XVrider
Posted on 07.21.2008
| Yamaha Virago 250
As far as millage goes , I was getting 67mpg.... and after the mods I am currently getting 59-60
An engine does four things... When you open up the blow, it is going to cause the engine to "lean out"
because of the ease at which the engine is able to evacuate, It will cause overheating... if the larger jet isn’t installed.
The trick is to drill the four holes at the lower exhaust pipe beyond the visible end plate . The exhaust tube in the center is about 7"
inches long and I drilled four holes in the baffle at the FAR END of the exhaust tube with a really bright light you can see the baffle at the far end through the length of the tube, as if you are looking through a gun barrel into the breach block. This method keeps the visible end plate intact , inspectable
and provides back pressure for the modification that you have performed(seven inches further inside). As a result, the sound of the engine becomes louder but at the same time sounds mellow and throaty verses ratty and annoying, You also have an added layer
of protection from going overboard with the drilling because you still have the end plate to help contain some of the free flowing
gasses. I have drilled the four holes up to 1/8 diameter before going overboard with power loss and excessive engine heat.
When you do take the dive, and re-jet your carb , this re-balances the "lean out" syndrome encountered from the free flowing exhaust
and restores normal operating temperatures and maintains engine longevity.The power gain is fairly impressive. With the higher gears, the engine at 60mph went from screaming to a well adjusted "purrring" along side with the big bikes. The new ratio did not subtract from the available power and the xv bike in my opinion is a more safe machine because of it. Signed Doug Miller, in extreme North Texas
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