Mk3 Head Steady Adjustment

Status
Not open for further replies.
G

GRM 450

Joined
Dec 30, 2008
Messages
990
Country flag
Hello, and the best to you all for Christmas and the New Year.

Mk3 headsteady had the spring hook over the rear barb and was adjusted to .5 to .2 of an inch gap between the mount and the barrel as per the book. (section C1, fig C1(a)
But I didn't measure the spring stretched length.

C1 chapter 7 says the spring is usually on the forward barb. But the picture fig C1(a) shows the spring on the rear barb?

This picture also shows the spring stretched to 1.47 to 1.53 inches.

If the spring on mine is on the rear barb the spring can't stretch that far and maintain the .5 to .2 gap.

Am I missing something or should the spring have been on the forward barb the whole time?

graeme
 
Hi Graeme,

I reckon the manal is wrong regarding the spring length. On Mk3s I've always started on the rear barb and with the 0.5" gap. My theory is if I run out of tension, and so far I never have, I'd move the spring to the front barb. On a couple of Mk2s I've fitted the spring to I found the tension way too high and resorted to a little hole elongating.

And the same to you,

Cash
 
Graeme,

The spring must be stretched to the nominal value of 1.5" to provide the required 140 lbs of lift to the cradle. The manual is correct in this matter. The alternative barbs are provided to allow for this AND the required clearance (for rebound). Use either barb. I've always had to use the forward barb to meet the spec on my Mk3, but I expect that this is bike-dependent; your results may vary.

Rick
 
It should be held in the normal riding position on its wheels, not on the the stand. As noted, the spring needs to be stretched to approx 1.5" to have the desired affect. Which tab produces that is of no consequence. THe spring tension is the vital item.
 
Mike's right. An alternative would be to use a paddock stand that supports the rear of the bike by the swingarm; this keeps the bike vertical, stable, and "on its wheels".
 
Don't forget the final setting will have to be done by trial and error, test ride adjust, until the sweet spot is found.

Best of luck,

Cash
 
However - I have to say that I couldn't tell any difference before/after installing the MK III spring on my 850...
 
As I wrote earlier, on a couple of Mk11 Commandos I found the spring was over stretched and had to elongate the barbed plate bolt holes to get it to work.

Cash
 
A new head-steady spring is available from several sources, on both sides of the Atlantic, for 6 bucks. Since the set-up spec is based on a functioning unit, why would you jury-rig the head steady to use a distorted spring?
 
Rick,
Sorry if I misled you;
Brand new springs and mounting brackets were used and on these Mk2s the spring would not fit over the first barb without over stretching it and lifting the motor up (My reference was a standard Mk3). One frame was a metric Italian make ??? I didn't check the other. The only conclusions I came to was the holes in the coil mounting bracket on the frame was 3/8" forward, or the motor was sitting farther back, or the kit was at fault. The ISOs were good etc so the easy solution was to move the barbed mount towards the motor, and it worked. Strangely another spring kit fitted straight onto a Combat.

Cash
 
The more I read about the Mk3 headsteady, in this thread and in the archives, the cheesier they sound. Hanging a vibrating engine off a spring to supplement the rubber isolation? What's next, matching springs for the front and rear isolastics, and all three spings pulling outwards? Okay, okay, gravity is already looking after that. I think the line between elegant engineering and bodging was crossed on this one.

Stephen Hill
Victoria, BC
 
The spring was added to the MkIII to compensate for the extra weight of the E-starter, associated monkeymotion gears, shafts yadda yadda and the heavier cylinder barrel. Perhaps an inelegant solution, but it proves the adage, "When you change something, you don't change one thing, you change everything."
 
Stephen Hill said:
The more I read about the Mk3 headsteady, in this thread and in the archives, the cheesier they sound. Hanging a vibrating engine off a spring to supplement the rubber isolation? What's next, matching springs for the front and rear isolastics, and all three spings pulling outwards? Okay, okay, gravity is already looking after that. I think the line between elegant engineering and bodging was crossed on this one.

Stephen Hill
Victoria, BC
Click to expand...

Might appear as a cheesy solution, but it works. I fitted one to my Mk2 and definetly noticed the improvement in Iso behaviour and it firms up the steering a bit. I recommend it as an upgrade to all standard Commandos with or without alternative head steadys such as the Dave Taylor tie rod.

Mick
 
Thanks, Cash, for clearing up my confusion. Sounds like you were trying to make the steady work in a non-standard configuration.

I believe that the Mk3 headsteady spring has value, but only if the spring adjustment is done while the other iso bits are loose. Once the spring carries the cradle weight, the cradle isos can be nipped up to spec, along with the lateral supports in the head steady. It's always made sense to me.
 
For numpty's like me,,,

Are you saying to have the bike on a padock stand or on it's wheels, then,

Loosten the front and rear iso's,

Loosten the head steady rubbers,

Then tension the spring to 1.5 inches,

Then re tighten the head steady rubbers, and re adjust the front and rear iso's?

Graeme
 
I don't believe that adjustment of the isos can have any effect on the head steady or visa versa. Tightening/loosening the iso adjustment/shims doesn't put pressure of any sort on the rubber parts in the iso assembly and cannot affect the "set" of the rubber donuts.
 
Errrr, I guess I don't follow Mike's comment. The isos allow a small vertical displacement of the cradle with respect to the frame via the compression of the rubbers (as well as a small horizontal movement as well). The spring is set up to apply 140 lbs of lift to the cradle with respect to the frame, creating close to a neutral point at the isos (the spring is actually not quite vertical, but follows the jug angle, about 9 degrees). By setting the isos after the spring is set up, we minimize the possibility of compressing the iso rubbers by the weight of the cradle. The weight of the engine, transmission, and cradle is approximately 140 lbs. The effect is likely small, but the technique seems reasonable to me.
 
Status
Not open for further replies.

Similar threads

travelerjerry
  • Locked
Mk3 Head Steady Offset Holes
Replies
5
Views
1,556
Hobot
Hobot
P
  • Locked
Dave Taylor Head Steady Adjustment
Replies
2
Views
1,202
plj850
P
rick in seattle
Standard Commando Mk3 Head Steady
Replies
1
Views
1,890
79x100
7
A
  • Locked
MK3 head steady
2
Replies
29
Views
6,823
cash
cash
Back
Top