Can't canter under saddle

What if someone lunged him with you on him, cantering so he gets the idea?  Do you ride western or English.  Have you tried standing in your stirrups so you aren't bumping him on the back?
 
Goodluck

What kind of bit are you using?
Any chance is structural alignment is off?
 

OK, I haven't tried lunging with me on him.  Two worries for me with this.  Our round pen is a bit small and he tends to really stay on the fence.  I'm not really comfortable being on a horse with any speed in there.  I'm still working with him to lunge on a line in a larger area so so I won't worry about the fence so much.  The second issue is cantering in a circle like that, his canter is soooo fast he can actually loose his footing sometimes even without a rider.  He will extend a trot like a harness racer and really has to be moving before he wants to change gears to ludicrous speed.  

I'm riding English at the moment.

I've tried standing in the stirrups.  He's pretty tolerant of bumping at the trot.  His trot is not the most smooth and regular trot so sometimes posting doesn't quite line up.  Those 3-4 strides I get at a canter are very smooth.  Nice rocking motion so I doubt I'm bumping him in a way that bothers him.  I'm pretty sure I'm not bumping him with my hands either, I've been giving him a bunch or rein and don't even contant him until he drops his head all the way.  

I'm using a plain full cheek snaffle right now.  

Its possible there may be some alignment issues.  Any ideas on how to tell and get them sorted?  Honestly I don't exactly know what you mean by alignment, but he's a gangly awkward adolescent and sometimes moves like it. 

BTW, hunterseat  is your undisclosed location the one that kind of sticks out into the Persian Gulf like a thumb?  Been there done that.  How long are you stuck there?

Honestly I don't exactly know what you mean by alignment,

I have a therapist who works on my horses occasionally.  I only know a little bit from what she tells me.  But stuff like muscles on one side being more developed than on the other side, pulling the skeletal structure out of alignment.  Equine chiropracters can sometimes work wonders.  I've recently learned how the teeth can affect everything down to the shape of their back hooves. THAT's cool.  The place where my horses are boarded during this deployment belongs to a natural equine dentist and is:
www.balancedhorsedentistry.com/testimonials.html
 
I'm at Camp Cupcake. And thankful for it! []

Forgot to say: If you square up your horse and look at his muscles from the rear of the front, see if he's symetrical, just out of curiosity. 
ALSO - thanks for your service my brutha/sista.... whichever. []

I can't say that I know exactly what I'm looking at, but he seems to be balanced and symetrical.  He doesn't appear uneven at all.  He does prefer to go around counter clock wise.  I don't find that unusual, a number of horses I've worked with have a favorite direction. 

And let me thank you for your service, I'm just sitting around at Lackland while you are out there getting it done.  I'll be back there soon enough though. 

I've been putting in for jobs in San Anton for years.  Now would be a really good time for me to finally get one!  You fly? I'm from the Memphis unit which has C5's.  I'm CE now but formally MXS.  DaneHaven is near Fredericksburg.  I'll be there soon after I touch down on US soil!  Hope to move there as soon as possible, actually!!  *fingers crossed*  Ya got any CE connections at Lackland? []

Lackland is a funny place.  Love it or hate it for most folks.  I'm in the hate category, but they sent me to Alaska for 6 years and then here.  I'm just not a hot weather or big city person.  It is dirt cheap to keep a horse here though.  I'm not a flyer and I don't know anyone at CE.  Sorry, I'm just an audio engineer for the band.  Good luck getting here though, I know a lot of folks really do like San Antonio, I'm just not one of them.

Would that be comnav?
 
I just want to get in that general direction.  It seems SA has more bases, thus a better chance for me.  
 

No not comnav.  I run, configure and repair concert sound systems for the band.  3N1X1V

True, lots of bases and opportunities here for folks with regular career fields.  I have 12 choices, and only a few that I might look forward to. 

I have some new goodies coming for the horsey.  I'll let you know how they work out.  Maybe I can get him to canter. 

When your horse canters and then goes back to a trot, does he ever seem to "hop" out of it? (not talking about bucking, I'm talking about hind foot movement) Also, when you are cleaning his hind feet, does he ever want to straighten one or the other of his legs out? I'm just wondering if he has a patella problem. If you can afford a vet visit, have him or her check your horse's patellas. My Arabian's patellas 'slip'. In his case, getting him in shape - strengthening the muscles attached to the patella - "fixes" the problem. One direction would probably be harder for the horse than the other.

You will want a larger circle than you have if your round pen is small. Do a fair amount of trotting for a while to help build those muscles (both directions). Begin asking for the canter but let him trot for a couple of rounds if he drops out of it. Then ask again. You want to be able to build up to more and more canter strides. Do enough to make progress but not so much as to cause him undue distress.

I really would recommend having the vet take a look because it's pretty easy for them to test for this. My vet found it in the pre-purchase exam but told me that getting him in shape would probably ameliorate the problem because his problem wasn't severe. Good luck.

Huh, that might be just the ticket!  I will sure have my vet look at him.  

Thanks very much.  I hadn't thought of an anatomical issue causing this. 

I'd sure like to hear what your vet thinks after he/she sees your pony. [] Thanks.

It might be a while, I don't think he's due for shots for a while.  He's doing fine otherwise, not sick.  I researched the condition and it seams that the best treatment is building muscle mass.  I'll let you know what he says when he sees him though.