IK'm sure it won't stay stock for long at all either.
Look at the start of the thread, this dude wants to build a 720!
Talk to guys like T Barker & CSR, they build these motors for a living & they know their oats, they will tell you the best combinations of bore & stroke you will need to make the machine you want.
I'm sure that they will give you the good oil on it, & if you then choose to spend your coin with one of them, then I'm sure you will get a great motor out of it.
The advice I have:
I'm not sure what the best combo of stroke & bore is, but one thing is for sure, replace the Con-Rod.
At 686, the stock rod is right on its limit, above that, it's a major rebuild just waiting to happen, a grenade with the pin already pulled.
Get your transmission checked out, & fixed if necessary.
The 01 transmission had a few weak points, they are well known & easily dealt with, so do it while your motor is apart.
Put a GYTR or Hinson clutch in your machine, the stocker will be on it's last legs I would suggest (at the age of your bike)
Put an L&A starter clutch in, you will never regret it, I did mine with the std Yamahahahahaha one first time round, & looked after it really carefully, & it still only lasted 18 months.
Put some money into a set of FCR carburetors, no point in putting all that effort into the motor & not fitting the carbs to suit.
Buy a set of Duals. Monster do a nice looking set of in-frame duals for the 660, they look the bees knees!
Put some money into the suspension & handling.
As a stocker, these bikes are high, narrow, & short.
They wheelie too easily (& plenty have been flipped), & they tip over real easy.
1/ Make it wider, put a decent aftermarket axle in it, with spacers. All the 450 mxers are 1350mm+ on the width, these are only 1100mm stock. So make it 1350 wide. Put a decent set of wider A-Arms, or a Diamond J widening kit in it. I made my own one of these, if you want, I can send autocad drawings of the required components.
At 1350 wide, these bikes are transformed!
2/ Make it lower, the weight is carried very high on these bikes, they have a tall motor, & the radiator & gas tank are mounted high also.
Do the flipped link mod. You will need to buy some parts to do this as the 01 linkage was different to the rest, but it is worth it!
3/ Make it longer, look at a longer swingarm. +2 - +4 is good for motorcross racing & general trail riding. Go longer if you're into drag racing.
4/ The shocks suk! Get some 450 shocks for the front, & look at some of the conversions other people have done on the rear. The 700 rear shock conversion looks like a good one. Or, if you have the money, get a set of elkas.
Good luck & have fun, these are a good bike to play on, & to work on.
