base gasket

[creature]

I want to have a bulletproof base gasket solution. My RD 400 is ported,the case is shaped to match the transfers as well. Problem is, not enough land left between the 2 cylinders.. I was meticulous when assembling last time, however, I developed a air leak. After I got the top end apart I noticed the gaskets were partially disintegrated. These were OEM base gaskets.I just cut my own gasket as a one piece, like a tz style from gasket material. Runs great. I wonder if it is possible to use o ring style base gaskets. How could I cut the groove and also shape the o rings? I dont want to blow it up by air leak(again lol) Seems like a good solution if it can be done. Chuck? 

[Yamaha 179]

I sell aftermarket base gaskets, both TZ style and RD style, in three thicknesses developed specially to avoid the problem you had.  The real problem with the OEM TZ gasket is the center web is very thin because the TZ cylinder is a mono-block and the transfers are made that way.  Even enlarged the RD transfer ports don't work well with that gasket and mine is larger so you get a good seal.  My TZ style base gaskets are available in .22mm, .35mm, and .56mm sizes.  price is $13 each or $11 if you buy more than one.  Postage is $3.58.  The RD gaskets come in the same sizes and are relieved in the center section to avoid your problem.  Prices for them are $7 each, no discount for multiples. 
Lyn Garland