To Drill or not to Drill

J. M. Leadbeater · May 9, 2015

I notice the reference to oil migrating down the gearbox main shaft into the clutch .
If this were to happen I would, these days now I am a LOT older and hopefully a tad wiser, look for the cause of the problem. For example has the bike owner polished the gearbox inspection cover blocking off the tiny breather hole causing the box to breath through the main shaft carrying oil with it....is the gearbox filled to the correct level with the correct grade of oil....is the clutch pushrod of the correct diameter (6mm). ...is the main shaft a genuine Norton one or a cheapo made in India etc which has an oversize hole through it. Personally the next time I rebuild a box I will probably fit a single sided sealed bearing to the main shaft so that oil within the gear case can lubricate the bearing but not allow it to migrate through the bearing and onto the main shaft. I was once told that a BMW car valve seal can be employed but as to its part number I have no idea....

Old Scratcher · May 9, 2015

I must admit. Some of those "crop circled" covers look damn sexy! I do have a couple of spare ones, amongst the truck load of spares that arrived with the Cafe Bike. So I may draw some nice designs on it, until I find one I can live with. I'll be fitting mesh to whatever I drill, as I live in a part of the world that's especially grimy. & I'll position them out of the rain & away from any splash zones. It'd be interesting to run both covers & see if there is much of a difference, & if that's am improvement worth the modification.

mikie3117 · May 9, 2015

I learned form work on my Ducati that the rotation of the clutch assy. actually sucks in air if an opening is made in the center.
Another opening will allow the exit of the warmer air. You can see this with a piece of paper when it is running. There are some neat screw in screens that allow this without drilling holes on a Norton. The air can bring in dirt though. It would be a shame to drill a hole in a nice Norton primary cover.
Check e-bay for the pre-made screens. They are less than $100 for a set.
Mike

pete.v · May 9, 2015

mikie3117 said:
I learned form work on my Ducati that the rotation of the clutch assy. actually sucks in air if an opening is made in the center.
Another opening will allow the exit of the warmer air. You can see this with a piece of paper when it is running. There are some neat screw in screens that allow this without drilling holes on a Norton. The air can bring in dirt though. It would be a shame to drill a hole in a nice Norton primary cover.
Check e-bay for the pre-made screens. They are less than $100 for a set.
Mike

http://www.eurojamb.com/norton-750-850- ... -1551.html

Old Scratcher · May 9, 2015

pete.v said:
http://www.eurojamb.com/norton-750-850- ... -1551.html

Oh Yeah! I LIKE those!
Good price too. I'm definitely giving them a go. I like the fact that no drilling's required too. :lol:

dynodave · May 9, 2015

save your cases
Drill out the 4 spot welds that hold the felt seal holder 060769 on the back of the primary .
remove holder... you can still buy new ones for a few bucks from AN
air can get in
shielded from the rain
works fine for me since 1988

ADDED
oops? saw next thread
if your is the MKIII then forget this^^^

Hobot · May 9, 2015

hobot is infamous driller so love to see useless material removed in artful functional ways. I like the case logos paint filled for a contrast so might consider a bright color fiber or foam layer held behind the fancy stone/beetle truck splash screen, holes, slashes or spirals. Remember there is not really a heat issue so no logic in trying to fudge protection for more efficient cooling so concentrate on making our eyes cause a throb in our junk.
one comic accepted venting would be some louvers.

Fast Eddie · May 10, 2015

Old Scratcher said:
pete.v said:

http://www.eurojamb.com/norton-750-850- ... -1551.html

Click to expand...

Oh Yeah! I LIKE those!
Good price too. I'm definitely giving them a go. I like the fact that no drilling's required too. :lol:

I like them too. Does anyone know if any of the UK suppliers sell similar?

Hobot · May 10, 2015

Dynodave method of leaving out the air blocking felt seal is cleaver way I first did Ms Peel but after finding How Feaking Good Peels different tri links were and boring sports bikers were took to leaping off my driveway culvert ~4ft drop into over grown rocky creek beds and raw woods ravines soon totally enclosed - sealed even that entry of water and grit. So by far Peels hot flings in hi summer heat was fully sealed no temp issues down there. Btw beside holes has anyone done engraving on cases as I am thinking about now.

acotrel · May 11, 2015

I have a theory about old bikes - we are only taking care of them until we die. When you drill holes in the chain case it can never again be used on a really concours bike. If the screw-in screens are OK, I'd use them. I try to never destroy British bike parts, they are not usually throw-away items.

Old Scratcher · May 11, 2015

acotrel said:
I have a theory about old bikes - we are only taking care of them until we die. When you drill holes in the chain case it can never again be used on a really concours bike. If the screw-in screens are OK, I'd use them. I try to never destroy British bike parts, they are not usually throw-away items.

I feel the same way, which is the reason I started this thread, & why I'm going for the screw in/no drill option, if I decide to do it at all. Knowing it's not an essential mod, or even needed, means it's no longer on the priority list. & if I do it at all, it'll be for cosmetic reasons, when the disposable income allows. Which considering the wish list if things I'd like to do to this bike, is a long way into the future. & whatever I do to this bike, it'll never be anything that can't easily be reversed to factory specs. I don't mind playing with these museum pieces. But I'll never forget what rare spares they are, & I'll always treat them with the respect & reverence that they deserve.

To Drill or not to Drill

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