TOPIC:

Anyone here measure their clutch springs for the static pressure? How do you go about doing that? Is there a specific spring tester to use for clutch springs? I have a spring tester from Pro form that is used in a vise but can't remember if it's for valve springs or if it can be used for clutch springs also. Goes from 0-300#. Are springs tested at a certain length....say 1".....and determine the pressure at 1" or do different springs need to be tested at different lengths....depending on the model of the spring?

I haven't tested mine, but here's what the Kawasaki KZ650-C1 manual says. The same springs are used on a whole bunch of different Kawasakis including a 1977 - 2005 KZ1000 models. Ed

Well...that's a start. I'll look up in my manual to see what the spec's for a stock spring is. I just need ti find a way to measure the tension.

Well I know a poor man's way of doing it if you have a decent set of bathroom scales.

Cut a piece of wood to the required length (three or four lengths would be best) and sit those on your scales. Put the spring on the scales next to the wood, and note the weight reading on the scales.

Then get a rigid board and put that on top - it will be resting on the spring, but if you push down on the board, the spring will compress and the board will start resting on the wooden lengths. Start adding weights on top of the board until the board is *just* resting on the wood. This means that the spring is now compressed down to the required length - if you cut the wooden pieces to 23.5mm, the spring will be at 23.5mm.

Now look at the weight reading on the scales - get that value and subract the value you measured before. That will be your tension at 23.5mm.

I've measured spring free length and noticed they can shrink by a couple of mm, is the spring tension test better than measuring the free length?

It bothers me that a motor left standing for years will have compressed valve spring(s), a good reason to turn a motor over every few months when in storage.

Really good springs can be left in tension for years, it is the electrons pushing each other apart IIRC.

Free length may not matter too much.

I may be wrong, but I'm under the impression that the test described in the manual (see my previous posting) tests the spring when it is partially compressed rather than at its free length. If that is true, I would expect the test length they specify to be roughly the length of the spring when the clutch is engaged and the specified spring tension at that length to be the tension needed to prevent the clutch from slipping under power. Ed

My 25 year old Barnett's were .040 thousands sagged and I could easily feel the difference by hand over them and the new ones........ can't help you on the testing of them (Barnett's are suppose to be 10% stronger than stock) ... and I'm gonna replace em a lot sooner from now on.

"Free length may not matter too much.
I may be wrong, but I'm under the impression that the test described in the manual (see my previous posting) tests the spring when it is partially compressed rather than at its free length."


Yes you are correct!! Take the springs to any engine shop that does valve work and ask them to test them for you just as the manual suggests... or buy five new ones. Probably cost about the same unless you know someone with a bench, valve spring tension tester.

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One of those spring testers would be great to have but they are very pricey. I have a box of springs that are either stock KZ, some H2 and an assortment of lock-up and slider springs. Knowing what each spring tension is would help in setting up clutch and knowing what a stock spring should be would be a good way to keep tabs on any clutch if ever an issue arises. Have a proform spring tester that is used in a vise but I think the guage would be to stiff for a clutch spring considering it was meant for valve springs. I'll have to see if I can find another guage that goes to 100# or so.....

I cut a pipe, with larger diameter than the spring, at the exact length the spring spec calls for. Then put the spring into the pipe, then put that onto a board, then put the board onto a bathroom scale, and push down on the spring with a flat block of wood. When the block of wood just come into contact with the edge of the pipe, look at the scale. If the weight is higher than the spec, the spring is good.

You will want to secure the pipe to the base board so it doesn't fall over.

Most springs, after a decade or two, will be right near their limit.

Good thread, keep it rolling.

i've got some what i was told are race and drag valve springs, but I was looking for a test like this to confirm it.

Anyone know what sort of percentage tension increase on R&D springs for a 550 ? I'm thinking check manual specs and add a certain percntage,