classic motorcycle forum

Motorcycle Discussions => British Bikes => Topic started by: bandit on March 15, 2008, 03:27:38 AM

Title: sealant
Post by: bandit on March 15, 2008, 03:27:38 AM

hi .would it be ok to use enginering grade silicone sealant between rocker box and cylinder head.in place of gasket??? norton es2.thanks gary.

Title: Re: sealant
Post by: geoffus on March 15, 2008, 10:42:00 AM

 :)
don't like using silicon on engines have seen too many were oil ways and oil pumps blocked by over use of silicon I will use on the gear boxes and primary chain cases if i have to but against using on engines
regards geoff

Title: Re: sealant
Post by: Blue on March 15, 2008, 08:40:41 PM

Not really advisable; silicone is too much of a 'permanent' type sealer and its not really made to stop oil.  not only that, but if you have to remove the rockerbox at a later date (and you almost certainly will) its painful to try and clean the old silicone off the surfaces.

my advise is to get a bit of grinding paste and a mirror (or similar glass panel), put some paste on the jointing face of the rockerbox and grind on the glass in a roughly circular motion until the face is nicely flat.  you can get sealants from companies like Loctite that they claim are liquid gasket - 'gasket goo' or similar.  use this instead of silicone - or better yet get a gasket/make a gasket from the appropriate material which should be available from dealers of seals (industrial rubber suppliers more often than not)

Title: Re: sealant
Post by: bandit on March 21, 2008, 04:28:55 PM

thanks for your help geoff+blue regards gary.

Title: Re: sealant
Post by: digger on March 26, 2008, 10:15:55 PM

Bandit; Silicone seal is soooo yesterday dude! Geoffus is right on about the oil way blocking property of silicone and Blue covers a most important point about fitting mating surfaces. Here are three products that I have great success with: No gasket - Yamaha’s, YAMABOND 4; I thin it up to 50/50 with MEK (READ THE WARNING ON THE LABEL) and paint it on. A light tap with a mallet will break parts loose easily. Mating surfaces must be completely clean, another use for that nasty MEK (seriously, this is a hazardous chemical). With a gasket – Yamabond4 on one side of the gasket and Hylomar HPF on the other side for easy off and on. The old Hylomar can be removed with MEK  (did I mention this is really nasty stuff?) new Hylomar applied and the gasket reused. For chain cases nothing I have found beats Permatex, The Right Stuff. It is everything silicone seal wants to be and more – it expands a little, stays flexible, and is truly oil resistant. Hope this helps. Digger

Title: Re: sealant
Post by: bandit on March 27, 2008, 01:29:32 AM

thank you digger for your help.bandit. ;D