upper engine mount

[angus67]

hey, guys. This weekend, I'm putting the top of a friend's engine back together(650), and was wondering if its alright to leave the upper engine mount off so that he can re-torque the head after a few runs?
He's also giving me a '80 front fender so I can snug it closer to my rear tire. I have a 72 rear fender on it now, and it sits kinda high.

 

[Travis]

I don't think it'll be a problem. Some guys don't even use the upper engine mount on their choppers.

 

[angus67]

yeah, I see that sometimes and wonder if they really ride it, though.
I mean, it was designed to be on there for a reason right?
Another thing about top engine mounts, I've seen some were they use round stock and tubeing, and re-design it all together. I like those. I might do that when I take it back apart after tunning.

 

[Gordon]

I believe the reason for the top mount is for rigidity, support for the frame. If you study the mounts, you'll discover that it completes triangulation of the frame. I found it very functional, drove around for a little while, for the same reason, to re-torque the head. Just a little tank-slapping at high speed cornering. Other than that, the bike is fine. Reinstalled the mount, much better handling.

 

[ardcorechoppers]

The "no top motor mount" debate has been going on forever.. And this may be a bit off topic but I have seen this type of discussion turn into a real shit storm.
Things to consider is that most bikes you see without the top mount are custom built frames and not hardtailed or modded stock one.
A custom frame is,if done correctly built from a thicker wall tubing then they used from the factory.
Ever wonder why there is a shit ton of bracing and gussets on a stock frame? its because even yamaha knew that the tubing needed it.
And yes guys that aren't running one and have custom frames do ride their bikes..
I put about 15k or more on mine last year..

 

[xs650rider]

ye it will be fine i did it with mine

 

[Travis]

xs650rider, long-term or just temporarily so you didn't have to deal with the mount when you re-torque the head after a rebuild?

 

[xs650rider]

only for a day of soft rideing .then crack up the nuts and put the mount bk on . its better safe than sorry

 

[inxs]

- you generally see this in racing circles...helps save time if you need to open the motor quickly...as stated above though these are custom frames...you also sometimes find motors that have been adapted so that heads can be removed in frame-means creating bolts to replace the studs, note..the threads are rolled not cut, this is not recommended for street-these motors are built with a season in mind

 

[Morgue13]

never had the upper mount on mine, runs fine never had a problem in the 5 years I've owned it (I have a hardtailed stock frame now) no problems with vibration or anything really I didnt even know it was missing till I got my second one and saw it had the upper mount lol (which is going to stay on my second bike)

 

[therealjamesdean]

My brother used to race an XS 750 in a Starracer frame, it had no top motor mounts and the top rear mount cracked at the cases. He had the cases welded and reinforced and it cracked again. After the second weld job, he made an upper engine mount and that was the trick... No more cracked cases! It does do something...

 

[Morgue13]

I can see that happening to a race bike they go through a beating

 

[therealjamesdean]

You can see the upper engine mount in this picture. It's the black bracket running to the frame downtubes...

 

[Morgue13]

WOW thats rad!

 

[ShermT110]

My Triumph mechanic told me to make sure I used the "head steadies" unless I wanted to torque the jugs every 100 miles....just sayin'

 

[burns]

You might have noticed that these motors shake a bit.

I'm pretty sure that's my Momma Yama bolts the head to the fame.
Not to stiffen the frame but to spread the load of the vibration.

I doubt that you need that top mount with a rephased motor but I suspect you will get fatigue failures without one with a stock crank.

 

[angus67]

i put it back on after a few heat cycles of riding /torqueing.