Question for the Experienced Experts on Drive Line Lash

[sib]

No complaint, just curiosity.  I noticed that when my V7-II is in 1st gear, with the engine off and the clutch fully engaged, I can push the bike back and forth about 3-4 inches.  I think this represents the total gear, spline, U-joint, and drive puck lash in the entire system, from engine output shaft to rear axle.  Is this considered to be a normal amount of lash?  Does anyone out there have a significantly different amount of lash?  Thanks.

Sam

[rocker59]

Guzzis have quite a bit of slack in the driveline.

[Arizona Wayne]

Quite frankly I don't think you are doing your bike drive line any favors.  If you want to measure driveline slop that shows wear, suspend your rear wheel with tranny in neutral and then rotate your rear wheel forward/aft.  When your drive line is tight, that means there is no excessive slop(wear).  Any looseness is a measurement of drive line wear.

[ohiorider]

I was under the impression that much of the slop was in the final drive.  Big surprise both times I pulled final drives.  Neither the R100GS  nor the 1200 Sport final drives exhibited more than a tiny bit, if any, slop, when I held the wheel hub and turned the pinion gear by hand.  Seems like most of the slop or play might be in the transmission dogs, and in the splines.  Why so much in Beemers and Guzzis?  I'm posing this as a question to those who know these bikes much better than I do ....... is it possible the trannys (specifically the shift dogs) are designed differently to deal with the engine-speed clutches?

[Vasco DG]

There is only a few thou backlash in the bevel gears. All of the 'Backlash' people are feeling is from the engagement dogs that engage to lock each gear set to the shaft for that particular ratio.

Pete

[Peter from Sch'dy]

I believe most of the backlash in my '07 Norge is from the cush drive assembly in the transmission. The Carc on my bike has minimal lash. I think I remember the early Brevas had a recall which was not extended to the other CARC bikes perhaps because the issue did not result in catastrophic failure, but rather just atrocious noise. Mine is very noisy if the clutch/throttle/shifter are used in a sloppy manner. It currently has 65000 miles without failure.
  How this may relate to your V7 in unknown.

Best,
Peter

[sib]

There is only a few thou backlash in the bevel gears. All of the 'Backlash' people are feeling is from the engagement dogs that engage to lock each gear set to the shaft for that particular ratio.

Pete

Now, that's an informative answer.  I hadn't thought about the shift dogs.  Makes sense.  Thanks!  So far, no one has actually answered my original question about whether 3-4 in was normal or excessive, but maybe someone eventually will.

[sib]

Quite frankly I don't think you are doing your bike drive line any favors....

I seriously doubt that gently pushing the bike back and forth is producing any more stress on the drive line than accelerating and decelerating at speed.  But, what do I know?

[oldbike54]

I seriously doubt that gently pushing the bike back and forth is producing any more stress on the drive line than accelerating and decelerating at speed.  But, what do I know?

 Enough to ask an intelligent question . No , you aren't harming the bike .

  Dusty

[Vasco DG]

I believe most of the backlash in my '07 Norge is from the cush drive assembly in the transmission. The Carc on my bike has minimal lash. I think I remember the early Brevas had a recall which was not extended to the other CARC bikes perhaps because the issue did not result in catastrophic failure, but rather just atrocious noise. Mine is very noisy if the clutch/throttle/shifter are used in a sloppy manner. It currently has 65000 miles without failure.
  How this may relate to your V7 in unknown.

Best,
Peter

d

The early Breva and Griso face cam preload issues were rectified by the time the Norge came on the scene. Any box will be noisy if you change gear sloppily.

Pete

[Peter from Sch'dy]

I'm trying to figure out why there would be such a large variance in the backlash from bike to bike. Mine, as well as others seem to have significantly more than yours and your customers. It seems to me that in the normal process of manufacturing and assembly, the one place with the highest potential to influence backlash would be the cush assembly where improper shimming could lead to excessive backlash. This is the reason for the recall, yes? Gears, dogs, bearings and other parts manufactured with dimensional control should be within a tolerance that would keep backlash pretty consistent from bike to bike . Where else would it come from?.

Best,
Peter

[Orange Guzzi]

I have my 03 Aluminium on the rack for a tire change now.  I was looking at the same thing. When I started following the drive line from the tire contact patch to the crankshaft, I found that there are lots of places for clearance slop to occur.  The accumulated effect is multiplied when you move the measurement from the center of the rear axle to the contact patch.  Rear drive spline, gear box rubbers, gear box pinion gears, drive shaft splines, output shaft, transmission gears, transmission dogs and springs in clutch plate all add up to a few degrees of free play.   I did find a massive amount of movement in cush drive rubbers which I replaced. 

[Peter from Sch'dy]

Inches of rotation as measured at the point where the tire touches the wheel:
1st gear 1.5"
2nd gear 1.75"
3rd gear 1.875"
4th gear 1.925"
5th gear 1.75"
6th gear 2.0"

[sib]

Inches of rotation as measured at the point where the tire touches the wheel:
1st gear 1.5"
2nd gear 1.75"
3rd gear 1.875"
4th gear 1.925"
5th gear 1.75"
6th gear 2.0"

I presume these numbers are for the Norge you mentioned in an earlier post.  It would be interesting to have comparison numbers for other models.  Thanks.

[Vasco DG]

You guys are determined to find something wrong with your bikes aren't you?

The early Brevas and Grisos made a horrendous noise because the stacked Bellville washers that controlled the face cam shock absorber were of inadequate springiness and collapsed allowing the cams to whack back and forward against each other making a horrible din. The cure was to place some shims under the end cap to add more preload. Later bikes had a different spring stack, problem solved. It contributed little to driveline backlash.

The backlash you are feeling in the driveline is 99% down to the mesh of the dogs in the gearbox and is normal and unavoidable.

The End.

Pete

[Peter from Sch'dy]

I presume these numbers are for the Norge you mentioned in an earlier post.  It would be interesting to have comparison numbers for other models.  Thanks.

Yes, 2007 Norge. It would be of interest to me as well.

Best,
Peter

[atavar]

I have similar numbers on my 2008 Norge.  Every mech I talk to is not surprised and says "yeah?"

[atavar]

On the plus side my '08 Norge shifts easily and noiselessly without the clutch on spirited accelerations.  Just find a neutral throttle and snick it to the next gear.. 

[rodekyll]

"Inches" of slop doesn't mean much in my opinion.  Depending on wheel diameter and where you measure it it means something different. I think degrees of rotation would be more informative.

[Peter from Sch'dy]

"Inches" of slop doesn't mean much in my opinion.  Depending on wheel diameter and where you measure it it means something different. I think degrees of rotation would be more informative.

Agreed.
But here's some more data from the garage anyway . Don't know how to easily measure degrees of rotation so will report radius at measurement point, backlash in inches in each gear, mileage, bike.

Eldo, 58000miles, 9"r
1st 1"
2nd .75
3rd 1.125
4th 1
5th 1.1

FZ1 51500 miles, 8.5r
1st 1.125
2nd 1.375
3rd 1.25
4th 1.5
5th 1.25
6th 1.125

SP111 67000 miles, 9r
1st .75
2nd .875
3rd 1
4th 1
5th 1

T3 51000 miles 9r
1st 1
2nd 1
3rd .875
4th 1
5th 1.125

Falco 16700 miles 8.5r
1st 1.5
2nd 1.75
3rd 1.5
4th 1.5
5th 1.75
6th 2

S2R 12300 miles 8.5r
1st 1.5
2nd 1.5
3rd 1.75
4th 1.5
5th 1.375
6th 1.625

Yeah, I've got too much time on my hands..

Best,
Peter

[sib]

"Inches" of slop doesn't mean much in my opinion.  Depending on wheel diameter and where you measure it it means something different. I think degrees of rotation would be more informative.

[Lecture mode on]:  When I was a university professor and ran a good size research group, I taught my grad students and postdocs to record and report the raw data whenever possible.  The measurement I reported here was the distance my wheel travelled, not degrees of rotation.  Now, If I let you know that my bike has OEM wheels and tires, the rear tire being size 130/80-17, then you can convert my distance measurement to degrees rotation, or any other derived number, if you wish.

I once calculated the speed of light in furlongs per fortnight.  The answer wasn't very useful.

[Kev m]

But here's some more data from the garage anyway . Don't know how to easily measure degrees of rotation so will report radius at measurement point, backlash in inches in each gear, mileage, bike.

<snip>

Yeah, I've got too much time on my hands..

    

[Peter from Sch'dy]

Conclusions based on this massive data?
1. With the possible exception of my Norge and Sam's V7, Guzzis have minimal driveline backlash as compared with transverse crank chain drive bikes.
2.  Eldo, T3 and SP111 were measured on 9" radius effectively increasing the backlash measurement over 8.5 radius as measured on everything else here.

The major design differences influencing backlash between my Norge and the older guzzis listed here is Norge has no splines or rubber cush in the rear wheel (my eldo has a T rear brake/wheel) which would decrease the available sources of backlash.
 

Best,
Peter

[sib]

Many thanks to Peter and the rest who contributed useful data.

[Orange Guzzi]

I completed my tire change on my bike (michlen pilot activs).  I added tire weights, ended up with the spoke weights.  Before I removed the rear tire and the rear end elevated, I put the bike in gear and rotated the tire in both directions.  I was surprised at how much free play I was getting from just the cush drive rubbers (24,000 miles).  I purchase a new set of rubbers from MGcycle for less than $20.00.  Cleaned everything up, greased and reassembled.  I took the  bike for a ride last night and was impressed with the results.  There is much less free play, seams to be less vibration from the wheel assembly bumping against the rear gearbox.  I did not expect such a noticeable difference for the better.

[rodekyll]

[Lecture mode on]:  When I was a university professor and ran a good size research group, I taught my grad students and postdocs to record and report the raw data whenever possible.  The measurement I reported here was the distance my wheel travelled, not degrees of rotation.  Now, If I let you know that my bike has OEM wheels and tires, the rear tire being size 130/80-17, then you can convert my distance measurement to degrees rotation, or any other derived number, if you wish.

I once calculated the speed of light in furlongs per fortnight.  The answer wasn't very useful.

 .. . or you could skip the furlongs, fortnights, and oem/2 conversions to whatever someone else's roll distance is relative to tire size and go with degrees which would be the straight-up same for everyone's wheel regardless . . . . oh . . . .wait.  college professor.  nevermind.

[Arizona Wayne]

When you measure driveline slop like I recommended, on centerstand, in neutral, fore/aft rotaton of the rear wheel, you are only measuring play in the driveline(U-joint).  Most all the other slop is out of play. 

[sib]

When you measure driveline slop like I recommended, on centerstand, in neutral, fore/aft rotaton of the rear wheel, you are only measuring play in the driveline(U-joint).  Most all the other slop is out of play. 

Can't quite figure that out.  Please enlighten.

[sib]

.. . or you could skip the furlongs, fortnights, and oem/2 conversions to whatever someone else's roll distance is relative to tire size and go with degrees which would be the straight-up same for everyone's wheel regardless . . . . oh . . . .wait.  college professor.  nevermind.

Well, like the professor tried to explain, what I measured is distance, not degrees.  Yes, I could have converted to degrees.  But then that wouldn't have been my measurement, it would have been my calculation based on my measurement.  Sorry, you'll have to take the make-up exam.

[Arizona Wayne]

Can't quite figure that out.  Please enlighten.

I don't try to be exact.  Just try to get an idea of the condition of my drive train for what parts may need replacement.  My motto, 'if it ain't broke, don't fix it.'