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front engine mount not sitting square?

Started by 1340evo, August 16, 2021, 01:55:58 AM

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Scotty

When I got my FXR I could not believe the vibration through the rev range and figured I got it cheap because it had a problem.
Having ridden solid mount motors and balanced twin cam motors as well as rubber mounted the FXR was the worst.
However after flipping the front motor mount because the last owner/dealer had put it in upside down and re-aligning the drive train (it was out a fair bit) it is as smooth as the rubber mount twin cams.
If I had never ridden a Harley before I might have thought that is how a FXR is but having ridden plenty of others it was obvious there was a problem.
So yes don't accept the vibes as normal when you know it can be better because you know what your riding and other people are just guessing as how much vibe you are feeling and they almost sound like a Harley dealer with "they all do that"  :hyst:

1340evo

Indeed, we'll see what the front mount does and I'll double check re-aligning the drive train...  see where we go from there   :wink:

Did you use any guide for re-aligning the drive train or just the HD manual?

HogMike

Quote from: 1340evo on August 21, 2021, 12:06:59 PM
Indeed, we'll see what the front mount does and I'll double check re-aligning the drive train...  see where we go from there   :wink:

Did you use any guide for re-aligning the drive train or just the HD manual?

IIRC
The H-D manual is pretty complete on the sequence how to do it.
I'd dig out the manual but it's down at the shop and I'm in "happy hour" mode at the present!

:missed:
HOGMIKE
SoCal

Scotty

Quote from: 1340evo on August 21, 2021, 12:06:59 PM
Indeed, we'll see what the front mount does and I'll double check re-aligning the drive train...  see where we go from there   :wink:

Did you use any guide for re-aligning the drive train or just the HD manual?

I have some tools that a forum member made for me quite a few years ago and they work on the FXR and FLT but the manual and couple of long fluro tubes (something straight) will get you there.

1340evo

I have two pieces of ali extrusion that I used before so will give it a shot, and follow the imortal instructions of the HD manual to the letter.
But thats for tomorrow as its late Saturday night here in the UK and I've had far too much to drink as usual  :beer:  :beer: :beer:

FSG

I do remember HD releasing either a SB or a TT relating to the mount and which was the right way up, trying to remember it now  :scratch:

OK Service Bulletin   M-1182 , Improved Front Rubber Mount  .......    to be found in the section

there was something else as well but for now   :scratch:

Scotty

Quote from: FSG on August 21, 2021, 06:10:46 PM
I do remember HD releasing either a SB or a TT relating to the mount and which was the right way up, trying to remember it now  :scratch:

OK Service Bulletin   M-1182 , Improved Front Rubber Mount  .......    to be found in the section

there was something else as well but for now   :scratch:

Yep exactly  how I said they go in. That was for -79C part number.

1340evo

Q... why would re-aligning the drive train address vibration issues at a given RPM? Or are we talking vibration in general for this one?

FSG

Quote from: Scotty on August 21, 2021, 07:56:29 PM
Quote from: FSG on August 21, 2021, 06:10:46 PM
I do remember HD releasing either a SB or a TT relating to the mount and which was the right way up, trying to remember it now  :scratch:

OK Service Bulletin   M-1182 , Improved Front Rubber Mount  .......    to be found in the section

there was something else as well but for now   :scratch:

Yep exactly  how I said they go in. That was for -79C part number.

4-sure   :up:

Scotty

Quote from: 1340evo on August 23, 2021, 02:20:30 PM
Q... why would re-aligning the drive train address vibration issues at a given RPM? Or are we talking vibration in general for this one?

Alignment helps with vibration across the rpm range. Any twist in the wheels and transmission/motor becomes a vibration at certain rpm's.
The straighter it is the less tension on all components and motor moves freely on rubber mount and thus less vibration.

1340evo

As you say, I guess you are not pre-loading / stressing the rubbers so they will work better. Any pre-load will result in more vibrations crossing into the frame.. sounds good to me.. will have a re-check :)

1340evo

August 26, 2021, 12:59:22 PM #61 Last Edit: August 26, 2021, 01:18:20 PM by 1340evo
Developments.. the Kinetic Structures mount arrived, so I wopped it on and went for a spin... Much better. It did settle a bit by a few mm but is way better than my last one.

But what it does do, is show the amount the engine bracket is not sitting square on the mount and in doing pre-loading it which I'm sure will go a long way towards my vibration issues!

But I can't work out whats causing it?

Front of the mount I measure a 7mm gap, the back of the mount I measure 4.3mm gap, so knowing its 50.3mm dia I can work out the extra angle required. (its about 3 deg)

But why isn't it right? Now I can make a new front mount no problem.. but why's it not correct to start with. My rear mounts are good (new) and now in the right position. Do the front metal bits come in different types. Has he put a FLH mount on a FXR for example?... any thoughts.


kd

How is the shaft to transmission bore wear?  That could contribute to it sagging in the rear.
KD

1340evo

August 26, 2021, 01:19:39 PM #63 Last Edit: August 26, 2021, 01:35:48 PM by 1340evo
you mean the rear swing arm shaft?... its fine, and the rear mounts are new...

If you calc it back to the rear mounts, they would have to be 35mm out to give a 3 deg angle at the front?

Wondering if he's bought a new front metal bit and its just crap.. could do with someone who has one off measuring the angle ?

Scotty

August 26, 2021, 03:20:19 PM #64 Last Edit: August 26, 2021, 03:26:45 PM by Scotty
Front engine mount is the same part number for FXR and FLH right up to the end so that is not the problem.

One issue I noticed putting these rubber mounts together is putting the rear shocks on will in some cases pull the transmission back and down if the engine is not done up and bolted down correctly.
Could be your issue but I am just thinking out aloud but would give a problem as you have noted.

1340evo

If anything, it's forward as the bolts right at the back of the slot, and as I say above, would need to be 35mm out to get a 3 deg difference at the front...
But, getting this correct I'm sure will help with vibration reduction...

Scotty

Quote from: 1340evo on August 26, 2021, 03:34:43 PM
If anything, it's forward as the bolts right at the back of the slot, and as I say above, would need to be 35mm out to get a 3 deg difference at the front...
But, getting this correct I'm sure will help with vibration reduction...

35mm? I don't think your math is correct it would only have to be a pushed forward and up a little bit at the rear to make the front mount go like that.
I am no engineer and cannot do the math but a fulcrum and a lever in mind suggest to me that you missed something doing the calcualation.

Short shocks back and down and long shocks up and forward.

1340evo

Why would the shock length influence the front mount angle / position?

I am an Engineer and the math's are right. To get the bracket to lay flat on top of the mount, you'd have to lift the back of the engine 35mm to recover the 3 deg or so its out.. 3 deg over around 660mm (front mount point to rear mount point) is more than you think ;)

HogMike

Quote from: 1340evo on August 27, 2021, 02:06:49 AM
Why would the shock length influence the front mount angle / position?

I am an Engineer and the math's are right. To get the bracket to lay flat on top of the mount, you'd have to lift the back of the engine 35mm to recover the 3 deg or so its out.. 3 deg over around 660mm (front mount point to rear mount point) is more than you think ;)

If you could find another fxr to compare dimensions from the drive train to the frame it may help.
I would not modify the mount until all other dimensions are verified: stabilizer links to frame, etc.
Are you sure the frame is not damaged?
My frame to engine mount looks to be parallel with the mount in place. Why yours is not is curious.
:idunno:
HOGMIKE
SoCal

1340evo

Everything else looks good.. I can ride the bike, take my hands off the bars, turns left same as it turns right so I'm sure it not bent, and it would have to be a mile out to cause this I'm sure.
When I got the bike, the rear mounts were on upside down (so on the wrong side) and the hole in the mount was around 5 o'clock.. I've since changed that putting the hole to 11 o'clock so that bits correct now. As it was, it must of been even worst?
I've bent a few bits of metal at work today and made some clamp plates for the existing mount. I can put it in the vice tonight and see if I can add another 3 deg to the bend. If not I'll take it to work next week and use the gas on it or make a new mount plate.
Other than the rear hole on the gearbox being lower than std in the casting (where there versions on this) I'm foxed.
Heads to frame clearance looks okay and equal etc.

May be its a new mount as it does look new for sure.. and its not been bent correctly in the first place??  :nix:

HogMike

If you can get another front mount (my book shows 47159-79A) I think I would go that way before trying to bend the one you have.

Regardless, even if you get everything to line up "properly" it may still vibrate.

I've had good luck with the concave style of bushing on my evo but it's not YOUR bike.

Good luck and keep us posted.
:smiled:
HOGMIKE
SoCal

Scotty

Quote from: 1340evo on August 27, 2021, 02:06:49 AM
Why would the shock length influence the front mount angle / position?

I don't know the reason but it pushes or pull the transmission mount away from being centered in the hole and puts pressure on the mount.
Seen it more than a few times now so I do not attach the shocks until the motor/tranny are aligned when installing in unknown combination.
Take the chrome buttons out the swingarm ends and see if the mount is centered and in the same position both sides.


capn

1340evo, Take it to a Harley dealer and see what they say.The baggers used those mounts till 06.

1340evo

well, it wont bend ... hitting it as hard as I can in a bigger vice that this on a sold steel bench... no way.. must be made by snap-on :)


98fxstc

If the obvious causes do not provide a solution, maybe the fit is due to a variation in the engine casting or a variation in the frame mounting location or a bit of both.
How about making up a wedge shaped spacer to fit with the front motor mount. (2.5 mm for 50mm dia )
Then everything will bolt up in its happy place ?