I have seen several comments that the new Milwaukee 8 has much less heat than it's predecessor and I am really trying to understand how this is so. I used to have a water cooled 1800VTX that generated plenty of heat so I am not buying it.


They did move the catalytic convertor further back so it's not radiating heat right to the rider/passenger but that can be done by eliminating the cat all together on the Rushmore models. That isn't less heat, that is just putting it in a better place. Isn't that where most of the heat is coming from, the exhaust?


Changing the heads a little isn't going to make that much difference in my opinion. At least not in Texas when it's 100F outside.

 

Any internal combustion engine is going to generate copious amounts of heat. It doesn't matter how it is cooled, whether it is air, water, or oil cooled. It will generate large amounts of heat well beyond the comfort level of people. The only real issue is how much heat the rider or passenger feels and how well the manufacturer was able to divert the radiant heat and keep it away from the rider. There are water cooled engines that will scorch a rider worse than an air cooled design. Engine placement, airflow, etc et..all these parameters come into play. Just because an engine is water cooled doesn't mean you won't feel copius amounts of heat.

With regards to the new M8, all the comments from reviewers on youtube and in the press have indicated that there is a marked and noticeable difference in the perception of heat by the rider. Why this is so is probably irrelevant to most people as it is the perception that counts. Whatever they did appears to work, at least based on the first comments coming in.

 

The extra .5 quart of oil is also helping with the heat. I rode both a Street Glide and Road Glide Ultra this weekend. The Street Glide, without cooled heads, was just a comfortable as the RGU. There truly is a night and day difference with M8's.

 

They also tucked the exhaust header away from the leg.

 

Just removing the cat from my CVO made a huge difference. I would assume moving the cat away from the riders leg is the major reason heat on the rider is better on the new motor.

 

The design of the combustion chamber has reduced surface area which means less heat transfer to the heads.

 

It's most likely this.


The most heat I feel comes from the pipes, not the heads.

 

Spent all day on them on Saturday. They're still hot. I didn't have a temperature gauge but it's all relative.

 

The Milwaukee 8's are either coolant cooled or oil cooled heads. That would certainly lower engine/oil temps.

My preference would be the Road King, Road Glide and Street Glide oil cooled heads. Less complicated and maintenance. Worked well in the XR1200's and Buell XB engines for over a decade.

 

On my 17 Limited the heat is definitely less but other was an11 Limited,so not a Rushmore, with a cam,exhaust etc...hotter than hell...but a blast to ride as long as you were moving