Topic: Damaged Cylinder Mating Faces - Advice Please

[The Lone Builder]

Having finally got my gear change mechanism in and functioning, I started upwards to install cylinders etc.

Whilst cleaning out the cylinder stud holes, I noticed some damage to the mating faces on the crankcase - see pic. I have no idea how/when this happened! 

I can definitely feel a dent in both although the inner one is deeper that the outer, which tapers off quite quickly.

Looking at the oil passages, it looks like any oil leaking through the inner dent will simply be recirculated. I am hoping that the bottom of the barrels, plus o-ring, plus gasket will stop any oil leaks going outwards.

Can I go ahead or am I being overly optimistic? 

If something needs to, and can, be done to repair the damage, what is it?

TIA

Sean

[pjlogue]

I would carefully dremel off the extruded part that got squished into the bore of where the cylinder bores seat then scruff up the indented top area, clean real well with Acetone and use JB weld  to fill in the indent.  Hone carefully any extra JB weld, clean and you should be good to go.  Be careful not to get any particles into the crank case if you aren't splitting the case.

-P.

[Jerry Rxman Griffin aka MuthaF'er]

IMO you PROBABLY would be OK just to eliminate the RAISED edges if they exist and put it together. Looks like you still have sealing surface area.

[PeWe]

No problem if no ridges. My case has not much material at all where you have that dent. Std hole diam is 74mm, mine is about 79mm.

[pjlogue]

I suggest filling in the dents with JB weld.  There are "O" rings on the bottom of the jugs that are intended to seal the cylinder inserts/cylinder casting.  Those dents will cause a leak.  Not sure why they had the "O" ring to prevent oil from getting between the inserts and casting but they did it for a purpose.  Perhaps to prevent the inserts from turning in the casting because of oil intrusion.

-P.

[754]

Dont fill it, if it ever comes out  goes into your oilm no reason to fill,
 The oil ring covers the sleeve to cylinder joint, it DOES NOT seal again here   your gasket does.

[pjlogue]

But wouldn't the O ring need support in order to seal the cylinder to insert joint?  I don't know how critical it is to keep oil out of the insert/casting surface.  May not make any difference.

-P.

[754]

It probably pushes against The gasket. The spigot of the cylinders cannot be a tight fit into the hole.

[The Lone Builder]

Thanks for the input.

In my hurry to get on, I took PJ's advice, as that was in my mind also. The pics show the finished result. All smooth.

Listening to 754, however, (Are you naturally a pessimist, or just experienced?  ) I am a little concerned about the possibility of one coming out - especially the smaller one - so I'm going to let it cure fully and then see if it looks even remotely loose - conscious of the possibility that I might loosen it!! If so I'll take it out and leave as is.

So I moved on a bit and was looking at my gaskets. The cylinder base gasket didn't seem to be a great fit when I dropped it onto the case - I actually thought maybe I had the wrong one – so I dropped it over the barrels to see how it fitted there.

Much better fit all round, but as the pic shows it is not symmetrical at the cam chain hole - one side sticks out into the channel.

Sounds like a daft question, but I do need to trim this, don't I?

Cheers

Sean

[disco]

I think you need to Flip it over. Left side to right side, so you end up with what is currently top side then facing down.

[lash]

I think you need to Flip it over. Left side to right side, so you end up with what is currently top side then facing down.

+1

[PeWe]

It probably pushes against The gasket. The spigot of the cylinders cannot be a tight fit into the hole.

And.... Std sleeves have no leaks to the air vent 1-2, 3-4 as big bores from 888cc can have when the bore going thru the alu to house the bigger sleeves

[The Lone Builder]

I think you need to Flip it over. Left side to right side, so you end up with what is currently top side then facing down.

 

One last (I hope) question; At the end where the channel flares out, the gasket is still straight. Is this how it's meant to be?

S

[754]

I think you need to flip that over...?the gasket fits over the pin from the cam chain tensioner slipper blade you will be installing.
 I see you have the best manual .

[disco]

Like this. (Yamiya gasket)