Mark, now you have my attention. I had a new TC90 in 72 and I have just bought a TS90 Honcho. Picking it up from Batemans Bay this Saturday. You know I can't remember anyone making an aftermarket head for them back in the day but I may be wrong.
Here is a pic of my TC90 when it was new (proof is the desert boots Mark ;D) and a bit of nostalgia for Huskibul.
Stan.
(http://i991.photobucket.com/albums/af39/gf079/Gregs%20Bikes/GregsTC9019721.jpg)
(http://i991.photobucket.com/albums/af39/gf079/Gregs%20Bikes/1971_TS90T_sales_980.jpg)
To add to this saga, I've just found a photo of a WEBCO head for a HODAKA fitted to a TS100 motor. Apparently it fits straight on.
I don't know off hand if the head stud pattern on a TS90 and TS100 are the same, the cylinder stud pattern is different.
According to Alpha-sport and ZEDDER the 90 and 100 heads are different. I have both heads here but won't be able to get to them till the weekend at the earliest.
Brent
I wondered about that as I did see this Hodaka head on Ebay US last week when Mark was asking about the availability of Webco heads for Honcho's.
Stan.
http://cgi.ebay.com/ebaymotors/hodaka-ace-100-webco-head-/270705316022