Tom, I went through all of my links and found this on legendsforce.com:
"The carburetors are Mikuni BS36 x 4 constant vaccum. Re-jetting is permitted. The engines are mounted 90 degrees counter to the way Yamaha designed them to be cooled by air flow. The #3 cyl. is a common problem area on these engines due to heat and the restricted air flow to the back cylinders. Have the carbs tuned to keep #3 and #4 from running lean. Venting fenders and hoods, while staying within rules, is recommended. See the FACTORY Professional Tuning Components website for good information on performance carburation setup."
It's not an answer to your question, but it brought up another question for me - we got a vented hood as an extra with the T48, but I never see anyone using one, so we didn't. Does the above suggest that we should?
Also found this, if it's of any help:
http://www.carbparts.com/mikuni/mikuni_tuning_info.htm