Start/stop is not the issue here. It doesn't actually sync to midi clock as I speed up/slow down the external clock. And sonar's tempo display never changes. I worked with a forum member ( FBB) on trying to resolve this, and I am absolutely sure that he has it working more or less correctly. (He could not get sonar's tempo to display correctly but could hear sonar change tempo.). We confirmed my settings were in line with his setup. I can only conclude from this that sonar's midi sync is sensitive to the type of signal it is receiving when slaved.

For me the tempo does not display correctly in Sonar either, but it does change as it should.
 
If he is syncing to an instrument or controller the midi clock is probably uninterupted so he may not see the multiple start/stop issue. I was syncing Sonar to Traktor 2 to run a vst lighting controller. 
 

When I use Sonar as a slave it is sync'd to a drum machine, either a Zoom MRT-3 or an Alesis SR-16. 
 
As Brando has mentioned the issue I have is that the tempo changes aren't recorded as such within Sonar, although they do happen in real time. Other than that it works for my needs, which are not extensive by any stretch of the imagination so perhaps I've never really bumped into any limitations, simply because my needs are fairly simple.

Anderton
I can also vouch that SONAR syncs to external clock...I've done it with everything from another computer to a Korg M3.
 
But as pointed out in the previous post, the device transmitting has to be set up correctly for whatever is synching to it. For example some MIDI masters have options for sending just MIDI clock, MIDI clock+start/stop commands, song position pointer, etc.

Sorry for the late reply guys, in hopes that either I was doing something wrong or I had some strange X3 System (my hardware) issue, I jumped to Platinum (Win 7/64, i5, emu 0404 PCIe) hoping this simple task would suddenly work. Don't judge, but I use a Korg PA ARRANGER for MIDI CLOCK SYNC and both Kontakt 5 in standalone and Ableton live 9 perfectly, EASILY, slave to the Korg PA. Just totally frustrated at this point as I'm 99.9% always playing live. Just very frustrated at this point because my two goto plug-ins (Strummed Acoustics and AAS GS2) require my DAW to perfectly slave.

All the replies make perfect sense and I keep thinking I've not followed your recommendations. That said, I should experience the same issues with Ableton and/or Kontakt but I don't. I'm not giving up yet but frustration is compounding. Sincerely, Thanks for both the interest and help. Should I find my mistake :( I'll definitely let you know.

Sonar can be configured to sync to midi, audio, or internal. However, it has been my understanding that as soon as there is audio in the project Sonar insists on audio timing. That might even include the case where there are no audio tracks, but synth tracks even if none are frozen. If that is true, it would cause all of the above frustration. However, the idea of locking timing to audio tracks does make sense when an audio recording has already dictated tempo.
 
Both audio and internal timing derive tempo from the tempo track. MIDI timing gives Sonar no information about tempo per se, just clock events that Sonar follows to spool out notes when they become due. The tempo track is just ignored. Recording tempo is not a Sonar thing. (though there is a way to recast measure boundaries)

bvideo
Sonar can be configured to sync to midi, audio, or internal. However, it has been my understanding that as soon as there is audio in the project Sonar insists on audio timing. That might even include the case where there are no audio tracks, but synth tracks even if none are frozen. If that is true, it would cause all of the above frustration. However, the idea of locking timing to audio tracks does make sense when an audio recording has already dictated tempo.
 
Both audio and internal timing derive tempo from the tempo track. MIDI timing gives Sonar no information about tempo per se, just clock events that Sonar follows to spool out notes when they become due. The tempo track is just ignored. Recording tempo is not a Sonar thing. (though there is a way to recast measure boundaries)

Well that would (imo) clearly be an oversight on Cake's part if that is the case - but I think you may be correct. In my own case I have been trying to get it to work using a rack of soft synths. No sync, no how, no way. The logic of why Cake set it up this way (if in fact it is so) escapes me. Nothing is frozen/bounced- no audio at all in the project. My reason for going with an external clock was because Cake doesn't provide a way to control/automate tempo. It's always something....

.........And really, if SONAR insists on audio sync (when audio is present)... Shouldn't it gray out the option for midi sync- instead of fooling users into thinking they can actually slave and sync?

Brando
Nothing is frozen/bounced- no audio at all in the project. My reason for going with an external clock was because Cake doesn't provide a way to control/automate tempo.

Soft synths are audio. Their output is pre-rendered/buffered in advance of playback and that rendering is necessarily based on the pre-existing project tempo. Synced playback of soft synths at a fixed tempo should work - and does in my experience - but if the source tempo is varying, the pre-rendered synth tracks are going to go out of sync with the source.
 
You can record, echo and play back MIDI driving hardware synths with SONAR slaved to a changing tempo from the Master, but you're going to have the same problem with soft synths that you would have with recorded audio tracks.
 
Other DAWs may not pre-render synth output in this way, and I've often wondered if it's really necessary for SONAR to do this, but it does, and that's going to prevent you controlling tempo in real time by any method unless you loop the MIDI out of and back into SONAR so that it's treated as live input (i.e. soft synth output isn't pre-rendered).
 
But then you're still going to have the limitation that SONAR doesn't display or record tempo changes from a MIDI Sync Master.

Hi Dave. Thanks for chiming in. Your knowledge of sonar is amazing. I get it - and could have saved myself the investment and aggravation. Yes, as you say, syncing to a fixed tempo is no problem, (but also no good to me).
I really just need to hope Cake decides to provide a way to automate tempo. (Not sure that's the solution for everyone looking for midi sync as slave when using softsynths, though).
Thanks to you (and also to BVideo) for pointing out the 'limitation'/design constraint. At least we have a definitive answer.
Much appreciated and thanks again for the help.

You mention that you have Ableton Live 9 - asyou probably know that is the DAW that excels for live sync tasks. I too much prefer Sonar, but external sync has never been its strong point. That said, no matter what the program you will experience some midi clock drift whenever there are sudden  tempo changes. Gradual tempo changes are the secret to staying perfectly in Sync. Midi in general is an area in desperate need of an update since it basically hasn't changed in 30 years. We are still stuck with a protocol written around the limitations of hardware midi file players and Commodore 64's with 64kb of ram!