Clyinder air leak found...what to do, how to fix.

argclh6670 · Post by **argclh6670** » 11:33 pm Mar 29 2015

I built a leak down tester to use after i redo topend on sons 95 kdx 200 but i wanted to test the tester sooner. So, before pulled jug i plugged it up and tried it out. I found a huge leak under the reed block at cylinder base to case, What i found was... Its right on the cases seam to cyl in rear, theres a very noticable difference in the level of case sides at that part of the seam. Also in the front too but not as severe as it was sealing fine. I should also add, cyl was torqued down to spec. Not sure how to go about addressing this when i go to reassemble after new topend. Ive attached a couple of photos to better explain issue. Please give suggestions....

Jaguar · Post by **Jaguar** » 12:25 am Mar 30 2015

glue the hell out of it!

Tioli · Post by **Tioli** » 06:40 am Mar 30 2015

Put a flat edge on it and move it around to get a feel for how it runs.

If you don't want to split the cases you could take the studs out and shave it. It's easy enough to clean the insides of the cases and marsking it all up below the top.

Clean with thinners, fine sand then smear of Devcon (aluminium epoxy) then clean up is also a option.

All depends on what the straight edge has to say.

My 2c

pumpguy · Post by **pumpguy** » 09:15 am Mar 30 2015

It appears you have a mis-matched set of cases. Both halves should be on the same plane and at a true right angle to the main bearing bores.

The "proper" way to remedy this is to completely strip the cases and have the high case milled down to match the low case. This should be done with both cases assembled together, bolted to the table of a horizontal milling machine. Can be done on a vertical Bridgeport type mill, but an angle plate is needed and the set-up is a little bit trickier.

This can also be done by hand using files, scrapers, a piece of true flat plate glass, and marking medium like Permatex Prussian Blue. This process is not difficult, but is tedious and requires careful workmanship.

Space and time don't allow a complete description of the process here, but if you want more information, send me a PM and I'll tell you more. My email is <oakservcs@aol.com>

s10gto · Post by **s10gto** » 09:22 am Mar 30 2015

I agree above 100%. This is the correct way to do it. It may not be a bad idea to do the bottom end also as I see a sleeve in that jug. Who knows what that engine has been through.

Post by **Julien D** » 09:49 am Mar 30 2015

My guess by looking at the pics is that a previous owner had a catastrophic failure, sleeved the jug, and replaced a broken case half. Case halves generally need to be purchased as a match set. Obviously that was not the case here. Removing the studs and having it shaved down would be the ideal fix.

s10gto · Post by **s10gto** » 09:59 am Mar 30 2015

Just something to note is you will want to have it machined as little as possible. Machining the base will raise the compression and change port timing.

argclh6670 · Post by **argclh6670** » 10:33 am Mar 30 2015

pumpguy wrote:It appears you have a mis-matched set of cases. Both halves should be on the same plane and at a true right angle to the main bearing bores.

The "proper" way to remedy this is to completely strip the cases and have the high case milled down to match the low case. This should be done with both cases assembled together, bolted to the table of a horizontal milling machine. Can be done on a vertical Bridgeport type mill, but an angle plate is needed and the set-up is a little bit trickier.

This can also be done by hand using files, scrapers, a piece of true flat plate glass, and marking medium like Permatex Prussian Blue. This process is not difficult, but is tedious and requires careful workmanship.

Space and time don't allow a complete description of the process here, but if you want more information, send me a PM and I'll tell you more. My email is <oakservcs@aol.com>

Email sent, id like to hear more about the process to determine if i should try n tackle this myself. Thanks.

chkdx · Post by **chkdx** » 11:13 am Mar 30 2015

Honestly, quickest / best fix might be to buy a matched set of used cases and transfer all the innards over. Even if you get this set of cases flat so it seals, the cylinder could easily end up tilted. A really sharp machinist with a mill can get it right, but that may be pretty costly, and still requires a complete teardown to do the machine work.

diymirage · Post by **diymirage** » 03:15 pm Mar 30 2015

buy yourself a second base gasket and cut it in half, using half of it as a spacer to bring the lower case up to the same level
then get yourself some high tack gasket sealant and use that to glue the second, full sized gasket on top of the half one

and that is in NO WAY the proper way to go about it BUT it will be a bandaid to keep you through the riding season and then next fall you can properly fix it

pumpguy · Post by **pumpguy** » 04:05 pm Mar 30 2015

This will work IF....the amount of mis-match between the 2 case halves is equal or very close to the gasket thickness. If off by more than just a couple thousandths of an inch, you're no better off than you were before.

To be sure, measure the gasket thickness with a micrometer, and the amount of case mis-match with a depth micrometer. A decent dial or digital caliper should give good measurements too.

If you do go this route, be very careful how you cut the gasket in half. You could end up with a nice air leak channel.

argclh6670 · Post by **argclh6670** » 10:32 pm Mar 30 2015

diymirage wrote:buy yourself a second base gasket and cut it in half, using half of it as a spacer to bring the lower case up to the same level
then get yourself some high tack gasket sealant and use that to glue the second, full sized gasket on top of the half one

and that is in NO WAY the proper way to go about it BUT it will be a bandaid to keep you through the riding season and then next fall you can properly fix it

Good suggestion. But, the case lines up fine on the exhaust side (doesnt leak).

canamfan · Post by **canamfan** » 04:55 pm Mar 31 2015

If it was mine I would take a large stiff flat file and carefully file down the high point. Then get a straight edge to make sure the case is level front to back. You might have to use some type of filler-sealant, ask at a part store. If it doesn't hold your not out much. Then you can go from there.

argclh6670 · Post by **argclh6670** » 12:09 am Apr 01 2015

canamfan wrote:If it was mine I would take a large stiff flat file and carefully file down the high point. Then get a straight edge to make sure the case is level front to back. You might have to use some type of filler-sealant, ask at a part store. If it doesn't hold your not out much. Then you can go from there.

Thats exactly what i did....took a fine file to it. Ive straightedged it, looks way better now. I have some threebond ill throw on there for just incase. Thanks to all for suggestions and ideas.

argclh6670 · Post by **argclh6670** » 02:05 pm Apr 09 2015

Everything worked out.....retested at 6psi for 13 mins had loss of .7psi . AnywYs, thanks for all the suggestions n support guys.

Mnmonster · Post by **Mnmonster** » 08:49 am Jun 16 2016

argclh6670 wrote:Everything worked out.....retested at 6psi for 13 mins had loss of .7psi . AnywYs, thanks for all the suggestions n support guys.

I have found pretty much the exact same issue that you had with your bike in this thread. Can you comment a little more on how you did the fix and how its holding up now?

Thanks!

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