Nick along edge of case half. What to do?

queen of spodes
Edited Date/Time 11/2/2014 7:23am
I spotted a small scratch on the case half of my vintage KX125 resto tonight. You can see the nick in the center of the photo below. This is an Ebay case because the oil bung on my original case was broken from PO.

Question is will Yamabond fill that in and seal, or am I fucked?



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Paw Paw 271
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Paw Paw 271 10/28/2014 6:19pm
10/28/2014 6:19pm
I see a lot of marks indicating the case was mishandled, but I fail to see a crack.

Paw Paw
queen of spodes 10/28/2014 7:24pm
10/28/2014 7:24pm
Paw Paw 271 wrote:
I see a lot of marks indicating the case was mishandled, but I fail to see a crack.

Paw Paw
It's a nick, not a crack. Looks like someone may have used a razor to clean the surface and it gouged slightly. No idea - that's how it came from Ebay seller.

Question is, can the nicks be filled in? Cases for this 1989 model are NLA and any NOS case halves are long gone. This is the third case set I've bought on Ebay and each turns up new surprises. This one is the best of the bunch.

Aceofspades 10/28/2014 8:08pm
10/28/2014 8:08pm
Put jb weld on it and smooth it out. Fixes it very nicely, and works on large nicks as well. Make sure there's no raised areas, so a little light sanding of the area might be needed to ensure flatness of the mating surfaces.

The Shop

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pete24
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pete24 10/29/2014 3:52am
10/29/2014 3:52am
bring it to a machine shop and have it surfaced , the guy that took it apart didnt use the proper screwdrivers when he pried it apart
lumpy790
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lumpy790 10/29/2014 7:16am
10/29/2014 7:16am
Kawabond/Yamabond should seal that small scratch....but I would also keep an eye on that area for a wet spot if it does leak. Dust will stick to the area if it does leak.
Paw Paw 271
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Paw Paw 271 10/29/2014 7:20am
10/29/2014 7:20am
I swair the original post said "crack". It has been changed.

Paw Paw
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2 Stroke Beast 10/29/2014 7:29am
10/29/2014 7:29am
If you want to know your bike is perfect take it to a machine shock to have it resurfaced but i would just put jb weld on the gasket surface and sand it flat either method works fine.
queen of spodes 10/29/2014 7:33am
10/29/2014 7:33am
Does resurfacing involve removing thickness from the case surface?

@Lumpy, the scratch is adjacent to the crankcase. A leak here would allow air in, creating a lean situation. Has to be sealed up one way or another.

@PawPaw, I changed the OP since I was thinking scratch and typed "crack". sorry for confusion.
2 Stroke Beast 10/29/2014 7:36am
10/29/2014 7:36am
queen of spodes wrote:
Does resurfacing involve removing thickness from the case surface? @Lumpy, the scratch is adjacent to the crankcase. A leak here would allow air in, creating a...
Does resurfacing involve removing thickness from the case surface?

@Lumpy, the scratch is adjacent to the crankcase. A leak here would allow air in, creating a lean situation. Has to be sealed up one way or another.

@PawPaw, I changed the OP since I was thinking scratch and typed "crack". sorry for confusion.
I would do the jb weld the machine shop will more than likely add a weld then shave the weld to the original specs
pete24
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pete24 10/29/2014 8:29am
10/29/2014 8:29am
the machine shop will just take a few thou off it till it cleans i have it done all the time matter of fact im assembling a LT500 rite now that i had to have every surface machined cuz of previous " mechanics"
casper
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casper 10/29/2014 10:56am
10/29/2014 10:56am Edited Date/Time 10/29/2014 10:57am
You can try this, it's used to fill imperfections in mating surfaces of heads. You spray in on the gasket before installing it. I use this on all my gaskets, not just for head gaskets.

moto38
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moto38 10/29/2014 3:38pm
10/29/2014 3:38pm Edited Date/Time 10/29/2014 3:43pm
I had to fix a situation similar to this. Contact-Cemented some medium grit sandpaper to a large piece of glass, and rubbed the case flat along it until all the nicks and gouges were gone. Just make sure the sandpaper is really well cemented to the glass and the pieces of sandpaper dont overlap eachother. Then rinse the case in a parts washer a few times to get rid of the shavings.

Of course all the engine internals (transmission, etc) have to be removed in order for the cases to lay flat on the glass
xnationalwrench 10/29/2014 6:53pm
10/29/2014 6:53pm
moto38 wrote:
I had to fix a situation similar to this. Contact-Cemented some medium grit sandpaper to a large piece of glass, and rubbed the case flat along...
I had to fix a situation similar to this. Contact-Cemented some medium grit sandpaper to a large piece of glass, and rubbed the case flat along it until all the nicks and gouges were gone. Just make sure the sandpaper is really well cemented to the glass and the pieces of sandpaper dont overlap eachother. Then rinse the case in a parts washer a few times to get rid of the shavings.

Of course all the engine internals (transmission, etc) have to be removed in order for the cases to lay flat on the glass
I recommend going in a figure 8 pattern also.
queen of spodes 10/30/2014 4:09am
10/30/2014 4:09am
casper wrote:
You can try this, it's used to fill imperfections in mating surfaces of heads. You spray in on the gasket before installing it. I use this...
You can try this, it's used to fill imperfections in mating surfaces of heads. You spray in on the gasket before installing it. I use this on all my gaskets, not just for head gaskets.

This is a centercase, no gasket used.
queen of spodes 10/30/2014 4:10am
10/30/2014 4:10am
moto38 wrote:
I had to fix a situation similar to this. Contact-Cemented some medium grit sandpaper to a large piece of glass, and rubbed the case flat along...
I had to fix a situation similar to this. Contact-Cemented some medium grit sandpaper to a large piece of glass, and rubbed the case flat along it until all the nicks and gouges were gone. Just make sure the sandpaper is really well cemented to the glass and the pieces of sandpaper dont overlap eachother. Then rinse the case in a parts washer a few times to get rid of the shavings.

Of course all the engine internals (transmission, etc) have to be removed in order for the cases to lay flat on the glass
In another thread on lapping case halves, a few people warned that taking too much material would cause transmission internals to bind. (?)
moto38
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moto38 10/30/2014 7:11am
10/30/2014 7:11am
moto38 wrote:
I had to fix a situation similar to this. Contact-Cemented some medium grit sandpaper to a large piece of glass, and rubbed the case flat along...
I had to fix a situation similar to this. Contact-Cemented some medium grit sandpaper to a large piece of glass, and rubbed the case flat along it until all the nicks and gouges were gone. Just make sure the sandpaper is really well cemented to the glass and the pieces of sandpaper dont overlap eachother. Then rinse the case in a parts washer a few times to get rid of the shavings.

Of course all the engine internals (transmission, etc) have to be removed in order for the cases to lay flat on the glass
queen of spodes wrote:
In another thread on lapping case halves, a few people warned that taking too much material would cause transmission internals to bind. (?)
I suppose it is possible, but since the gouges arent very deep, it shouldnt affect any clearances for the transmission. It didnt for me, anyway.

Pit Row

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sclark309d
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sclark309d 10/30/2014 9:33am
10/30/2014 9:33am
casper wrote:
You can try this, it's used to fill imperfections in mating surfaces of heads. You spray in on the gasket before installing it. I use this...
You can try this, it's used to fill imperfections in mating surfaces of heads. You spray in on the gasket before installing it. I use this on all my gaskets, not just for head gaskets.

queen of spodes wrote:
This is a centercase, no gasket used.
it's just a sealant in your case.

I've done several cases like this. I used to be one of those "weld it up then machine it down properly" guys, but have since decided it's just an old bike and just a sealing surface. It needs to be flat, and remain in place when the case halves are screwed together. No drama

I now fill those kinds of nicks/scratches with JB Weld, then smooth somewhat with a plastic smoother, as if you were applying body putty.

After it cures, do a quick lapping as described above to assure flatness, then assemble with the sealer of your choice.

I've had good results with the Yamabond type sealers.
queen of spodes 10/30/2014 6:25pm
10/30/2014 6:25pm
I lapped the cases a bit more tonight, cleaned them up good then applied a little JB Weld to the nick circled above. Looks like a good even coverage through my magnifying glass (growing old sucks right?).

harescrambled
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harescrambled 10/31/2014 2:03am
10/31/2014 2:03am
I dunno...I've hand lapped several sets of cases, including the engine in the bike my sig results came from, and I haven't had any issues. Tranny side clearances are usually sufficient for a few times on the lapping surface without binding. As long as your crankshaft doesn't bind you should be fine to lap it. (prior to lapping cases, I measure the width of the crankshaft, assemble the cases with the main bearings in them and the crank out, and measure the width between the bearing center races to get my clearances. Never had a problem
ToolMaker
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ToolMaker 11/2/2014 7:23am
11/2/2014 7:23am
Yamabond should be more than sufficient on that. But to be sure I would use a good cleaning agent
on the edge of the case so you get best bond possible. Yamabaond cures to a very rigid finish. The
pressure change from outside the case to inside the case has no chance of breaching that if you clean the
aluminum well first.
TM

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