Base gasket or not.

htown16 · May 8, 2012

Was watching my Mick Hemmings DVD while getting my barrels ready to put on. He used a base gasket with no sealer. What's the thoughts? I had to pull the top end off my Triumph to fix a leaky base gasket. Awful lot of work for a small problem but it was spewing oil.

Torontonian · May 8, 2012

I use a base gasket with a light smear of copper silicone to both sides ,paying attention to even less around the tiny oil return hole area.

pete.v · May 8, 2012

Gasket with spray copper coat both sides.

VintAge · May 8, 2012

Everybody has their favorite gasket compound or sealer and most use it all the time. Now, if the two surfaces are PERFECT and the gasket is good quality and undamaged, why would you need a sealer? But we don't live in a perfect world.

We use Copper Coat or Permatex Ultra Grey, depending. I think a mistake the inexperienced often make, however, is using too MUCH - it's sealer, not mortar.

concours · May 8, 2012

my '74 850 requires no gasket.

shrugger · May 9, 2012

Loctite Grey ATV. And only enough to give it a grey-ish color.

splatt · May 9, 2012

shrugger said:
Loctite Grey ATV. And only enough to give it a grey-ish color.

I quite like that sealant, doesn't stand out like dogs balls, but it started leaking on my 850 after about 10000km, possibly not the sealants fault, and more likely a shit thru bolt helicoil

concours · May 9, 2012

RTV is a poor choice for that application. Loctite #518 is a much better suited sealant. Does either task, seals without a gasket, or makes a perfect dressing for a gasket. I've used it successfully for years. Read all about it here: http://tds.loctite.com/tds5/docs/518-EN.PDF

grandpaul · May 9, 2012

Yep, 518 is for flanges. The cylinder base is a flange.

shrugger · May 9, 2012

Aha, I have no compunction against changing my mind. The 518 looks good to me.

pete.v · May 9, 2012

518 is good to 302 degrees, where a the copper coat is good to 500 degrees and a little too goopy for me. Be cautious around oil holes with goopy stuff.

Many people put next to nothing in this area. I would suspect the IF the surfaces are true (required for any solution you choose) a single coat on both sides would do the trick.

The trick is that these surface areas can be difficult to true up to each other to such a degree to attain long term success without a gasket. Oh sure, it's been done, but it's nothing that I would gamble with. And if I may add, No gasket may void your warrentee. :lol:
http://www.permatex.com/products/Automo ... ealant.htm

lcrken · May 9, 2012

Back in the day, I recall a remommendation from Norton to leave out the base gasket and use Hylomar sealant. I've forgotten where I saw that recommendation, but it was in the early '70s. When I first started racing my PR in '72 or '73, I still had the original engine with the paper base gasket. It worked ok, but with a slight oil seepage out the edge of the gasket, until I rebuilt it to race specs with significantly higher compression. At that point, it blew the paper gasket out. I've never used a base gasket since, on either the race bikes or street bikes. I've used a variety of sealants, including Hylomar, Locktite Master Gasket, silicone (bad idea), and Yamabond/Threebond. They all worked for me, but now I just use Hylomar.

Ken

concours · May 9, 2012

pvisseriii said:
518 is good to 302 degrees, where a the copper coat is good to 500 degrees and a little too goopy for me. Be cautious around oil holes with goopy stuff.

Many people put next to nothing in this area. I would suspect the IF the surfaces are true (required for any solution you choose) a single coat on both sides would do the trick.

The trick is that these surface areas can be difficult to true up to each other to such a degree to attain long term success without a gasket. Oh sure, it's been done, but it's nothing that I would gamble with. And if I may add, No gasket may void your warrentee. :lol:
http://www.permatex.com/products/Automo ... ealant.htm

That's the benefit of anaerobic sealer.... the excess will not create big boogers to clog oil passages. That 302F number shown on the chart is just the end of the test data, all values are levelled out. I don't see max temp rating. If the base flange of the cylinder gets to 302F, you've got more to worry about than an oil leak.

B+Bogus · May 9, 2012

No base gasket on my MkIIA 850 - as per the factory spec.

I use Welseal, which never sets, and is doing a great job so far.
I used the stuff on my T140 and all the cylinder base nuts rattled loose on the first ride, leaving me with an engine almost in 2 halves at the side of the road.
What a mess

I nipped everything up as a 'get U home', thinking I'd have to strip and rebuild, but it remained oiltight, and hasn't needed any further work in 5 years.

concours · May 9, 2012

Yamabond (Threebond) is also a kick ass sealer, either alone, or as a gasket dressing. Comonly used on base flanges on aircraft engines to stop the oil drool.

lcrken · May 9, 2012

One of the reasons I settled on Hylomar over other sealants is that it is quite easy to clean up. When I was racing, I had engines apart regularly, and really appreciated being able to clean off the old sealant without a lot of difficulty. It is also much easier to separate the cylinder from the crankcases with Hylomar than with Yamabond, which glues them together pretty well. Still, they all seemed to work fine for their purpose.

Ken

concours · May 9, 2012

lcrken said:
One of the reasons I settled on Hylomar over other sealants is that it is quite easy to clean up. When I was racing, I had engines apart regularly, and really appreciated being able to clean off the old sealant without a lot of difficulty. It is also much easier to separate the cylinder from the crankcases with Hylomar than with Yamabond, which glues them together pretty well. Still, they all seemed to work fine for their purpose.

Ken

I'm with you there... Yamabond is pretty well adhered, but comes off. The beauty of 518 is, the gasket peels off like a sticky-note from your computer monitor. If you've ever scraped a base gasket from a twin cylinder liquid cooled two stroke between 8 studs and two conrods (with frame beside and over it in a REV chassis) you can really appreciate the peel factor.

northern750 · May 9, 2012

One of the things I've always liked about the liquid (not silicone) based Yamabond or Threebond is that it is lacquer based and wipes off with a cloth soaked in lacquer thinner. Also, it doesn't seem to break off and clog oil screens like RTV based sealants.

I haven't worked with Hylomar much, how is it removed?

DogT · May 9, 2012

As I remember, I put a bit of Hylomar blue racing formula on it.

Dave
69S

htown16 · May 11, 2012

Thanks to all for replies. Did use the gasket with very light coating of Hondabond, mainly because I already had some.

Base gasket or not.

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