Different Yamaha 701 versions question . . .

[sjvogt]

I am in the process of building a twin carb Yamaha 701 for use in a 95 Waveblaster and I have a few questions regarding the interchangeability (is that a word?) of the various 701 parts. Here is a list of what I have so far:

62T case
62T cylinder
61X cylinder
62T head
61X stator/flywheel/cdi

From what I've read elsewhere, the 61X electrics will work fine with a 62T case etc as long as I make sure all the components are one or the other. Please confirm.

Is there any difference/benefit to using the 62T cylinder vs using the 61X cylinder? Does one have more sleeve thickness etc? Do I need to use a certain head with a certain cylinder or are they interchangeable? Do any of the heads have benefits over the others? Do they all have fittings for the temp sensor/water fittings/etc?

On a related note, why did the 96+ Superjet and Blaster have 62T cases/61X cylinders/64U heads? Why didn't they use 62T components from top to bottom? What would be the drawback to using all 62T components?

Any and all help would be greatly appreciated. Either reply here or contact me at sjvogt@hotmail.com Thanks in advance.

[Joe St. Louis]

The 61X cyl has a smaller exhaust port and will give you better take off, which is why Yamaha stuck with the 61X cyl on the Super jet. The 62T case has a larger intake area and a slightly larger crank case volume which will allow more fuel and air to enter. When you combine the two 62T case + 61X cyl you will get more fuel-air mixture in the combustion chamber than a complete 61X engine, but not as much as a complete 62T engine, hence the need for the special 64U head. Since you have a 62T case,cyl,head combo, I would recommend using that. You may have to get a 62T CDI or you may be able to get it to work by adjusting the stator. The 62T head will not work well with the 61X cyl, unless you modify one or the other. Sleeve thickness is only a problem with the 760. You might want to make sure that 62T cyl you have is not a 760 since they both used the same casting. :D