Cylinder base gasket.

Tim L

XS650 Addict
Messages
238
Reaction score
18
Points
18
Location
UK
Hi all,
On the first 2 XS engines I did a 100% re-build on there were no leaks at all. I have just finished the third one and started doing some miles on it and it leaks like a sieve. I have taken the engine out of the frame and stripped the top end to replace all the seals and gaskets. I was thinking about using sealant on the cylinder base gasket but the sealant will have started to dry long before I get to torquing everything down.
Has anyone found a good way to ensure there is a good seal on the cylinder head base gasket?
I had leaks around the valve covers, cam shaft seals and head gasket as well. It looked like a classic Triumph!!!
 
Are we talking cylinder base gasket
And another one Cylinder head gasket aka 2 different
The cylinder base gasket I have 3 -- 4 times smeared Permatex ( or another brand ) on with no leaks
Some connoisseurs might object to this but it has worked for me.
I pretty much smear that on all places.
I have worn bikes so the surfaces can be uneven and warped ..
Last time i did the reassemble the pistons hit the base gasket so I ordered a new one and replaced it.

Cylinder head gasket I believe should go in dry and torqued down according to tightening pattern.
I did that carefully last time small steps and exactly to pattern.

After the first run in ..oil change a re -torque was necessary especially the bolts outermost to the sides needed a bit more
This was without leaks ..Needs to be checked now and then.
It takes a while before permatex hardens so if that is applied on base ..the weight of the cylinder will push it together.
And do most of the sealing without nuts being tightened.

I can see that you are experienced so a bit more care on the tightening and a little more Sealant and a couple of re torques.
Should do it.
With the seals the trick is to apply oil and be careful pushing the axle through. Twisting movement can help.
 
Yes, not head gasket. I am getting a bit 'old and confused'!
The base gasket was leaking so I was going to put some sealant on it but the sealant might start to go off before I get to torquing everything down. Just wondered if anyone had experience of a sealant that takes a long time to cure so it would be workable for longer. I might not be torquing it down for a day or two after the barrels go on.
Also rocker covers leaked and camshaft oil seals.
Maybe I have just got a leaky one this time. It's an age thing!!!
 
Last edited:
I used Permatex copper spray for the base gasket and head gasket,
389CBCAF-AF3E-4984-820F-C6B908972864.jpeg 169BE5B4-A6BC-404B-97F7-933D7208DC21.jpeg574219AF-3DBA-4919-AC23-5F39C3B86CF1.jpeg
Hylomar Blue for all other gaskets, and to seal the rocker box to the head,
62EFD223-581E-41DC-B1D6-73F044E261B1.jpeg 88B7B7DA-70A4-4280-9795-8C80C89605AC.jpeg
Yamabond smeared around all engine seals,
4D04013A-39AA-439A-BC83-F4A738B3DEBB.jpeg
And here’s a little tip for you. I used to use Hylomar on the sump plate gasket, but eventually the gasket starts to tear. Now I smear anti seize on both sides of the gasket and when you remove the bolts for an oil change, the sump plate usually just falls off, and the gasket lasts a long time.
By the way, I just tore the top end down on my engine that I build a couple years ago and both ,the copper gasket spray and Hylomar treated surfaces came apart very easily and cleaned up easily.
 
As far as the valve covers go, even though the top cover has alignment dowels, I like to loosely install all the valve covers before tightening it down. This insures perfect alignment around the valve covers.
 
I am interested in this thread because I am trying to collect info for a top end rebuild later this year.
I dont want to hijack this thread - if you think I should start a new one - please advise.
I will try to summarise what I have gathered so far:
Base Gasket - Hylomar Blue (eggGary) - Copper Spray (mailman).
Head gasket - nothing at all - copper spray (mailman).
Rocker cover - Hylomar Blue (eggGary) (Mailman).
Clutch Cover - Grease (5Twins) - Hylomar Blue (eggGary and Mailman)
Bottom oil filter - never seize (mailman) - others?? - I can imagine any sealant on the engine side would be awkward to clean off ??.
Valve inspection covers - Im even more confused here - I thought they had O rings and Gaskets - why is any sealant needed at all - I am going to guess here - Hylomar Blue (eggGary)(mailman).
As you can see I am trying to organise all the bits and pieces I have gathered from you guys since I joined - I'm a bit confused on what are the right choices.
I guess some sealants are easier to clean off than others which I understand would be a factor.
Could somebody clean up the above info for me please.
Regards Ray.
 
As you can see I am trying to organise all the bits and pieces I have gathered from you guys since I joined - I'm a bit confused on what are the right choices.
I guess some sealants are easier to clean off than others which I understand would be a factor.
Could somebody clean up the above info for me please.

I think what this illustrates is that there isn't a 'right' answer here, it's down to what the individual has used before and has worked for them.
IMO any of the suggestions you refer to would be OK.
 
Any thoughts whether Hylomar has a shelf life? I have a tube that’s been around for 15+ years. Looks ok when squeezed out but I wanted to get some opinions before I put it to use. Is it fuel resistant? Thx
 
Any thoughts whether Hylomar has a shelf life? I have a tube that’s been around for 15+ years. Looks ok when squeezed out but I wanted to get some opinions before I put it to use. Is it fuel resistant? Thx

I had a tube that was a couple of years old, stored in a garage cabinet. It had gotten very thick and hard to squeeze out. I replaced it just this week. I do however live in a very hot climate and my garage is like an oven in the summer. Almost anything liquid, like glue or caulk, or car wax, dies a horrible death in my garage. :D
 
In the few i've done I put the base gasket in dry. I clean the top of the case and bottom of the jugs.
Never leaked yet.
I think if I did use a sealer I would want one that dries before i assemble. If wet the gasket may squeeze out.
Someone mentioned the pistons hitting the gasket, so he bought a new one. The base gasket can't hit the pistons. The steel sleeve slide down through the base gasket a couple inches. How can they hit.
Perhaps he is confusing the base gasket with the head gasket. On a very large over bore piston the stock gasket might get hit by the pistons.
Leo
 
Same experience as per XSLeo's first 2 sentences just above. Also, the Haynes manual said not to use a sealant so I didn't. Maybe because it might make disassembly difficult at a later date?? Could those 2 red O rings at the bottom of the cylinders be the issue with leaking oil. The base gasket will fit 2 different ways by rotating 180 degrees. Both work but one gives full cover of the mating surfaces and the other leaves some overhang that requires trimming.

The original Yamaha head gasket has pre-applied sealant on the front and rear of the area around the cam chain tunnel. My Athena gasket did not have this so I applied a little RTV high temperature. NOS XS650 Gasket:
Front
Front.png

Rear
Back.png

Another example:
Example.png
 
Last edited:
In the few i've done I put the base gasket in dry. I clean the top of the case and bottom of the jugs.
Never leaked yet.
I think if I did use a sealer I would want one that dries before i assemble. If wet the gasket may squeeze out.
Someone mentioned the pistons hitting the gasket, so he bought a new one. The base gasket can't hit the pistons. The steel sleeve slide down through the base gasket a couple inches. How can they hit.
Perhaps he is confusing the base gasket with the head gasket. On a very large over bore piston the stock gasket might get hit by the pistons.
Leo

I fumbled with the installation of the pistons into cylinder
( if I remember right , )
I tried to push pistons in from under ..had them in a slightly slanted ..position
with the piston pins and circlips in
and pressing down gradually on the cylinder hitting with the fist
Using a wooden stick to get the rings into their grooves , and into the cylinder.
Slanted helps because one can gradually step by step get them in with a lot of oil on the upside
I did not lock the crank properly at first attempt so it moved with cylinder and if i recall correct the underside of the piston hit the gasket. S*it happens
Slanted not yet inserted in the bore a bit out of center.
Something did hit ---That i remember cylinder with sleeves are lined on the bolts-- So it goes straight down
Second time i locked the crank rotation .. a socket and handle resting on the kick axle so it could not move
Worked perfectly second time and with pistons in cylinder it lines up and cannot hit the gasket.
Certainly not if all the way in.
Not 100 % certain since when things go wrong .. focus is more on damage control.
But the gasket did get a hit .. It perhaps would have worked but I replaced it.
 
If you are prepared to inspect every several hundred miles then copper and Hylomar are all you need.
I used various thicknesses of copper gasket for head and base for several years. If you understand how wet and dry bulb (weather, humidity,temperature) affect an engine then fine, I'm boring you. If not you have some reading to do.
It's called racing. If I can't out do you with cubic dollars I'll keep up with meticulous preparation and tuning.
Then again as a racer I had my own failings. I needed every advantage I could find.
If I knew the head was coming off after a heat race it went down on an annealed copper head gasket coated with non stick Pam, and the base got Red aviation Hi-Tack.

it is what it was ...
 
I've had good luck with CopperCoat on the the head gasket, YamahaBond on the rocker box and red grease on everything else .
But then what do I know.
Key is clean and flat surfaces.
 
Back
Top