Conrod bearing play - How much is too much? 1979 AMF Harley-Davidson XLH1000 Ironhead Sportster

Here you can clearly see the difference between a healthy rear bearing and a dying front one. It was OK back in April (I have audio recordings and no knock was evident then) so my guess is some oilway or other became blocked during a period of inactivity. It's last MOT test was 2010, so it could have lain dormant for a decade. Symptoms were an audible knock of metal on metal like a rhythmic hammer blow, both on tickover and under load. This was accompanied by harsh vibration, particularly under load. I compensated by fitting a 45 tooth rear sprocket and treating fourth as an overdrive, but this work had to be done sooner or later.

[@mfsperring]

I have always interpreted " some movement is acceptable " to mean don't make it too tight. Lol Great video by the way. I'm about to tear down my 75 and even if I don't get that far down this time it will be useful when I do in the future. Cheers!

[@ImminghamIronhead]

Mine were pretty bad, but the main vibration was down to one of the flywheels being loose. The keyway was buggered so someone had cut a new one and sold it on (it has a 1980 crank now); the whole bike was a litany of bodged repairs and I've just discovered the gearbox has an extra spacer it doesn't need. God knows why it seemed to fit the last three times I had it out, but it wouldn't sit right this time and that turned out to be the reason.

[@cobrasneverdie1]

i think its also worth noting the fsm also gives different values for different runs of the manual, the 70-76 manual reads 11/64's and 3/64's while the 70-78 reads 3/64's and 1/64 respectively. its anyones guess as to why this is, and i havent found a strong consensus other than up and down is what really matters. its also worth mentioning for your year that side to side is no longer recommended and up and down is whats important. spraying some wd40 or parts cleaner into the races will remove the oil and allow you to feel for the play if there is any, just make sure to oil it back up when your done with your test. hope this helps anyone also wondering the same thing,

[@donaldalbershardt6854]

If there is no Up and Down with Dry Bearings it's GOOD..PERIOD 👍

[@dougankrum3328]

Even when new, the front rod will 'move' more from side to side........I've owned 3 1972 sporty....after a just a few thousand miles...the front rod will be sloppy loose sideways. I would probably not hesitate to use this crank assembly. the rear looks pretty good....My 1946 Knuckle is like this also.

[@ImminghamIronhead]

The front one felt really wobbly compared to the rear, but the source of the noise and vibration turned out to be one of the flywheels had sheared something and come loose. It has a late 1980 crank in it now.

[@cobrasneverdie1]

i was just doing the same thing today, mine is right on the boarder of tolerance and i should probably measure again before reassembly. fsm states 3/64 for the front and 1/64 for the rear. yours does seem a bit excessive though.

[@ImminghamIronhead]

Mine was beyond doubt, and when the crank came out one of the flywheels was loose and a keyway had been gouged so it's got a 1980 crank in it now.

[@VeritasEtAequitas]

Depends which manual. Different years spec different measurements even for the same parts, 57-up.

[@ImminghamIronhead]

@@VeritasEtAequitas Yup, everything from the spark plug gaps onwards is different for every year. Harley-Davidson may not change models often, but they don't leave them alone from one minute to the next.

[@acurarl9929]

Do you have a measurement on that ??? Like 60 tho 150 tho ???

[@ImminghamIronhead]

Unfortunately not. Mine was so evidently bad I didn't need to check it that closely. The hammer sound was something different though; it turned out one of the flywheels was loose on the crank pin. It has a 1980 crank now.