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Author Topic: Instability on C5  (Read 11844 times)

gashousegorilla

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Re: Instability on C5
« Reply #60 on: August 20, 2010, 09:33:12 AM »
 Ya, what the hell? Get on the horn bob, wake up that engineer!! Please ::)
An thaibhsí atá rattling ag an doras agus tá sé an diabhal sa chathaoir.

gashousegorilla

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Re: Instability on C5
« Reply #61 on: August 20, 2010, 11:35:34 AM »
The only spacer that's in your swingarm is a tube that goes between the bushings - which are pressed into the swing arm pivot. They aren't selective - and tightening the through bolt SHOULD pull it all together ...... Same with the wheel spacers - no selection here ..... and tightening the spindle should pull it all to "zero" ..... I want to what what voodoo went on there as well ..... I'M thinkin' someone just found a loose bolt - or took apart, scratched their heads and inadvertently put it back together right ..... it's a mystery!
Yes, definatley what I found on the swing arm, no play at all at the pivot, flex was at the rear of the swing arm.
An thaibhsí atá rattling ag an doras agus tá sé an diabhal sa chathaoir.

ScooterBob

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Re: Instability on C5
« Reply #62 on: August 20, 2010, 11:54:09 AM »
Yes, definatley what I found on the swing arm, no play at all at the pivot, flex was at the rear of the swing arm.

I find that really odd ..... the section of the swingarm that sticks out past the triangulation of the pivot, shock bottom and shock top is pretty short - and PIG IRON .... it shouldn't flex - even when riding pretty hard. What kind of monkey motion did you get there? Lemme know. I'm QUITE curious at this point ......
Spare the pig iron - spoil the part!

singhg5

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Re: Instability on C5
« Reply #63 on: August 20, 2010, 12:11:24 PM »
The visiting RE engineer had the entire rear suspension dismantlled, including the rear wheel, hub and the front sprocket. He found the wear pattern on both sprocs equal and hence they were put back as before. 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. ;D

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.

If you guys know, the Indian version comes with a seat pre installed which slots with the fastners where the rear suspension goes and its front is bolted the fram below the front seat. My two cents, the removal of the rear seat created a gap at the rear upper bolts which allowed the rear supension space to pull on either sides, creating the oscillation. I also saw the upper bushes of the shockers pulled sideways. Let me know if this theory holds any water.


Bradey:

Time for champagne ! Glad to hear you can ride it the way it is supposed to be - Hey, you gaddaa waalaa and Hero Honda, move over for the Bullet is coming at 80 mph !  :)

Do you think it is the replacement of spacer in swing arm that solved the problem or is it the shims on the rear shocks that cured the problem ?  If you remove the shims from rear shocks, can you see if the oscillations come back ?  Or you don't want to try it and just want to enjoy the smooth ride ?
« Last Edit: August 20, 2010, 12:16:15 PM by singhg5 »
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gashousegorilla

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Re: Instability on C5
« Reply #64 on: August 20, 2010, 12:17:43 PM »

Bradey:

Time for champagne ! Glad to hear you can ride it the way it is supposed to be - Hey, you gaddaa waalaa and Hero Honda, move over for the Bullet is coming at 80 mph !  :)

Do you think it is the replacement of spacer in swing arm that solved the problem or it is the shims on the rear shocks that cured the problem ?  If you remove the shims from rear shocks, can you see if the oscillations come back ?  Or you don't want to try it and just want to enjoy the smooth ride ?
Champagne for him, not for us quite yet. Still trying to figure out what he means?
An thaibhsí atá rattling ag an doras agus tá sé an diabhal sa chathaoir.

gashousegorilla

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Re: Instability on C5
« Reply #65 on: August 20, 2010, 12:35:16 PM »
I find that really odd ..... the section of the swingarm that sticks out past the triangulation of the pivot, shock bottom and shock top is pretty short - and PIG IRON .... it shouldn't flex - even when riding pretty hard. What kind of monkey motion did you get there? Lemme know. I'm QUITE curious at this point ......
Let me clarify, yes the axle plates and shock mount area is pretty Stout.What I mean is the week design from that point back to the pivot tube.It flexes, no gusseting or support, or arch shaped design at the pivot tube. It's basically just 3 pieces of pipe, welded in the shape of Japanese arch, Know what I mean? Like a roof on a pergala or trellis. I think it's too long for that shape, it's longer on the C-5, then on the G-5, so I read. Take one out, and push it in at the axle plates, Like Suzanne simmers does with her machine, and you'll see what I mean.
An thaibhsí atá rattling ag an doras agus tá sé an diabhal sa chathaoir.

Ducati Scotty

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Re: Instability on C5
« Reply #66 on: August 20, 2010, 12:39:11 PM »
I think what he means is that the top schock mount bolt on the Indian C5 from outside to inside goes like this: acorn nut, shock, fat seat bracket, frame (corrected) acorn nut, washer, fat seat bracket, shock, frame.  We in the US get a different seat and don't get the spacing the fat seat bracket provides to effectively make the top shock mount wide enough to be held squarely and snugly by the shock mopunt bolt.  My guess is that piece is 3/32" to 1/8" thick.

So, remove top shock mount, insert a few washers, put shock back on, bolt it up.

I was out yesterday.  65 if fine,  it will wiggle if I wiggle the bars but nothing terrible.  70, is fine but wiggling the bars makes an unsettling oscilation that clears itself but makes me not want to go faster.  I'm going to take a peek at my bike later, maybe get some washers.

Bradey, any chance of a picture to clarify what they did on your bike?

Scott
« Last Edit: August 20, 2010, 04:48:19 PM by Ducati Scotty »

Ducati Scotty

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Re: Instability on C5
« Reply #67 on: August 20, 2010, 12:48:48 PM »
Duh!  I already have the accessory rear pillion which seems to be exactly what he's describing fro the way it mounts!  BUT I can maybe remove it and do some experiments this weekend :)

Scott

ScooterBob

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Re: Instability on C5
« Reply #68 on: August 20, 2010, 12:55:34 PM »
Let me clarify, yes the axle plates and shock mount area is pretty Stout.What I mean is the week design from that point back to the pivot tube.It flexes, no gusseting or support, or arch shaped design at the pivot tube. It's basically just 3 pieces of pipe, welded in the shape of Japanese arch, Know what I mean? Like a roof on a pergala or trellis. I think it's too long for that shape, it's longer on the C-5, then on the G-5, so I read. Take one out, and push it in at the axle plates, Like Suzanne simmers does with her machine, and you'll see what I mean.

OH! - Copy THAT, GHG! I know what you are saying here now. The wheel spindle itself is an integral part of that system - it adds the "in and out" stability to the legs .... sort of triangulating it with the pivot. I DO agree with you, however, that for SERIOUS thrashing, the thing should be gusseted - or as you suggest - made from a "U"-bend tube. It would be easy to gusset the thing, though ..... Maybe that will be on my list if I can get the one that I'm riding to crack a weld .... Muah-ha-ha-ha-ha!
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singhg5

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Re: Instability on C5
« Reply #69 on: August 20, 2010, 01:17:47 PM »
Champagne for him, not for us quite yet. Still trying to figure out what he means?

Dan:

We will try to find out from him what he means or as Scott has just posted a bit of experimentation may reveal the solution to this problem for your bike too.

Looking at this issue from all different angles, it seems that the chasis design per se holds fine as long as ALL the small parts that attach to it have EXACT dimensions and spaces to not disturb its geometry.  It seems to be a sensitve desgin not a forgiving or stable design and is easily imbalanced with a slight change.  

My suggestion would be to follow what the engineer did to Bradey's bike one step at a time - to see if anything helps.  Ask Scooter Bob to send you a new spacer for rear wheel and replace it and go for a spin.  If that does not work, change spacer for swing arm.  Then go for shims on rear shock.  

When the bike is stationary, some parts seem fine BUT one cannot see what happens to that part when it is running at 70 mph.  

Hang in there - lots of brains are working to help you out. 
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r80rt

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Re: Instability on C5
« Reply #70 on: August 20, 2010, 01:21:30 PM »
I just went and a 45 mile ride at varying speeds up to 75mph, on glorious new pavement and the cracked up old stuff with the washer spacers in place. While I had no problems before, it now some how seems better,  don't know if it's a change in vibration or what, but it is something I can feel. I thinks it's worth the effort.
On the eighth day God created the C5, and it was better looking than anything on the planet.
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SSR

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Re: Instability on C5
« Reply #71 on: August 20, 2010, 01:46:50 PM »
Do forgive me for my non technical explanation but I'll try to explain what Bradhey means.

On all the C5's an I am assuming the export versions as well. The rear seat frame slides out of the rear shock mounting bolts. If you observe the LH side shock upper mounting bolt, upon removal of the rear seat frame there is a bit of space left between the shock mounting and nut. Its because the rear bolt is longer then the RH side bolt to accommodate the side handle. Once you remove the rear seat frame, there is a bit of gap left and the nut does not cover up the remaining gap or the mounting bracket for the shocker flexes inwards to accommodate the gap and the alignment of the shocker on the top leans to one side a wee bit.

You need three washel to be placed before the nut can be tightened and the top shock mounting remains inline to the bottom. Long way back I had got a spacer made to exact size to fill up the gap.

In my case it did not helped with the instability.

Two days ago I had the luck to replace the tube twice in 2hrs(misfortunes of punctures)
and after that my bike ran straight without a single twitch. All I remember doing was tightening up the rear axle as hard as I could with my hands.

I wonder if you guys could try tightening the rear axle shaft to the brim and see if that helps.

gashousegorilla

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Re: Instability on C5
« Reply #72 on: August 20, 2010, 02:14:44 PM »
DOY!!!! I did not pick up on the rear accessory seat the first thousend times I read over it, either, cause I don't got one. So excess play at the top rear shock mounts huh? Maybe, will check it when I get home. I'm still a little sceptical like scooterbob about the axle spacer and the swing arm pivot tube spacer. If the axle spacer was the wrong length, the alignment would be off, which it is not on my bike. Again with the pivot tube spacer, OK on my bike, no play in that area. I think that engineer was just covering all the bases, by replacing them.  I think the shock mount thing is more plausible. will try it tonight.
An thaibhsí atá rattling ag an doras agus tá sé an diabhal sa chathaoir.

r80rt

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Re: Instability on C5
« Reply #73 on: August 20, 2010, 02:18:15 PM »
You could always put on some struts and run her ridgid to see what tells you.
On the eighth day God created the C5, and it was better looking than anything on the planet.
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SSR

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Re: Instability on C5
« Reply #74 on: August 20, 2010, 02:31:51 PM »
You could always put on some struts and run her ridgid to see what tells you.

I like your idea and I quite agree with what scooter bob say's that a little something off trigers those wacky moments and sometimes its perfect.

Can anyone just try tightening up the rear axle shaft as much possible  and see if that helps.

I had the instability before I got the puncture but after putting a new tube and fixing the wheel back, it was gone. I didn't touch anything else except tightening the rear axle way too much. Usually I keep 28Psi at rear which helps a lot but this time it was 32Psi and it behaved far better.

What if the the shocks are not vertically centered on the swing arm, can that create problems ?