Another Dyna vibration issue
Outstanding HDF Member
Joined: Aug 2012
Posts: 3,217
Likes: 90
From: Detroit
Sorry for going slightly off topic, but what are minimum RPMs safe for the engine (2014 TC 103)? My experience with cars and other bikes is - if it feels or sounds like it's struggling up the revs or change gear. What slightly different with my Dyna is that it sounds and feels fine around 1500-2100, then it's shaking and doesn't feel right and then t's smooth again above 2500. Is that 1500-2100 range safe for the engine e.g. for low speed city riding?
Minimum safe rpm is idle speed.
Contrary to old wives tales which get repeated over and over on the internet, low rpms don't place any extra stress on rods or bearings. Quite the opposite, stress on rods, rod bearings and pistons increases with the square of the rpm, so it's high rpms that put the most stress on these parts.
Another load factor, aside from rpm, is how hard the combustion in the cylinder is pushing on these parts. Combustion pressure is highest around the torque peak, not at ultra-low rpms, so that's another strike against those who claim that low rpm operation is hard on engine components.
I've oversimplified some of this a little bit, but that's the gist of what's going on.
Last edited by Warp Factor; Aug 13, 2014 at 04:06 PM.
Elite HDF Member
Joined: Apr 2008
Posts: 4,718
Likes: 11
From: Back in the Good Ole USA. South Carolina to be exact.
That's a fairly normal vibration pattern for all the rubbermounts. Shakes at idle, smooths out some by 1500, gets rough again, smooths out over 2500. Putting at 1500 should be fine.
Minimum safe rpm is idle speed.
Contrary to old wives tales which get repeated over and over on the internet, low rpms don't place any extra stress on rods or bearings. Quite the opposite, stress on rods, rod bearings and pistons increases with the square of the rpm, so it's high rpms that put the most stress on these parts.
Another load factor, aside from rpm, is how hard the combustion in the cylinder is pushing on these parts. Combustion pressure is highest around the torque peak, not at ultra-low rpms, so that's another strike against those who claim that low rpm operation is hard on engine components.
I've oversimplified some of this a little bit, but that's the gist of what's going on.
Minimum safe rpm is idle speed.
Contrary to old wives tales which get repeated over and over on the internet, low rpms don't place any extra stress on rods or bearings. Quite the opposite, stress on rods, rod bearings and pistons increases with the square of the rpm, so it's high rpms that put the most stress on these parts.
Another load factor, aside from rpm, is how hard the combustion in the cylinder is pushing on these parts. Combustion pressure is highest around the torque peak, not at ultra-low rpms, so that's another strike against those who claim that low rpm operation is hard on engine components.
I've oversimplified some of this a little bit, but that's the gist of what's going on.
Here is an article on Bearing failure and they specifically mention damage from lugging. http://www.knowyourparts.com/technic...earing-damage/
2nd the BS flag
low rpm's or "idle speed" at operating temp is a point at which the oil pressure is at it's lowest! metal to metal contact is at it's most likely window of opportunity. add the inherent "twin lope". "lugging" is absolutely the worst thing you can do to your motor, compensator, primary chain/tensioner, and absolutely rod bearings, piston pin, mains. don't lug for fun/show.
Outstanding HDF Member
Joined: Aug 2012
Posts: 3,217
Likes: 90
From: Detroit
I'm calling BS on this. If you are putting along at 1500 RPM you should expect excessive vibration because you are Lugging your engine and there is potential damage.
Here is an article on Bearing failure and they specifically mention damage from lugging. http://www.knowyourparts.com/technic...earing-damage/
Here is an article on Bearing failure and they specifically mention damage from lugging. http://www.knowyourparts.com/technic...earing-damage/
However, many cars with plain bearing bottom ends are going down the freeway now at about 1500 rpms, for emissions and fuel economy reasons, and these engines hold up much better than engines of the past which were spinning much faster.
Outstanding HDF Member
Joined: Aug 2012
Posts: 3,217
Likes: 90
From: Detroit
But Harleys are roller bearing bottom end engines, and roller bearings don't need pressure like a plain bearing, nor will they hold pressure like a plain bearing. What they need is adequate volume.
By the way, my supercharged Corvette is turning 1200 rpm when cruising down the freeway at 65 mph. That's with original factory gearing. Someone should have told the engineers at GM that "lugging" destroys engines.
A lot of this stuff about "lugging" comes from the old days, when a combination of low rpm and high throttle opening was likely to result in detonation. Detonation is an engine killer, for sure, but computer engine controls and detonation sensors (which Harleys have) have pretty much taken care of it.
Last edited by Warp Factor; Aug 14, 2014 at 05:29 PM.
Outstanding HDF Member
Joined: Nov 2013
Posts: 2,358
Likes: 34
Jc, your problems could describe mine perfectly. If you want to save yourself a lot of work go read my "evo shake" thread in the evo section. I have replaced or checked everything and some things triple and along the way I've found a lot of damaged parts that needed replacement but did not fix the 2000 rpm shudder shake or vibration and I've put a crazy amount of hours and effort into it. PM me or post here if you have specific questions as if you think of something I'll tell you if I've done it already and save you the time.
What I've learned is that I still find stuff wrong but what has made the bike rideable for me is the vibratechnics front mount made it more manageable. It was better than the stock mount by far and made it more stabile both straight and in corners. 12 " apes with 5" lead rolls in the ends absorb enough that I can hang on and ride it. With the stock short bars it's not rideable and will shake so hard you can't see straight. I didn't want apes but it is what it is for now. You still feel it in the seat and pegs but until I figure it out at least it's rideable.
Most recently, not in the thread, is a new ignition, jetting and plug wires. The wires and carb were faulty as well. Basically everything I check has an issue but isn't the one making the problem! I've been told it's the crank and it probably is. Mine smooths out up high as well and is like glass on the highway, I just don't ride the highways.
What I've learned is that I still find stuff wrong but what has made the bike rideable for me is the vibratechnics front mount made it more manageable. It was better than the stock mount by far and made it more stabile both straight and in corners. 12 " apes with 5" lead rolls in the ends absorb enough that I can hang on and ride it. With the stock short bars it's not rideable and will shake so hard you can't see straight. I didn't want apes but it is what it is for now. You still feel it in the seat and pegs but until I figure it out at least it's rideable.
Most recently, not in the thread, is a new ignition, jetting and plug wires. The wires and carb were faulty as well. Basically everything I check has an issue but isn't the one making the problem! I've been told it's the crank and it probably is. Mine smooths out up high as well and is like glass on the highway, I just don't ride the highways.
Elite HDF Member
Joined: Apr 2008
Posts: 4,718
Likes: 11
From: Back in the Good Ole USA. South Carolina to be exact.
Engine lugging can distort the crankcase and/or crankshaft, affecting the connecting rod and/or main bearings.
Outstanding HDF Member
Joined: Aug 2012
Posts: 3,217
Likes: 90
From: Detroit
As I explained before, combustion forces are highest around the torque peak (around 3-3500 on a stock Harley), and inertia forces are highest at the highest attainable rpm. What is the source of these forces which supposedly distort the crankcase and crankshaft at very low rpms?
Sure, we've distorted blocks and crankshafts pretty badly on things like blown alcohol automotive-style engines (and slightly crowned crankshaft journals or bearing inserts are sometimes use to deal with this distortion to keep from wiping out the edge of the bearing), but this has nothing to do with low rpm operation. It was because they were making about 1500 ft/lbs of torque, making around 4 horsepower per cubic inch, and turning mega rpms.
Last edited by Warp Factor; Aug 15, 2014 at 07:07 PM.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Stage II
Joined: Mar 2020
Posts: 2
Likes: 1
From: Florida
That's a fairly normal vibration pattern for all the rubbermounts. Shakes at idle, smooths out some by 1500, gets rough again, smooths out over 2500. Putting at 1500 should be fine.
Minimum safe rpm is idle speed.
Contrary to old wives tales which get repeated over and over on the internet, low rpms don't place any extra stress on rods or bearings. Quite the opposite, stress on rods, rod bearings and pistons increases with the square of the rpm, so it's high rpms that put the most stress on these parts.
Another load factor, aside from rpm, is how hard the combustion in the cylinder is pushing on these parts. Combustion pressure is highest around the torque peak, not at ultra-low rpms, so that's another strike against those who claim that low rpm operation is hard on engine components.
I've oversimplified some of this a little bit, but that's the gist of what's going on.
Minimum safe rpm is idle speed.
Contrary to old wives tales which get repeated over and over on the internet, low rpms don't place any extra stress on rods or bearings. Quite the opposite, stress on rods, rod bearings and pistons increases with the square of the rpm, so it's high rpms that put the most stress on these parts.
Another load factor, aside from rpm, is how hard the combustion in the cylinder is pushing on these parts. Combustion pressure is highest around the torque peak, not at ultra-low rpms, so that's another strike against those who claim that low rpm operation is hard on engine components.
I've oversimplified some of this a little bit, but that's the gist of what's going on.
I started off about 6hrs ago, searching for why my 98 wide glide, after a ruff road with a passenger, now feels like its gonna rattle apart at idle, and wants to pitch a little from side to side over the littlest bump or groove in the road. Pop lowered the rear a bit when he had it, but Its none of his mods, cuz it ran perfect until that raggedy cratered shortcut. Ill admit that im not the most gentle rider, but its a little scary to ride now, and Its gotta be something simple. I saw this, and had to respectfully object. Thank you tho, cuz it dawned on me, that being the hardcore old school biker that will always rides apes, jockey shift and suicide clutch, and wont have a starter on his bike but will always kickstart.. not to mention it was his bike first.. recollecting the whole LUG lesson, I know just where to take the ol glider. Thanks guys!
Road Warrior
Joined: Mar 2018
Posts: 1,949
Likes: 951
From: Redneck Riviera
I beg to differ sir, and must respectfully disagree. Ive heard my pop explain it a dozen times, but I didnt really understand until he tore his FLH apart, and explained it in great detail, as he cross referenced an article in sum HD mag that he had xeroxed. Ill be damned if I remember everything, but I saw and understood at that time, that basically when u "LUG" ur hog, the mixture in proportion to your speed/load is such that the explosion is eventually going to work its way thru the piston rings.
I started off about 6hrs ago, searching for why my 98 wide glide, after a ruff road with a passenger, now feels like its gonna rattle apart at idle, and wants to pitch a little from side to side over the littlest bump or groove in the road. Pop lowered the rear a bit when he had it, but Its none of his mods, cuz it ran perfect until that raggedy cratered shortcut. Ill admit that im not the most gentle rider, but its a little scary to ride now, and Its gotta be something simple. I saw this, and had to respectfully object. Thank you tho, cuz it dawned on me, that being the hardcore old school biker that will always rides apes, jockey shift and suicide clutch, and wont have a starter on his bike but will always kickstart.. not to mention it was his bike first.. recollecting the whole LUG lesson, I know just where to take the ol glider. Thanks guys!
I started off about 6hrs ago, searching for why my 98 wide glide, after a ruff road with a passenger, now feels like its gonna rattle apart at idle, and wants to pitch a little from side to side over the littlest bump or groove in the road. Pop lowered the rear a bit when he had it, but Its none of his mods, cuz it ran perfect until that raggedy cratered shortcut. Ill admit that im not the most gentle rider, but its a little scary to ride now, and Its gotta be something simple. I saw this, and had to respectfully object. Thank you tho, cuz it dawned on me, that being the hardcore old school biker that will always rides apes, jockey shift and suicide clutch, and wont have a starter on his bike but will always kickstart.. not to mention it was his bike first.. recollecting the whole LUG lesson, I know just where to take the ol glider. Thanks guys!
