what can i do about smelly dirty mouth in folds of dogs mouth Sure i read something about peroxide but not sure says on one site i looked up to clean with a mild solution of peroxide but what % to water do i add? 

I've known this as Cocker Mouth as they are a breed that apparently gets this as well.

Try cleaning with saline solution  after every meal and last thing at night.    Make up the solution by dissolving 1 teaspoon of kitchen salt in 1 pint of warm water. When using make sure it is at room temperature. Ideal for cleaning cuts and abrasions as well.

Being a cocker slave I have to keep a very close eye on my girls mouths as they are prone to lip fold dermatitis. I have never used the peroxide so cannot advise on that, but would like to suggest you try:

One tablespoon of organic apple cider vinegar mixed well with two drops of lavender oil and two drops of tea tree oil applied carefully to the folds of the lip.

When the soreness has gone, I just use the organic apple cider vinegar twice weekly to stop reoccurrence. I also use a small amount of coconut oil afterwards which helps repel the saliva.

Hope this helps...

My friend's cocker had this.  Once smelled,  never forgotten

After the vet made things worse by giving antibiotic cream and hibiscrub,  making the dog ill with d+v,  as well as sore,  friend started bathing daily with saline solution,  then dried and followed by a dab of

Johnson's Tea Tree cream

Worked well and it acts as a barrier to moisture.   Once it was under control,  it only needed doing once or twice a week to keep it away :-)

She has another cocker to care for now, I shall tell her about the cider vinegar and coconut oil - sounds like a good preventative :-)