Good Vibrations..

46th Georgia said:
I grew up on 3 cylinder Kawasaki's
Click to expand...
A friend had a Kaw 500 triple that had to be the quickest if not the fastest bike I ever road.
I had a CB750F cafe that I had upped with 1000cc kit (RC Engineering) which was quite quick itself at the time. We were out riding and he wanted to swap so we did. He told me something to this effect....
I know you ride that 1000 and you think this 500 is half the bike; but don't fool yourself and pay attention when you crank that throttle.
I remember saying sure thing or something to that effect as we were changing bikes.
I mean we had been riding side by side and I pretty much felt like I could have left him whenever I wanted...
So I get on his beast and I take off.
Didn’t take me long to snap that throttle.
I think I was still in second gear.
Dayyyuuuuummmm.
No cameras or video available back in the day or I'm pretty sure you would have seen me hanging out the back in the infamous superman pose.
The more I tried to pull myself up the harder I was pinning that throttle back.
Not sure how but I did manage to roll the throttle forward before I grenaded my buddy's engine.
He was laughing so hard and my grin said it all.
I couldn't wait to do it again.
Prepared for the result, I did. Fun machine.
Fun yet scary. Scary because the rocketship only had a single disc up front and a drum in the year.
Additional it seemed to get squirrelly as quickly as it would accelerate. Especially in comparison to my 750. Lots of fun that day.
 
BluzPlayer said:
A friend had a Kaw 500 triple that had to be the quickest if not the fastest bike I ever road.
I had a CB750F cafe that I had upped with 1000cc kit (RC Engineering) which was quite quick itself at the time. We were out riding and he wanted to swap so we did. He told me something to this effect....
I know you ride that 1000 and you think this 500 is half the bike; but don't fool yourself and pay attention when you crank that throttle.
I remember saying sure thing or something to that effect as we were changing bikes.
I mean we had been riding side by side and I pretty much felt like I could have left him whenever I wanted...
So I get on his beast and I take off.
Didn’t take me long to snap that throttle.
I think I was still in second gear.
Dayyyuuuuummmm.
No cameras or video available back in the day or I'm pretty sure you would have seen me hanging out the back in the infamous superman pose.
The more I tried to pull myself up the harder I was pinning that throttle back.
Not sure how but I did manage to roll the throttle forward before I grenaded my buddy's engine.
He was laughing so hard and my grin said it all.
I couldn't wait to do it again.
Prepared for the result, I did. Fun machine.
Fun yet scary. Scary because the rocketship only had a single disc up front and a drum in the year.
Additional it seemed to get squirrelly as quickly as it would accelerate. Especially in comparison to my 750. Lots of fun that day.
Click to expand...
I had a 750 triple with chambers (non street legal), carburetors from Denco Performance and it had been put on a diet by the PO, as it only weighed about 375lbs vs the 425 lbs a stocker weighed. That bike was absolutely terrifying. It made up for the eye watering acceleration by having crappy brakes and bad handling. Didn't have it long, that's why I'm still here.
 
fred nurk said:
what happend to the set of carbys you were going to sell to me.
Click to expand...
Your name's not ringing any bells. Of course I've had multiple enquiries about XS650 stuff I've had for sale, 99/100 I never heard from them again after they messed me around getting postage costs, wrapping the item up and so on. Which one were you?
 
Another thing to consider: The engine has four mounting points: Top, bottom, rear and front, mounting in rubber wouldn't result in any unsurmountable problems for three of them, what if the bottom mount was simply done away with?
 
Yes @toglhot.
I believe it was @takehikes that made the same suggestion. Something I had not considered.
It will definitely be easy enough to test once at that point and so it would seem silly not to try that configuration. If it ends up being part of the equation, stiffness of the frame at that location would be easy to address as well should it be required. Mock up will be starting soon with the initial focus on the mounts. I will be utilizing empty cases so no vibration testing for a while.
The mounting system (stock as well as modified) should be done and ready for when the motor is built. That would be step one. In fact I am hoping to have a couple of options prepared for different configurations. Thanks
 
Not read trough or thought through Just thinking out loud here
The front end as stock in my view can get " Lively " I have been on my way off the road on both sides at least 2 times.
So softening the upper engine mount or lower front with rubber springs or remove
Can have the risk as I see it to soften the front even more.
And Suzukis fours off the time period or little later .. could wobble
 
toglhot said:
Another thing to consider: The engine has four mounting points: Top, bottom, rear and front, mounting in rubber wouldn't result in any unsurmountable problems for three of them, what if the bottom mount was simply done away with?
Click to expand...
That's how Hall did it with the Ascot TT... front, rear and top.


redmax-halco-ascott-tt-_12014650304_o.jpg
 
Hey @Jan_P
The idea is to mount the front mount solid through the two frame rails to maintain stiffness and to isolate the engine from the engine side of the mounts. Again, nothing is set in stone.
There will be testing. Safety of operations is always paramount. That never changes.
 
Jim said:
That's how Hall did it with the Ascot TT... front, rear and top.
Click to expand...
As that was successful on a race bike with the additional stresses involved it makes me think the possibility is indeed possible.
We all know that is a different bike, different frame. Still, they are similar enough in design and type that it shows some promise.
Nice add Jim
 
I’m sure all the mounts make it stiff but at what price? Always compromises. I could see dumping the lower through bolt and the single bolt rear mount. That leaves rear, front, top mounts. I’m thinking that’s plenty. Esthetically the whole top mount should go.
I am chopping my 81 special 2 and may delete those two lower bolts.
 
gggGary said:
... Having one engine mount at the rear act as a pivot creating an arm with roughly a foot of length from the piston centerline how much vertical movement of the motor mass are we talking about? the curve of an arc at the end of a 1 foot arm with a 1/4" oscillation would be what? a couple thousandths? @TwoManyXS1Bs math skills needed here..........
Click to expand...

Ouch, my head hurts.

Just for fun, check out Paul's rear motor mount:

Post in thread 'UK Board Tracker Build Thread' https://www.xs650.com/threads/uk-board-tracker-build-thread.43512/post-442552

Long ago, I pondered on a vibration isolator fitted into the steering neck, or stem, similar to the front telescopic fork tube design, but heavily damped short-throw. The steering would remain stable, but the frame would be able to do its vibrating thing, independent of the steering system. Basically isolating the up/down vibrations.

Leaving the engine bolted, as is, into the frame, eliminates all that motor mount challenge. Plus, the total vibrating mass (engine, frame, everything else) remains heavy, reducing the vibratory displacement.

Was contemplating 2 concepts,

-Short-throw, damped, sliding cylinders for the steering neck and triple tree.

-A girder-style front end, with regular telescopic fork tubes instead of the rigid girder.

The handlebars, headlight, instruments would all be attached to the front steering system, isolating them from the engine/frame vibrations.

I'm too old and tired for this.
But would love to see an eager-beaver accept the pursuit...
 
Hey @Jim ever wonder why the taillight license plate rear fender get so beat up on parallel twins? think on it.
Take a bit of time, go over it in your mind.
 
Ok.
You guys inspired me to take a deeper look into my ideas on utilizing isolated motor mounts.
Been a minute since I had the frame and engine together so I was riffing from memory.
I was in the shop and pulled down the hardtail frame grabbed one of the empty cases along with the motor mounts.
Didn't take long to realize why you long timers that have wrenched on these bikes for eons had so much trepidation. Yet you still managed to inspire me toward my goal and provided critical links that provided even more points of light.
I think I only received one laughing face.
Well deserved no doubt.
Regardless I will still be continuing the pursuit albeit with a renewed set of goals.
After a great deal of deep diving (PADI Certified)
I am abandoning my initial thought of using side to side (horizontal) dampening on the three key points (front, top, side) for vertical dampening.
Studies I have read seem to indicate the the vibratory movements horizontally can have a diminishing effect on the handling, especially through curves and even more so when flipping the bike from one bend to the other. Not dreaming of imitating Barry Sheen any longer and not a sport bike build; however as I pointed out I fully expect the bike to be a performer.
That leaves dampening on the vertical plane.
Ala @Jim as well as the Ascott TT.
My approach will employ the same basic ideas but slightly different. Having the frame, motor casing, and stock mounts on the table in front of me after having flooded my brain with all the ideas from the community as well as the work done on that Ascott brought me a vision.
I see a path forward. It will no doubt involve some changes to the frame where as before I was hopeful of accomplishing my goals without those changes. (Insert laughter here).
So this unquestionably be a one off.
One of the key reasons I will be tweaking the frame has to do with the added decision I have made to incline the cylinders between 10 and 15 degrees imitating the Ascott build. This forward tilting of the motor has been attributed to increased handling and has been considered one of the key elements contributing to those improvements on the Ascott. Doesn't hurt that it just plain looks good. Extra volume sump pan and no worries with the oiling. Most here know I am working on a hardtail and that I have absolutely no qualms about making further changes to the frame. Of course there is plenty of work ahead which has yet to begin, but one must start with clear vision. Problems will exist going forward but without question can be overcome.
Center of Gravity being moved with the inclination and it's effects are yet another subject of study as I press on. Accepting that frame mods will need to be made it is still my intent to keep them at a minimum.
Thanks again for helping to push this idea further than I had originally envisioned.
 
A La Oil sump distribution is reckoned with already I suppose? Not that I question this as an oversight but seem to recall another thread on such a matter.
'TT'
 
Tinker Taylor said:
A La Oil sump distribution is reckoned with already I suppose? Not that I question this as an oversight but seem to recall another thread on such a matter.
Click to expand...
Hey Tinker.
They inclined the engine 15 degrees on the Ascott TT build with no issues reported regarding the oiling system. I am not certain but I don't think they added capacity either. The deeper sump is something I was intending for the build anyway. I like the additional oil. I will be looking at the possibility of oil starvation specifically once I have the mounting configuration dialed in. I think I can use just a lower case opened for visibilty. I should be able to lean the frame as well to get an idea what the effects on the levels may be. The premise for me is that this has already been done with success. Only need to apply the principles used to my chassis. And yes modifications will be needed.
I think that was what you were asking??
 
Yea TT.
The write up about the Halco stated thet Yamaha was consulted about tilting the motor 15 degrees and they signed off on it as a non issue.
Anyways messing around a bit more I snapped a couple of pics with the frame on the table.
One with the cases mounted in the stock position. One with the cases tilted 15 degrees forward. Only a tentative position, to help me get a visual. List of can't go back without a whole lotta work clean up on frame made.
Sure be a whole lot easier just to slip bolts in as is. But what fun is that.
 

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