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I have 1968/9 TR6 P. I've ridden it for about 16 or 17 years in Kenya. its always vibrated more than my BMW R80 G/S (which doesn't really vibrate at all)
So my question is, what's normal? I find it uncomfortable cruising at anything that you'd consider a reasonable speed, 60mph / 100km +
I have a Boyer electronic ignition timed at 38 degrees before TDC. All the engine mounts are tight etc. I have to fit new stantions at some point soon as well as head stock bearings.
So what's normal acceptable vibration? Eyes shaking, teeth shuddering? There're not many around in Kenya and I haven't found one to compare to yet.
Any thoughts greatly appreciated
Guy

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If the handlebars are no thicker than a baseball bat at 6500 rpm its probably normal.

At least, that was my own impression after trying out my buddy's ducati one day and getting back on my T120.

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Thanks Kevin,
I've got soft foam grips and put a couple of heavy expanding bolts down the ends of the handle bars. I've not ridden it hard since fitting them. A lot of vibration seems to come up through the seat..I'm doing a longish run this weekend and I'll really give my attention although my sense is it not in the realms of unacceptable. Its a single carb and I'm running a mukuni over the original AMAL.
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Are your handlebars rigidly mounted, then? I have the stock rubber bushings on my OIF triple tree. I had them out once and the increase in handlebar vibration was significant. If your bar mounts are solid you may want to try some sort of more flexible mount.

Last edited by kevin; 02/27/15 2:29 pm.
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The severity of engine vibration is VERY hard to describe and the perception of it even more so. On a good day, no bitching from the wife, acceptable weather, a full moon and stuff like that, it may seem quite all right, on off days, not so much.
Other than that, it's often surprising how much difference a new needle jet (or carb) can make, or new sprockets and chain, or even new rear shock absorbers. Yes really! A worn primary transmission won't do much good either, the list of possible sources is almost endless...
Some engines are just off, balance wise, and the only remedy is a re-balance job, possibly a dynamic one.
A friend of mine put a Nourish big journal crank in his Bonnie (with the 8 valve kit) and claims the vibes just vanished.
A good late TR6 should be quite acceptable though, but possibly not compared to a BMW...

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Vibration down the center line of the bike is likely to be either power pulses or primary imbalance which is "adjustable" with a change in balance factor, or a percentage of flywheel weight compared to reciprocating weight. It should be around 85% for your bike but anywhere from high 60's to 85% will work, just shifting the point at which the bike vibrates around the rev range.

I found that 68-72% with a relatively high gearing gave me the smoothest engine I've ever seen. But that was on a Bonnie where port biasing did not play into it.

The Tr6 can suffer from an imbalance of power from one side to the next due to incoming fuel charge being diverted unequally to each cylinder. Also, unequal timing from one side to the next, or unbalanced carbs would do it. Not the case here, I think.

Lets not forget the primary drive. Triumph found it helpful at one point to begin balancing the clutch basket, so don't forget that when searching for the culprit.


Odd bikes, Triumphs. Seems no two bikes ride and feel identical to each other.....


Cheers,
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You do seem to get the occasional serious vibrator, though mostly they're pretty OK in my experience (late 650s and mostly 750s). My TR7 is very smooth. My T120V vibrated like a road drill, it was so bad I couldn't live with it and had to sell it. I made sure the bloke buying it had a test ride before agreeing!


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Check the head steady is nice and tight.

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+1 for checking the head steady/top engine mount. Is it missing altogether?

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Thanks guys, All excellent advice. I was thinking about the rear Shocks as well as the front forks. Clutch and primary hadn't occurred to me, but I will look there too. My instinct is there too much vibe on the bike as it is, so I'll go through all these point in the next week or so.
Most of the riding I've done on it around town and the vibration is sort acceptable.
A lot to think about and apply. Thanks again,
Guy

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My '64 TR6 has almost no vibration that I can detect. When I got it running, I was surprised because I had always heard them called the British jackhammer. My crank is the way Meriden made it. I never even checked the balance factor. Could you have a bad main bearing(s)?


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Thanks Ray, There seem to be some good ones and bad ones. Typical British quality control and why there is virtually no British Bike industry to speak of now..
I'm going to go through all the suggestions you chaps have made and see what improvements I can make.
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Typical British quality control and why there is virtually no British Bike industry to speak of now..

You could open a whole bucket of worms with that statement.... if only it was that simple.

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It would be well worth balancing the wheels. Static balancing is fine but it is a bit of an art. It's surprising how much extra comfort properly balanced wheels gives.

One case I looked at in the 1980's was a 750 Bonnie. The guy had fitted a new rear tire but not 'popped it out on the rim' properly! I rode beside for a short distance and saw the wheel flapping up and down what must have been the full travel of the Shocks! The guy seemed oblivious...

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I'll be systematic with it as well as checking all the obvious stuff...

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And what great industrial precedents were set in Kenya?

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I hammered two pieses of a cut up divers welt weight into two 4-inch lead sausages some years ago
These were driven into the bar ends of my BSA A65T.

It helped to make the bars more quiet.
Ofcourse bar weights do not remove the cause of the vibrations.


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Triumph 650/750 smooth? Not really and every one I ever rode vibrated noticeably at 60 mph. Old HD Sporters might be a bit worse. Moto Guzzi and Ducati's V twins are very smooth in comparison.


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Like Excalibur said, wheel balance is critical, I know from personal experience. In one build I said that the rear wheel balance was "good enough" but it shook the whole bike and made the front end hop.

Something like Ger, I use lead in the handlebar, lead shot in my case.

The '07 Guzzi I rode for 4 years had a low frequency vibration (dull thudding) that would give me a 12-hour apres-ride headache.




Last edited by kurt fischer; 02/28/15 10:10 am.

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yes.. the can of worms....I guess it all started in East Africa - Homo Habilis and the olduvai gorge flint tools maybe the off spanner later on....not a lot help with my vibration though...

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Originally Posted by Hillbilly bike
Triumph 650/750 smooth? Not really and every one I ever rode vibrated noticeably at 60 mph. Old HD Sporters might be a bit worse. Moto Guzzi and Ducati's V twins are very smooth in comparison.


They don't have to be. Besides, every other Wednesday, Triumph released a bike that didn't vibrate at all....

Harley didn't put rubber mounted handlebars on a Sporty for nothing. Without it, I doubt you could hold onto the bars at all.

As far as BMW being smooth. I've only ever ridden a 650 and I was surprised at how much it did vibrate.

I had pondered many a night about how to rubber mount a Triumph engine. Then I met a man who had been balancing them for over 20 years. I followed his advice and made quite a few Triumphs that were smooth as butter. One in particular, a '62 Bonnie, had no noticeable vibration at all at 70mph.

My current bike has a little vibration now and that bothers me a bit. Most of you, though, would think it is one of the smoothest Triumphs you've ever ridden.

It doesn't have to be a buzzy annoying vibrating Triumph, and if it is, you can do something about it.


Cheers,
Bill


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I had loads of Triumph and Norton twins (& the occasional single & triple) up to about 1984. From then up to 2000, due to poverty, I had mainly Jap bikes. I missed the 'proper bike' thing and as soon as I could afford it I got myself a Ducatir 900SS (bevel, not belt). Beautiful but I lived in fear of it needing the valves setting up and trade it for the first of several round fin Guzzis. I considered the Guzzis fairly smooth. But every time I rode them I'd find myself thinking: "This is almost as nice as my old Triumph..." The penny finally dropped in 2012 and I sold all my Guzzis and bought my TR7.

The first thing that really struck me, riding one of these for the first time in almost 30 years, was how smooth it was. The Guzzi seemed to be propelled by a series of rapid power strokes which i could feel through the whole bike, but the Tiger just growled sweetly and went along the road without any vibes at all, or hardly any.

I can rev it to 5000 on the centrestand on the oil-soaked plywood floor of my shed and it won;t make any attempt to move backwards (not in the habit of doing this but it was necessary when strobing the timing).

As I said a few posts back, they vary a lot, between surprisingly smooth and unacceptably rough. I can only guess that crankshaft balance is the variable that makes the difference.


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Fair enough. A good comeback that!

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You mentioned vibrations through the seat. My 1969 TR6R has the original seat foam, now rock-hard, this spring I'll get it re-foamed at a local shop. And check that you have all the seat bumpers in place contacting the frame rails, you know, those hard rubber mushrooms.

Also, another part of my vibration management, I use Rizoma handlebars on my bikes, thick-wall aluminum, I like the feel, less flex than steel, and seems to me less vibration comes through them, too.

Also, I've learned not to grip the tank with my knees.

Hmmm... what else ... tight spot in the secondary chain? chain too tight? rear wheel mis-aligned?

When I got the bike in 1974 at age 32, it seemed very smooth. Since then, I think I have changed regarding vibration more than the bike has.

Last edited by kurt fischer; 02/28/15 7:28 pm.

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Yes, a very good point about the chain. Tight spots/ wear in both primary and drive chains are a source of vibration that is often overlooked. Good, well adjusted chains do make a difference!

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