diaphram springs

just wanted to see what people think that have done carb work. ok all these bikes are 30 years young now and alout of people complain about how the throttle isnt as crispy as it once was. and rebuild the carbs still doesnt fix the problem. over time springs loose their tension im wondering if its possible for the diaphram springs loose a little tension .if so wouldnt that make alout of difference part throttle if you have 1 weaker then another under part throttle would raise the needle more and make it richer. there is alout of tension on those little springs after 30 years i would think they would compress a bit and get weaker making throttle responce spongy

 

it's called age. and nothing you can do about it.

as for the sprints. i guess it's possible but if that's the case. you would notice a difference in height between all 4.

all mine stand at the exact same height.

if the springs are worn out. it would make the throttle easier, not harder. becuase, like you said. they've lost there tension.

 

The Problem is not the Springs.

The Problem is The Carb Bore.

The Bore "Shrinks" with Aluma-Oxidation buildup.
The Piston Begins to bind and chatter.

I wrote a piece for the Membership called:
"Clunk Test"

Read this article and take care of you Carbs.
It brings-back the Performance that age took away.

"Your Carbs Need To Go CLUNK"
http://xjbikes.com/Forums/viewtopic/t=1 ... +test.html

 

im kinda confused in what you are saying

 

Rick my carbs are fine .

 

wouldn't all the springs get weaker together ?
if you do find a weak one just drop a dime in there with it

 

Don't forget you are dealing with gravity, here, as well, so put a dime in all four & think yourself lucky, if you were on mars, it would cost you 13 bucks a pop.

 

all depends

 

so if i was to start riding the "wall of death" my carbs could lean out and my plugs would turn white, i hate when that happens

 

cutlass79500, don't forget the bike is tilted to the left when on the side stand so the sun shines on the right carb more taking longer to cool off

 

Don't get gravity confused with centrifugal force.

 

i get the point wont post any more on this topic

 

I don't want anyone to start losing sleep, start biting their fingernails or pulling-out their hair over this Diaphragm Piston Spring issue.

If we had a List of things that Absolutely SHOULD be serviced of Replaced after 28 ~ 30 years on the Bike.

Diaphragm Springs wouldn't be near the top.

(( Don't Racing Teams and some Pod-Squad Rider's clip a coil or two off the Spring's hoping for Power and Richer Mixtures when they race or to experiment with Pods? ))

 

i've replaced many a springs on cars. AND, they DO NOT stand the same height as new ones. they wear down and sag. they've lost there resilience and can't stand as tall as new ones.


a brand new spring will always stand taller then a old worn out spring. if the old spring had the same height as the new spring. it would't be worn out and the car wouldn't sag.

you can't have a worn out spring stand as tall. it's just not possible without reconditioning it. OR, AS SOME BACKYARD MECHANICS LIKE TO DO. THEY PUT THOSE SQUARES IN THE SPRINGS TO HELP THEM STAND UP AGAIN.

i was an auto mechanic for 12 years before retiring to a different career. i've rebuilt many suspensions.

 

Snowy, you can't compare suspension springs with the fine springs in a CV carb.

 

cutlass brought it up, not me. LOL.

 

Why not?

Spring theory is spring theory, regardless of the wire diameter.

 

He just did

 

Get a grip, stand a shock spring on end & see how much it compresses from it's own weight, now do it with a diaphram spring, do I need to go on.

 

spring theory starts right after winter theory, like it or not thats da truff

 

And it all goes back to string theory.

 

this is just a theory might not make any difference at all. im going to test my theory i have 2 sets of virago carbs 40 mm hitachi im going to hook a vacuum soarce up to them i have a big shop vac im going to check the height that the slide rises on each. 1 set of carbs has 9k on them the other has 33k on them. if i get a different height on the slides on each 1 i will pull the springs get the installed height make a jig so i can measure spring height with different weights see what i come up with . right now i have plenty of time to do this im disabled for 3 months maybe more before i go back to work cant sit or stand for long periods the reason i used springs on a car was an example the right front spring allways gets weaker then the rest from the torque of the motor. these springs are so small i would think they would get weaker faster. since they work off the amount of vac the butterflies let in if you had a little bit weaker spring under low vac situations 1 slide might be pulling the needle up a little higher then the others . you have herd of putting a 20 thousands washer under the clip on the slide to make it a little richer on part throttle situations usually if you have aftermarket exhaust or a free flowing air cleaner . once again its just a theory i could be wrong with all this time on my hands gives me something to do. also the jet kit that i got for my v max had 2 sets of springs to change how fast the slide moves im sure the spring rate is different but cant feel it compressing them with my fingers and it did make a difference changing them with no other changes on the low end on the dyno runs

 

OK, fine and dandy except for one thing:

Weak springs would allow the slides to rise more easily than they did originally. This would mean "early" opening of the mains by the slide needles, producing a rich condition.

I'll bet you could search these forums a really long time to find an XJ owner fighting a rich condition.

I'm thinking moot point? Maybe, maybe not--

Tell ya what: I have two 550s and two spare racks of Mikunis. I know where NOS Mikuni carb diaphragm springs can be had for $24 ea. If you wanna buy and send me a brand new spring, I will compare it to all 16 original, used springs in my possession, and see if there is any discernable difference.

OR

Question for the theorists out there: What if a person had a BRAND NEW, NOS carburetor unused but of course assembled. And has been sitting assembled for some 28+ years, with its spring compressed.

But never used; its spring has not seen hundreds of thousands of operational and hundreds of heat cycles.

Is THAT spring "new" enough to be compared to the springs from even a low-mileage rack of old carbs? Or would the "new" spring need to be BRAND NEW, never compressed?

I happen to be the owner of a brand new NOS 28mm Mikuni. ($25 off eBay, you guys musta been sleeping.)

Should I compare the spring from the brand new but assembled for all those years carb with a USED one? Or do we need a brand new, uncompressed spring for a proper comparison?

 

torque of the motor doesn't have an effect on springs wearing down. it's the weight of the car itself.

when i want to automotive school. it was said that springs wear down more when a car just sits on it's own weight. for extended periods of time. rather then actual driving conditions.

overall theory would suggest the drivers side spring going faster. becuase a driver in the car is 200+ pounds more then the empty passenger seat.

car sits level with no one in it. throw a 200 pound person in the drivers seat and now the car leans left a little. take a tape measure and meausre from the ground up to front bumper. both sides of the car. with no one in it. then remeasure with a body in the drivers seat. the left side bumper is now lower.

having the perfect aligment on a vehicle was impossible for that simple fact. easy to obtain when it's sitting on the rack with the machine mounted up. put a person in the drivers seat and now the alignment is changed. the heavier the person the more it changes.

 

I was thinking the right front tire hits more potholes and other bumps harder than the left, causing the spring to fully cycle more. There's also the crown of the road leaning the car constantly right. We ride in the left wheel track partly because it's smoother.

(the right rear tire picks up more nails and screws)

No need to mail springs - -
Spring length lying down - 93 MM
" " " " standing up - 92 MM
" " " " while dangling - 94 MM
From a used Maxim 650 carb, miles unknown.

 

So is it worth comparing a brand-new but has been compressed for 28+ years to a truly USED spring?

Or does the fact that it's been sitting compressed make it just as "used" as a USED spring?

 

I am a simple guy.
Therefore, I think this is a simple operation.
The spring provides tension until the throttle is opened (the bodies go up).
When the throttle is disengaged, the springs return the bodies to there original position providing they are "clunkable" lol.

Done.

 

<sigh...> Ohhhhh.... I get it now. You don't know spring theory. It goes like this.

f=-kx

where f is force, x is deflection, and k is the spring constant.

It's called Hooke's law of elasticity.

Note that "diameter" does not appear in the equation. Also note that "application" doesn't appear either.

The shock spring obeys Hooke's law.
The diaphragm spring obeys Hooke's law.

As illustrated by the equation above the shock spring simply has a greater spring constant, and hence, will deflect less than the diaphram spring for the same applied force.

So, yes... Feel free to go on, but before you do...

Hooke's law.

Look it up.

While you do that, I'll say it again... Spring theory is spring theory, regardless of the wire diameter.

 

god i hate it when a university graduate out talks us with hooke's law.

 

Haha... Yeah, I'm sorry about that. :lol:

But he started it!!! He was supposed to say "Oh I get it, the theory should be the same regardless of the diameter."

 

Theory?

If designed correctly, age should have no effect.
If designed correctly, deflection distance should have no effect
If designed correctly, number of cycles should have no effect.

Things that do have an effect? Temperature (if high enough). Deflection beyond the elastic limit. Corrosion. Internal stresses in the material left over from the manufacturing process.

But you asked a specific question, and if I'm gonna step out here and start spouting theory... then I ought to be willing to produce an answer I'm willing to stand by. So, my answer is thus...

In theory, if designed and applied correctly, the spring in the unused carb should be identical to the day it was put in there.
In theory, if designed and applied correctly, the spring in the used carb should be identical to the day it was put in there.

My humble opinion is that this discussion is a goose chase... Before you go replacing diaphram springs, clean your visor instead. The drag reduction from that big bug you took off will free up more power and have more of an effect than making sure all of your diaphram springs are identical. :lol:

 

Tell that to my GF.

 

I've been monitoring this thread and I must say "I don't know either"
Being a mechanical engineer but with limited spring design experience, I would be up for an experiment too.

I know the MANY springs can not handle complete compression frequently. BUT some have no problems with that at all. It all has to do with the diameter of the wire, diameter of the spring, and pitch of the windings. These variables also determine the longevity of said spring under normal usage and life span.
That being said, the diaphragm springs have very robust and consistent design parameters (small diameter wire, comparatively large spring diameter, and very fine pitch). The wire undergoes very little stress in moving from fully extended to fully compressed postion.

BUT, the biker in my tells me that the X that I had 20 years ago would feel like it was trying to buck me off when the diaphragms finally opened....my current ride not quite as noticable (although still definately there).

25 years of partially compressed combined with thousands of cycles has got to weaken the springs. How much? It would be easy to test if we had some nice NEW, FRESH springs (never installed).

The old stretching routine will give me an idea if it would make any difference on performance but I would just be guessing.

Per Bigfitz> It's probably rich during the transition which would probably give you a bit of a lag and lack-luster acceleration compared to new.
I doubt that it would last long enough to give a rich signal color on the plugs since the time that it's rich would be minimal.

The "coin under spring" option someone else mentioned was probably more effective by addition weight to the plunger opposed to adding spring tension. That plunger is undoubtedly that heavy by design otherwise they would use a different material.

SO, Len....how long are the springs SUPPOSED to be on my carbs? AND, how much for a brand new set? so I can do some testing. I'll even spring for two dyno runs to compare

 

Condescending cove aren't you Rice-Burner, my comment was that the comparison was poor because of the vast difference in application & the diaphram spring is also assisted by weight & gravity.

 

They ain't cheap! Around $ 22 each, but...........

I tend to think that the change in performance due to new springs would be minmal, at best, and any measured change in performance over typical condition used springs could well be due to some other type of factors.......unless, of course, the old springs were beat up or altered in some meaningful way.

I know that I sound like a broken record at times, but.........it's hard to beat a stock system for best overall performance. If rebuilding the carbs, adjusting the valves, and synch/colortuning doesn't give you enough performance, then you might want to invest in a bike with a bigger engine. The pods/dyno-jet/etc. route to trying to get a small amount of extra performance out of these engines is rarely worth the time, effort, and $$, although, it certainly is a great way to get lots of practical experience in working on the carbs, etc.

Multi-carb engines are finicky devices that require an almost "perfect" state of tune in order to perform as designed. Unless you're in the race-engine building biz, the trial-and-(mostly failed)-efforts approach to getting more performance out of these engines can be really frustrating. Be careful......bad advice and old wive's tales and snake-oil salesmen tend to abound in such realms........


And Mike, here is the info you requested, all dimensions please allow +/- a few thousandth's, as these springs are tough to measure accurately:

21.20mm ID
23.00mm OD
0.88mm wire thickness
107.70mm tall

 

Sorry 'bout that. It's not usually my way, but the tone of your previous message got to me a little.

My point is that it's really not a poor comparison. Despite the obvious physical differences between the two springs, they are in fact extremely similar in application and comparisons between the two are perfectly valid.

They are both steel springs, which in application, are both held in partial compression at all times. There's really not much more to it than that.

So again, sorry... We theory guys get a little worked up when the laws of physics get bruised.

 

Before you guys spend a whole bunch of time measuring springs... Remember that the unloaded free length of these springs really means nothing.

The only parameter that matters is the amount of force required to compress the spring to the length(s) it assumes in application. By that, I mean, you need to measure the force required to hold it to the two extremes of it's travel, partially compressed with the carb slide down, and again when compressed more with the carb slide all the way up.

If those two forces are the same between two springs, then those two springs should behave identical in application.

The full unloaded free length doesn't matter squat.

 

And one more thing (sorry for the "Holy overposting Batman")...

I think RickCoMatic said it best...

Being a theory guy, I'll absolutely read (with great interest) anyone's post who is going to scientifically test these things, but I'm not inclined to be the one to run those tests! :lol:

 

i got in mr. peabody's wayback machine and seem to remember a honda (i think) with keihin's (i think) that were cv carbs with a heavy brass slide and no spring at all
that ring anyones bell or should i go drink another beer

 

WHAT no springs, that would put Burnarr back in his box.

 

here's the deal.

IF in fact that springs do wear out. the bottom line is this. would be easier uprise in the throttles. AND. the throttle would probably rise higher then if the springs were new and unused.

THE BAD. less tension pushing the throttles back down.

NOW. let's change the subject from hooke's law to moore's law.
(E=2 divide by MC). does that theory still hold????


ROFL.

 

To bad the subject changed.
It was beginning to get tedious.

But, I did have an old "Slinky" toy that I was going to award to whoever made the most ridiculous claim about springs.

That offer has expired.
I'm keeping the Slinky and giving it to my grand daughter when she's old enough to put it on Ebay.

 

Once this Dead Horse has been beaten so severely as to be totally unrecognizable ... Maybe you can all get together and solve this ages-old argument:

"What... is the Airspeed Velocity of an Unladen Swallow?"

European.

 

Sorry Rick,
I was too busy working to measure my springs

Got to it tonight though..So, my USED springs measure longer than Len's brand new ones. And springs from three different racks are all within .5mm.

I plugged the parameters into my design program and there is such a tiny amount of stress applied to the springs that the life expectancy (# of cycles) was such a huge number I didn't even write it down.

I would say that the diaphragms would probably rot off the plungers before these springs change loading dynamics even the tiniest of amount.

I just had to beat the horse one more time

OH...and what temperature, altitude, and relative humidity are we tracking the swallow (we need to know the density of the air!) :roll:

 

Woahhhh... NO springs? Awww geeez. Now I gotta come out of my box again... :lol:

So once the differential pressure was great enough to start moving the slide up, physics dictates that it will keep moving up until it reaches equilibrium, right? And if there's no spring and the slide is just fighting gravity (which can be considered to be a constant), then where would the slide stop? End of travel all the way up??

I'm sure no vintage carb expert, but I'm thinking there's got to be more to it than that. I'm not saying that they didn't do it. I mean, this sure wouldn't be the first hair-brained idea put into place in the history of the carb, but I think there's some other detail missing? :?

And by the way... I'd be happy to buy you another beer!

My name is Rice-Burnarr.
My quest is to Eschew Obfuscation
And my favorite color is red.

No... Blue.