850 unloaded valve spring measurements

I am looking to see if my valve spring are within the Unloaded allowed tolerances... the manuals has 2 different set of values for spring heights... maybe 1 is for750... 1.7 outer... 1.531 inner.....& the other is for a 850 .... 1.618 outer... 1.482 inner... The head that I am rebuilding is a rh 10 head... not for sure of the year manufactured... just coming out of the shop & measuring on a flat 1/4 plate .. using a machinist sliding T ...the outers lowest reading is 1.6... the inners lowest reading is 1.46... I'm thinking I should be ok... if any body know what the acceptable tolerances would be let me know...

Also when I disassembled the head there was heat washers under the exhaust valve springs only... does anybody know if there should be heat washers under all 4 valve springs................. let me know..... Tripower

The manual I have lists the same numbers for the 750 and the 850. The manual is factory, but of unknown date. It lists inner free length as 1.482" and outer as 1.618. I have only seen the insulating washers under the exhaust springs.

If the springs are short I usually replace them as long as it is all apart. When building motors I was taught to keep the cylinders as equal as possible. You will have to decide if you want to reuse the springs. I'm pretty sure nothing bad will happen as long as the springs are not broken.

Greg

I guess you didn't like the answers you got the first time you asked. sorry about that.....

But the length isn't going to tell you a whole lot about how the springs are going to work. Measured pressure does, at a given length you can set the pressures you need by shimmimg.

And yes, there should only be heat washers on the exhaust and seals on the inlet guides.

The length will really only indicate if a spring has settled in use....if it comes up short you will change it...fine....but if it doesn't...do you know the full history of the spring? or how it is going to perform? and for how long?

The question about the heat washers indicate you didn't build it last time......so....measure all you want.....but....

You own a bike worth thousands.....it is already torn down.....how much a set of new standard springs? Less than £30 in the UK.

Steve is right, it's good to replace 40 yr old springs even if their free length is in spec.
The book says outer spring 1.618 free length, 1.500 minimum. Inner spring 1.482, 1.375 minimum

Fitted spring length 1.259 for the intake, 1.284 for the exhaust.

That is for the std Norton springs. after market springs may be different. To get the correct seat pressure you need to measure the installed spring height.

Thanks for the reply... I ordered a set of black diamond valve springs yesterday..... this is my first bastard Norton build so I tend to refer to manuals so when I have conflicting information I will bring it up for discussions, because I need to make my own notes ..... Thanks

The meaning of life ..... is to live it ............................... Tripower

tripower said:

Thanks for the reply... I ordered a set of black diamond valve springs yesterday..... this is my first bastard Norton build so I tend to refer to manuals so when I have conflicting information I will bring it up for discussions, because I need to make my own notes ..... Thanks

The meaning of life ..... is to live it ............................... Tripower

Click to expand...

every Norton build is a bastard..... :wink:

...unfortunately the manuals give limited information, often based on the tools the author expects you to have available, some you will, some you never will for a one off operation....

Hopefully the Black Diamond springs are supplied with additional data regarding installation....

I don't know about Black Diamond valve springs but I have seen some aftermarket retainers hit the stem seals with cams with .395 lift or more.
Check clearance at full lift and that you don't have spring bind.