Motorcycle Repair: working on old engine, mc repair, head gasket

Question
I recently bought a very original Honda TL250E (Aust)1975 model trials bike. It appears the engine has never been disassembled. I want to de-carbon it (looks caked from exhaust port, even though runs well). I am concerned about siezed threads, and obtaining gaskets. I think this model has a different head gasket from the XL250K model?
Any suggestions gratefully recieved.
I notice many info sites for little bro. TL125, particularly in UK, but virtually nothing on the (better?) 250 model. Why so ?  

Answer
Hi Ian,

Due to the age of the MC, finding parts is a challenge. Not sure why the TL125 is more popular on the internet. Try the following site:

www.bjracing.com/tl250.htm <---TL250 parts source

Send me your email address if you want MC repair files. "mshively1@woh.rr.com"

Respectfully,
Mark Shively