Tachometer drive leak fix (2016)

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Anyone still doing the bore-and-add the small Honda seal to stop the tach drive from leaking? I want to do this to the flood victim and the fix on the SS clone engine has finally begun to weep after all these years. Used to be a part # in the International Norton Owner's Member Handbook of Tips.
 
Anyone with a good drill press can bore out the tachometer drive aluminum body , only deep enough to accept the modern seal. Mine works great. I use a later type non- scrolled tach shaft with this seal. A Rawhide American seal, but I can't find the number right now , like about 2 dollars. Fit a reed breather to eliminate backpressure too.
 
Yes, I have the drill press, just need a lead to the seal part #. I might just pick the old one out of the '71 and take it to a Honda dealer to see if they can find a couple. If I had the #, I'd just order 2 from Bike Bandit.
 
xbacksideslider said:
I just used a seal out of a Harbor Freight assortment kit.

Thanks, I'll check into that. The '71 is already drilled, so it would have to fit that counterbore.
 
Thanks, bill, for the Honda part number. Found 2 on Fleabay for 12.98 shipped.
 
So what did the # turn out to be?? I'm thinking of doing one too.
 
O.K. , found my notes. Tachometer drive leak fix. Drill out lower end of aluminum housing to tap in a seal. ( The part that enters the motor ). Seal is SKF 2450 HM14R in a small green box. Choose a later non-scrolled shaft. Fit a crankcase breather too...hope that helps. :)
 
gtsun said:
So what did the # turn out to be?? I'm thinking of doing one too.

The Honda seal is 91207-222-000, but they are rapidly becoming unobtanium. The normal parts suppliers don't stock them and the only ones available are nos here and there. I found some on Fleabay, but the prices are breathtaking. I think I will get some of the SKF seals for the flood victim and future use and save the extra Honda item for the SS clone, since it's tach drive is already bored for that one.
 
The Honda seal is slightly larger o.d. at 14mm compared to the SKF at .49" Also, the I.d. of the Honda is a smidge bigger at 7mm compared to the SKF's .25" Old Honda seal I just removed (installed circa 1983, now beginning to weep) measures 7.15mm i.d.
 
I found my tacho drive still leaked after fitting a seal until I added a crankcase breather.
 
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Fullauto said:
I found my tacho drive still leaked after fitting a seal until I added a crankcase breather.
Yea +1
When I got the reed valve kit from Comnoz it cured this leak path.
Cheers,
Thomas
CNN
 
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I have a Comstock sump breather fit with a standard 74 tach drive o-ring seal. It has never leaked, even for the past year and a half after a total motor rebuild.

Until last week.

Now it is chasing clean up the cable and coming out of the tach housing.

I am assuming that the heat from my Maney style exhaust has somewhat sped up the demise of the o-ring on the tach drive shaft, since the nut on the cable housing is mere millimeters from the exhaust.

Thoughts on that theory?

Would the lower seal in this mod last any longer if it is indeed the heat?
 
$33 at Old Britts. Hardly worth hassling with at that price. Plus it helps keep them in business.
 
Yeah, I get that.

However, IIRC I think I have the scrolled drive gear (cant find any pics of that from the tear down), which would defeat the purpose of the seal. So, I would need a new drive gear as well and those are about $65.

If the heat from the header bending directly next to the drive housing is what is causing the o-ring to fail, then isnt it likely to cause the seal to fail as well?

And if so, I wouldnt want to pop for both if the failure would repeat. I would just replace the o-ring periodically when it dies.

I am wondering if anyone with the Maney or @Brooking 850 exhausts see this problem?
 
My tach drive leaked since Day 1. The fix back then (from Norton News) was just to add a second o-ring. This lasted me about 40 yrs until I had the piece machined for a real seal.
 
I wouldn't be concerned if the leak was at the tach drive, but it is spewing out the top of the cable into the tach and running down the headlight shell and fork.
 
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