Truth be known in a two stroke just about the perfect size engine for a Senior Kaydet (Any Version Senior) is a .61 when the airplane is to be used in the training environment. Yes it will handle more and I have one with four engines but for this gentlemans senario the 91 will work.

Some considerations will be neccessary such as prop diameter but the solution to this fuel tank fiasco you have going is really very simple. The problem arises from the fact that you are trying to hard mount the tank bung into the firewall with RTV. I don,t care what any instructions may tell you this old method is very problamatic and can cause much heartache.

Consider this while its commonly advised to wrap a tank or otherwise pack in foam to help prevent fuel foaming, this to preclude running problems. Now we go and stick the tank bung in a hole in firewall (The one spot on any airframe to experiance the most vibration) with a little RTV around it. Whats wrong with this picture?

As someone said a little earlier in this thread but was ignored "back the tank up a little". The Senior front end is hugh. There is plenty of room and an as long as you pay attention to the tank/spraybar relationship you will have not problems.

This tank would be ideal for your installation and 13 oz is plenty I would go no larger. Remember most of your flying time will be at just above idle. The hayes tank (genuine hayes not the cheap arf ripoffs) is about the best most trouble free tank you can use and requries no tube bending.

http://www3.towerhobbies.com/cgi-bin...&I=LXK832&P=ML

John