Carb Jetting question and Cam chain guide

[RogerL]

Hi all,

I have a question with regards to jetting. I am rebuilding a gs650 motor and have gone with larger pistons (0.5+). I also plan on running the pod filters instead of the air box and I ill e looking at either the MAC 4 to 1 exhaust or a custom exhaust( as I currently do not have the original headers ). So, my question is, What am I looking at for jets? Do I need to increase the jets, if so how much, or is this going to be one of those trial and error endeavors. I have a jet kit with 3 different sizes, just not sure where to start.

2nd question:
The cam chain guide...when does it need to be replaced? Mine has a few crack in it but it's not missing any pieces. Has about 50k km on it. Normally I'd just replace it, but they're so damn expensive!!! ($250cdn range)

Thanks in advance

[Guest]

Which guide? The head or the pivot the cam chain tensioner presses on. Usually these last the life of the engine unless you used a manual cam chain tensioner and turned your chain into a band saw.
Try a Dynojet stage three kit for the carbs.

[solarae]

For our CV carbs, I thought this link was informative: http://www.factorypro.com/tech/tech_...m_engines.html

[Nessism]

If the cracks in the guide are deep I'd look for a new one that it's cracked. Pretty sure the same guide is used on the 550 so they should be out there.

[RogerL]

Thanks for the links. Those will definitely help. How deep is too deep, in regards to the grooves on the guide? I don't think they're excessive, more just curious what the tolerances are.