Good Vibrations..

[Tinker Taylor]

You could get into a pretty nasty elliptical coupling.... one that could turn out to be worse than the vibe we're trying to get rid of.

There is a science to vibrational synchronicity and its effects, so I agree with the above that a tendency for the engine to change its pattern could disrupt the constant required to maintain perfect balance or throw it into a disharmonious pattern.
The other question I haven't seen mentioned is whether the dampening of the engine will disrupt any electrical ground common to that system?
'TT'

 

[BluzPlayer]

Hmmm.
Lots of grear input guys.
Thanks for the links gggGary.
Great information.
I will say my eyes have been opened.
I by no means am thinking there is a possibility of eliminating the vibes and that is perfectly fine as I like to feel my bike. I just feel that an impact can be made in this pursuit. Again I do understand that I could meet with total failure.
Or perhaps the reduction could be so small that the effort is not worthwhile. Again it is the total package of countermeasures that will hopefully work together. Primarily the balancing of the rotating assy and the runout on the crank.

I know when I was hot rodding cars and not just for the strip but for handling as well. The high torque motors would snap a stock motor mount.
I had to go to solid mounts to get the performance I wanted. Of course that locked the vibrations right to the frame. As a young cat I didn't mind at all. In fact I rather liked the way it rocked the front end as the engine loped along.
Looked mean. Sounded mean. That was tolerable in the car sitting in a well cushioned seat. Still I eventually made hybrid mounts where two steel bars were run through the stock rubber mounts and welded to the steel backing plates.
It gave some cushioning of the vibes but I never managed to snap one.

I said all that to say that I do realize the linkage between the solid mounts and performance on the xs650. Of course many on here know that upcoming build (The Punisher) is a hardtail.
It is not going to be built to eat up the curves the way I used to on my sport bikes. I doubt I will be doing much light to light racing as I have in my youth. I am older now and those elements no longer carry the weight they once did in my decisions. That doesn't mean I don't expect the bike to perform well. Just not at that level.

Yes indeed Togl, that lower bolt as I said is thd sticking point that glares at me. I'm hopeful that reduction in three of the 4 locations will show significant improvement. The lower bolt being near the very lowest point of the engine may have the least effect. Then again it could be the point of greatest transfer for all I know.
I do have a thought or two in regards to that bolt but whether my thoughts are feasible remains to be seen. I've started asking this now so I can create a plan of action prior to mocking up the bike which is awaiting a few parts to begin.
Thanks again to everyone that has contributed.
A lot a great thoughts on the subject.

 

[takehikes]

Hmmm.
Lots of grear input guys.
Thanks for the links gggGary.
Great information.
I will say my eyes have been opened.
I by no means am thinking there is a possibility of eliminating the vibes and that is perfectly fine as I like to feel my bike. I just feel that an impact can be made in this pursuit. Again I do understand that I could meet with total failure.
Or perhaps the reduction could be so small that the effort is not worthwhile. Again it is the total package of countermeasures that will hopefully work together. Primarily the balancing of the rotating assy and the runout on the crank.

I know when I was hot rodding cars and not just for the strip but for handling as well. The high torque motors would snap a stock motor mount.
I had to go to solid mounts to get the performance I wanted. Of course that locked the vibrations right to the frame. As a young cat I didn't mind at all. In fact I rather liked the way it rocked the front end as the engine loped along.
Looked mean. Sounded mean. That was tolerable in the car sitting in a well cushioned seat. Still I eventually made hybrid mounts where two steel bars were run through the stock rubber mounts and welded to the steel backing plates.
It gave some cushioning of the vibes but I never managed to snap one.

I said all that to say that I do realize the linkage between the solid mounts and performance on the xs650. Of course many on here know that upcoming build (The Punisher) is a hardtail.
It is not going to be built to eat up the curves the way I used to on my sport bikes. I doubt I will be doing much light to light racing as I have in my youth. I am older now and those elements no longer carry the weight they once did in my decisions. That doesn't mean I don't expect the bike to perform well. Just not at that level.

Yes indeed Togl, that lower bolt as I said is thd sticking point that glares at me. I'm hopeful that reduction in three of the 4 locations will show significant improvement. The lower bolt being near the very lowest point of the engine may have the least effect. Then again it could be the point of greatest transfer for all I know.
I do have a thought or two in regards to that bolt but whether my thoughts are feasible remains to be seen. I've started asking this now so I can create a plan of action prior to mocking up the bike which is awaiting a few parts to begin.
Thanks again to everyone that has contributed.
A lot a great thoughts on the subject.

I look at how many places this engine mounts and know just by experience that some can go and my first thought was that lower through bolt.

 

[BluzPlayer]

I look at how many places this engine mounts and know just by experience that some can go and my first thought was that lower through bolt.

Wow.
And that thought never occurred to me.
It something that will get consideration as well as being very simple to test.
Again all testing will be measureable so there will be actual numbers for comparisons.
Well not all testing. Seat of the pants testing always has it's place.

 

[bosco659]

It's an interesting engineering problem which many people have tried to solve in different ways. The problem Norton ran into with the Commando was it didn't handle as well as the earlier Featherbed bikes, hence expensive solutions like the Vernier adjustment. The story there runs out, like a stream into desert sand - the company went bust and the alleged problems have been blamed on owners not knowing how to set up the adjustable isolastic mounts. (Yes, Norton Commandos are being built now but they are different beasts which I know SFA about.)

Eric Buell had a go at the problem with a rubber mounted Sportster engine. I've owned & ridden three Buell X1s, at which point I always say some people never learn. He succeeded in making the Sportster engine go like stink and the handling was superb but the plot vibrated like . . . I don't think we're supposed to say that these days. But let's say after a medium to long run your vision was blurred and your gentleman parts were numb. Rest assured, sensation returns in time.

Good luck with your venture, BluzPlayer!

I can appreciate the comment about blurred vision and numbness. Been there. Lol.

Installed new rubber for the handlebar dampers (OEM), removed an extra washer that was between the riser and top rubber and lubed them up so I’m hoping I’ll get less vibration through the handlebars this season. If this isn’t an adequate improvement I may try doing weight to the bars.

 

[Jim]

I look at how many places this engine mounts and know just by experience that some can go and my first thought was that lower through bolt.

I think it's too easy to look at an engine mount as "just" an engine mount. Like many bikes of the day... and current ones for that matter, the frame was designed to use the engine as an integral structural member to increase frame stiffness...and therefor, handling.
Can you delete some of the engine mounts and still have the engine firmly held in place? Sure you can... but then the "noodle" conundrum pops up.
Can we fix that by welding/bolting on more crossmembers and stiffeners? Sure, but then we're left with a porker that handles like a bread truck and measures the quarter mile in yawns...
Can we eliminate some of the pork? Sure. Let's make the engine an integral part of the frame and use the engines heft to add stiffness... then we can cut off all the excess brackets and stiffeners.

Then we can all scratch our heads at the gazillion bolts Yamaha used to mount the engine and chase our tails 'round the circle once again.

The guys that engineered these bikes back in the day were well trained and competent engineers. Believe me, I understand the desire to scoff at just how rotten they were at their job... it's an urge I constantly resist.... but if "smooth, fast and Barry Sheene like handling" were a piece of cake, all bikes would be like that.

 

[46th Georgia]

imho you can have (only one) bolted mount, my suggestion would be the lower rear. (furthest from the up and down piston shaking plane. That mount would act as a pivot for all the other mount's flexing.
A rephase is easier........... ;^)

What's your opinion of rephasing?

 

[Mailman]

If you want a bike that’s both vintage and smooth, get yourself an old air head BMW. Smooth as a baby’s butt!

 

[gggGary]

I've only ridden two, but for a very short period and was busy troubleshooting other issues for the owners, so didn't really consider how the vibration changed.
There's a rephase crank/cam set here but long story it's never gone into a motor.

 

[Raymond]

. . . The guys that engineered these bikes back in the day were well trained and competent engineers . . .

They were. But XS650 history tells us they head-hunted Percy Tait to assist with handling. He was not impressed with the way they assessed handling - on a billiard-table smooth circuit. Made them add bumps and imperfections to upset the bike and make the frame flex. The story goes that his input led to the strengthened frames introduced in, was it 1977? Perhaps a case of seat of the pants trumps design principles & calculations etc done by good engineers.

And of course, as you said, better handling came at the cost of weight.

Bob, didn't used to like the old BMWs but that has changed over the years and these days that 1973 R75/5 is one of my dream sickles.

 

[BluzPlayer]

Barry Sheen..
Now that brings back some memories.
Had his poster on my wall.
Haven't thought about him in some time.
My days of attacking the twisties ala Barry are long gone. Frame stiffness is a primary consideration. But I am open to all possibilities and combinations.
Yes Yamaha and it's engineers were competent.
The 650 was their first first forage into what was then a big 4 cycle street bike. They borrowed heavily. They also had other considerations beyond maximizing the potential.
Price points, production, existing components from other lines, etc.
I believe some things were done because they were easier and cheaper. Some things most likely done because they had been using them with success previously. The engineering is not overly impressive. Was never cutting edge. Improvements are there to be made. Perhaps not in this particular endeavor, but I'm not afraid to try and fail. It goes without saying that the objective I have in mind is not going to be applicable to all builds.

 

[Jim]

The story goes that his input led to the strengthened frames introduced in, was it 1977? Perhaps a case of seat of the pants trumps design principles & calculations etc done by good engineers.

Good point Raymond.
... and lest anyone misunderstand, I'm not sayin' it can't be done... or there's no room for improvement, the Ascot TT disproves that notion. All I'm saying is easy fixes like a single hard mount and rubber everywhere else ain't gonna get you there.

 

[Jim]

No offense to your suggestion Gary. Jus' picked that as an example.

 

[gggGary]

The thing about re-engineering 50 year old technology is that....................

It's still got a lot of other 50 year old bugaboos.

 

[Raymond]

I think there's a broad consensus here. Jim, you are correct, nobody is saying there's no room for improvement, there always will be. The Yamaha engineers achieved a good balance of power, handling, brakes to satisfy the market in the late '60s early 70's and as BluzPlayer points out they had to do that while also meeting considerations of cost to end up with a bike Yamaha could sell at a profit. Production costs, use of parts inventory, timescale to market, what the opposition was doing - all those boring business things we don't need to worry about. Considering it was the first time they built a 4-stroke, they did a job.

 

[Jim]

Considering it was the first time they built a 4-stroke, they did a job.

Considering we still covet these machines 50+yrs later... I'd say they exceeded expectations by a wide margin.
Never in their wildest dreams....

 

[grizld1]

For the record, the frame redesign came with the 1974 TX650A (same year as 20 mm. wristpins and detuned cam).

 

[BluzPlayer]

You guys are the best.
But that is what has made this forum the pinnacle of information on these machines.
Far more feedback than I anticipated and filled with some ideas I had not even thought to consider. Some things are obvious to all of us, but some of the nuggets were new ideas for me. This is an example of why I believe in the community sharing of ideas and experiences can be so effective. There a many other topics (such as Gonzo) that are an example of this dynamic within this site. Since the application of these mounts will most likely be designed for my type of bike and riding style it may well turn out as more of a one off although it is my intention that any mods I do end up with should be doable on any bike without major mods. May not be possible but it is the intent. And it may not fit anyone else's riding style even if it is possible. That is why I'm so greatful for the contributions made to the post.

 

[46th Georgia]

Considering we still covet these machines 50+yrs later... I'd say they exceeded expectations by a wide margin.
Never in their wildest dreams....

I grew up on 3 cylinder Kawasaki's and Suzuki's and I still think they are cool, plus I had a CB750, that being said, I do not have the emotional attachment that I had for my XS that I sold in '83. I don't think there is as much of a following for any other vintage Japanese bike, with the possible exception of the CB750.

 

[grizld1]

BP, you've hinted at something that draws a lot of folks to the old twin. Some owners are motivated to keep the old bikes going because they bought 'em young, kept riding them, and have developed a valued repository of memories, friendships, and skills. Others got into the XS650 with their eyes wide open to the many defects of the machine for the creative challenge of making a better ride. (Still others tweak 'em for the sake of image and cosmetics and wind up with trailer art, but I won't rant about that). Good luck with your project.