So I'm a Harley mechanic, but my first new bike was an 89 CBR600. Totaled it years ago but always wanted another one. Picked up a bike from a friend for free but it needs a new cylinder head. Found a good head and have the old head off, but here's where I'm not sure what to do and would appreciate advice.

Do I have to change out the cylinder base gasket?

On a Harley you absolutely do but the Harley cylinders aren't held down by anything other than the head bolts so taking off the head loosens pressure on the gasket.

The CBR, otoh, has a bolt that holds the cylinder down, but it is only on one side so it seems like pressure would come off most of the gasket. Honestly I'm not even sure what the purpose of the cylinder bolt is.

So do I need to pull the cylinder assembly off and swap out that gasket? I have ring compressors (but not piston bases as mentioned in the shop manual although I have some HD stuff that might do in a pinch) so I assume it's not too difficult, but I'd rather not do more than I have to.

Thanks for any advice.

 

Any time I remove something with a gasket, I always replace the gasket. I'd rather replace it, than have to tear it back down later and replace it because of a leak.

 

You're talking about the gasket between the jugs and the bottom case, correct?

 

The Honda Service Manual shows the replacement of head gasket and assembling the head. The cylinder jugs are in place and no where does it say that the gasket between the cylinders and the case should be replaced as long as they are not split apart.


I think that's what you are asking.

 

I am talking about the gasket between the case and the cylinders. I have removed the heads. What I'm not sure is if taking off the heads has broken the seal between cylinders and case. I will probably replace it anyway, just to be safe, but if there were absolutely no reason to, then it is just extra work and more money.

 

Read my post above. The Service Manual says nothing about replacing this gasket when doing the head. I don't think it needs to be changed unless it is damaged or leaking.

 

Well, turns out it doesn't seem to be possible to buy anything but a complete engine gasket kit anyway. That being said, I will have a cylinder base gasket and o-rings, so I might as well do the whole shooting match while I'm in there.