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M8 Powertrain alignment

Started by Thermodyne, May 06, 2021, 11:38:45 AM

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Thermodyne

I have a 2019 FLTRU that has a misalignment in the power train  It needs to be shifted to the right for the front link bolt to line up with the hole in the frame.  This is the amount of mismatch with the scooter upright on the table in the wheel vise.  No jack and not leaning to one side or the other.



On older scooters keeping the links free of load has been part of keeping the motor vibrations under control, and the manuals speak to being able to just drop the bolts through the links with no resistance.  The 2019 manual says bolt it up and torque it.  And on my twin cam, this bolt lines right up with the hole.

Now this scooter has had more engine vibration since day one, than the 18 it replaced, so I'm wondering if this is why.

And I'm wondering if I should fab up an adjustable link to install with no load, or just use this one and lever the motor over to line it up?

In asking folks around here, the answers run from "they are all like that" to "never had that issue on one"  And the ones who think they are all like that, just make em  fit. 

What do youens think?  And have any of you run into this on the M8 baggers?



HogMike

Quote from: Thermodyne on May 06, 2021, 11:38:45 AM
I have a 2019 FLTRU that has a misalignment in the power train  It needs to be shifted to the right for the front link bolt to line up with the hole in the frame.  This is the amount of mismatch with the scooter upright on the table in the wheel vise.  No jack and not leaning to one side or the other.



On older scooters keeping the links free of load has been part of keeping the motor vibrations under control, and the manuals speak to being able to just drop the bolts through the links with no resistance.  The 2019 manual says bolt it up and torque it.  And on my twin cam, this bolt lines right up with the hole.

Now this scooter has had more engine vibration since day one, than the 18 it replaced, so I'm wondering if this is why.

And I'm wondering if I should fab up an adjustable link to install with no load, or just use this one and lever the motor over to line it up?

In asking folks around here, the answers run from "they are all like that" to "never had that issue on one"  And the ones who think they are all like that, just make em  fit. 

What do youens think?  And have any of you run into this on the M8 baggers?


I just got my 2019 cvo limited back together end of November and took a bunch of pictures on disassembly.
Put everything back on and the linkage rod lined right up.
I could see that maybe it would take a little nudge to drop the bolt through, but it WAS pretty close.
No vibration increases that I have noticed and I usually check things out every oil change.

"Make 'em fit" well, maybe within reason?
:missed:
HOGMIKE
SoCal

Tacocaster

Don't force it or "lever the motor over". Don't even "crank on the adjustors till it fits". Nothing good ever comes from that approach.

Without knowing the history of your bike it's hard to say what originally caused this but you can make it right, if you have at least some mechanical ability.

You have an SM, correct? Is there not a section on Vehicle Alignment in it anymore? Newer SM's - I know they've been pulling technical detail out of them over the years.

If you decide to do the alignment yourself, it's not hard at all but can take some time. You'll need a few tools likely (a couple of line lasers & a digital level that shows deviation). I also recommend removing the adjustors and "working them" a bit to free them up as they can be stiff. Put them back in with the same orientation.

There's a few good vids on YouTube for earlier Twin Cams that will walk you through. Although your dealing with a '19, the basics are the same.
We're all A-holes. It's to what degree that makes us different.

Thermodyne

Scooter has never been down and only has 5500 miles on it.  So its most likely that it was built this way.

Been doing some digging into this and there is not a "factory approved" alignment procedure on the frame that has been released for public consumption that I can find, its either good or you replace it.  That's prolly why insurance companies are so quick to right them off these days.   But there are some aftermarket systems that check alignment with various methods.  And they use an adjustable dog bone to correct rear swing arm shafts that are not perpendicular to the ground.  They measure the distance between the shock mounts and use the dog bone to equalize it left to right. 

Since there is absolutely no adjustment for the 4 lower mounts, and the scooter tracks just fine, I think I will just level the frame off of the side plate and then see where the motor is in relation to it.

Then it looks like I can use an old three point link to replace the dog bone.  I'll set it up so it slips on, then count the turns to make it equal the length of oem.  Then try it both ways.

If it likes being shorter than oem, then I'll fab up something that looks decent and replace it.  If not, I'll put the dog bone back on.

Thermodyne

OK, I sat down and thought this through.  After watching a Rack and Pull video on how they straighten frames, it sort of dawned on me.  They drop the shocks and use an adjustable  dog bone to equalize the distance between the shock mounts.  The scooter in the video was said to have some sort of handling issue, which they suggest you see them about rather that just replacing the shocks.  But I'm thinking shocks might also fix the issue.  And that this is an issue that people have been fixing with shocks all along

I think the issue is caused by the rear shocks.  One OEM shock carrying most all of the weight.  The frame being the fixed points, the swing arm is able to influence the rest of the power train, within the limits of the elastomer in the 4 motor mounts.  So the heavy sprung shock induces a higher load on the left side.  That moves the left rear corner down a smidge.  Which in turn moves right front mount up a smidge.  That causes the dog bone mounting point to move to the left and because of the distance above the lower mounts, it moves more than a smidge.   And a scooter that has been sitting on the wheels for a year or more with oem shocks, is not going to spring back into proper alignment when you remove the shocks.  Those for mounts will need time to relax back into their unloaded positions. 

Past that, the link is almost the same length as an old 3 point link, so there are lots of sources for adjustable links. 

Don D


swingarm

Quote from: Thermodyne on May 06, 2021, 04:34:16 PM
OK, I sat down and thought this through.  After watching a Rack and Pull video on how they straighten frames, it sort of dawned on me.  They drop the shocks and use an adjustable  dog bone to equalize the distance between the shock mounts.  The scooter in the video was said to have some sort of handling issue, which they suggest you see them about rather that just replacing the shocks.  But I'm thinking shocks might also fix the issue.  And that this is an issue that people have been fixing with shocks all along

I think the issue is caused by the rear shocks.  One OEM shock carrying most all of the weight.  The frame being the fixed points, the swing arm is able to influence the rest of the power train, within the limits of the elastomer in the 4 motor mounts.  So the heavy sprung shock induces a higher load on the left side.  That moves the left rear corner down a smidge.  Which in turn moves right front mount up a smidge.  That causes the dog bone mounting point to move to the left and because of the distance above the lower mounts, it moves more than a smidge.   And a scooter that has been sitting on the wheels for a year or more with oem shocks, is not going to spring back into proper alignment when you remove the shocks.  Those for mounts will need time to relax back into their unloaded positions. 

Past that, the link is almost the same length as an old 3 point link, so there are lots of sources for adjustable links.

I think you are correct.

BigT

I had the same alignment issue when I did my 124" build. I did some internet research and it was a simple fix as putting the jack on the front left side of the motor and lifting it into position. Absolutely no issues 20,000 miles later. No vibrations or cruising straight down the road.

Thermodyne

Issue resolved.

Replacing the shocks corrected the misalignment.  Right after I bolted the shocks on, the misalignment had reduced by about half.  Then after sitting over night, it lined right up today.




tommy g

Curious as to how you like those shock, they look good.
09 FLSTC
85 FXEF

Thermodyne

No idea yet, scooter is still on the lift.  I should know later this week, just need to flush the front side of the antilock system and its ready to go.

Thermodyne

Update on the shocks.  They started out on the stiff side, but eased up a little after they got some miles on them

The scooter handles a lot better now then before, but it also got cartridge's in the front and a rear strut at the same time.

For the price, its a real good shock.

hrdtail78

I have never relied on the bolt alignment to indicate anything.   With stock shocks.  They put a different load on each side of the swing arm because each shock has a different job.  Best way to tell.   Align your front tire with back using protractors on disc and then use protractors to check vertical alignment of rotors. 

But you can't go wrong with those shocks. 
Semper Fi