Motor Mount Elimination

halfmile

halfmile

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I searched this forum but found no matches for this question (probably a good reason) but what would be the consequences of eliminating the lower rear motor mount on the main frame center tube and or also the top mount? Has anyone ever done this and if so what were the results. Any help or comments greatly appreciated.
 
That engine really rocks, and has been known to break the upper mounts. Other than that, I have no further comments, others will soon chime in.:popcorn:

Scott
 
I would think if you eliminated any of the mounts the extra forces on the existing mounts would be increased naturally, how log it would take to have your engine break loose would only be a matter of time
 
My advise is don't do it.
I have seen the rear mount case boss broken on an XS sidecar where the builder skimped on engine mounts.
Air cooled RD 350's used to break the back mounts on the cases if the front engine mounts came loose as well.
 
Never seen someone not run the rear mount but lots of the chopper crowd eliminate the top mount.....
 
nj1639 said:
That would be form over function.
Click to expand...
No top mount or rear mount looks stupid because as for the top mount, it looks like something should be there, and the rear mount is needed. What little torque our bikes do have (? 45 ft/s?) would have the engine dancing and flinging off chains, bunching up and breaking your cases, or whipping you in the head, or flying thru a windshield of a bus full of nuns!
Many run without top mont, i am not one, and i have a frisco tank on a chop. They report no ill effects, but would you report a failure if all these guys told you dont do it? Not.
Hughs hand biult has upper mount parts that aren't the puzzle that the stockers are
 
angus67 said:
No top mount or rear mount looks stupid because as for the top mount, it looks like something should be there, and the rear mount is needed. What little torque our bikes do have (? 45 ft/s?) would have the engine dancing and flinging off chains, bunching up and breaking your cases, or whipping you in the head, or flying thru a windshield of a bus full of nuns!
Many run without top mont, i am not one, and i have a frisco tank on a chop. They report no ill effects, but would you report a failure if all these guys told you dont do it? Not.
Hughs hand biult has upper mount parts that aren't the puzzle that the stockers are
Click to expand...
Hugh's top mount also serves the purpose allowing you to run low and skinny tunnel tanks. I had a low tunnel wassell that wouldn't fit with the stock mount but would with Hughs.
 
Y no rear mount anyway? It doesnt look over engineered like the top mount. Its just a triangle.
 
Hi halfmile,
the XS650 engine is a cross between a power unit and a paint-shaker and all of an XS650's solid-bolted engine to frame connections help
in uniting the two into a single vibration resistant unit.
Removing one, let alone two of those connections can only weaken the unit's integrity and that's a bad thing.
Mind you, rubber mounting the engine alters things entirely, perhaps a rubber mounted engine could be attached to the frame in fewer places
but you'd need to build a stronger frame.
 
This is not a wise idea for all the reasons quoted above plus the fact that when the engine breaks loose, the chain will could lock up the rear wheel causing the rider to go down. The resulting crash wouldn't be pretty.
 
Hi and thanks to all for the reply`s. I recently purchased a VooDoo fabrication board track style hardtail I haven`t started on yet but since it rained all day yesterday I apparently had nothing else to do but go out into the shop and think myself into a state of confusion. I`ve never owned, ridden, or built a hardtail before so I was just kicking around some idea`s for the build. HHB windowed mounts look great so they`ll probably get used. 2M`s links were very helpful. Thanks.
 
After removing my bulky, but thin in spots, original top mounting brackets that were broken from stress.......I copied the HHB upper mounts, without the windows. I am using a narrow tunnel Wassel style tank, the original mounts were too wide to use with this tank and were broken anyways. It's my opinion that the HHB brackets with the windows are too weak to use after seeing my broken mounts.

Scott
 
Hi all:

I have read quite a bit on the history of the XS1 / TX / XS650 and a continuing theme was that the frame on the earlier bikes lacked rigidity and this led to not so great handling. As I recall it, the '74 (??) was a concerted attempt to greatly increase the strength and rigidity of the bikes frame mainly by reinforcing the neck region around the steering head and also the swing arm pivots.

Having said that, a question in my mind is - did the earlier bikes have an engine mount configuration like that later ones? I know that the "grill" mount down between the down-tubes behind the front wheel was an addition at some point but what about the top mount that secures the cylinder head to the frame tunnel tubes beneath the fuel tank?

I may really may not be correct here but I'll bet that the engine mount hardware arrangement was a result of a lot of testing and design work and that it really is needed to ensure that the bike is safe and handles properly.

Pete
 
I have never had any problems removing top mount and have done many. Bottom mounts I would keep . On Café bikes I keep top mount for looks and on choppers I remove it for cleaner look. Now I have built many bikes just not XS650 and have altered frames in many directions and never twisted a frame or broke a motor mount. You are dealing with a 35 plus year old frame and a under powered motor so I would look at frame carefully to make sure there are no stress cracks before you do anything. Frames that I had to deal with for cracks or torn motor mounts were in accidents and took a hard hit. Most of your new frames have 3 or 4 mounts and no bottom mount. AGAIN you are dealing with OLD BIKE double check for bad rust and stress cracks FIRST.
 

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