New Milwaukee 8 oil-cooled engine runs VERY hot
 

I bought a new 2107 HD Ultra in December 2016. It has the “precision oil cooled” engine, not the water cooled engine. I prefer to keep it simple and I figured that was one less system to cause problems or leaks.

Since I bought it in the winter, I rode it on reasonably nice days (temps in the 40’s) in January and February. I noticed that the Engine Idle Temp Management System (EITMS) would activate and go into one-cylinder operation at idle at stops. I thought that odd, but figured Harley set the trigger temperature fairly low to make sure the engine didn’t get too hot at stops.

As the weather warmed up, I noted that the EITMS would activate all the time at stops. I also noted that it seemed very hot right under the tank, with the “hot smell.” I figured it was because the bike was new and all the coatings hadn’t been baked yet.

I have a Dynojet PowerVision that I had on my previous bike, a 2008 Electraglide Classic (96” engine, 37,000 miles when I traded it in). I wanted to put it on the new bike to monitor temps and other data from the ECU. I liked being able to do that on my old bike. I had to order a new cable from Dynojet because the new bikes use a 6-pin data port, whereas my old bike used a 4-pin data port.

When I plugged it into the data port, and went for a ride, I saw the temps rapidly rise to and then well above 300 degrees during regular riding on cool to moderate days, not hot days in stop and go. The temp readout got up to the 350-360 range on 70-80 degree days in highway riding (again, not stop and go traffic). Now I was beginning to get concerned and wondering if the temperature sensor was faulty, so when I got home from one ride I got out my Milwaukee Tools infrared thermometer and aimed it at the rear cylinder head near the spark plug, and it read 357 degrees. That’s literally hot enough to cook on! In contrast, my 2008 EG would get to about 240-250 degrees in highway riding in similar conditions. That’s over a 100-degree difference! NOTE: I have NOT changed the tuning; I'm only using it to read data from the ECU.

I then took the bike back to the dealer in Fairfax Virginia to ask about the high temps. The service manager said that they couldn’t rely on an aftermarket temperature measurement, and asked if I had the Check Engine Light come on. No it hadn’t, so he said that if the engine was overheating, the CEL would come on so he didn’t think anything was wrong. He agreed to read the ECU codes and check for anything odd at my next service (5000 miles, probably in a month or two).

If there isn’t any CEL, I doubt they will see any stored codes indicating overheating. So, now I’m thinking about what else might be wrong, or whether the new M8 engine has some serious design flaws (wouldn’t be the first time for the MoCo). This kind of heat will eventually cause cracks in the head (most likely between the exhaust ports), prematurely worn valve guides, possible coking of oil, piston ring failure, and other possible problems.

Has anyone else measured the temps on the new M8 oil-cooled engine yet? Am I the first to find this out? Or maybe this is only a problem with my engine (oil jet or return line plugged or something like that).

Until this is resolved, I suggest that any of you considering buying a new M8 oil-cooled bike to either wait, or go with the water-cooled engine, and get a 4+ year extended warranty to go with it. Fortunately, I did.
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These engines do run hotter than previous...it's pretty well documented. You have an early bike so your EITMS was defaulted to "activated". HD issued a TSB to reprogram the ECUs to set the default to "deactivated". The system is operating normally; if it annoys you simply deactivate it or ask your dealer to perform the reflash.

Probably not gonna run hot enough to hurt it...designed for it. Ride the thang...

Before I ever left the dealership with my bike I had the EITMS turned off. Heat? Should have been on some of the 103's or 96's I have ridden. My Road King isn't even bad but I have a Captain Itch Crotch Cooler on that bike.

BTW, complaining about the M8 is usually the most popular dulled out thread in the M8 section.

Whats well documented is that you can not compare temps with your old twincam, the data points are different. These M8's have much less felt heat. I have had two of them, been in Death Valley, across the USA and back and stuck in gridlock. No comparison.

My last Twin Cam never ran hot until I put the PowerVision on it. Then it said it was hot.

It wasn’t really any hotter, but now I had a number to look at so I thought it was hotter. I don’t think I’m gonna mount it on my M8...

I haven't moved up to the M8's yet but I have a '13 CVO with the 110 Engine.

Getting rid of the catalytic converter, adding True Dual exhausts, a tuner (with a dyno tune) and a set of Wards Fans has kept my engine running cool for several years. Until my LED dipstick "gave up the ghost", I'd check my oil level and oil temp during a mid-day fuel stop when I was on a trip. I NEVER saw the oil temp above 241 degrees and that was with the auxiliary fans in use.

There is another reason. For environmental regulations all the new bikes run extremely lean. Therefor they develop more heat than 'normal'. My FLHTK 2015 was running on factory tuning software and was also according my oiltemp meter rather hot. After tuning at Stage 2 Screaming Eagle (after approval tests for a license plate) the temp became lower, the fuel consumption a little higher and my EITMS rarely activated where before it was reguraly. My oil temp lowered as well.

Yup, a richer air/fuel mixture will cool the engine. Exactly what a Stage 1 did to my 103. Sounds like the M8 runs hot because of EPA regulations.

Precisely that.

But, as far as air cooled motors go, a head temp of 350° is common. Once it gets above 450-475, the aluminum will begin to lose it's temper. (temper as in hardness from heat treating. Of course it will probably be mad too)

I rented a '17 Road King in Hawaii last May. One thing I noticed was that the idle was all over the place in Honolulu traffic. (Worse than LA). Probably due to that idle thing you guys were talking about.

Kinda wonder how hot the M8 would get in Texas, Arizona or Central California heat. In CenCal, I give out before the bike gets too hot. My older Deluxe sees head temps of 320 during the summer heat when it's over 100°.