I have a 2007 Suzuki Boulevard S40 650cc can you tell me the correct tire pressure for front and rear?

According to the owners manual: 29psi for the front tire and 36 psi.
But, most stock tires themselves indicate they are 40psi tires. A quick reading through multiple threads indicates most riders follow the tire manufacture due to the ride feeling "mushy" at a lower psi.

Source:http://www.cyclechaos.com/4um/f26/tire-pressure-c50-boulevard-13299/

Check the tire itself, out of round, uneven wear, it could also be out of balance, also check all your front end nuts and bolts and that your forks are aligned correctly!

There is a sticker on the frame or swing arm that tells you the recommend front and rear tire pressure. You will get a stiffer ride but you will also get more even wear (less cupping) and better cornering if you run a slightly higher pressure. 35 psi front and 35 psi rear works well.

There is a label on the chrome belt cover on mine with the pressure amounts 2005. Single rider 29 front 33 rear. hope this helps

It could be road conditions, but check the condition of your tires for any damage or incorrect air pressure. Have you changed tire brands lately? Go over the front and rear suspension with wrenches to make sure nothing is coming loose. An improperly mounted tire on the wheel rim can cause strange things. Hope some of this helps!

Inflate to the pressure indicated on the sidewall of your tires ...

27 psi front and rear and it takes 4 litres inc oil filter change bud