Tips for getting isolastic gap even all around

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ewgoforth

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Hi,

I've tried removing and reinstalling the main rubbers and spinning the mount around as I have the spindle clamped in a vice, they reduce, but don't eliminate the problem.

My understanding is the problem is the inner sleeves of the various isolastic bushes and buffers aren't totally parallel with the tube. What do the rest of you do?

Eric
 
Not quite clear on you issue. Generally I try to get the same amount of shim on both sides, but it doesn't happen too ofter. Usually there will be .005" difference. .020 on on side and .015 on the other. Some time it will be the same amout of shimming on both sides. I try to take my best guess on one side then I work from the easy side (dirve). If I have a .010 shim one the TS then I have .005, .010 , and a .010 and a .005 to make .015 on the other.

As far as rubbers and bushes are concerned, unless all rusted up in there the bushes are just there and taking up space in a prescribed manner. Rubber will rot or get mushy. As far as being parallel within the tube, I can't say that is a facter unles the rubbers are so perished that they are no longer effective.

Anyhow, what symptom are you dealing with.

Just to add, although there are suggested numbers to go for, what you need is the bike to perform (vibrate) to your needs. You may need to add or take away to get it the way you like.
 
pete.v said:
Not quite clear on you issue. Generally I try to get the same amount of shim on both sides, but it doesn't happen too ofter. Usually there will be .005" difference. .020 on on side and .015 on the other. Some time it will be the same amout of shimming on both sides. I try to take my best guess on one side then I work from the easy side (dirve). If I have a .010 shim one the TS then I have .005, .010 , and a .010 and a .005 to make .015 on the other.

As far as rubbers and bushes are concerned, unless all rusted up in there the bushes are just there and taking up space in a prescribed manner. Rubber will rot or get mushy. As far as being parallel within the tube, I can't say that is a facter unles the rubbers are so perished that they are no longer effective.

Anyhow, what symptom are you dealing with.

Just to add, although there are suggested numbers to go for, what you need is the bike to perform to your needs. You may need to add or take away to get it the way you like.
Click to expand...

The problem is that the gap isn't even when I move around and measure it in different spots, while going around in a circle. I'll have .07 in the tightest spot and maybe .011 in the loosest. I see this even when I'm doing it off the bike. The tube measures really evenly all the way around.

-Eric
 
I don't think that is all that uncommon. It's the cradle) sitting in there all loose and free. It should be pried to one side to check and if everything isn't just so, reading will very as you rotate around. Take the best reading you can and test ride to suit. You must test ride to get it right. As with many setting in the books, many are suggested starting points. I feel Iso's are of this nature.

Your numbers seem pretty darn good and again, the ride will tell.
 
ewgoforth said:
The problem is that the gap isn't even when I move around and measure it in different spots, while going around in a circle. I'll have .07 in the tightest spot and maybe .011 in the loosest. I see this even when I'm doing it off the bike. The tube measures really evenly all the way around.
Click to expand...

Try again with the head steady fully slackened off?
 
Personally, I wouldn't worry about it, I doubt there's much you can do about it anyhow. I put new donuts on my bike and removed the front iso unit to put on a Hemmings adjuster and in just a year the donuts had taken a definite sag of about 1/4" towards the bottom. But then I've got the early frame with the center stand mounted off the frame too. I did then install the springs off the head to the frame, and it helped with the sag a bit, but not completely. About all that did was get rid of some of the idling vibrations.
 
ewgoforth said:
The tube measures really evenly all the way around.
Click to expand...

Are the faces of the tube end caps and collars completely flat?
Are you using the old PTFE washers-as they could have worn unevenly?
 
L.A.B. said:
ewgoforth said:
The tube measures really evenly all the way around.
Click to expand...

Are the faces of the tube end caps and collars completely flat?
Are you using the old PTFE washers-as they could have worn unevenly?
Click to expand...

This is with brand new PTFE washers. I've checked the tube using a Vernier caliper and it's within 1 thou all around. I'll have to check the collars more closely. I'll double check the clearance variation with the isolastic on and off the bike.

I was just thinking that with the unit installed on the bike the frame's mounting lugs could move the virtual center tube around relative to the isolastic mount. By the virtual center tube, I'm referring to the spacer tube, isolastic bushes, and the collar. These all get pressed together to make a tube, attached to the frame that should be perfectly parallel to the outer tube.

-Eric
 
One of the inherent problems with these is that the spacer cup which fits over the tubes is not a tight fit, so it flogs around wearing more and more. Just get it as close as you can. Even 5thou gap is ok so long as you are happy with the result. [ handling or vibration ]. One of the best and simplest things you can do also is copy Ludwig's head support. As he says. Nothing to go wrong.
Dereck
 
Set your desired clearance at the tightest point, but as others have mentioned, there is some slop in the cupped washer. I typically loosen the head steady and pry the engine to the opposite side using a large bessy clamp between the frame and the engine. Hold the cupped washer tight against the tube with one hand, and measure with the other.
 
I'm not trying to plagiarize any one here, but I got this off the net somewhere and had it in my files
for future reference -

The last time that I removed my front Isolastic mount to shim it, I also noticed that the clearances were very uneven. I decided to have the ends of the tube machined parallel at a local machine shop. The machinist checked the tube in several places and found that the maximum variation in the length of the tube was like one or two thousands. This was puzzling since the variation in clearance was something like eight thousands. After looking at the mount I realised that this was due to the outer, main bushes not being perfectly square in the tube. Since these bushes locate the throughbolt, they locate the outer collars. So the problem in uneven clearances was that the collars were not square, the endcaps were square.

After working with the bushes I was able to get the clearance variation reduced, but figured that the factory tool might the ticket for getting these perfectly square in the tube. I call Phil Radford at Fair Spares and told him what I had discovered and asked him what he thought about the factory tool. While he didn't really knock the factory tool, he said that what he did to get these square and also to get the clearances equal on each side was to fully assemble the mount and torque it down as though you were going to check the clearances off the bike. Then clamp the mount in a vice and turn the through bolt.

When the through bolt is torqued down the a shoulder on the collar presses against the pressed in sleeve on the bush which presses against the spacer tube. So what you have is metal-to-metal contact all the way through the mount. So if you've lubed the bushes with silicone grease they will turn when you turn the throughbolt. I had the mount back on the bike when I was told this but I plan on trying it the next time that I take it off. I'd imagine that the clearances should be uniform after two or three revolutions of the bush.
 
zotz said:
I'm not trying to plagiarize any one here, but I got this off the net somewhere and had it in my files
for future reference -

The last time that I removed my front Isolastic mount to shim it, I also noticed that the clearances were very uneven. I decided to have the ends of the tube machined parallel at a local machine shop. The machinist checked the tube in several places and found that the maximum variation in the length of the tube was like one or two thousands. This was puzzling since the variation in clearance was something like eight thousands. After looking at the mount I realised that this was due to the outer, main bushes not being perfectly square in the tube. Since these bushes locate the throughbolt, they locate the outer collars. So the problem in uneven clearances was that the collars were not square, the endcaps were square.

After working with the bushes I was able to get the clearance variation reduced, but figured that the factory tool might the ticket for getting these perfectly square in the tube. I call Phil Radford at Fair Spares and told him what I had discovered and asked him what he thought about the factory tool. While he didn't really knock the factory tool, he said that what he did to get these square and also to get the clearances equal on each side was to fully assemble the mount and torque it down as though you were going to check the clearances off the bike. Then clamp the mount in a vice and turn the through bolt.

When the through bolt is torqued down the a shoulder on the collar presses against the pressed in sleeve on the bush which presses against the spacer tube. So what you have is metal-to-metal contact all the way through the mount. So if you've lubed the bushes with silicone grease they will turn when you turn the throughbolt. I had the mount back on the bike when I was told this but I plan on trying it the next time that I take it off. I'd imagine that the clearances should be uniform after two or three revolutions of the bush.
Click to expand...

I'm not sure where you got that from, but I'm pretty sure it was something that I wrote years ago. At any rate, it doesn't sound like anyone else really pays much attention to it.
 
Feeler gauges are over rated for this aren't they?

I just went to with nipping them up and slackening them off.

I don't have the shop manual to hand, but doesn't it say something like one turn from nipped up equals 0.005" ? I may have this wrong, but it does give precise guidance to this affect.
 
I use a dial indicator (with magnetic base) between the frame and engine adjacent to the ISO of interest and force the engine left and right while taking a reading.

As other have noted here, I have found the machining accuracy of the ISO components lacking; distortion also come into play.
 
Fast Eddie said:
Feeler gauges are over rated for this aren't they?

I just went to with nipping them up and slackening them off.
Click to expand...

That's what I do too... I tighten them and go for a test ride. If I get to much buzz, I slacken them off slowly until I am satisfied that they are as tight as I can get them without being "too" buzzy. Yesterday I removed my back wheel to retighten my Keegler modification. I also retightened my Iso's. I went for a ride and,....... Wow, buzzy handlebars. I got home and slackened off my front Iso... no feeler guage needed..
 
ewgoforth said:
I'm using shims, so feeler guages are the only way to go.
Click to expand...

Fairy Nuff Eric. That'll teach me for assuming !!

I'm actually now quite interested in the outcome though, so please do keep us posted.
 
Dances with Shrapnel said:
I use a dial indicator (with magnetic base) between the frame and engine adjacent to the ISO of interest and force the engine left and right while taking a reading.
Click to expand...
Ditto. Lest anyone think that slop introduced by the kick shaft might throw the readings, I tried it both with no load, then with side-force applied to the kick start shaft. No difference.

Tips for getting isolastic gap even all around


Nathan
 
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