valve spring pressure

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I measured my valve spring pressures at ~80lb (lowest 78, highest 84), at the spring lengths specified in the manual (1.259" and 1.284" outer spring length for intake and exhaust, respectively. the inner lengths at whatever the stepped washers put them at). This should be the seated (closed) pressure, if I understand the threads on measuring spring pressure correctly.

The closest thing to a spec for what the pressures should be is 80 to 100lb, from https://www.accessnorton.com/NortonCommando/valve-spring-seating-pressure.10667/

The question: should I get new springs, or shim the old ones, or leave them as is?

As far as I know they are the original springs, and I'm running a JS0 cam (stock profile) with them.
 
I measured my valve spring pressures at ~80lb (lowest 78, highest 84), at the spring lengths specified in the manual (1.259" and 1.284" outer spring length for intake and exhaust, respectively. the inner lengths at whatever the stepped washers put them at). This should be the seated (closed) pressure, if I understand the threads on measuring spring pressure correctly.

The closest thing to a spec for what the pressures should be is 80 to 100lb, from https://www.accessnorton.com/NortonCommando/valve-spring-seating-pressure.10667/

The question: should I get new springs, or shim the old ones, or leave them as is?

As far as I know they are the original springs, and I'm running a JS0 cam (stock profile) with them.
With a stock cam you shouldn't be getting anywhere near coil bind. Shimming might get you where you want to go. What are you trying to accomplish with shims?
 
I measured my valve spring pressures at ~80lb (lowest 78, highest 84), at the spring lengths specified in the manual (1.259" and 1.284" outer spring length for intake and exhaust, respectively. the inner lengths at whatever the stepped washers put them at). This should be the seated (closed) pressure, if I understand the threads on measuring spring pressure correctly.

The closest thing to a spec for what the pressures should be is 80 to 100lb, from https://www.accessnorton.com/NortonCommando/valve-spring-seating-pressure.10667/

The question: should I get new springs, or shim the old ones, or leave them as is?

As far as I know they are the original springs, and I'm running a JS0 cam (stock profile) with them.

If you have a JS Motorsport camshaft it should have been supplied with recommended assembled height, seated pressure (poundage) and pressure at full lift.
Of course you should buy new springs after spending what looks to be $449 for the cam alone.

Should you try and shim old springs to get a poundage, no, should you shim a new or known to be good spring to get an assembled height, yes which by default if it is a quality spring will have the then correct compressed poundage.

A simple undersize height collar, collar plus what the dial gauge says is assembled spring height. (Isolators or springs cups where fit)
Without a pondage tester it would then rely on the assembled height.

The JS cam comes back to recommended springs and their specs.

valve spring pressure
 
Oddly enough (or not) the new out of the bag Andover Norton inner and outer valve springs were very close to the cylinder head assembled height in the workshop manual suggesting they were in the optimum compressed height for their poundage. (Not over or under compressed)
The engine would bounce nicely settling back to the same location (Isolastic housing on centre with the frame lug holes) repeatedly.

valve spring pressure
 
Oddly enough (or not) the new out of the bag Andover Norton inner and outer valve springs were very close to the cylinder head assembled height in the workshop manual suggesting they were in the optimum compressed height for their poundage. (Not over or under compressed)
The engine would bounce nicely settling back to the same location (Isolastic housing on centre with the frame lug holes) repeatedly.

View attachment 95876
I don't think you've got those valve springs in right place TW ;-)
 
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With a stock cam you shouldn't be getting anywhere near coil bind. Shimming might get you where you want to go. What are you trying to accomplish with shims?
The shims would be to get the correct poundage, as mine are currently bellow/on the edge of what they should be.
If you have a JS Motorsport camshaft it should have been supplied with recommended assembled height, seated pressure (poundage) and pressure at full lift.
Of course you should buy new springs after spending what looks to be $449 for the cam alone.

Should you try and shim old springs to get a poundage, no, should you shim a new or known to be good spring to get an assembled height, yes which by default if it is a quality spring will have the then correct compressed poundage.

A simple undersize height collar, collar plus what the dial gauge says is assembled spring height. (Isolators or springs cups where fit)
Without a pondage tester it would then rely on the assembled height.

The JS cam comes back to recommended springs and their specs.

View attachment 95868
Getting new springs does make sense, just want to make sure that they are infact needed.

The JS Motorsport cam did not come with any sort of spring specs, just a "how to time the cam" sheet (maybe because it's a stock grind, so I'm just supposed to use the stock?) The trouble is that I'm not sure exactly what the stock is supposed to be (other then the assembled length), and how much deviation is acceptable... maybe I'm not looking in the right place. Should I be getting the correct poundage from the cam manufacturer? Or just use the assembled length - I though that was less accurate then the poundage, from https://www.accessnorton.com/Norton...r-measuring-valve-spring-pressure-2020.30985/
 
If your worried I'd just email or phone Jim at JS Motosport. A few years back I measured lots of valve springs fora 500 twin race bike. I remember the cam baseline spring pressures were around 70 to 80 lb. Over the nose of the cam a standard spring and lift got up to about 150 160 lb while racing springs could measure up to 250 lb before coil bind. British spares stopped seling the 250 lb ones because in their words they tore up cams and followers. For racing I went up to 220 lb over the nose for a 500 reved to 8000.

If your springs are measuring around 70 to 80 on the baseline then they are probably fine. But personally if I thought they were 50 year old I'd replace them.
 
Ok. I have emailed JS Motorsports, but haven't gotten anything definitive for non-orriginal and non-JS motorsports springs (which makes sense).
But personally if I thought they were 50 year old I'd replace them.
That makes sense, and is probably what I will do. looking at Kibblewhite springs.

I would still be interested in what the original spring poundage/ ideal original spring poundage is supposed to be, but as far as I can tell either no one knows the exact number or there is to much variation to give one specific number.
 

May be it could help ...........

Very helpful! I
if you didn't watch the video, he (Jim Comstock) says that he sets the stock springs at 95lb seated, which brings it to ~202lb at full lift for a stock cam. That's on the higher side of the 80-100 range I referenced above, but if its correct (video is from 2018, so not to old...) my springs definitely need to be replaced.
 
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