CMB RS 91/101 engine balance

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dwilfong

dwilfong

Well-Known Member
Joined
Jul 1, 2008
Messages
5,968
DSCN4094.JPG DSCN4095.JPG DSCN4096.JPG DSCN4097.JPG DSCN4098.JPG DSCN4099.JPG DSCN4100.JPG DSCN4101.JPG OK I had a problem with the 91RS I am building it shook so hard I could not see the needle it was just a blurrrrrrrrr.
So made me a rig to press it apart and press it back together.
The tube is bored out so the crank half's fit like sex in there.
Did a test run and it came out less then .001 run out. Close enough for me.
So next will be the bob weight build and press back apart. then time to build the razor blade rig to balance it on. then press it back together.
 
Last edited:
hey Julian, i guess the fishing must have slowed down some?? :D Dave, as always,love the way your brain works,always looking for something better!! Mikie..
 
The sea trout and weak fish are like Parana in the lights at night on are dock.
 
OK got it on the blades with a Bob weight 52% of the total rotating mass.
I had to drill a hole in the counter weights to lighten up the crank at that end.
I can make adjustments to the % by adding Tungsten slugs in the holes if needed with out pressing the crank apart.
Will see how it spins up 52% first.DSCN4102.JPG DSCN4104.JPG DSCN4105.JPG DSCN4106.JPG
 
OK so here we go ........
Found out WHY this eng was shaking the boat apart.
Balance the crank and went to press it back together and some thing did not look right.
I made a spacer block to maintain the distance between the crank half's when pressing it together.
Well it did not let the crank pin go all the way threw the one end.
HMMMMMM WTF........
So I rechecked the stock cranks I had to see what was up. I have 4 cranks all together.
WELL WELL I see said the blind man.......This crank has way thicker counter weights than all the other 3 cranks.
SO WTF ...........
Some one have a answer to why this is????????????
It was so out of balance the eng was shaking the boat apart on the stand.
Will see how it is now with it balanced at 52% of the rotating mass.
 
dwilfong said:
OK so here we go ........
Found out WHY this eng was shaking the boat apart.
Balance the crank and went to press it back together and some thing did not look right.
I made a spacer block to maintain the distance between the crank half's when pressing it together.
Well it did not let the crank pin go all the way threw the one end.
HMMMMMM WTF........
So I rechecked the stock cranks I had to see what was up. I have 4 cranks all together.
WELL WELL I see said the blind man.......This crank has way thicker counter weights than all the other 3 cranks.
SO WTF ...........
Some one have a answer to why this is????????????
It was so out of balance the eng was shaking the boat apart on the stand.
Will see how it is now with it balanced at 52% of the rotating mass.
Click to expand...
Dave,is there a way to lighten the crack and then re-balance for more RPM'S or is it not worth it?
 
well it worked out just fine......no more vibration....smooth as butter now
Next to see how it revs.......
 

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