Very Basic Example
Ok, I am going to do this short and sweet because I am short on time.
I have wondered why so many people have called me lately and told me they checked their 900 crank run-out and its perfect......I said wait a minute...... what do you mean by perfect ?? they would say under a .001 I would follow up by saying WOW!!!! you are one of the lucky ones.
I would say how did you chk it they said like i saw on Snowest 900 Thread..... I said well ok then........ End of story, Well until I checked this thread this morning.
Lets get started -
First look at the 2 pictures I posted.
Second look at the pictures millwall posted ( Not picking on you Millwall ) Many crankshaft shops have made this mistake.
Third look at the pictues sloan188 posted ( VIA Polaris service manual )
To understand is to allow you to perform the task correctly.
Now keep in mind the photos you have seen. ( you might have to read this thread several times )
If you took this thread and the pictures you saw, and you believe what you saw you should have been completely confused. WHY ? you ask ?
Ok, The Polaris manual shows and old style crankshaft that is in fact sitting on a OEM Polaris issue crank stand.
Where as Millwall has an early release 900 crankshaft that is very rare because if you look close it does not show the common rubber center seals.........this one has sealed bearings like in the small block motors and you could actually sit this 900 crank on a center holder like the old Polaris stand but it would sit crooked because of the bearing lock ring which can be removed then it would sit square the the stand. ( if it sits crooked you can still accurately check it )
That being said notice the pictures I posted as the common 900 crank most people see it has 2 center rubber seals just inside the bearings.
Now notice where i have my V Blocks...........Hint - They are very narrow. ( Built them this way as to get them inbetween the wheel and the lock ring )
This post is all about V-Blocks......And the key here is V-Block location.
I took a picture of a 900 crankshaft that is in 5 pieces...........why you ask ??
Here's where you need to pay attention - If the crankshaft is 5 seperate pieces what good does it do to have the dial indicator on the crankshaft on the same piece that the V -Block is sitting on ???
For gods sake people !!! If the V-Block is under either the Mag Wheel or the PTO wheel and the indicator is also on that wheel every crankshaft is going to look almost perfect.
The center pin of the 900 crankshaft is the one place that is a constant.
The V-Blocks MUST be under the 2 center bearings....and then the indicator must be on the outside of either the MAG or PTO end.
There are ( 4 ) press points !!! Did you hear ME ??? I said ( 4 ) press points outside the center pin, the reason to check runout is to infact see if these ( 4 ) press points are infact tru in relation to the center pin.
sloan188 's picture is the only accurate thing in this thread and no one can even use it because the polaris stand does not work with center rubber seals because the crank will NOT sit down on the bearings it will sit on the seals and wobble all over the place.
There are a few VERY well knowen crankshaft builders in the USA that check crankshafts just as this thread shows to and when I get them in this shop brand new cranks will not even turn in a torqued crankcase.
I am sorry I don't have more time I hope you can understand what i saying here.
Dan
