Kodman
New member
i am thinking of doing a big bore to my mountain max but i wanna keep it reliable to, is this possible? and if so what kit do you guys recommend?
Backwoods M Max
New member
If done properly it shouldn't effect long term reliability too much, but there are other things to consider. The 780 big bore kit for the 700 sx motor has been around for a while and supported by various vendors with different degrees of porting to take it to the next level.
As the local vendor for VW TDI performance parts said to me once, "VW has to make sure that anybody can neglect one of these things and it still has to survive. We modify our cars because we're car people. We can tell when something isn't right and not ignore it, and take care of these engines the way they need to be so they are still reliable"
With that in mind you have to ask yourself, am I the kind of person who can read plugs, tune carbs and interpret the feedback of a motor that has been pushed to the ragged edge in time to prevent the motor burning down? Do I want the hassle of running triple pipes where I may have to jet my sled from day to day? Am I ready to put up with the irritability brought on myself by building a mod motor?
How many miles are on the sled you are considering big boring? Anything with over a few thousand miles and I would want to have the crank rebuilt, so I know it's fresh to handle the extra stress that's being placed on it. Part of the reliability that the red head is famous for is that it operates at very low compression and has a 3rd cylinder to share the strain that's asked of it. And while not the same as a de tuned diesel in a small commuter car, Yamaha is putting there reputation on that motor so they need to know that it will hold up to the neglect of joe sledder taking it in for carb cleaning in the fall then running the lungs off it all winter without so much as a peek at the plugs.
As the local vendor for VW TDI performance parts said to me once, "VW has to make sure that anybody can neglect one of these things and it still has to survive. We modify our cars because we're car people. We can tell when something isn't right and not ignore it, and take care of these engines the way they need to be so they are still reliable"
With that in mind you have to ask yourself, am I the kind of person who can read plugs, tune carbs and interpret the feedback of a motor that has been pushed to the ragged edge in time to prevent the motor burning down? Do I want the hassle of running triple pipes where I may have to jet my sled from day to day? Am I ready to put up with the irritability brought on myself by building a mod motor?
How many miles are on the sled you are considering big boring? Anything with over a few thousand miles and I would want to have the crank rebuilt, so I know it's fresh to handle the extra stress that's being placed on it. Part of the reliability that the red head is famous for is that it operates at very low compression and has a 3rd cylinder to share the strain that's asked of it. And while not the same as a de tuned diesel in a small commuter car, Yamaha is putting there reputation on that motor so they need to know that it will hold up to the neglect of joe sledder taking it in for carb cleaning in the fall then running the lungs off it all winter without so much as a peek at the plugs.