Hello,

I need advice on what fluid to use to quite/smooth my shifts. I believe its running on SYN3 in primary/transmission box, based on what previous owner stated. Bike has only 7k miles on it and its loud on shifts all the way through and finding N sometimes is tricky.

I was pretty much set on getting M1 75w90, but then read that even Mobil does not officially recommend to use it. I run Castrol synthetic 20w50 in the engine, and still have 3 bottles left, on label says its good for primary use, but many say that gear oil will yield better results?

My bike model is 08 nightster, live in AZ.

1) Castrol power RS V-Twin 20w-50 oil
2) Mobil 1 75w90
3) Valvoline synthetic 75w90
4) Valvoline high performance 75w90
5) Formula+
6) Redline 80W with shockproof
7) Red Line (50304) MT-90 75W-90
8) Red Line 57904 (75W90) Synthetic Gear Oil
9) Lucas Oil 10047 SAE 75W-90
10) Other

 

I actually use Mobil 1 racing 4T. It feels very smooth to me, and when I contacted Mobil they said this was there best clutch oil.

 

In my sporty trans/primary I would not run any synthetic. Have been running Formula + for years, but I've used Castrol 20-50 also with no issues.

I don't think I get an abnormal clunk when shifting, never have a problem finding neutral.

Make sure clutch is adjusted properly, both behind the derby cover and at the cable.

Also, probably the number 1 reason for trouble finding neutral is that the fluid level is too high, causing the clutch plates to drag.

 

Ditto here. My bike has Formula+ and I don't have trouble finding N.

And for me, the first gear clunk is a reassuring sign that all is well.

 

I use RevTech tranny lube and unless I'm bonkers the clutch engages more positively and the it shifts smoother and quieter. But that stuff is pretty subjective.

 

I run the syn3. Never had any trouble finding N.

 

Formula + is a GL1 gear lube but tests out to GL3 specs. 100C viscosity is just over 20. So any motor oil that is 20 or above at 100C will work well. Problem is most motor oils in 20w50 are more like 18cSt. Amsoil, M1, and Power RS are above the formula+ cSt viscosity at 100C so they will work well when it warms up.

You could use any GL1-GL3 lube in a sportster primary but good luck finding any. My local TSC has them lubes, in 5 gallon buckets. Easier to go get the HD F+ every 10K so thats what I do.

Edit

Just noticed you got the Power RS. Use it in the Primary. It is a strong oil. I use it in my motor and 3,000 miles on anyother oil I used and the top end got noisy and the oil was obviously burnt out of life. I have just over 3K on my latest Power RS change and it is still quiet up top and running stong. It easily goes to 5,000 miles. It also has the highest cSt viscosity of any 20w50 synthetic on the market at 21.2cSt. Almost a 60w. Also has the highest viscosity index of the top syn 20w50 oils at 157. Topping out amsoil MCV, M1, and syn3. It is the best motor oil I have ever filled a MC engine with hands down.

 

I use formula+ Always insure your adjustments are according to HD specs.

Having said that, go ahead and try different lubricants if you want, maybe you can tell a difference. I doubt its worth the effort though.

 

I got a welcome surprise

Drag Specialties Primary Fluid is what I am running now and it works surprisingly well
or 6.50 a bottle

 

I changed last week to trick shift trans fluid. Its a type f equivalent. Started to get a little slippage and trick shift took care of it. I am using the energy 1 extra plate clutch kit and the fluid was advised by Ken at energy 1 as an alternative to me running formula+