What is the use of these shims?

[RempageR1]

Hi,

When searching for some info I found this picture on Sean`s facebook site:



Can someone explain what these shims do? During assembly, the bearing is placed a bit to the right and when the crankcases are joined, the cover plates are attached moving the bearing to the left (ensuring it sits perfectly against the cover plates and there is no gap at that side. Since it would normally not move all the way to the left, it seem to me the shims would not engage between the cases and the bearing.

Question behind the question: My `85 bike doesn't have these shims and I`m wondering if I should add them.

 

[one2dmax]

The shims are used to set the tooth engagement. In this picture I have the shaft shifted over to allow for easier installation of the lower half of the engine case. Once that is done I push this shaft back and install the retainer plates. There are shims in this location if/as needed as well as shims on the mid gear going out of the back of the engine if and as needed. Almost always there is at least one shim here but it may be possible that one was not required.

 

[gentsvmax]

I watched a guy set-up a ford 9', he tried to explain the importance of the correct load, lash, backlash and gear pattern and how running gears cut at these angles and radius can run loose, too tight and too hot or noisy if not correctly shimmed. Well, like I said, he tried to explain it. I could understand the use of the dial indicator, the inking if the gears to "read the pattern". What is amazing is his knowledge based on time and experience of how and where the torque is applied to the gears. I know those shims, for as simple as they seem can make or break the longevity of the final drive.

 

[MaxMidnight]

The shims are used to set the tooth engagement.

...or to put it another way, it set how deep the teeth of the pinion mesh with the crown wheel. Often referred to as 'depth of mesh'.

Have a look ath this:

 

[sdt354]

If I didn't see any shims installed I'd check the lash/engagement and verify that it's in spec. Just to make sure it wasn't neglected previously by someone else. Damon's video covers it well. The manual addresses it also.

 

[RempageR1]

If I didn't see any shims installed I'd check the lash/engagement and verify that it's in spec. Just to make sure it wasn't neglected previously by someone else. Damon's video covers it well. The manual addresses it also.

Thanks, I did the lash measurement and was a little out of spec (0.18mm vs 0.05-0.15mm), so for the outgoing shaft I ordered some smaller spacers which should fix the excess lash I have now.

The shims of the ring gear are calculated by using the numbers on the ring gear and a number on the crankcase. The thing is, the crankcase doesn't have any number stamped on it so I have no way of measuring it. The ring gear does has a '-0' stamped on it but that`s literally only half of the equation.

Based on the excellent video posted by MaxMidnight, I did some additional studying and found out you can measure the thrust and coast contact using special grease. Example:

So I will try and see if I can do the same type of measurement. Hopefully some normal chain grease also works, if not hopefully you guys can point me to a readily available substance I could use to measure this. If none are available, I`ll try to find this grease somewhere.

Finally, I learned that if there is too much play in the pinion, there will be a whine noise when coasting, which is exactly what I heard. Fun stuff!

 

[RempageR1]

Also a very nice example:

 

[Radioguylogs]

Hopefully some normal chain grease also works, if not hopefully you guys can point me to a readily available substance I could use to measure this. If none are available, I`ll try to find this grease somewhere.

There is a product called "Prussian Blue" that is a grease made especially for this purpose. I think I ordered my online.

I bought some and tried to use it to shim my V65 output gears, but honestly, I could not interpret these results authoritatively:

 

[MaxMidnight]

From what I can see on your pics you have applied it far too heavy.

When used as as Marking Blue it is used for marking out although I can see no reason why it couldn't be used to check wear patterns.
You would normally dilute it with methylated spirit and apply a thin coat. Once this has dried a scriber would be used to mark out where machining is required.

When mixed with grease to create a non-drying medium it is used to check the flatness of a surface.

A bit more detail here.

 

[Radioguylogs]

Steve:

I suspected it was too thick also.

 

[sdt354]

Simulating a load to get a good engagement reading?

 

[caseyjones955]

We used plain ol' ink in truck/diesel tech, load up the gears with a pry, rotate in the driven direction and read the teeth. It can get monotonous but this should not be skipped, especially if new or different parts are being replaced. A final drive with proper lubrication and backlash should outlast the vehicle 3x over. Not counting the overzealous motorist and spider gear incompatibility that wouldn't apply to bikes anyway. I would never hurt a spider gearset, honest...

If you dont have anything else go ahead and sacrifice an ink pen, it's worked for me in a pinch. One of those old timer tricks I was lucky enough to learn.

 

[Redbone]

Lots of good info here, saved it for use on Redbone or my Super Tenere which has a very similar looking shaft drive.

 

[RempageR1]

Thanks for all the great info. I reshimmed the pinion to get the backlash in spec again. After that, I tried putting some ink on the ring gear but that didn't work that well as the ink remained. Doing the opposite (inking the pinion and then looking at the ink transfer on the ring) resulted in ink remains that were in the center of the ring gear, so it should be fine now. Thanks for all the help!

 

[sdt354]

Back when learning to set up rearend gears we used "White Lead" to mark tooth engagement. I've used thick grease too. Both need to be cleaned before final assembly. Or, as in Damon's video, and the Yamy manual, use a dial indicator and a DIY made locking tool.