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Big Bore Kit - Big Problem

T

toanjo

Member
Hey I need some help... badly. A friend of mine took his sportster apart and swapped out the cylinder heads/pistons (883 -> 1200). After reassembly he found that there was a small leak of oil from the rear cylinder, clutch side (small air bubble). I assisted with part of the re-assembly so I know what happened for the most part.

At the time he figured that we screwed up the head gasket. Rather than spend $100 on new gaskets, he sent the bike to the dealer. After all, he didnt know what went wrong and didnt want to make the same mistake twice. The dealer came back with the following pictures.

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The dealer said that a piece of metal was lodged between the cylinder head and the crank case.

Now we would swear that it was impossible for the piece of metal to get in there and cause this problem. We even washed the cylinder heads in the kitchen sink prior to re-assembly according to one of the how-tos we were following. However, the damage is there and it wouldnt get there on its own.

The other thing thats odd is that the dent is on the push rod side, not the clutch pedal side where he saw the leak.

So my question is, what are the options to fix this? The dealer suggested a new crank case, which is big bucks. And im not talking about a 10 point white tale.

Are there other gaskets that might seal the dent? I know some engines use copper gaskets instead of the paper ones.

Thanks
 
Could always fill in the Diviots with JB weld or Liquid Metal then smooth out and a Gasket should seal then .. Or the mor exp way is to have someone Weld it and build it back up then grind it back to where it should be
 
I like the liquid gasket because it will seal and level itself out. Any hard filler (welding or JB) will require very exact smoothing.
 
+1 for the JB Weld. That is in a no pressure area, so there will be no real forces exerted on it. The hard filler, even though it will take a little extra effort to smooth, will make the repair permanent.
That way, should you ever have it apart again, you will have no future sealing problems.
 
I have built a few car engines, and rebuilt some pretty well used dirtbike motors. I have always used Permatex for "iffy" seals. They make a whole line of products for different applications. Since from the pictures it doesn't look like you defect goes all the way from inner to outer case, I think welding or liquid metal might be a little overkill for a first step. Plus you said it didn't leak oil in that spot anyway on initial fire up.

From Permatex - Adhesive & Sealant Solutions...Made for the Professional

MotoSeal® 1 Ultimate Gasket Maker Grey

For two and four cycle engines. Solvent-based bond fully seals within 20 minutes. Forms a tough flexible bond that is highly effective on irregular and uneven joint surfaces. Ideal for use on frequently disassembled engines. Resists gasoline and other damaging fluids. Withstands temperatures 350°F (177°C) continuous, 400°F (204°C) intermittent.
 
I like the liquid gasket idea. if you try that and it didnt work then you could always try the liquid metal idea after, however i dont think that you will need to do that.
 
Wow, thanks everyone. This gives us a lot of options that we didnt have before. I think I will approach this with a plan A/B/C. Liquid gasket, jb weld, complete crank case replacement or sell the bike.

Plus the fact that others have done this before (or at least similar things) builds confidence.

I will definitely let everyone know how this goes.
 
JB Weld is excellent for low pressure areas...I have used it to seal 3" cracks in the water jackets of a jet boat engine, and it survived vatting the block 2 years later during rebuild time.
 
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