Top Motor Mount

Message

aroracer72 · #1 Post by **aroracer72** » Fri May 13, 2005 3:39 pm

Im not shure if this is known by others.......but why the heck do our cases crack at the swingarm pivot channel???!!!

Heres my diagnosis. I bilieve it is due to the motor (the top) moving side to side when under power. See....we have no top motor mount for our engines!!...This is stupid..and im positive this is te reason some of our cases crack. So after my case cracked....i got to work on coming up with a simple...yet effective and sturdy top motor mount. Since all the tweaking is occuring side to side....you have to make a mount that will of course, hold the motor from moving side to side at the top.

MY FIX:
My fix is to place one square hard rubber cubes on either side of our engines....inbetween the valve cover area and the frame spars. All you ave to do is remove your plastics(rear)....and your seat and tank. Then you place the chunk on both sides in the same spot...and secure them by glue..straps...what ever you please. Make shure you use high temp ruber..cause you dont want it to melt!!.

What do you guys think???
CHAD

jacobw · #2 Post by **jacobw** » Fri May 13, 2005 3:53 pm

I am not postive the motor is torquing and cranking this. Seems kinda far fetched maybe some isolated cases let us know what you come up with.

NRath · #3 Post by **NRath** » Fri May 13, 2005 3:56 pm

I think your wrong about there being side to side torque loading. The cases crack from the excessive vibration that was coincidentally introduced at about the same time the weaker SSM cases came out.

jacobw · #4 Post by **jacobw** » Fri May 13, 2005 4:08 pm

I think you are right on about the vibrations cracking the cases. If the crank is updated and balanced and the motor mount is put on you will have no problems. I also think the motor is torquing side to side then we have major problems. With the mounting points on the swing-arm and the front 2 motor mounts there really is no where for the motor to move. I would say the reason that yamaha and honda put top motor mounts they have a steel frame that flexes and cracks with abuse and they use the motor mount to stiffen the frame with the motor to allow less flex of the frame. Cannondale does not have the fram flexing and cracking issue. Vibration I can buy but the motor flexxing I am not. Others chime in I may be completly off track also.

aroracer72 · #5 Post by **aroracer72** » Fri May 13, 2005 7:13 pm

I posted because every other quad has top motor mounts. And our dales have more torque/just the same...but we have no top mount. When you hit the gas.....it will pull sideways and wanna move the motor....so thats when in some cases the case cant take the twisting...and it cracks. I asked my dad...and hes a engineer..and hes almost certain this is the reason....but im not shure.
CHAD

quadprorider · #6 Post by **quadprorider** » Fri May 13, 2005 11:16 pm

Try it! What's the worst that can happen? I don't think you could do any damage by just adding some rubber cube supports....:eek:

aroracer72 · #7 Post by **aroracer72** » Sat May 14, 2005 1:51 am

already am. And here....ill explain the details of why the top of the motor will move the move when under torque.

We have a motor mount front and back....both towards the bottom. When you hit the gas...and torque is applied....the first thing that it will try and do is pull the motor backwards. But, because we have wide/solid mounts front and back....it is stopped...and now trhe motor will wanna ytweak a different way. So instead of the motor tweaking front to back....its ghoing to pull down on the engine. The two mounts will prevent the bottom from moving much....so were does all this torque go????....to the top.....which pulls down........which results in the top of the motor moviding ide to side. If your specific case has the slightest flaw..this flexxing will take its toll on the case...hence crfacking it.

So theres my explanation..lol......its cheap insurance tro prevent something troublesome.
CHAD

cannondale27 · #8 Post by **cannondale27** » Sat May 14, 2005 2:05 am

Actually Cannondale designed the heads for a top mount.Early heads the bung to the left of exhaust is even tapped and drilled for it.Back in 250r days it was always a issue that came up.Some folks ran the top mount which did stiffen frame some and supposedly helped other mounts out.Others (Duncan for sure)didnt run the mount because it put strain on the cylinder and head supposedly causing leaky head gaskets and wear in cylinder.I ran both styles and never noticed any difference.The frame motor mounts cracked either way and any difference in wear wasnt seen.I dont think rubber will make any difference since it gives too much.If you make a solid mount something should be noticed.Question is what?

4strokemadman · #9 Post by **4strokemadman** » Sat May 14, 2005 11:40 pm

One thing to think about is the additional stress you will put on the head with a top motor mount. We were working on a top mount, but results were mixed and weren't conclusive if it actually helped or hurt things. We did have some weird cam bucket failures with the top mount, the theory was it was stressing the head and causing the bores to ovalize. Remember the engine is moving, but so is the frame. So the question we asked ourselves was, would the frame add more stress to the engine, or would it reduce the stress..... This is an interesting topic and is something that needs more data and testing.

kdeal · #10 Post by **kdeal** » Sun May 15, 2005 3:09 pm

I agree with 4storkemadman. Remember, both your frame and engine is aluminum here. Where as previous bikes would have had a mild steel frame with aluminum/mag motors. there would be much more flexing in the steel frame.