Hot Primary Harley Twin Cam Discuss Hot Primary in the Motorcycles forums; I have a 09 FLHX and after a ride the primary cover is as hot as the pipes. Even after letting the bike sit for an hour or so the ...

[cdnmike28]

I have a 09 FLHX and after a ride the primary cover is as hot as the pipes. Even after letting the bike sit for an hour or so the primary cover is still too hot to touch (even when the pipes have cooled). I recently changed my primary oil (using synthetic amsoil 20w50) but it did not make a difference. I spoke to an independent mechanic and he said he had never experienced it, but he could only assume the primary was taking on, and retaining the heat from the engine. He suggested trying an oil cooler. I also spoke with the mechanic at my local HD dealership and he said he has heard a few people with this complaint, and suspects its just the way the 96" engine runs. He said nobody that he has talked to has experienced any mechanical problems from this excess heat-yet. I'm just wondering if anyone else has had a similar experience, or if they have any thoughts on why it may be getting so hot. I'm not sure if it makes any difference but I have a stage 1 air cleaner, slip on's, and I'm running a power commander V. I also checked my plugs and they look pretty good, the bike may be running a bit hot but nothing extreme.

[frisco-rigid]

Hey cdn

If there are no other probs and Nothing else wrong in the Primary (which you would prob hear great evidence of) creating lotsa excess heat, then it is simply the heat of the motor (lots) and tranny (some) conducting to the primary covers..
There's much more mass there to retain the heat than in the thin-walled pipes which will dissipate the heat from the exhaust gasses quickly..

My Belt drives are totally open and ventilated and still get Very hot with conducted heat,,,,,, you outa feel them after a day in this Phoenix Valley summer heat..

An oil cooler will help to keep the motor oil cooler (I use them) but will do little to nothing for that conducted heat from the motor..

All the newer HD's run pretty lean which contributes to a much hotter motor Inside & Out..

A re-mapping/adjusting of the A/F will prob do Much more to lower motor-heat than an oil cooler,, but I do still highly recommend an oil cooler too for oil longevity and efficiency, i.e. if you run in High summer heat too..

Have a ball

[cdnmike28]

Thanks, Frisco

[diesel2]

My 2007 FXDL primary gets very hot on the warmer days up here in Toronto and real hot on the 80 plus degree days up here. Can not touch or keep your hand on to long even when moving as I test it with my hand. On cooler days it does not get so hot. Some of the heat I am sure comes from the engine. There is a lot of moving parts in side the primary that will create the heat for sure.The primary surface is great, but not finned which would help to cool the primary. I also run the Amsoil 20W50 in the primary, trans and the engine.

[cdnmike28]

Thanks Diesel, glad to know I am not the only one

[Rocky]

My 07 Electra Glide Classic gets hot and I use AMSOIL 20-50. I change it every 5,000 just like the engine and tranny with no adverse effect. No big chunks in the oil or on the plug. I have over 25K on it.

[cdnmike28]

Hi Rocky, I use the Amsoil in all 3 holes, and I change about every 3000 miles as I'm a little cautious. I just can't believe the heat the 96"'s throw off compared to the 88's. If the 96" throws off this much heat how are the 103's and 110's?

[aceharleywrench]

Try using Primary chaincase lube instead of the Amsoil & see if the temp drops.I know people swear by it,but no way in hell am I running 20w50 in my primary or trans.

[Spade5]

I have noticed the same thing and with the transmission as well. I don't think they get as hot as the exhaust but they stay hot longer most likely due to the oil whereas there is nothing in the exhaust but air which is a poor heat retainer.

I think we worry too much about the heat issue but if you get in a situation where you think your engine gets too hot, change the oil. Cheap insurance and it can only help. Anything bolted to the engine is going to draw heat as heat tries to go to less heat and achieve a balance. Add some internal friction and it is going to get hot.

I also think that the 96 inchers have slightly better cooling fins than the 88 to help compensate for the leaner running condition. I think you will feel more heat simply because the fins are doing their job.

Although some lubricants are "better" than others, I don't think there is a magic pill.

No expertise here, just my opinion.

That's just what happens when you have all those cubic inches of mad power being made just inches away.