Would over-lubing decrease velocity?

Only use as much as necessary, over lubing is a bad thing, it does not take much....too much can cause damage. Spring in a springer? You use a bit of heavy tar, not lube....better off with too little than to much, also you use different lube for different parts....

You maybe better off to watch a U tube video on it ....or google it..
 
Yes - excess lube and/or tar will generally decrease velocity.

However, the biggest issue is if you put too much lube on your piston seal, it will generally ignite in your compression tube and cause damage to your gun. Usually not anything too serious, just a blown piston or breach seal you'll need to replace. But, not something I would want to do on the regular if you catch my drift. In regards to the guys on YouTube putting WD40 or some other oil in their compression tubes to make them diesel...I wouldn't do that. 

In regards to lubing the spring, too much tar and guides that are too tight will reduce your velocity. Guides that are looser will increase your velocity. The trade off is that with tighter, properly sized guides you will generally have a much nicer shot cycle.

I tuned my TX200 in the few months before going to EBR - however, I was unable to shoot it due to a cluster $#*@ of errors FedEx. In the process of tuning it, I started using GPL-206 and found it was very smooth, but for whatever reason it would work its way forward off of my piston seal not matter how much (or how little) I used and caused some consistency issues. I ended up using some Bum-Slide which as far as I can tell is Super Lube mixed with some Moly. There is GPL-206 on my piston and the piston rings. That stuff is slick.

That being said, a lot of springer FT shooters who are way, WAY better than me use GPL-205 or 206 religiously and swear by it.

But with that stuff, less is definitely more.

If you have tuned your gun already and are recording velocity that you think is too low, check your piston seal diameter. If it is oversized, you will have lower velocity. You may have to take some material off of the outer edge of your piston seal before you install a new one. After I had everything in my TX I was only getting 10.5 fpe and could not for the life of me figure it what it was. I tried everything, different guides, different lubes, different springs, but nothing would work - then I ripped the whole gun apart, measured the seal and found it was just slightly oversized. Sanded it down and the gun hopped right up to 11.3 (ish) FPE where it belonged.

That being said, with that stuff, less is definitely more.

Happy shooting! Enjoy the journey and embrace the frustration of a sproinger.

Best,

Nico