Suzuki 2 Strokes

When I built my cafe 550 I used copper spray-a-gasket on the head gaskets. Still sealed up as far as I know. On this current build that I had to tear down again I used the same stuff. When tearing it down I noticed it was starting to spring a leak on the left jug - even though I only ran it a short time.
Getting ready to put it back together. I know not to use anything on the base gaskets (though I may oil soak them a while). I have plenty of this copper spray-a-gasket left in the can. . Is there something better out there that I should be using? Everything was good and tight when I tore it down, but there was a trail starting out toward the front on the left side. Head was torqued to 29 ft.lbs. So what do you guys use for the head gaskets? I refuse to put them on dry as that's really asking for it. This copper spray-a-gasket high temp sealant is made by Permatex. I like the fact that it's a spray cause it's easy to get a nice even coat. It says it's especially designed for exhaust manifolds, head gaskets and turbocharger flanges.
Take that foreign language off the damn can. This is America.

Like you, I fit base gaskets with just the lightest smear of grease on each side. On the head gaskets I paint on a thin line of blue Hylomar with a modelling brush. Problem is that one-piece head on 3 individual jugs - all the bits move a little relative to each other and eventually spring a leak.

Touch up / clean up head and jug surfaces, put gaskets on dry: either stock 0.040" fiber/metal gasket or 0.020" metal.

Put a little light weigth oil on head bolts threads/nuts so torques more smooth;y/readlily and use stock specs and tightening order.

I also lightly grease paper base gaskets but put head gaskets on dry. The sealing surface in the GT380 and 550 is the crushable metal ring around the cylinder periphery anyway, I believe. Agree the studs should be clean so the nuts can be turned with fingers for even torquing up. I go mid-spec on torque and re-do them 2-3 times after early heat cycles then leave them alone. I've never had a head leak in 30+ years doing this. I have always used Suzuki gaskets. I do accept that the one-piece head could be a problem if distorted, though I've not seen it myself. The torquing order 'should' minimise this risk, as each cylinder is done separately, on the diagonals, starting with the centre pot.
Mike

I reckon it's good practise to leave the base nuts lightly nipped but un-tightened, and then torque up the head bolts first, only then tighten/torque up the cylinder base nuts.
This assures that the head joint (most critical) is as good as it can be, and any minor discrepancy in cylinder assembly height will be at the cylinder base where it will be less important.
Agree with dry head gasket and lightly greased base gasket and lubricated threads.

joolstacho wrote: This assures that the head joint (most critical) is as good as it can be, and any minor discrepancy in cylinder assembly height will be at the cylinder base where it will be less important.

I dont know about a base leak being less important , a vacuum leak here can lean out the mixture and fry a cylinder . Testing the deck height of the three cylinders mounted up to the engine is the way to go , if all three are not level at the head surface they should be .

Let’s assume the leak is very small. I don't think base gasket will cause you to lean out. However, a head gasket leek will erode the metal surface in short time causing the leak to grow and ruin the metal surfaces.

Good point about the individual jugs being near same height Not an issue with mono block like GT750. I have not so far had a height problem with individual cylinders mated with mono heads be it old bikes or snowmobiles. Been lucky

Having micrometers left over from my machinist days, I did exactly that. I checked all 3 , deck to base. Total variation was .006 with the center being the shortest.. The center is first to torque and the ends can easily pull down a few thou. I have seen that tolerance spelled out somewhere and if I recall correctly it was ,010. These jugs are the originals so that's the way it came from the factory. I'd say perfect is rare luck. It would be nice, but not likely.. Remember we are talking mass production here, so they must have had a tolerance to work with or stay within.
I did lay a straight edge across the three after the base nuts were tightened. You could barely see any daylight over the center cylinder.