gearbox rebuild-? gasket goo?

[davidmuir]

do folks try and 'get away with' rebuilding gearboxes with dry gaskets?- bit dubious!

[iain1967s]

I used a thin coating of Pematex Aviation No.3 on both sides of all paper gaskets.

[davidmuir]

that's what i was thinking of!...........had too many leaks on British motorcycles to be convinced of the 'dry is fine' route!

[Peter Laidler]

Me too David and Iain. Dry gaskets were from the 60's era where motorcycle and car gearboxes would be tested for flatness on a calibrated surface plate after work. Scraping the high spots and..... and..... I can see you and other ex bikers smiling as we speak. Permatex or equivalent does it for my Commando

[bwaminispeed]

I soak the gaskets in heavy oil just prior to assembly......I only use sealer in a few specific spots......Mostly, just the corners of the half round front engine to gearbox seal......

They were assembled dry at the factory.....For the most part, the leaky engine legacy, was mostly the seals, not the gaskets.....

[Polarsilver]

I put a smear of Grease prior mounting the Block to Gearbox.. reason is this will also help ( in my opinion) the O Ring to seal also the Half Moon Seal,.. also despite all our good & best efforts one day the Power Unit will need to be taken apart & then no issues with residual Sealant snot into the Oil or Gearbox .. never had an issue with oil leakage from this area .. Yet
Just to say i add whenever i can plenty of Crank Case Breathing .. so perhaps this is the secret fix

[GraemeC]

I also trim the block to gearbox gasket to make sure it sits around the O-ring and not on it. The original ones used to sit clear of it, but the ones available now overlap.
Does it make any difference? Don't know - but it makes me feel better

[Costafortune]

I put a smear of Grease prior mounting the Block to Gearbox.. reason is this will also help ( in my opinion) the O Ring to seal also the Half Moon Seal,.. also despite all our good & best efforts one day the Power Unit will need to be taken apart & then no issues with residual Sealant snot into the Oil or Gearbox .. never had an issue with oil leakage from this area .. Yet
Just to say i add whenever i can plenty of Crank Case Breathing .. so perhaps this is the secret fix

Grease is the best sealer on a paper gasket - once it's got hot it really does its stuff.

[TECH396]

I was interested in the replies here. In the 70s I was taught by a "Senior" to use White Lithium grease, and that was it. Never had any issues with leaks from there. It was explained at the time, that using sealant would create up to .003" extra thickness "that you don't want" ,,as he put it..

[cpr1]

I use this, found it quite good https://www.chemico.co.uk/jointingcement.html

[850man]

I have used Threebond 1215 sealant for many years now. If it is good enough for Toyota then you know you will end up with an oil leak free A series.

[DougR]

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I also trim the block to gearbox gasket to make sure it sits around the O-ring and not on it. The original ones used to sit clear of it, but the ones available now overlap.
Does it make any difference? Don't know - but it makes me feel better

I have noticed this as well. There were no replies to the post from GraemeC. Does anyone have an opinion about having the gasket overlap the o-ring? I have to say that I never noticed this before which makes me think that as Graeme says, previous gaskets had a bigger hole. Why has this changed and is the best solution to trim the gasket? Cheers, Doug.

[timmy201]

I think from memory I overlapped my gasket over the o ring. In hindsight perhaps I should have opened up the hole on the gasket

The o ring is pre pump, so the oil pressure on that side shouldn’t be very high?