Cylinder base sealant -- not the same old Q.

[mneblett]

I'm getting ready to re-install my cylinders ('88 R100RT). In the past I've used very thin coats of Three-Bond and Hylomar for base sealants. My Three-Bond tube is dead (apparently cured in place after the first use), and I've read in my searches that Hylomar is oil-soluable, so I won't be using that product again.

I'll probably go find another tube of Three-Bond, but since I have two days before any bike shops are open again, I thought I'd post this Q:

In addition to Three-Bond, I've seen various recommended sealants, primarily high-temp RTV, including Permatex Ultra Grey. I have a tube of Permatex Ultra Black high temp RTV -- any reason I could not use that instead of the Ultra Grey?

Oh, and while I'm at it, I'll pitch this Q out there: What about no sealant at all?? There's an o-ring about the cylinder base and two about the upper stud oil passages -- is the sealant just belt-and-suspenders or really needed? Putting it another way, what has been the results of not using a sealant in addition to the o-rings? (of course, I mean *actual* experience, not "well, I haven't tried it but I don't think it will work").

Thanks!
Mark Neblett
Fairfax, VA

 

[20774]

Mark -

Ted Porter recommends the Ultra Gray...if the formula is the same for the black, you could probably use it. Maybe the reason for the gray is because any slight excess won't be that visible when it squishes out upon installation. ??

I would probably use the extra sealant just as another barrier to the weeping. Nothing's perfect in terms of the o-rings and there are always minor imperfections that the sealant will help to fill.

It doesn't take that much time and could make the bike weep/mist free...why not?

 

[robsryder]

I've used the blue Hylomar as a sealant on various airhead cylinder base gaskets. I'll continue to use Hylomar as I've had good results. I expect that any of the "...bond" products (e.g., hondabond, yamabond, etc.) would work as well. The key is having clean surfaces to begin with and then using a very thin coating. I don't think that I'd use the RTV in this location as it seems difficult to keep a very thin coating. YMMV! Care should be taken to keep the goop from the oil passages near the top studs. I also replace the small o-rings on those studs when I reseat the cylinders.

 

[AnnapolisAirhead]

+1 on Ultra Grey. Bob's BMW recommended it as well.

I think though, that this is a belt and suspenders kind of thing because of the o-ring as Kurt pointed out, so the others would likely work too. I found the Ultra Grey easy to keep a consistent, thin coating and to clean up upon disassembly (DAMHIK, I've never learned from accidental success!). It should be thin enough where there really is no excess to clean up though, according to what I've read (Porter, Snowbum).

The PO had used RTV and it was gooped everywhere, even on the pushrod seals What a mess that was to get clean.

I heard similar good things about Yammabond but have not used it.

 

[20774]

Here's a website that I had saved showing the "thinness" necessary for the sealant.

http://www.gunsmoke.com/motorcycling/r100gs/sealant/index.html

 

[pglaves]

Most RTV is slightly acidic and smells a bit like vinegar while it is uncured. Ultra Gray and similar products (Three Bond, Yamabond, etc) are not acidic and do not smell like vinegar. Look carefully at the packaging. You are looking for a sealant that specifically states it is acceptable for aluminum block engines, water pumps, oil pumps, etc.

Permatex Ultra Gray is suitable, cheap, and readily available at most decent auto parts stores - Autozone, O'Reilly's, etc. Even I would run out and get some if I needed it, and for me running out to town means 53 miles one way. But I'd take a bike.

 

[mneblett]

Thanks guys -- looks like no on the Ultra Black

 

[evergreen]

Hi Mark:

You might want to try this. I used it on my /5 years ago at thte recommendation of a friend who is an ex-Porsche mechanic. He said it was particularly effective with assemblies that expand and contract greatly like our airheads.

http://www.permatex.com/products/Automotive/automotive_gasketing/anaerobic_gasket_makers/Permatex_Anaerobic_Gasket_Maker_b.htm

The plus of the anaerobic nature of the product is that it won't cure if exposed to air, so it won't clog any of the oil passages on the top cylinder head studs.

Greg

 

[BUBBAZANETTI]

don't go searching for the yamabond product mentioned in many of the tech articles on this subject. it's an exhausting and outright frustrating search as the product seems to have been discontinued in the last year or two. i must have called 15 places, stopped by 5 shops in the city and finally on the day i had scheduled to do my prt seals, the guy who owned the garage i kept my bike at just let me borrow a tube!

as i mentioned in another thread, he said he'd always done them dry if they had a large o-ring and said he never had trouble. one of mine started leaking about 5 months out.

 

[mneblett]

Thanks again to all -- I picked up a tube of Ultra Grey this afternoon. Now all I need is a stretch of weather above 19F to start putting the bits back together!

 

[Yarddog]

Oh, the weather was horrible here, today too...78 degrees...simply TOO chilly to do anything but get on the pancone and ride...just don't know WHAT I'm gonna do!!! LOL