850 style centerstand failure

Ron L

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For the last couple seasons I noticed that my centerstand (braced style) on my 750 Roadster would make an odd "twang" when I retracted it. Being the lazy bum that I am, I kept delaying putting it on the lift and checking it out.

Last Saturday I stopped for gas and the stand went soft as I lifted the bike up. Since I was a couple miles from home I figured to just take it easy as the stand was obviously bent, but appeared to be clear from the road. Didn't make it. About a mile or so from the house, the broken stand somehow bounced up and hit the chain, removing the clip from the master link and allowing the chain to whip off the sprockets, taking a piece of the guard off the inner primary chaincase at the same time.

I brought the bike back in the truck and unloaded to take a closer look. The center stand had cracked around the hole drilled for the spring and the crack had traveled nearly all the way around the tube. This may have been one of the reproduction stands, as the foot pedal looks different from the others I have in the shop, so maybe the metal wasn't up to the task.

Moral to the story is, occasionally check the spring hole in the center stand. If it shows a crack, get it welded and reinforced pronto. Luckily I have an extra chaincase and centerstand, but the damage could have been worse.
 
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I am going to remove the centre stand on my MKIII completely.

When I ordered a bunch 'o' parts from Matt at CNW I asked about the centre stand and he suggested I simply take it off and put it on a shelf somewhere. I didn't really realize his reasoning until he explained to me that on the MKIII, the centre stand is attached to the tranny cradle and puts stress on the isolastics.

The side stand always seemed a bit sketchy to me but he assured me that I can store my bike all winter on the side stand no problem.

I looked at a lot of the CNW rebuilds on their site and quite a lot of them have had the centre stand removed completely.

Ron L, I know my response has no real answer to your question, but I asume your centre stand is attached to thef ram differently than on my MKIII.

Any MKIII owners out there that have removed the centre stand?
 
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I have a MKIII with a center-stand and plan to keep it on the bike for several reasons.

1) It helps with certain maintenance tasks, such as checking trans fluid level and changing tires.

2) It prevents the side-stand from damage/collapse while kick-starting. I'm concerned about loading the side-stand excessively during my kick-start routine.

I think 2) is my biggest concern of the two.

Jason
 
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Jason Curtiss said:
I have a MKIII with a center-stand and plan to keep it on the bike for several reasons.

1) It helps with certain maintenance tasks, such as checking trans fluid level and changing tires.

2) It prevents the side-stand from damage/collapse while kick-starting. I'm concerned about loading the side-stand excessively during my kick-start routine.

I think 2) is my biggest concern of the two.

Jason

Good points.

I have a motorcycle jack but I can see if I'm in the middle of nowhere where the centre stand would come in handy.

I kick strat mine without using a stand. Maybe that's why I get tired so quickly. :D

I havn't fully decided to take mine off but I think if I do, I'll simply reattach it when I go out of town incase of a flat ect.
 

Ron L

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Jason,
I usually kickstart on the centerstand, but on soft ground I kick it with the side stand deployed, but holding the bike upright on it's wheels. That way there is no stress on the side stand.

Coco,
I don't follow Matt's reasoning. If you use the center stand, the weight of the frame, wheels, and fuel tank are supported by the isolastics. If you use the side stand, the weight of the engine, tranny, cradle and exhaust are supported by the isolastics. Weight-wise I think it's a wash. His real reason is probably due to his practice of lowering the bikes he builds and the centerstand would create greater handling issues and would require shortening in order to deploy it without the assistance of a crane.

I really had no question, just wanting to alert everyone that even the stronger 850 stands can fail and to watch for cracking at the spring hole.
 
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Ron L said:
Jason,
If you use the center stand, the weight of the frame, wheels, and fuel tank are supported by the isolastics. If you use the side stand, the weight of the engine, tranny, cradle and exhaust are supported by the isolastics. Weight-wise I think it's a wash.
I really had no question, just wanting to alert everyone that even the stronger 850 stands can fail and to watch for cracking at the spring hole.

I quite agree, Ron.

This is something that has always puzzled me about the factory Iso setting instructions. If the bike is on blocks under the frame rails, then the weight of engine / gearbox / primary / swing arm / rear wheel is dangling on the rubbers. Presumably one should actually jack the wheels progressively to arive at a point where the rubbers are not stressed. I suspect that the whole lot would fall over at that point. :)

I have had a mainstand split from the spring hole as well. Makes a hell of a noise doesn't it ? Luckily mine was at low speed as I pulled away.

It's also a good idea to check the spring and lugs from the sidestand regularly as well. I dread to think what would happen if the spring detatched and the stand swung over-centre. :shock:
 
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I have seen the results of leaving the side stand down and then driving off, the first left was the last one for a very long time. The man has some stainless bones now. He just got distracted by some bad directions.
We have been welding on half pieces of pipe on these stands right from brand new. I also bored a stand for ball bearing pivots from brand new. It works much smoother for lifting but it does have a side effect, it hits the ground on hard bumps easer than my 850 with no ball bearings.
 
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I had my center-stand break apart too..and once dropped or broke the spring while underway...bouncy, bouncy. Mine is now welded back together with solid rod hammered into the tubing and then welded over it now...heavy but won't break again... :D

Had the center stand off for years, and got so sick of having to use a box or something under the bike to adjust chain, replace tire, etc, that I was very happy to get it back on again. Advantages of having one, far out-weigh the disadvantages of leaving it on. Also have half pipe braized on to the bottom of the legs...gets it up high enough to do maintainance. Makes bike harder to get up on the stand, yes, due to the increased length and the leverage required, but acceptable for anyone under 70 or so... :wink:

Mine has nuts welded inside the tranny cradle, bushings mounted in the bolt holes on the stand and allen head shoulder screws w/holes for safety wiring. Original bolts and egg shaped holes were a bummer.... :?

Seem to think, I did what 79 said, when I adjusted the isos...cargo-strapped the bike upright on the bike lift, so it sat on the wheels, then used a jack and piece of wood to raise the engine cradle and get the stress off the isos...if my memory serves me right...maybe...kind of...might be...etc
 
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This morning, I wanted to remove a piece of paper from under the center stand so I lifted the bike a few mm. while it rested on its left leg.... And then it happened: the left leg broke off ! :evil:
I couldn't hold it so the bike fell on its left side.


850 style centerstand failure


The biggest damage were scratches on the fairing window - which in the meantime I could remove for the most part.
I console myself with the idea that it's better that my bike falls down in my garage than on the road but I really hope that the frame is a bit stronger.... :shock:
 
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When I was discussing Commando lowering with Matt at CNW he told me you quite often loose the centrestand when lowering, for obvious reasons...so maybe he bins them because of this?
I lowered mine 30mm, but I cut 30mm off the stand and welded it back up. Probably more reason to watch it closely.
The stand on my MK2A is also attached to the cradle. Not good really, for the ISo's
Some folk say you shouldn't start the bike on the centrestand because of the stress it puts on the Isolastics.
 
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Hi Guys,

Not to beat a dead horse, but a paddock stand is an ideal substitute for the center stand while the bike is garaged. It's easier to use, especially on a lowered bike, and lifts the rear of the bike in a natural way, by the swingarm. From a stress point of view, it's equivalent to standing the bike on its two tires, but allows the rear tire to freely rotate or be removed, for that matter. The stand IS a bit awkward on trips, however. Both of my bikes spend winters on their paddock stands.
 
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Paul said:
This morning, I wanted to remove a piece of paper from under the center stand so I lifted the bike a few mm. while it rested on its left leg.... And then it happened: the left leg broke off ! :evil:
I couldn't hold it so the bike fell on its left side.

What a coincidence that was, just in time to add to this thread.

I feel your pain, love your bike!
 
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just in time to add to this thread. :?:

The previous post was from March 30, 2007 !

After my "experience" this morning, I used the "search" function to watch if anyone posted a similar incident in the past.
I thought it would be a good idea to post a "reply" on this thread just to contribute to the very usefull database of this forum.

:|
 
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Haw! I'll have to pay more attention. At least I got to compliment you on your nice ride!
 
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Hi Ron and Coco,

I believe Matt is correct. The weight of the cradle assemble, with engine and transmission, is approximately 150 lbs (the exhausts are at least partially supported by the frame via the elastic connectors). The whole point of the head steady adjustment is to carry, at least statically, the weight of the cradle assembly via the main frame tube, thus unloading the two isos. Thus, on the side stand, the isos are in a neutral loading state. Lifting the bike by the cradle places the entire 450 pounds of bike weight on the two isos. The worst possible trauma to the isos results from kick-starting the bike while on its center stand, which could drive the load to 700 pounds or so (the bike weight plus the load of an accellerating 200-pound rider (speaking for myself, of course)).
 
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Rick;
Then if you have a Dave Taylor type headsteady the vertical load won't be supported therefore even with both wheels on the ground the weight of the swing arm assembly, cradle, engine and at least a percent of the rest of the frame body and rider weight will still be on the iso's?

I think if we look at this from a statics point of view it may not matter whether the bike is supported by the wheels or the center stand, the iso's still bear the load only the direction of the force would be different. In other words the weight and loads don't go away they just change direction.

I suspect that a more critical issue would be for the rubber in the iso's hardening and taking a set from the load being constant in one direction for a long period of time. A good reason to replace those 30+ year old iso's with fresh rubber.

Anyway, IMO the iso's appear fairly robust and I don't think failures are very common if at all and I suppose either with or without the center stand they should hold up just fine.

Scooter
 

maylar

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My center stand also has cracked around the spring hole. Too bad the hole is in a bad spot for periodic inspection without major contortions. And thank goodness for a MIG welder in my shop..
 

Ron L

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I believe Matt is correct. The weight of the cradle assemble, with engine and transmission, is approximately 150 lbs (the exhausts are at least partially supported by the frame via the elastic connectors). The whole point of the head steady adjustment is to carry, at least statically, the weight of the cradle assembly via the main frame tube, thus unloading the two isos. Thus, on the side stand, the isos are in a neutral loading state. Lifting the bike by the cradle places the entire 450 pounds of bike weight on the two isos. The worst possible trauma to the isos results from kick-starting the bike while on its center stand, which could drive the load to 700 pounds or so (the bike weight plus the load of an accellerating 200-pound rider (speaking for myself, of course)).

Not quite. The head steady is just that, to steady the engine. It was never designed to carry a load. The only support are two bonded exhaust mounts! The entire mass of the engine/swingarm assembly is supported by the two isolastics and the rear wheel.

Lifting a '68-'70 model by the centerstand (frame mount) loads the isos only by the additional weight the rear wheel supports when off the stand. (Assuming it lifts the wheel off the ground.) A late model relieves the entire engine cradle rear wheel mass from the Isos and is actually supporting the frame, tank, seat, etc. from the isolastic mounts. With the frame weighing only 26#, the total is somewhat less than the weight of the engine/trans assembly it carries off the stand.

In the case of the late model, starting on the centerstand imparts NO additional force through the isolastics as the stand is mounted to the cradle. Starting on the wheels, however, does transmit extra force through the engine mounts. But in my opinion this is negligible.

What is more important is you are transmitting that kickstart force through the stand in either case. That's why they break. I know the best practice is to kickstart only with the bike resting on it's wheels, but with rearsets it is much simpler to do it from the right side of the bike on the stand. Guilty as charged.

Besides, with a well tuned bike it doesn't take leaping on the kickstart, or even a full kick to light the fire.
 
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Hi Ron,

I have to admit my comments were directed only toward the Mk3. The manual calls for an adjustment of the head steady springs (two in parallel at 140#/in each) of 1/2 inch of extension before nipping up the isos, while the bike is supported either by its wheels or its lower frame. The total spring force of 140 pounds approximately balances the weight of the cradle assembly, and the isos are then nipped up in an unloaded state. Supporting the bike on the center stand loads the isos with the differential between the total bike weight of 450 pounds and the cradle weight, or a net of 300 pounds (not the 450 pounds I claimed on my previous post). Adding to this is the downward force on the frame as the rider raises himself up prior to kicking. The force of the kick itself is entirely born by the centerstand, and does nothing to further load the isos. The result, as you put it very well in your posts, is hundreds of pounds of force on the center stand, and the resulting damage you described. I'm spoiled by my electric starter.
 
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