How to make a stock 660 live

I hear there is a lot of flaws to the 660 engine like broken woodruff keys broken cases etc. what should be done to a stock 660 to be able to hold wide open throttle for long period of time with trouble free use. Mine has 1700 miles i really dont want to do a full rebuild anytime soon

change the oil.  I would wait until you have to open it up to do the upgrades.  A better piston, and if you split the cases the middle drive support should be on the list. some of the guys who are reporting problems have already been into the engines.

Ok so piston is one problem and the center drive brakes?

Ok so piston is one problem and the center drive brakes?

I think a lot of the center drive failures are a result from something coming loose inside.  I think some thread-loc could prevent a lot of middle drive failure, but one you are in there you might as well add the support.  When it comes time to replace my piston I won't go stock.

The middle drive is a ring/pinion inside engine that spins the driveshafts. There are 4 bolts that hold the middle drive plate in place. Yamaha did not use thread-loc of any type and these bolts. Over time these bolts work loose and most failures (including mine) had 1 bolt fell out. The factory plate isn't very strong and once loose breaks out at bolt holes. First good bind or accleration will cause break, when it breaks it breaks the engine case at it's anchor it's attached to. Also the oil pump relief gets knocked out causing loss of oil circulation. Next because you don't realize what happened you give it the gas and continue to break stuff until you realize your screwed or run out of beer.

While your rebuilding whole engine go ahead and get aftermarket middle plate, good connecting rod and piston and your good to go fast.

doughjk wrote:

The middle drive is a ring/pinion inside engine that spins the driveshafts. There are 4 bolts that hold the middle drive plate in place. Yamaha did not use thread-loc of any type and these bolts. Over time these bolts work loose and most failures (including mine) had 1 bolt fell out. The factory plate isn't very strong and once loose breaks out at bolt holes. First good bind or accleration will cause break, when it breaks it breaks the engine case at it's anchor it's attached to. Also the oil pump relief gets knocked out causing loss of oil circulation. Next because you don't realize what happened you give it the gas and continue to break stuff until you realize your screwed or run out of beer.

While your rebuilding whole engine go ahead and get aftermarket middle plate, good connecting rod and piston and your good to go fast.

So the MORAL of the story is don't take so damn much beer with you.

Kenny G wrote:

doughjk wrote:

The middle drive is a ring/pinion inside engine that spins the driveshafts. There are 4 bolts that hold the middle drive plate in place. Yamaha did not use thread-loc of any type and these bolts. Over time these bolts work loose and most failures (including mine) had 1 bolt fell out. The factory plate isn't very strong and once loose breaks out at bolt holes. First good bind or accleration will cause break, when it breaks it breaks the engine case at it's anchor it's attached to. Also the oil pump relief gets knocked out causing loss of oil circulation. Next because you don't realize what happened you give it the gas and continue to break stuff until you realize your screwed or run out of beer.

While your rebuilding whole engine go ahead and get aftermarket middle plate, good connecting rod and piston and your good to go fast.

So the MORAL of the story is don't take so damn much beer with you.

Hey Kenny, Think my wife hijacked your log in

Joe, that was a good write up on the middle drive, just had to lmao when you brought up running out of beer. Hell these Rhinos would probably run for ever if we never emptied the coolers. Good stuff!

Kenny G wrote:

Joe, that was a good write up on the middle drive, just had to lmao when you brought up running out of beer. Hell these Rhinos would probably run for ever if we never emptied the coolers. Good stuff!

Yea, got a bigger cooler now. Sucks to get that out of beer headache knee deep in mud dragging me or somebody home.

Not trying to jack this guys thread but I see you have a custom cage, that's my next project. What you got? Looking for ideas

Foxman92 wrote:

I hear there is a lot of flaws to the 660 engine like broken woodruff keys broken cases etc. what should be done to a stock 660 to be able to hold wide open throttle for long period of time with trouble free use. Mine has 1700 miles i really dont want to do a full rebuild anytime soon

Okay Foxman, we got sidetracked along the way. Rhino's are very dependable and the 660 is a great engine. The middle drive plate would be fine for stock engine and tires if factory would have used loc-tite.  Most people put bigger tires and other power adders, then it becomes weak link that can cost a ton to repair. Connecting rod and piston really need to be upgraded if you have aftermarket CDI that increases engine RPM's, again probably fine for stock engine.

doughjk wrote:

Kenny G wrote:

Joe, that was a good write up on the middle drive, just had to lmao when you brought up running out of beer. Hell these Rhinos would probably run for ever if we never emptied the coolers. Good stuff!

Yea, got a bigger cooler now. Sucks to get that out of beer headache knee deep in mud dragging me or somebody home.

Not trying to jack this guys thread but I see you have a custom cage, that's my next project. What you got? Looking for ideas

Joe, some good pics of the cage over on 'Members Rides', page 1, Kenny G's 06/450 Bitchin Trail.

Foxman92 wrote:

I hear there is a lot of flaws to the 660 engine like broken woodruff keys broken cases etc. what should be done to a stock 660 to be able to hold wide open throttle for long period of time with trouble free use. Mine has 1700 miles i really dont want to do a full rebuild anytime soon

1700 miles is nothing. I believe mine has a little over 9000. Havent had any major issue other than rear axles and last summer the needle valve fell out of the carborator stranding me for a couple of hours while I followed my tracks and found it. Next time Im outside I will have to look at the OD again.

As long as you do preventive maint is should last a while.

JR

When the middle drive plate goes does it make a lot of noise? An when it goes is it still possible to drive it?

doughjk wrote:

Foxman92 wrote:

I hear there is a lot of flaws to the 660 engine like broken woodruff keys broken cases etc. what should be done to a stock 660 to be able to hold wide open throttle for long period of time with trouble free use. Mine has 1700 miles i really dont want to do a full rebuild anytime soon

Okay Foxman, we got sidetracked along the way. Rhino's are very dependable and the 660 is a great engine. The middle drive plate would be fine for stock engine and tires if factory would have used loc-tite.  Most people put bigger tires and other power adders, then it becomes weak link that can cost a ton to repair. Connecting rod and piston really need to be upgraded if you have aftermarket CDI that increases engine RPM's, again probably fine for stock engine.

Exactly what I worry about with 9k on motor I am soon to get all of my goodies from James. Sheave, CDI and some other stuff.
 During hunting off season will probably invest in piston and Rod. Any recommendation for an otherwise stock 660

Thanks

JR

Djbison wrote:

When the middle drive plate goes does it make a lot of noise? An when it goes is it still possible to drive it?

The engine will run fine and it's possible the gears may keep enough teeth to move a very short distance ( mine went about 6 foot). if you hear a pop followed by grinding sound and jerky grinding to stop, it just broke. Caution about continuing to run engine is break probably took out oil pump. Going hunting but i'll try to post pics in a couple of days

cammoup wrote:

doughjk wrote:

Foxman92 wrote:

I hear there is a lot of flaws to the 660 engine like broken woodruff keys broken cases etc. what should be done to a stock 660 to be able to hold wide open throttle for long period of time with trouble free use. Mine has 1700 miles i really dont want to do a full rebuild anytime soon

Okay Foxman, we got sidetracked along the way. Rhino's are very dependable and the 660 is a great engine. The middle drive plate would be fine for stock engine and tires if factory would have used loc-tite.  Most people put bigger tires and other power adders, then it becomes weak link that can cost a ton to repair. Connecting rod and piston really need to be upgraded if you have aftermarket CDI that increases engine RPM's, again probably fine for stock engine.

Exactly what I worry about with 9k on motor I am soon to get all of my goodies from James. Sheave, CDI and some other stuff.
 During hunting off season will probably invest in piston and Rod. Any recommendation for an otherwise stock 660

Thanks

JR

Lots of people on here smarter than me at going fast, I don't have mine set up to go fast. I have a CP piston (over kill) thing looks like a piece of jewelry. Then I have the Hotrods stoker crank and rod, some people like some don't (again i don't go fast) so it'd been great for me. A really good rod with install and shipping can easily get very expensive. You'll need to look at you're budget and get the best parts that fit your budget.