Ex-racer can't get his right lead. :/

Maybe he was punished while racing for being on the right lead.  Do you ever see him get the right lead while playing or lunging?  Any injuries to his right leg/foot/shoulder?  If you see him get the lead when you aren't mounted, then it could be a saddle fitting or training issue.  If he never gets the lead, could be a soreness issue somewhere.

He will get his right lead every once in a while. After about 20 or so tries. And he'll keep it for as long as he can, but it seems like he struggles to keep it. I've had the farrier and the vet check him and they say he's perfectly healthy. I should try lunging him?

I'd be asking New Vocations this question.  They have a ton of resources and they've placed a ton of ex racers.  I just looked at their site and they have a facebook page.  Go there and ask and I bet you'll get some responses! 
http://www.facebook.com/people/New-Vocations/1592813533

Ok racing is all left lead. Unless they go the WRONG way around the track. So it is trained into his mind not to go right.
 
I would say if you can get him in the right lead even for a little time PRAISE him get him thinking it is a good thing. Make him think it is ok to be in the right lead. It may take a long time for him to think it is ok.
matt

How are you asking for the lead? I know if he's an ex-racer it's probably all he knows, but gently put pressure at the back of his left rib cage and see if he yields his hind quarters, if he does, you should be able to ask him to push over on to his right rear while tipping his nose to the right and kiss and get him into the lope while holding your position till he is loping, and then he should be on the right lead... but that's just how I have learned to ask for leads so it may not work. If he doesn't yield his hindquarters at all, that could be another reason, you should be able to get him to basically pivot on his front feet and spin his butt around them. Like opposite of a spin lol, if he doesn't know how to do this teach him on the ground first, and then under saddle. And then try working on leads. Also make sure your weight in the saddle is shifted on left side of the seat so that your out of his way, and over exaggerate it, and vise versa for the left lead, I hope this helps.

Thank you everyone for your suggestions and help. :]

I also have an ex-racer who about a year ago could not get his right lead. It seemed very hard for him. What i started doing was almost turning him the opposite way so he could not over bend and asking for it. I also found that he did lead changes when I turned him unexpectedly. If I take a jump to the right and he lands on the left lead, I will turn a bit early and he will swap to the right lead. I suggest working in corners and when he does get it, reward him. Ask for it in that corner each time and after repeating this a dozen or so times he will learn that he gets the right lead in that corner. As for being stiff and seems like it is hard for him to hold, that is very understandable. That still happens with my horse. He doesn't like going to the right. With practice he will gain more muscle in the right side of his body. I would also try lounging him to the right and see if you can't get him to pick the correct lead up both ways. Reward him by letting him go to the lead he likes. If he doesn't pick up the correct lead the first time, don't get frustrated with him, just stop him and retry. This all has to do with his racing days I suspect, because in recent posts you mentioned that the vet gave him a clean bill of health He will learn in time. Keep working on it! You two will do fine. If you want to see and example of what I do, here is a link to a video on youtube.
http://www.youtube.com/watch?v=_DTzCfg5OHU

Best of Luck!!
Erin