I would be able to squeeze the piston rings in by hand as I pushed the barrel down, was cut short by the realisation that I would need three hands. A quick trip to Demon Tweeks for a pair of ring compressors made the job a doddle!



    New gaskets and pushrod tube seals, with just a smear of sealant should hopefully reduce the leaks from that area. With the barrel tightened down, the head was eased on and the cleaned rocker boxes fitted, again with gaskets this time. Quick check of the valve clearances, and we're ready to give it a go!
    After a few gentle kicks with the kill switch pressed, I crossed my fingers, and gave it a welly. The bike burbled happily into life and I kept it at a low tickover until I was certain the oil was circulating. I was pleased to see that there was no smoke from the exhaust, but less pleased by the amount of oil that was dripping from various points. A quick spin to see what the gearing changes had achieved, and to put the engine under load, then back in the garage. My intention had been to drop the oil straight away anyhow, to check for any debris and flush out any muck I may have dislodged. One of the leaks turned out to be the sump plug. Now I know why that had silicone all round it, the threads are knackered! Thankfully the plug, not the sump, so that was easily cured.
    After giving the engine a good clean, and running it again with fresh oil, it turns out that some of the leaks were just old residue that had got hot and run off. The base of the engine and pushrod tubes were dry as a bone. The primary chaincase had a leak from some previous damage, careful gasket positioning, and a helicoiled thread reduced this to a weep.
    Happy with my progress, lets have a look at the gearbox side.....
    Mark
    Just when you've got this rat race licked, here come faster rats!

  13. #13
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    Just when you've got this rat race licked, here come faster rats!

  14. #14
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    Enjoying your progress.

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    Short of pictures for this part, as my phone decided to jumble the photos together, rendering them unusable.
    The clutch action was very stiff and didn't seem to have much travel. I'd cleaned up the tabs on the clutch plates and made sure everything worked properly on that side of the motor, so now to look at the other side. The actuating arm is behind the gearbox cover, so I undid the bolts and carefully pulled the cover off. There is an "inspection plate" on the top, which is obviously not a Triumph original feature. No idea what that could be for, but at the moment its a good ingress point for water, and of course mud. The boot for the clutch cable was torn and ill fitting, another way in for it. Not ideal for the intended use, and explains why half a pint of emulsified green slop fell out when I finally got it off.



    The actuating arm swivel, where the cable nipple sits, had quite a lot of free play in it, so a washer and a new split pin tightened that up. The arm turns a worm gear in a housing, which moves the push rod. There was grit in the worm gear, stopping it from moving freely. That cleaned up and oiled made it smoother, and the two together translated to a couple of mm more travel to the push rod. I then looked at the gear lever spring housing, and decided that could do with a clean up. Big mistake.



    The springs sensed their new found freedom when I took the cover off, and sprang to opposing corners of the garage, taking the tiny top hat washers with them. As my garage is too full, too disorganised, and the floor too dirty, retrieving them was going to prove a challenge!
    Much swearing and crawling around the floor later, all components recovered, cleaned and reinstalled. Mental note not to undo that again unless absolutely necessary.
    With everything bolted back together and fresh oil in, the clutch action is much better. Discarding the original pressure plate for an alloy one is a popular mod, not a huge amount of difference for the money, but looks shiny doesn't it?





    Mark
    Just when you've got this rat race licked, here come faster rats!

  16. #16
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    Re-took some of the photos that had been lost.

    If you look at the cylinder head bolt centre screen, you can see where it has been cut away.



    Not the best picture, but the distributor hole plugged with a hose tail to make a breather.



    Shiny new oil pressure relief valve. The original had an open plunger as a tell tale, not the best for trials.



    Mark
    Just when you've got this rat race licked, here come faster rats!

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