years of bad cases

[softailcavie]

what year evo motor had bad cases thanks

[springer-]

Different year EVO cases have different problems.  The factory made many changes to the cases over the years, some good some not so good.

Here are a couple different issues too look out for.

1 The thickness of the spigot hole behind the rear lifter block in some of the later year cases.  I am not sure of the exact years effected but it was around '92-'97.  I believe this particular issue effect 2 or 3 years before the factory changed it back.  This is of particular interest if considering boring the spigot holes for a 96" Big Bore.  These particular years crack at the location shown in the picture.  I have even seen them cracked with a stock 80" engine.  I don't have any actual measurements on the spigot thickness of the "bad" ones.  They stand right out if you compare the case to an earlier case.  This case is not one of the effected cases, I will measure it and post the info in a couple days.




2 Another problem area on several years (during the 80's I believe) is the rear engine mount.  The pinion side case can crack at the rear engine mount.  This is specifically an issue on the cases that have a 90 degree corner machined in the case where the RED arrow point.  Note on this case there is a 45 degree chamfer and not a 90 degree angle.  The ones with the 90 degree corner crack where the YELLOW arrow is. I have seen them crack as much as 1.5" down the length of the engine mount.  Because this is at the oil scrapper there is often a oil leak involved.  It can be hard to find since you might not expect the case to have a large crack in it.



Note the BLUE arrows in both pictures.  The Pinion side case half is much thinner at this area, it is the side that cracks.



3 In the '89-'91 time frame, the left side case bearing race can become loose.  The case is cast around a steel insert that holds the bearing race.  The insert can become loose and cause several hard to troubleshoot issues.  Most commonly the transfer of oil from the engine into the primary.  A common misdiagnosis is a bad seal.  After replacing the seal, it continues to transfer oil to the primary.  It can also work in the opposite direction removing the primary fluid from the primary but this is less common in my experience.  The loose race can also contribute to excessive vibration and end play in the pinion shaft, since the flywheels can move back and forth.

In this picture below you can see the insert is flush with the aluminum case.



This picture shows the same insert with a little pressure on it.  It is clearly lifted indicating it is loose.  This should not move at all.



These are a little closer.



 

It moves a lot more than it looks in the picture.  Here is a video showing it moving.  Once you identify it, you can really notice it.

Here is a Video of the case insert.  Click then select OPEN to view.


4 The lip for the primary O-ring is another problem area on all years.  Check it closely if you have it apart.  In the O-ring groove at the thinnest part it can crack.  The crack can cause leaks at the primary to case seal.  I have seen these cracks go more than half way around the O-ring groove and still be hard to notice if you are not looking for them.




5 At some point and I am not sure when, the factory started using Heli-Coils in the primary cover bolt holes.  If using a stock set of EVO cases, check for Heli-Coils.  It is a simple mod and should be done if they aren't there.  Arrow points to Heli-Coil.




6 Here is a pic of a 1990 case.  The front spigot hole has a oil passage located VERY close to the bore.  While this oil passage is plugged, if the case is bored it can also crack.

[Norton Commando]

Springer,

Thanks a million for posting the excellent history of the EVO engine case problems.

[heritage2]

mine was a 1990 . it cracked across the oil feed hole to the front lifter block and right down int the cyl bore to the main brg . I still would like to know what caused it . I have heard every thing from detonation to overheating  I replaced the cases with a 92 set so it will probably happen again 

[kiwidave]

wow, yes indeed that sure was an amazing post! thanks from here also.

1989-93 has always been the most commonly quoted time frame for these issues.

[paulkay]

Wanted this one sooo much been trying to get it to print, finally got it done and added to my Evo manuals. My 1987 pulled the last crack by that oil passage down the inside and into the lifter block on the outside. THANK YOU!!