Bridge mute question, Epi EA-260

Well... first of all, that's not an EA-260. That's an earlier model; the 5120e, which (except for the color and the headstock decal) is identical to the Aria 5120 of the same vintage. This one here is an EA-260. But, other than the cheaper bridge (mute was not available) and tailpiece, they are virtually the same bass; and it's an easy mistake. Anyway...
Yeah, unfortunately bridge mutes tend to do that; especially if they're the all or nothing kind. Mutes like the ones on my 4001/4003 Rick can be fine tuned a bit (and yes, I do use them), but even with those, a lot of mute equals screwed up intonation. Replacing the foam certainly won't hurt; neither will experimenting with different materials and thicknesses. It might be possible to find something the right thickness that will work for you with that mute, but you'll have to experiment a bit... Personally, I like the stuff Rick sells for their mutes. It's just scraps from the foam pieces under their pick ups (waste not, want not, I guess), but it's really squishy, and I think it works well. In any case; good luck with it (and it's a nice looking bass, by the way...)

 

I have essentially the same bass, a Univox, with the same mute. I've never noticed the strings going sharp when the mute is engaged, which makes me wonder how strong the spring on yours is! I also wonder if you're not being more critical than the audience would - is is really audible that it's sharp?? I rather doubt it.

You might try replacing the rubber strip with something softer, or perhaps swapping springs to one that isn't as strong.

 

I have a bass that looks identical to the one pictured by unbrokenchain and have had it for more than 30 years. The sticker inside the body says that the model # is EA-260. So now I have to question, does the 5120e still use the same (EA-260) model number?

BTW unbrokenchain, I have the same bridge as your instrument has. I have no problem with the bridge mute causing the instrument to go sharp, and it still has the original rubber pad on it. The spring is worn out and the device has to be moved both ways by the player. I wouldn’t think spring tension would make that much difference. I would definitely lean more towards the rubber pad. It may be worn, dried out or something like that. I’d be looking for that if I were you. Also, mine finally got a shim under the neck about 10 years ago and it made a tremendous difference in the playability of the guitar.