Originally Posted by DK Custom

I don't know what the numbers are.

I do know we get at least one call a week from someone with a Twin Cam that has run their engine at "normal" operating temps of 300-320*, that has less than 50K miles (many times less than 20K miles) that is having their engine rebuilt because it has failed a leak down test due to cylinder and/or valve problems from heat.

I do know that every one of these bikes was still running. HD has done an amazing job at designing them to keep running, even after suffering heat damage.

Just because it is running, and just because the owner does not notice the loss of power, because it occurred over a period of time, does not mean it did not suffer damage due to running at the "normal" 300-320*.

Perhaps it would be better to describe it by saying that when the temps cross the 270* mark there is above normal wear occurring. Maybe that is more easily accepted/understood than saying longevity is being reduced.

I am coming to the realization that many interpret reduced longevity to mean that the engine is going to blow up sooner than it would normally.

This is not what I mean. All parts wear out, and as they wear out tolerances get looser and there is a corresponding reduction in power and efficiency.

When an engine is subjected to high heat, those parts wear out more quickly, resulting in a reduction in longevity of useful (within tolerance) life, and there is a significant drop in performance.

It is really easy for most anyone to see how heat affects a Twin Cam. Ride a known route, somewhat aggressively, while the temperature, as displayed on the PV by ET, is between 180* and 240*.

Ride the same route, the same way, while the temperature, as displayed on the PV by ET, is above 270*.

The bike will be markedly more sluggish when above 270*. This is because of two main reasons:

1. HD has the bike set to retard the timing when it gets that hot, to try and cool it down to protect it from damage.

2. The metal in the engine is expanding at different rates (and too much) loosening up tolerances resulting in lower performance.

Instead of riding, this same thing can be seen by putting the bike on the dyno. Do some pulls with the ET at 220*-240*, then let the temp go up to 270* or higher, and do the same pulls. You will see a significant drop in horsepower and torque.


Thank you for the DA post. It has helped me to realize that many have not understood the term "reduced longevity" as I have meant it, and I will be more clear in the future.

Originally Posted by mjwebb

Being in a HOG Chapter and going on so many rides and putting on many many miles with lots of people on long and short trips you get to see and hear their stories, the topic just doesn't come up often

Originally Posted by mjwebb

good stuff and does help clarify your professional experiences....my point was mainly that the folks that would have the most statistical analysis, research, trends, etc are the ones in the business of producing the engines and obviously wasn't enough concern to change them or stop shipping them with conventional oil for nearly 2 decades and the non Touring TC's don't even get oil coolers...and you are 100% correct about heat vs performance as well..It's always been painfully obvious how much better my Harleys run in cooler ambient temps than when it's hot out. Being in a HOG Chapter and going on so many rides and putting on many many miles with lots of people on long and short trips you get to see and hear their stories, the topic just doesn't come up often..one gal we ride with has a Stage 2 2006 SG she bought new and will hit 100,000 miles this year...never any engine damage and it's seen tons of hot Summer rides for over a decade..it'll also be interesting to see what we learn by the end of this Summer about the oil cooled M8's.. thanks

P.S. re: "Thank you for the DA post." had to go back and reread my post, thought DA meant Dumb *** at first...which wouldn't have been the first for me! LOL

Originally Posted by mjwebb

ok, just playing Devils Advocate...regarding not good for longevity perception..17 years of TC's...what, maybe 100,000 sold per year as a SWAG? X 17....now in reality what % of the ~1.7 million sold have experienced shortened engine lifespans due to excessivley hot engine temps? I don't have a clue, but I don't believe it's as bad as it's being made to sound...and what % of those that did have issues could be attributed to poor maintenance and fluid changes, hopped up, ridden abusively, etc. I mean, Harley has been building these a looooong time and must be doing something right over gazillions of real World miles..just my perspective..not saying heat ain't the enemy because we all know it is, which is the reason the fan assist oil cooler was the first thing I bought and agree with doing things to help manage oil temps..but ain't throwing the kitchen sink of mucho dinero at my bike because I'm afraid of it being a ticking time bomb

Originally Posted by SWThomas

A company recommending their own product? Amazing!

Seriously, mine hasn't gotten hot enough to make me uncomfortable yet. And I've ridden it in some slow/stop/go traffic in 90 degree heat.

Originally Posted by psyshack

One thing that came to my attention early on as my M8 King was dying because of low oil pressure was heat,,, tons of heat. It was shutting the rear cylinder off in 60f traffic after a hwy run. As the engine got ever so slightly louder the running temps kept creeping up. Thus the oil cooling loop became a insulator not a dissipater.

While many will opt for Harleys upgraded rad and integrated fan controller. Which I think the Milwaukee retards should have made standard on all the M8's. I'm going to mount a Noctua PWN Ind. Fan on the backside of the oem oil rad. Mount a thermistor up under the headlight and one between the cylinders and put a Arduino under the seat to control the fan. I will set it up like a outdoor reset used in the boiler and chiller world to control oil temps.

Originally Posted by artsbest

To make such posts totally unnecessary (heat issues posts that is) why doesn't HD get with it and incorporate incognito-like radiators on ALL of their engines? I mean this is 2017.

Just look at what Nikola is attempting to implement into the trucking world.... a one hydrogen-electric semi-truck.

Originally Posted by texaswiz

I wonder if you have your Emergency Heat Mode enabled on your bike?

If so, does it kick in like mine does when the ambient temp gets to 81 degrees outside? I can pull off the highway after riding 70 mph and into a fuel stop and the rear cylinder drops out before I can shut the engine down. Don't have to be in stop and go traffic before it gets hot enough to kick in. This seems to be too soon for me, especially if there is no stop & go or city riding taking place. The dealer says they don't know if that is right or not because they have little experience yet.

Originally Posted by Max Headflow

I wouldn't worry about when the motor starts to drop the rear cylinder.. The sooner the better.. Why wait until it heats up? ECM don't know how long you are gonna be stuck in traffic.. The only issue I can think off is you got a 1 in 4 chance the throttle response is delayed by 70 milliseconds. Heck there is already some delay based on the fly by wire.