Tach seal mod for 850 Commando (2010)

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Mark Cigainero

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Can you do the tach seal mod for a Commando on a drill press or is a mill needed??? Where do you get the seal. I need to do it on several bikes. Thanks Mark Cigainero
 
I did mine in a vise with a VSR electric drill and used a Honda seal (forget the part number) but it used to be in the USNOA's tech digest. I have it stashed somewhere. The Honda part may or may not be available any longer.
 
Check the Old Britts website, under Tech Articles.
Fred has a concise write-up with bore size and part numbers.
 
T.C. said:
Fred has a concise write-up with bore size and part numbers.
Click to expand...


I did this modification some years ago, as I happened to have an odd (if I remember correctly) 7 x 14 x 4 mm rotary shaft seal amongst my supply of spares which looked as if it would do the job.
I drilled the underside of my MkIII's tacho housing to a depth of approximately 4mm using a 14.0 mm drill bit with a hand held electric drill, and then Loctited the seal in position, and it's never leaked since.
 
Does anyone have the standard trade dimensions for that Honda seal P/N 91207-222-000 ?

If this image is accurate,
Looks like 7 x 14.5 x 5
Can anyone confirm?
Tach seal mod for 850 Commando (2010)
 
Last edited:
https://www.motionindustries.com/productDetail.jsp?sku=01293548

CR 2450 now SKF $3.49

You might want to note that there were 2 designs of tach housing and shaft. You will have difficulty assembling the type with the o-ring groove toward the top of the shaft.
Once you put a seal you might want to put a bit of oil/grease in the housing or the shaft will be running dry...

This mod was listed in the first USNOA tech digest done in the early 80's.
 
Last edited:
If you don't want to mess with it, there are folks who do the job for you. Phil at Fair Spares America does the mod, as well as AMR in Tucson.
 
dynodave said:
https://www.motionindustries.com/productDetail.jsp?sku=01293548

CR 2450 now SKF $3.49

You might want to note that there were 2 designs of tach housing and shaft. You will have difficulty assembling the type with the o-ring groove toward the top of the shaft.
Once you put a seal you might want to put a bit of oil/grease in the housing or the shaft will be running dry...

This mod was listed in the first USNOA tech digest done in the early 80's.
Click to expand...
I did the seal mod 7 years ago, annointed the shaft above with moly grease a few times. It’s pushin oil now. I just thought I might have one in old machinery parts.
 
B+Bogus said:
For the less adventurous there's this...

https://andover-norton.co.uk/en/sho...-drive-housing-with-oil-seal-06-1090-06-5200-
Click to expand...

1. Good to see the seal is put in the correct way to hold in crankcase pressure...have seen others put it in the wrong way.

but:

2. but I much prefer the 2450 seal which is .5"OD which allows the gear (.575") to thrust against the aluminum metal of the housing instead of the larger metric seal... which causes the tach gear to thrust on rubber because the seal is bigger than the gear OD...especially since the top gear chamfer widely varies and is almost always significantly smaller than the 14.5mm.

swooshdave said:
Tach Seal
Click to expand...
 
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