I have a 98 Fat Boy. 80 Cu. In. evolution engine. Oil pressure is great cold. If I get in town and have to stop at lights on hot days, the oil pressure really starts to drop at idle. Sometimes as low as 3 to 4 psi. I can just touch throttle slightly and it will raise. Oil level in tank is correct. I use Castrol 20-50 full synthetic oil and the idle speed is correct. Any ideas on this would be helpful. Thought about going to a different pump but not sure. Thanks for you help.

yeh, I don't know
but someone here will be able to square you away.
Good luck!

How many miles on the engine? Did you recently do a oil change? When did it start to act like this? Do you have an oil pressure gauge?

1. The oil pump could be worn out and needs to be replaced.
2. It could be you have bad oil and a simple oil change could fix the problem.
3. Oil pressure gauge is faulty and you need to replace?

I would start with an oil change to see if that works you may have worn oil or got a bad batch. If you say that the pressure is good when cold this may not be a problem with the gauge.

If it comes down to needing a oil pump S&S is one of our sponsors here you should look into their pumps as they have very high quality parts. Whenever I need parts I always look to them first. I highly recommend them their tech support is the best too. There is a review here on it.

viewtopic.php?f=86&t=1612

What is the oil pressure supposed to be? How much is it off?

I did an oil pump on my bike. wasn't that hard, but it was part of a larger project.