Left exhaust valve options ????
 

If you are following the the thread "We are a little stump" I have been in search of the reason our 06 300 has a different power curve than our 08 300. The only thing that has been obvious is the central exhaust valve is shaped different.In searching part numbers for the 2 bikes to see if there is a difference we noticed that there are 3 different options for the left exhaust valve. I went to GasGas USA to look at this. Maybe I am looking at the view wrong or the description wrong but just looking for other peoples opinion if this could be possible to have different left exhaust valves ???

Out of interest - what is the difference in power curves

Looking at the parts manuals the cylinders are the same '06 & '08.

The left side exhaust valve part numbers are the same '06 & '08. The optional left side valve with H designation is Homologation version which restricts for emissions. The H version is completely round. The standard version has a channel in it. If you have the H version, replace it immediately with the standard version - it will make a noticeable difference.

The '06 central exhaust valve is different from the '08. You could swap them fairly readily (without removing the cylinder) and see what difference it makes.

Can anybody explain the diff in shape or post up picks of the centre valve?

Good to know. I just figured that they were the same. I have the old style on my bike.

The 06 power is way stronger a little past the bottom.(lower midrange through mid range) The 08 has plenty of lugging power and has a pretty good mid to upper hit but has nowhere near the low mid hit that the 06 has.We have covered just about every possibility except pulling the heads off to look inside. The central exhaust valves are definitely different.The 06, in my opinion ,is less restrictive.

Aslo check to see if the left side valves are the same between '06/'08 by looking up the exhaust port. If you have the restricted H version left side valve on your '08 it would reduce low/mid compared to the '06.