[ScooterBob]

It looks like BRADLEY and the RE engineer have found the answer.

Maybe ...... but I'm a little "skeptible" - he says:

He then checked the spacer of the rear wheel and decided to change it, as also the spacer in the swing arm. Refiited everything back and I tested the bike till 130 KPH/81 MPH. It was stable, in fact I did try to weave it at those speed, but it did not oscillate. Grin
Now for the tricky part (what the engineer did not know). The attending mechanic unknowingly added few shims on either sides of the rear shockers (upper bolts), cause he thought the gap was too big for the bolts to hold it tightly.

What did he change the spacers TO? There are no selective parts in the rear of the bike. If there was an obvious manufacturing problem - such as the carriage for the swingarm being too wide - it would have been easy to see as the swingarm would move from side to side. Same with the shock top clamping .... grabbing and yanking would make them "klunk" , I'd think. It makes sense, however that doing some sort of voodoo to the back end of the bike would take the mystery waggle OUT of it - but WHAT voodoo was done? I want to know MORE, dammit!!  

[r80rt]

Maybe the replaced shims weren't up to specs?

[ScooterBob]

My guess is that it's a torque reaction from the engine.

When the engine is around torque peak, the pull on the chain when you  accel and decel, cause something in the back end to flex around in some way.
Could be a loose swing-arm bolt, or flex in the bushings, or flex in the swing-arm itself, or flex in the chassis or mountings.

From what I've been reading here, it seems to be tied to engine behavior around the torque peak rpm, which is where the strongest torque reaction would  be.
If it pulls the wheel alingment slightly out of line because of the pull on the chain, that could do it.

ACE - You are probably right here - but I'm ASSURED that all is tight in the back of the bike ..... but I'm not there to pry the crap out of everything to see. That being said, though - I think GHG is taking due care and precaution to check all of this sort of thing so he doesn't end up chasing his tail (no pun intended ...  ) We'll just have to wait and see. Your ascertainment is probably right on the mark with the engine reaching the torque peak (it has a good bit!) and setting things in motion - literally. I'm almost willing to bet that there is something loose in the back of that bird. With MINE it was the bearing coming apart - although it didn't telegraph its demise for about three days - it just had a little "mystery" high speed weave that I really, basically ignored ......

[ScooterBob]

Maybe the replaced shims weren't up to specs?

Unless they were just crushed and cupped beyond all recognition ..... there ain't no real "spec" ...... That's why I'd like MORE info on what was done .... or to be there and lay my OWN healing hands of faith upon the cursed machine ...... I dunno ..... 

[gashousegorilla]

GHG - After thinking ALL the way around the point ..... This is what we know - tell me if I am wrong here ......

the wheels are in line with each other
the wheel bearings are good
the swingarm bearings/bushings are good
the tire pressures are good
the engine is in tight
the head bearings are the right pre-load
fork oil is good
handlebars are adjusted correctly
rear shocks are the same
nothing visible is OBVIOUSLY broken
you didn't start riding a motorcycle the day before yesterday .....

We also know that

if the WHEELS are straight - the BIKE will go straight
the bike WEAVES - not WOBBLES, indicating that the REAR of the chassis is loose
YOUR chassis is the same as MY chassis - and mine is rock steady at speeds
MY bike probably IS bent - proving the first point
YOUR bike probably ISN'T bent

So WHAT - in the chassis behind the CG is flexing/bending/springing/running out of true/ not tracking straight? There HAS to be something in there to cause that - and I'm about ruling out engine vibration because the frequency to excite the frame to that sort of harmonic would almost have to be applied consistently in a lab setting for an hour to get the derivative Hz to do that ..... There HAS to be something pretty out of whack - obvious - to cause that .......... Thinking caps on, now! I wish I had that bike under me .......  

Yes all good bob. I'm thinking back to when I had the swing arm off, and remembering having a slight bit of difficulty taking on and off one of the rear shocks, forget now which one, but I can easily check. If I am remembering correctly, again not in front of the bike, the problem was at the top shock mount on one side only, it was a little tuff getting the top of the shock on the stud. Not as much clearance, as on the other side, in the area of where the fender/ frame support bar is. In between,Ya Know? I guess at the time I just chalked it up to a little different bend in the bar? Remember I was fixated on the swing arm at the time. Maybe another Clue? 

[ScooterBob]

GHG - That could, indeed be another clue! Due diligence here will pay off, I think ..... On MY end for diligence .... I just got back from a ride on the old 19" wheel, wide bar test mule that was snatched out from under me to be a demo bike (it got a whopping 28 miles and a purple pipe as a demo - big deal!)

Riding that bike was interesting compared to the little heep that I've been used to. First off - it has the upright riding position that is more comfortable than a Lazy Boy - up to about 60mph ..... then you have to hang on for dear life to keep the wind from blowing one's upright arse right off the back! Hanging onto the grips and leaning forward helps here, tho .... so does riding through town at a gentleman's pace! I got to barrel across some recently "chomped up for re-paving" concrete - you know - where the road has been "sanded" with those spikes on a drum to make grooves in it? I hit that at bout 45mph. The bike squirmed a little - but did nothing untoward. All the "wiggle" was because of the grooves - not the old headshake. On to the BIG road.

I wound up tight through all the gears, taking advantage of a bit of a downhill stretch so as not to get a ticket for speeding by flailing the throttle for miles on end. The bike was dead steady all the way up to the rev limiter in top gear. I DID have to hang on pretty tightly because as I said - the bars promote an upright seating position. Leaning forward and lightening up on my grip didn't affect anything at all, either. I also leaned back on the seat a little and let my arms be straight - nothing again. On the way BACK I rolled it hard as well and had the good fortune to not only follow a large truck - but I got blasted by a couple of PASSING trucks as well - all at some speed. Again - the BLAST - but no woogley behaviour ...... So there you have it.

BTW - This would be a SUPER bike for someone looking for the Proper British Ride. The seating position is, again absolutely PERFECT below 60 - and the bike has other "extras" to make it really nice ....... and it's a good runner, too. I'll use it for a "gentle rider" I suppose - tune and tweek - until it gets a new home.

[gashousegorilla]

t ..... There HAS to be something pretty out of whack - obvious - to cause that .......... Thinking caps on, now! I wish I had that bike under me .......  

Ya know bob , it may come to that. Land O Lakes?, Small mouth?, Northern Pike?, Walleye? Work'in on bikes? Although it would take me a while to get out there with the bike in It's present form

[gashousegorilla]

GHG - That could, indeed be another clue! Due diligence here will pay off, I think ..... On MY end for diligence .... I just got back from a ride on the old 19" wheel, wide bar test mule that was snatched out from under me to be a demo bike (it got a whopping 28 miles and a purple pipe as a demo - big deal!)

Riding that bike was interesting compared to the little heep that I've been used to. First off - it has the upright riding position that is more comfortable than a Lazy Boy - up to about 60mph ..... then you have to hang on for dear life to keep the wind from blowing one's upright arse right off the back! Hanging onto the grips and leaning forward helps here, tho .... so does riding through town at a gentleman's pace! I got to barrel across some recently "chomped up for re-paving" concrete - you know - where the road has been "sanded" with those spikes on a drum to make grooves in it? I hit that at bout 45mph. The bike squirmed a little - but did nothing untoward. All the "wiggle" was because of the grooves - not the old headshake. On to the BIG road.

I wound up tight through all the gears, taking advantage of a bit of a downhill stretch so as not to get a ticket for speeding by flailing the throttle for miles on end. The bike was dead steady all the way up to the rev limiter in top gear. I DID have to hang on pretty tightly because as I said - the bars promote an upright seating position. Leaning forward and lightening up on my grip didn't affect anything at all, either. I also leaned back on the seat a little and let my arms be straight - nothing again. On the way BACK I rolled it hard as well and had the good fortune to not only follow a large truck - but I got blasted by a couple of PASSING trucks as well - all at some speed. Again - the BLAST - but no woogley behaviour ...... So there you have it.

BTW - This would be a SUPER bike for someone looking for the Proper British Ride. The seating position is, again absolutely PERFECT below 60 - and the bike has other "extras" to make it really nice ....... and it's a good runner, too. I'll use it for a "gentle rider" I suppose - tune and tweek - until it gets a new home.

Thanks bob,That was a perfect test and comparison of our two bikes. Both pretty identical. So now we know for sure a good C-5 with a 19" wheel up front, handles like a charm.And  I did not waste money by putting it on,cause I like it Yes wind buffeting would be normal.That  bike of yours is exactly the set up i was shooting for with mine, and would expect the same results. I could deal with a little wind buffeting,comes with the territory. It does look sooo much better this way.Alright,off to the garage to take a look at those shocks,I'll let you know.

[gashousegorilla]

I think GHG is taking due care and precaution to check all of this sort of thing so he doesn't end up chasing his tail (no pun intended ...  ).

Scooterbob . don't you know nuff'in, GOrillas Don't got no tails. It's more like them crazy chimps spinning around in his cage.

[ScooterBob]

GHG - You grease MONKEY!! Hahaha! - Let me know what you find. BTW - I LOVE the set-up on the 19" blaoney bike just for cruisin' ...... but the Cafe-bars are the BOMB for carvin' it up!

[gashousegorilla]

GHG - You grease MONKEY!! Hahaha! - Let me know what you find. BTW - I LOVE the set-up on the 19" blaoney bike just for cruisin' ...... but the Cafe-bars are the BOMB for carvin' it up!

I'm wit dat, got me a nice cafe already though. Listen bob I ain't see'in it with this shock thing, in the garage now, what i see is an egg corn nut, lock washer, flat washer, center stand handle. All socked up real nice agenst the monting tab, putting good pressure on the shock bushing spacer. And that egg corn nut ain't bottoming out inside.What I do see is about a 1/16 of an inch side to side slope inside that top and bottom shock mounts. You know, the rubber bushing sliding back and forth over the spacer, up ag'in the stud or bolt tabs.Also, how do you check the charge on these shocks, with those crazy barrels on the side?

[ScooterBob]

Hmmmmm - If the shocks are tight in the mountings - and adjusted the same .... that pretty well rules THAT out. There IS a possibility that they are unequally gas charged - but there is no real way to check that - Trust me here - DON'T try to take em apart without a wall to shoot the parts into .....

Just out of curiosity - if a fellow took a stout stick and put it through the wheel on the up side of one side of the swingarm and the downside of the other - could you get any movement out of the swingarm? I'm convinced that SOMETHING in the back of the bike is able to move where it shouldn't ...... I'm thinking side-to-side motion - but it MAY be a torsional motion that allows the rear wheel to lean and steer ..... get me? This is starting to really vex me! I'm SO thinking around and around in circles ....... 

[gashousegorilla]

Hmmmmm - If the shocks are tight in the mountings - and adjusted the same .... that pretty well rules THAT out. There IS a possibility that they are unequally gas charged - but there is no real way to check that - Trust me here - DON'T try to take em apart without a wall to shoot the parts into .....

Just out of curiosity - if a fellow took a stout stick and put it through the wheel on the up side of one side of the swingarm and the downside of the other - could you get any movement out of the swingarm? I'm convinced that SOMETHING in the back of the bike is able to move where it shouldn't ...... I'm thinking side-to-side motion - but it MAY be a torsional motion that allows the rear wheel to lean and steer ..... get me? This is starting to really vex me! I'm SO thinking around and around in circles ....... 

Hear that bob.Remember bob, I put that brace in the swing arm,  it ain't go'in no where.I know we been all over for the last couple of months, but after all the normal checks. That was the first thing I did. Like we talked about earlier.Remember the thread on Bronze swing arm bushings for C-5? I already braced the swing arm. "the Gorilla Brace" And I know what your thinking, but this stability issue is what lead to the brace. Remember,I gained a good solid 10mph with it? Then lost most of it with the 19' wheel?

[gashousegorilla]

I think I just found some stress at the rear end. I'm taking out the mounting screws,(to do the shock washer thing)on the rear fender and one of them damn near shot across the floor.You know, the ones mounted to those 'bout 3/4" very sturdy rear fender stay's? The one on the left pushed over to the right, now it's not centered over the rear wheel. Remember the clue about me having a hard time getting the shock mounted around it? Maybe  it's something, maybe not. Must check further.

[gashousegorilla]

 I'm convinced that SOMETHING in the back of the bike is able to move where it shouldn't ...... I'm thinking side-to-side motion - but it MAY be a torsional motion that allows the rear wheel to lean and steer ..... get me? This is starting to really vex me! I'm SO thinking around and around in circles ....... 

Correct again , stop vexing, I think we got her. Check out the other thread on Stability.Scooterbob you are the man!!!
Dan.