When is a crank not usable anymore?

Joined
Jul 31, 2014
Likes
47
Location
Canada
#1
I mic’d the rotation of my crank on my 61x and it’s 4 thousands of an inch off of true. Is this still ok? Will it grenade the first time I run it? Will it be fine to run? Has anyone run into this before and what did you end up doing? All help is appreciated. Thanks
 
Joined
Nov 13, 2006
Likes
314
#2
assuming you measured it at the flywheel snout?
it won't grenade on you but 4 thou is a fair bit of runout and will only get worse over time.0 to1 thou is acceptable,3 to 4 is pushing it.
either get it rebuilt or put new one in.
 

Tyler Zane

Open Your Eyes
Site Supporter
Joined
Jun 2, 2010
Likes
490
Location
Panama City Beach, FL
#3
Bearings should be smooth and quiet. It should be free of cosmetic damage and rust. Rod end play should definitely be in spec for me to run.
 
Last edited:

DAG

No Risk It, No Bisquick
Joined
Apr 19, 2006
Likes
3,335
Location
Charlotte, NC
#14
.004 is 3 times over spec.

The question isn't will it run, the question is for how long. As long as you are prepared for the worse case scenario (blows up on you while you're riding and leaves you stranded). Hopefully you don't take that into the surf
 

Blue

Port for the Sport
Joined
Oct 2, 2008
Likes
445
Location
St Cloud Florida
#15
Probably great for a 61x beater ski for the kids where cases are cheap but may be not so good in a ported set of cases where you have more money at stake.

Sent from my SM-N950U using Tapatalk
 

Christian_83

Xscream
Site Supporter
Joined
Feb 4, 2006
Likes
1,080
Location
Denmark
#16
This is "out of the box" (or 5 hours from brand new) PHP light weight pork chop crank. In a high spec engine.
so thats 4 times OEM max limit (i have 0.05mm in my manual).
So i think you will be ok with your crank.
 
Joined
Nov 13, 2006
Likes
314
#17
@christian_83,Your way of checking runout on this light crank is wrong.support the end bearings or better yet support the crank tail and snout directly on v blocks
 

Christian_83

Xscream
Site Supporter
Joined
Feb 4, 2006
Likes
1,080
Location
Denmark
#18
@christian_83,Your way of checking runout on this light crank is wrong.support the end bearings or better yet support the crank tail and snout directly on v blocks
Well they guy who helped me check the runout, and later trued the crank, has 15 years+ building jetski engines (not just bolting parts together) But rebuilding cranks, porting engines, custom machining ect.
So not to sound ignorant, but im confident Bo has his stuff together :)
 
Top Bottom