When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
I have a twin cam from a 02 nigh train, and I need to replace the front piston. My question is about the connecting rods. Should there be play/movement in the rods at the crankshaft? Its hard to explain.
I have a twin cam from a 02 nigh train, and I need to replace the front piston. My question is about the connecting rods. Should there be play/movement in the rods at the crankshaft? Its hard to explain.
The rod to crank pin is 0.0004-0.0017. You not going to be able to fill that. One may be able to see it with a dial indicator but just a small amount not coming straight at the indicator reading off the end is going to move the needle.
Check it for smoothness by pulling up and moving rod fwd and back thru the cylinder opening.
Be sure to inspect the cylinder and make sure it's OK , remove the ridge ring and check it for taper and has enough to break the glaze for the new rings to seat.
PS.. stick around and let us know how it goes.
And for sure, welcome to the HDFORUM.
Last edited by Jackie Paper; Aug 17, 2025 at 07:52 PM.
The rod to crank pin is 0.0004-0.0017. You not going to be able to fill that. One may be able to see it with a dial indicator but just a small amount not coming straight at the indicator reading off the end is going to move the needle.
Check it for smoothness by pulling up and moving rod fwd and back thru the cylinder opening.
Be sure to inspect the cylinder and make sure it's OK , remove the ridge ring and check it for taper and has enough to break the glaze for the new rings to seat.
PS.. stick around and let us know how it goes.
And for sure, welcome to the HDFORUM.
While the rod side play at the bearing could be 0.005 to 0.015, the shake at the small end typically be as high as 3/32" on the front rod.. Rear will be considerably less. You need to stop using AI and add in a little experience.
BTW 0 at the front small end is another thing to be concerned about..
at one time hd used to have a side shake procedure in the FSM. that is gone so the only measurement is the big end clearance between rod and flywheel. the FSM says no up/down movement that is detectable unless of course you have instruments capable of the ten thousandths range.
oops!!
not ten thousandths but 10 one hundred thousandths.
i used to have a digital unit but it took a dump. mechanical units are a bit tricky, i have one that i use to zero my vise on the mill table that can read below .001 but you really need a smooth and did i say smooth surface.
hd really tighten up things when the evo can out. the only thing hd has not done is precision cast, but then again, sand cast is cheaper and recyclable.
really not that much hand fit anymore as with the bolted taper crank pins, that improvement probably saved a bunch of flywheels since they were like glass and cracked easily.
Harley-Davidson Fat Boy Becomes a Dark, Decepticon-Inspired Custom
Slideshow: Killer Custom's latest build relies on styling changes rather than performance upgrades, giving the cruiser an entirely different personality.
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Slideshow: The bar-and-shield logo shows up on far more than motorcycles, some of the company's most unexpected products have nothing to do with riding.
Slideshow: From the troubled AMF years to modern misfires, these bikes earned reputations for reliability issues, questionable engineering, or disappointing performance.
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Slideshow: The Swiss custom shop has taken a Harley Softail and stretched it into something so long and low that it looks closer to a rolling sculpture than a conventional motorcycle.
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Slideshow: A standard cruiser becomes an intricate metal canvas in the hands of a Swiss custom house known for pushing Harley-Davidson platforms far beyond their factory brief.
Connecting rod movement
