Cracked case and oil leak!

Hi guys,

I wondered if anyone else has had this problem? I have a small crack in the case at the rear engine mount. Its in a recess that if you take the side casing off, looks to be where the kickstarted mechanism spring fits against. I have included a couple of pictures. I have cleaned it up and used JB Weld to try and seal it but it seams by going over to kickstart only, its causing extra stress on this area and is leaking again. A yamaha engineer here in the UK, I spoke to said its a fairly common problem and if so has anyone else experienced it. On a side note I took the XS250 motor apart on the bench and its gone in exactly the same place. Either I'm just unlucky to have found two engines with the same problem or this is a common fault????

That may be a casting mark. I have never seen one with a crack in that location. Maybe your custom frame is causing stresses in a place it was not able to handle. I have had used and taken apart 7 xs400 motors in the last 15 years and never seen one with this before.

I've checked on the 250 and it's definitely not a casting mark as both have different cracks but in the same place. it seems to be the return stop for the kick start throw. As it returns it hits the same spot inside the case and this is where it's cracked internally and externally. As the engine warms up its spraying oil out of the mark in the picture.

The frame I built couldn't really be stressing that area because the mounts and rails are identical to the original frame, but also wouldn't crack up in that area due to mounting lugs probably going first, this crack is very localised.

I now have two engines I can't use!! Guess I'll be looking for another engine or case and hope that they're OK too!!!? Seems a shame after all the effort to build the bike!!

Thanks for the response though!

Have you tried getting to the inside surface of the casings, cleaning them and then JB Welding them from inside?

I've talked to a few people who have admitted to having hidden JBWeld repairs that have held well.
Failing that, aluminum welding ought to fix them.

You can't find anybody to weld the case? and maybe add a little more material in that spot to reinforce?

I'm a coded welder/fabricator and more than capable of welding it but having spent 7 months building the bike only to discover the casings cracked I tried to JB Weld it from the outside just so I didn't have to strip the whole engine!! JB Weld obviously didn't work and can't really be used inside the case due to position of crack and component position.

Looks like I'm stripping the bike! Never mind!