Seal advice please

Hi all,

been quiet but have been working away slowly but steadily on the old beast. Have a couple of questions about seals and if any one can assist, I'd appreciate it. I've got the transmission covers off, trying to track down a leak (or leaks) from somewhere on this side. I've replaced the kick-start seal (just keeping an o-ring here) and the gearbox input/output shaft seal so far in this exercise.

Next item is the felt seal on the gearbox shaft. I'd ordered replacement parts prior to pulling it down and find that the felt seal is well and truly knackered. It is held in place by two identical plates that seem to be spot-welded together. Can I just replace the seal or does it have to be done by removing these plates and then welding the new ones together again? If I have to replace the plates can I just pop-rivet the two together or use some other manner to secure them?

I see the main seal is also visibly weeping now it's all apart. Bet this was the real culprit all along. I've got the old seal out and it's a little on the hard side to be terribly effective any more. It has an o.d. of 1.75 inch, an i.d. of 1.15 inch (approximate - I don't have a vernier or micrometer). So... not wanting to wait over a week for an interstate replacement to put it all back together, is this seal generic and if so, what is a more accurate description for a correct replacement so I can go a seal-hunting?

As always, thanks in advance,
Dave.

Dave,

you can replace the felt seal by prying the old one out and replacing it with the new one. No disassembly of the steel retainer plates required. It helps to soak the felt seal in oil before inserting it. Seems to make it easier to compress the felt.

Don't know about the crankshaft seal. I've always just used Norton replacements. I've had better luck with the ones that are fully coated in rubber, as opposed to the ones with a bare steel shell.

Ken

Ditto on the felt seal wetting it to work back in the plates, but I use water instead of oil, as the water will dry out leaving clean felt but oil soaked means its starts out oil soaked to drool.

Kick lever oil ring is made too loose to seal well so a trick is to put cigargett foil in the groove to tighten up the O ring on shaft and then with the parts lightly oiled smear on some silly cone and install and wait over night before moving. That worked about as well as machined seal mod I had done on another gear box.

Search breather posts for even more better sealing success, to point rust on fasteners becomes an issue.

Thanks guys, much appreciated.
Will try water with the rear seal. Looks like I'm stuck with the genuine item for the crank. The kickstart... hmm... I'll have a look at the work required to replace the o-ring with a seal. DIY type job?

Where it's at at the moment:

Just that little dribble.

Dave,

Do you have a crankcase PCV valve? If not, its near impossible to seal the crankshaft. Too much crankcase pressure buildup.

Yeah, been wondering about that Jim. Wasn't sure if it was wet-sumping or crankcase pressurisation that has done the seal in. The plastic is still quite pliable and the lip in good condition - it hasn't failed from age/wear.

If you want, replace those 3 crank case bolts with studs and nuts. The crankcase thread is 5/16-18 and you can get at the auto store a 1" stud 5/16-18 on one side and 5/16-24 on the other. Put them in the crank with red locktite and hopefully the crank to primary leak is gone. Make sure they don't interfere with the crank. Makes it easier to put the gasket and primary inside cover on too. You will have to grind down the lower stud inside the primary to clear the chain. Get some thin large pattern washers to put under the nuts, don't use a washer under the lower one. Use blue locktite on the primary side nuts.





Hobot recommendation. I liked it.

Dave
69S

Dave, for the gearbox kickstart and gear lever shafts there are X shaped seals available that are more efficient than the simple O-ring standard type. Your crankshaft primary side seal is the metal shrouded one, I have found that these can leak around the outside, there is a rubber bodied replacement that is a tighter fit - Norvil sells these if you order a crank-seal. Regarding the felt washer between the two plates, I normally soak it in oil and compress it between two plates in a vise, the oil is viscous enough to prevent it expanding before you get it in between the plates, by the time you have compressed it there isn't sufficient oil left to worry about. I have also fitted a one way breather valve on mine.

Here is an old post of mine.

"Instead of replacing that worthless oring with another, here is a simple and effective solution.
You must still pop the cover off. Then heat the case around where the oring is with a propane torch or heat gun to pop out the kickshaft bushing.
You can buy this seal, Timkin #240731, seal number 9815 1.25 x 1 x .125 at your local oilseal dealer for around $6.00.
Lay the seal in there with a little locktite, pop the bushing in and you will be good to go and the cover will not be harmed."

Here is a picture of a motor with 2 reed type check valves installed. One comes up off the regular breather( most common) and the other incorporated in into the timing case.

Thanks DaveM, DogT and Pvisserii - so many worthwhile mods, so little spare cash!

Ordered new plastic-covered seal from APC Motorcycles in Brisbane. Should be here mid week.

Investigating the rear further, the old felt jobbie came out in shreds. There was then no way that the new felt seal was going in, with water, oil or compression. I compared the gap to that of the two new plates I have pressed together and found it was well closed up (about 1 mm!) Decided to open it up to the same amount by gently prising the soft steel with a screwdriver. That didn't end well, the steel cracked where the chain or something had rubbed against it (sometime in the distant past) and machined it down to razor-blade thickness. Oh well, I've got new plates, may as well use 'em. Drilled out three of the spot welds and on the fourth the top plate comes lose and slices into the palm of my left hand. Ouch! Damn! (Other expletives!) You EEDJUT! Don't waste the claret Dave, Red Cross donation in a couple of weeks - save it 'till then! Try new plates and felt - yep, that'll do donkey, wrap it in rags, chuck it in the car and will give it to sheetmetal guy for spot welding tomorrow.
Where's the friggin' bandaids...

You are talking about that little spot-welded moving set of plates in the the inner primary, no?

I couldn't find a local to spot weld mine for me, so - thank you Matt Rambow - I drilled four little holes and installed the tiniest little bolts/nuts you ever saw, with copious blue loctite. Obviously, getting the felt seal isn't an issue when you can take the sucker apart...

Works fine so far....!

Yep, they're the ones Brian. Got the new plates spot welded in today. All hunky-dory. Just waiting for my new main seal to rock up in the post. In the meantime - researching crankcase venting and non-return valves ...

Well the plastic coated seal has yet to arrive. Paid for 3-day mail, but it's pointless as they didn't "process" the order until mid-week and thus didn't ship it until Thursday! With Monday being a public holiday here in Aus, the seal won't turn up until Tuesday next week. Crazy. So I had to ride into Elizabeth Street this morning to go to that shop that shall remain nameless. Normally I'd rather chew my arm off than go there. Still, now have a seal.
What I'm thinking of doing is putting the lightest film of auto Silastic around the outside face where it contacts the bore to make sure there's no weep past the outside. Acceptable process?