Primary - Engine Gasket Treatment

Woody850 · Dec 24, 2017

I am about to replace the inner Primary casing and have a new gasket to seal at the engine part No. 06.0711. Usually I always treat such gaskets to a coating film of oil but I am not sure if that is sufficient.
Do any of you use silicon sealant or are there other ways this to keep oiltight without impairing the spacing?

RoadScholar · Dec 24, 2017

If you use a belt primary drive the gasket becomes, in essence, a spacer/cushion and needs no treatment. If you have the traditional wet primary then virtually anything from nothing to International Space Station approved sealers can be used, depending on the condition of the to-be-sealed surfaces. I use a light coat of Permatex Hi-Tac, but let it dry on the gasket for at least 30 minutes, preferably an hour, before fitting the gasket. By letting the sealer dry you increase the odds of being able to easily remove the gasket next time around.

Acetone or MEK, sparingly applied to an old gasket makes removal a lot easier, do this with a small brush in a well ventilated area, and not around children; a VOC mask, if you are on a campaign...

MexicoMike · Dec 24, 2017

Woody850 said:
I am about to replace the inner Primary casing and have a new gasket to seal at the engine part No. 06.0711. Usually I always treat such gaskets to a coating film of oil but I am not sure if that is sufficient.
Do any of you use silicon sealant or are there other ways this to keep oiltight without impairing the spacing?

I have a personal dislike for and do not use silicone gasket sealer and basically consider it a tool of the devil. Admittedly, this is NOT because it's a faulty product but because it is usually misused - glopped on and resulting in copious squeeze-out both outside, and, more critically, INSIDE the engine. I also do not like the fact that it essentially glues the parts together. For years now for marine, auto, and bike engine/tranny work I have been using Permatex Moto-Seal which is essentially the same thing that Honda and other companies use under their own trade name (HondBond, YamaBond, etc). It is not silicone based.

FWIW, leakage at sealing surfaces is typically caused by warped or otherwise faulty mating surfaces. If the surfaces are true and clean, typical gaskets don't need any sealant unless specifically required per the service manual. Overtightening components will warp/distort mating surfaces. Sometimes new components aren't all that great and some work with some wet/dry sandpaper and a sheet of glass is necessary. Carbs/aluminimum intake runners are especially prone to this.

Woody850 · Dec 24, 2017

Very informative, thanks I’ll see if I can get hold of some Permatex.

Brendan S · Dec 24, 2017

Woody850 said:
I am about to replace the inner Primary casing and have a new gasket to seal at the engine part No. 06.0711. Usually I always treat such gaskets to a coating film of oil but I am not sure if that is sufficient.
Do any of you use silicon sealant or are there other ways this to keep oiltight without impairing the spacing?

I am a fan of Blue Hylomar. Remains sticky. Cleans up with carb cleaner. The last tube I got from a Harley dealer. Once upon a time Harbor Freight had it for cheap.

rvich · Dec 24, 2017

I agree that silicone is not a good sealant to use on an engine. Because the squeeze out will break off and clog oil galleries. But I notice it is the sealer of recommendation these days on my truck differential. I used it there because like the primary on a Commando, it won't really hurt anything if some breaks loose inside. However, I read a tip here in a long ago thread that I have used on my primary and think it is worth repeating.

Because of the large area of the sealing surface on a primary case, being fastened with a single bolt at the center, it is a good one to worry about whether the faces are true. But if you pull out the gasket (O-ring) and put a small bead of silicone gasket maker in the bottom of the groove, you can then put in the O-ring, replace the outer case and tension it but do not tighten it down until after the silcone kicks off. This process allows the O-ring to form to the outer case mating face and match any irregularities in it. After the silicone kicks, you can remove the outer case, clean off any areas that may need it, and then put it on with enough tension to compress the O-ring.

Following this, made a big difference in the leakage, or lack of it on my primary. I don't know who the tip originated from, but am thankful they posted it.

BrianG · Dec 24, 2017

rvich said:
I agree that silicone is not a good sealant to use on an engine. Because the squeeze out will break off and clog oil galleries. But I notice it is the sealer of recommendation these days on my truck differential. I used it there because like the primary on a Commando, it won't really hurt anything if some breaks loose inside. However, I read a tip here in a long ago thread that I have used on my primary and think it is worth repeating.

Because of the large area of the sealing surface on a primary case, being fastened with a single bolt at the center, it is a good one to worry about whether the faces are true. But if you pull out the gasket (O-ring) and put a small bead of silicone gasket maker in the bottom of the groove, you can then put in the O-ring, replace the outer case and tension it but do not tighten it down until after the silcone kicks off. This process allows the O-ring to form to the outer case mating face and match any irregularities in it. After the silicone kicks, you can remove the outer case, clean off any areas that may need it, and then put it on with enough tension to compress the O-ring.

Following this, made a big difference in the leakage, or lack of it on my primary. I don't know who the tip originated from, but am thankful they posted it.

I have done this as well but using a little heavy bearing grease behind the o-ring. It also works, and is easier to clean up the residue after tightening the center bolt, and to redo the next time.

Kvinnhering · Dec 25, 2017

Because of the large area of the sealing surface on a primary case, being fastened with a single bolt at the center, it is a good one to worry about whether the faces are true. But if you pull out the gasket (O-ring) and put a small bead of silicone gasket maker in the bottom of the groove, you can then put in the O-ring, replace the outer case and tension it but do not tighten it down until after the silcone kicks off. This process allows the O-ring to form to the outer case mating face and match any irregularities in it. After the silicone kicks, you can remove the outer case, clean off any areas that may need it, and then put it on with enough tension to compress the O-ring.

Totally agree with you. This is the method I have the best experience with.

lcrken · Dec 26, 2017

Brendan S said:
I am a fan of Blue Hylomar. Remains sticky. Cleans up with carb cleaner. The last tube I got from a Harley dealer. Once upon a time Harbor Freight had it for cheap.

+1 on Hylomar for the engine-to-inner primary gasket the OP is asking about. It's my favorite for dressing most paper gaskets, as well as metal-to-metal joins. Several other goops also work quite well, but I like Hylomar for several of its properties, including self-healing and easy cleanup.

Ken

rvich · Dec 26, 2017

lcrken said:
+1 on Hylomar for the engine-to-inner primary gasket the OP is asking about. It's my favorite for dressing most paper gaskets, as well as metal-to-metal joins. Several other goops also work quite well, but I like Hylomar for several of its properties, including self-healing and easy cleanup.

Ken

Ken, in typical fashion I wandered off course in defense of using silicone is some applications rather than actually addressing the original question directly.

For the record, I don't use anything on that gasket, instead I put some sealer on the bolts that hold the primary to the case. Hylomar, or any similar "non-setting" sealant would work well for this. If the bolts are sealed, the gasket doesn't have much work to do except provide an interface and spacing.

lcrken · Dec 26, 2017

rvich said:
Ken, in typical fashion I wandered off course in defense of using silicone is some applications rather than actually addressing the original question directly.

For the record, I don't use anything on that gasket, instead I put some sealer on the bolts that hold the primary to the case. Hylomar, or any similar "non-setting" sealant would work well for this. If the bolts are sealed, the gasket doesn't have much work to do except provide an interface and spacing.

Actually, for this application, I think you are correct that the gasket itself doesn't really need additional sealer to prevent leaks. I mostly use something on it to make it easier to remove the primary without having to scrape the old gasket off and fit a new one. I use blue Loctite to provide a seal at the bolts. The only time I ever had a problem with leaks there was when I had a warped inner primary cover. That's when I learned about the need for adjusting the center bolt properly.

Ken

Woody850 · Jan 10, 2018

lcrken said:
+1 on Hylomar for the engine-to-inner primary gasket the OP is asking about. It's my favorite for dressing most paper gaskets, as well as metal-to-metal joins. Several other goops also work quite well, but I like Hylomar for several of its properties, including self-healing and easy cleanup.

Ken

I think I will go down Ken's road with Hylomar but to quote something I read for easy disassembly was to coat the primary side of the gasket with Hylomar and the other side of the gasket with grease. Has anybody done that with successful results. I can't imagine the grease giving a seal somehow.

John

Woody850 · Jan 10, 2018

To branch off another problem I have discovered is the previous owner who also stripped the gearbox before me on replacing the selector fork shaft he screwed it in so far that it punched a hole in the housing behind the drive sprocket. At the moment I have sealed it with a blob of silicon. Any ideas here or is the best fix welding OR could that distort the boxes internals.

John

concours · Jan 10, 2018

Woody850 said:
To branch off another problem I have discovered is the previous owner who also stripped the gearbox before me on replacing the selector fork shaft he screwed it in so far that it punched a hole in the housing behind the drive sprocket. At the moment I have sealed it with a blob of silicon. Any ideas here or is the best fix welding OR could that distort the boxes internals.

John

A small, easy weld repair, no detrimental distortion.
Edit.. never mind, no coffee.

concours · Jan 10, 2018

Woody850 said:
I think I will go down Ken's road with Hylomar but to quote something I read for easy disassembly was to coat the primary side of the gasket with Hylomar and the other side of the gasket with grease. Has anybody done that with successful results. I can't imagine the grease giving a seal somehow.

John

Loctite 518 makes gaskets come off like sticky-notes, and seals tight.

marinatlas · Jan 10, 2018

Woody850 said:
To branch off another problem I have discovered is the previous owner who also stripped the gearbox before me on replacing the selector fork shaft he screwed it in so far that it punched a hole in the housing behind the drive sprocket. At the moment I have sealed it with a blob of silicon. Any ideas here or is the best fix welding OR could that distort the boxes internals.

John

Hi, if I understand well you are speaking about the threaded hole where goes the fork selector shaft , and for me it is not blind hole it's going through the case .

concours · Jan 10, 2018

marinatlas said:
Hi, if I understand well you are speaking about the threaded hole where goes the fork selector shaft , and for me it is not blind hole it's going through the case .

Right!!

Woody850 · Jan 10, 2018

This is for me good news which makes me very happy. Thank you for the answer, but it doesn't seem to be a very oiltight set up.

concours · Jan 10, 2018

Woody850 said:
This is for me good news which makes me very happy. Thank you for the answer, but it doesn't seem to be a very oiltight set up.

Threebond, or 518 again. Dry.

Woody850 · Jan 10, 2018

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Primary - Engine Gasket Treatment

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