Changing primary case oil
Harley Oil & LubricationDiscuss Changing primary case oil in the Harley Tech & Harley How-to forums; I'm fairly new to the biking sport, but I like to do some of the routine maintenance myself, like changing the motor oil and other fluids. I follow Harley's instructions ...
I'm fairly new to the biking sport, but I like to do some of the routine maintenance myself, like changing the motor oil and other fluids. I follow Harley's instructions to the T, but I'm unclear on why they tell you to remove the primary case cover to change the primary case oil. The Aug. issue of AIM shows the tech pouring the fluid through the chain inspection cover that he has removed along with the derby cover. So, what's the purpose of removing the derby cover? ...so that you can see if the oil comes to the bottom of the clutch diagpragm spring? The service manual for my bike (an '05 Heritage Classic) says to add 26 ounces of fluid. If I do that shouldn't that guarantee me that I will have put in enough fluid? Obviously, if I don't have to remove the derby cover, I can save the cost of the gasket which is about 8 bucks.
I adjust my clutch at the same interval as the fluid, and you definately need the derby off to do it. The oring used on your bike is a "quad" ring- square, basically, and I've re-used the quad ring off the '03 heritage a couple times. It's a good time to check the primary chain for it's adjustment, too. In doing so, you have to find the most stretched part of the chain to adjust accurately. This is covered in the manual as well. Good luck- I'll check back to answer any questions I can. By the way, I'm a mechanic, but not on bikes. Just to let you know!
Thanks, I wasn't thinking about adjusting the clutch, but what you say makes sense. I'm not sure what you mean, however, about the o-ring. My bike has a gasket for the derby cover that I discard when I change the fluid. Are you saying that I can reuse it? Wouldn't it run the risk of leaking?
No, I didn't know they had changed to a gasket. A gasket will need to be replaced. O-rings should be replaced, but I've gotten away with re-using them a couple times. Anyway, I've learned something today! You're better off with the gasket for sure. The orings are sometimes difficult.
As for why they want the cover off, my guess is the clutch is being adjusted at the same time. This also allows you to get the fluid level exactly correct too, as you mentioned. The capacities given in the manual are close, but the level needs to be verified before running the bike. If not, an over filled primary will leak, and cause clutch issues as well.
On my 04 sporty I only pop the dirby cover if I need to adjust clutch. I have only needed to adjust it once in the last 20,000. I normaly just drain the primary when its hot. Take off the chain inspection cover. Use a funnel to pour in proper amount of fluid. I then give the chain a touch to see if needs to be adjusted and button it all back up.
I do an oil and primary change together. Only replaced gaskets once. I inspect the gasket. If it still looks good and soft. Not hard and cracked I reuse it. I do not believe in throwing money out the window. If by some chance they did leak I can change on the fly. No big Deal. I just have to get bike level so the new oil dont come out the derby cover.
I have not leaked yet. At least not in that area of the bike.
Harley stealer makes a lot of dough on bike maintenance and parts needed.
Sometimes its a little overkill to make a few more dollars.
Oldguy, I've got an '05 Heritage Classic as well. The O-ring is on the drain plug in the the primary case, underneath the clutch area. The O-ring is subject to damage and should be replace each time the plug is removed (I get mine for twenty five cents). It's cheap insurance against leaks, and your gonna' have the plug out to drain the oil anyway.
I forgot about that "O-ring". You cant change that on the fly without loosing lube. Yup its a cheap gasket to replace. So yeah it may be worth the 25 cents for a new one.
I agree with you. An overfilled primary results in hard shifting and clutch engagement. The capacity in the primary for my bike (in the manual) is 22 to 26 oz. But to the bottom of the diaphragm spring (the proper level) is 24 oz. Now I know that, and just add that amount now without removable of the derby cover. Remember to inspect and replace (if needed) the drain plug o-ring. The inspection gasket is less critical.
Changing primary case oil 
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