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?s on replacing fork seals...

wicks

Tuned and Synch'ed
Joined
Nov 26, 2012
Messages
39
1 - is there a difference if I use 2 stacked or single replacement from MG cycle?

2 - looking at manuals, can't determine easiest way to do this, hoping I can take the front wheel and drop legs off without taking apart triples, etc...
 
Wick these are very easy to do as the cartridge damper is the lower(outer) retainer (Top and bottom allen head bolts) and from memory there is a small locator/tab/indent in the bottom of the outer so undo the top of the cartidge to drop the outer. I can stand correction on this
I have used two single shaft seals lots of times, but the fork legs are a 'slight' undersized 35mm so as the outer slides wear there is extra play and the non standard seals will leak as they are designed to be a rotory shaft seal not a slide seal
The seal size is 35 x 47 x 7 and i've had them in black, blue and brown over the years. I'm going to try some from Pyramid Parts online next time
 
The fork tubes and damper spring assembly can stay in place. I use a transmission jack under the engine to hold up the bike. Drain slider and undo allen bolts at the bottom after the wheel and fender has been removed. There a key in the slider to receive the spring cup. I use a Leak Proof seals held in by an old de-lipped seal. Lasted about 15 years. Time to do it again but my B11 gets all the attention and riding now.
 
Thanks much. Key in the slider??

So these will not work (work as long)? Part number/link?

http://www.mgcycle.com/product_info.php ... ts_id=1361
they'll be fine
Raphs refering to the item I described as locator /tab/indent. There is a small notch or something which stops the bottom of the damper and spring mount/seat from spinning in the lower when you tighten the bottom bolt( which is inside the axle clamps .
you will make sense of it when you pull it down.
do one at a time then you have the other to refer to if it doesn't make sense. all the early tonti 's are the same

grab a cheapo Haynes manual or guzziology or sumthin to work with as it will be usefull as you go on to replace all the various seals as they blow :whistle: :whistle:
 
Thanks... Hope you're not too serious about seals...I do want to ride this thing. The fellow I bought it from just did front and rear trans seals but it already seems to be dripping a bit from the bell housing. :/
 
Sniff the drip....if it smells like G/box oil then it is, if not it could be the rear main seal or camshaft plug or the breather return system(check your rubber hose on top of the bell housing, could be split or hard)

this bike is going to have some seals that are very old unless they have been replaced recently and these will fail.!!!! Some will be more apparant than others , and some will last longer. But they cant last 40 years!!!!
get some feel for the bike while you can but plan a major strip if you want a long term reliable ride.

I'm not trying to scare you it's just the way it is
 
The fork seals are not really critical - they are there just to keep the small amount of oil (it has no damping effect so you can pretty much use anything including ATF) in the forks. I would stick on gaiters - they prolong the life of the stanchions significantly.

No doubt the dampers are shot - the OEM units are cheap and not very effective. There are expensive and much better aftermarket units.

If it is engine oil the causes are in order of likelihood:

-Rear main seal gone
- Hoses to breather box perished/clamps loose
- No loctite on bearing carrier bolts (use loctite PST) - the lower bolts go through to the crankcase
- cam plug leaking (tip engine on front and pour in loctite bearing lock - the green stuff). I would do this out of hand just to avoid a potential problem.

I would definitely pressure test the engine (pressurise to no more than 5psi and check with warm soapy water) prior to reassembly cause reinstalling the engine twice is a definite pain.

If gearbox oil:
- Mainshaft seal
- clutch pushrod seals - I use two in this case back to back.

As Contractor20 says it is a 40 year old bike; you have to treat it like an airplane and replace things that have a definite shelf life like rubber, wires that move etc.

Chris R
 
Just did the new fork seals - thanks for all the tips. My problem is that when I poured in the 50 cc of ATF as spec'd in the manual, about half of it poured straight out through the new seals (with bubbles). Made absolutely no sense as there wasn't even any pressure, and they fit on snugly and all seemed well with the replacement. I even took the time to polish up the legs nicely, only to have everything receive a fresh ATF bath.

What could have gone wrong? Seals were tight around the tubes, and tapped into the top of the legs tightly as well...
 
Without being there it is hard to say. Did you put the seal in the slider first then put the slider on the tube? That is the correct way for the old style forks without bushings. If you tried to drive the seal with the tubes in the slider, you may have nicked the tubes.
 
No nicks...removed legs from tubes, removed old seals, cleaned out, replaced drain plug, cleaned tubes, tapped new seals into legs, slid new dust caps onto tubes, refit legs aligning tab on spring seat to leg base, removed tube caps up top, refilled 50ccs of ATF each leg. As I refilled tubes with tube tops open, ATF immediately traveled down tubes, and up between tubes and legs, and dribbled about 20ccs of ATF from the new seal (which fit snugly around tubes all seemed well) on both legs. The right tube made noticeable air bubbles coming out with the ATF at seal. :S

Could I have put the seals on upside down and would that cause them to lose all their function?
 
No, you'd have been fitting the seals with the cavities up. They could easily have burped out fluid if there was an airlock (hence bubbles). Clean it up and use it for a few miles, if it keeps leaking then there's a problem. The ATF is only to lube between the tubes and sliders so it won't affect damping
 
You do need to have an equal amount of oil in each fork leg. I'd recommend draining the oil out, then adding the correct amount of oil to each side. Uneven oil levels will have a detrimental effect on fork action.
 
Thanks...I will ride it a bit but I'm gonna wrap the legs and forks in rags first. ;) Is the 50ccs too much oil? Is it maybe overspec'd so it will totally fill up the forks and overflow depending on where the leg is on the tube?

The mystery to me is why the new seals completely failed when I poured in the ATF. Seems like they could fail under pressure, but not just pouring oil in.
 
Series4 said:
No, you'd have been fitting the seals with the cavities up.

Unclear - the cavity (spring) should be visible, or the other way around?
 
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