# How to calculate Mid Valve Float?

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I have been reading a lot of posts about MV float and I must be missing something when it comes to calculating the float of the MV. Below is thye stack I have in 2010 crf 250 and I cant calculate the 0.3mm float which I have been told it sould be.

20x0.1

20x0.1

20x0.1

18x0.1

16x0.1

14x0.1

12x0.1

11x0.1

11x0.1

17x0.3

17x0.3

spring

spacer 7.92x5.44

cup

Can somebody point mw in the right direction??

Thanks

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For the earlier model CRF's, it was generally as follows:

sum up the shim thickness:

6-20x.10x8mm .inn dia.

4-17x.10x8mm .inn dia.

Total = 1.0 mm

piston recess=1.0 mm

Collar/spacer: 2.20mm

So, MV Float = (OEM Spacer Length) -(Shim total thickness) - (Recess in piston) = 0.20 mm float.

So I am not sure how the float is calculated on the newer CRF forks.

• 1

just measure it

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10 CRF250 mid has kybish base plate with recess.

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theres a few ways,

easiest is get some feeler gauges and measure what you have.

2nd, take off the piston, mid stack and remove everything except the collar and 1 of the 17X0.30 base shims, but the piston on, find a spacer and bolt it doen onto the top of the spacer - with the 17X0.30 sitting on top of the cup, measure the distance between piston face and the top of the 17X0.30.

say this is 2mm for example.

now put the mid shims and other 17X0.30 together and measure those.

say these total 1.7mm

2.0 - 1.7 gives you 0.3mm float.

mark.

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theres a few ways,

easiest is get some feeler gauges and measure what you have.

2nd, take off the piston, mid stack and remove everything except the collar and 1 of the 17X0.30 base shims, but the piston on, find a spacer and bolt it doen onto the top of the spacer - with the 17X0.30 sitting on top of the cup, measure the distance between piston face and the top of the 17X0.30.

say this is 2mm for example.

now put the mid shims and other 17X0.30 together and measure those.

say these total 1.7mm

2.0 - 1.7 gives you 0.3mm float.

mark.

Ok thanks for this but i must still be missing something, if i run throu your calc above it still doesn't work out.

first I have the spacer which is 5.44mm,

The cup has a 2mm recess

the piston has a 1mm recess

So if i bolt it together as discribed it would be as follows:

5.44-2-1=2.44mm

plus one of the 17x 0.3mm shims should give me a distance to the piston of 2.41mm

now i double checked the shim stack and i missed one shim out above so the total thickness of all the stack including the the first 17mm is 2mm.

Therefore 2.41-2 = 0.41mm of calculated float??

Is this correct or am i still missing something???

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Just measure between the bottom 17.3 and the cup.

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Mistake is a cup recess.

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the 17X0.30 sits on thop of the cup, so forget the recess

just build the mid without the shims and the spring - leave one 17X0.30 sat on the cup, then do the measurements.

or like russ says with it built up measure between the bottom of the 17X0.30 and the top of the cup with a feeler blade to find your float, this is the easiest way!

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I agree.

Personally I do measuremets with feeler gauges between piston and face shim.

It allow to compare both mid stacks correctly. I feel how feeler pass easy or tightly. Sometimes i built same stacks, but float was slightly different.

I cant even guess how to measure between piston and 17.3 shim accurately.

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I will measure it, but there must be an easy mathmatical way of calculating it if we have all the measurements? Does anybody know what it should be as std?

Mid com.

20.1 (3)

18.1

16.1

14.1

12.1

11.1

11.3 (2)

17.3 (2)

5.44

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I agree.

.

I cant even guess how to measure between piston and 17.3 shim accurately.

Its between the last 17.3 and the OD edge cup. Just easier IMO