Mismatch case

[Waternut]

Looking into buying the top half of a 62t case from someone who destroyed their bottom case to eventually replace my 61x case. I was hoping to match his top half with my bottom halve. I know the cases are matched sets but what kind of success do people have when mismatching cases?

I figure this might be a cheap way to get into a 62t case but if it'll potentially cause air leaks or seal seating issues, it's not worth it.

 

[jetski9010]

I have ran mismatched cases with no problem. Just clean both gasket surfaces really good and use the proper sealant and you sould be ok.

 

[SUPERJET-113]

I have ran mismatched cases with no problem.

X2
Just make sure the crank fits and spins freely and cases close all normal.
i ran mismatched cases in my Waveblaster II for a couple years(760 w/ dual 44's). Also ran some mis-matched 61X cases in a SN for a few years.

 

[kevbo]

Assemble the case and measure the bore. If its too loose the bearings will slide and slowly eat up the case. If it is too tight there is a chance that the bearings can overheat. An offset can cause an overload failure.

 

[egbrig]

There is a reason cases are matched. You can always calculate how much it will cost to replace the engine if your wrong vs. buy a matched set and its that (in the back of your mind) when's it going to boom. Yes, you could have the cases line honed to the correct clearances. Pay today or pay much more tommorow.

 

[Big Kahuna]

good advice.

 

[wsuwrhr]

Yep, it might work....but what if it doesn't?

Not worth the risk.

Brian

There is a reason cases are matched. You can always calculate how much it will cost to replace the engine if your wrong vs. buy a matched set and its that (in the back of your mind) when's it going to boom. Yes, you could have the cases line honed to the correct clearances. Pay today or pay much more tommorow.

 

[WAB]

all the bottom cases are marked 6m6 I thought??

 

[Waternut]

They are all 6m6 bottom cases but I believe the halves are line reamed together and therefore a matched set. They should all be close but I wanted to find out how close they are and if it would be a problem.

 

[wsuwrhr]

They are all 6m6 bottom cases but I believe the halves are line reamed together and therefore a matched set. They should all be close but I wanted to find out how close they are and if it would be a problem.

They are all close, but as far as machining goes, they could be MILES apart.

.002-.005 inches/.05-.12 MM is pretty close, but as far as a bearing surface goes, this is a mile.

Might work, but what if it doesn't.


Brian

 

[nightrider05]

The way I look at it is as follows:

They are machine made. Machines wear out. Meaning every set is different as the machine wears down just a tad bit.

I personally don't mismatch cases. Never have and never will.

 

[kevbo]

Just measure the bore and see what you have. The bearings dont care if the case is mismatched as long as the bore is correct.

 

[Waternut]

Well I ended up buying the bottom case off the guy too even though it was a little damaged. If I can fix the case for fairly cheap, I'll do it. If not, at least I'll have something to compare too.

 

[waxhead]

Gee I have done it a few times on engines back in the day
8mm strokers that have let go as they are to thin and gone through when something blew out
Never had an issue, its japanese engineering here very very close tolerances

You make the choice yourself if you would do it or not but I would do it on my own engines no problem at all

 

[SUPERJET-113]

There is a reason cases are matched. You can always calculate how much it will cost to replace the engine if your wrong vs. buy a matched set and its that (in the back of your mind) when's it going to boom. Yes, you could have the cases line honed to the correct clearances. Pay today or pay much more tommorow.

Hog wash.
If the crank spins freely and they seal your in.
I have done it several times in the past 20 years on Yamaha twin cases.
Let me know if you have any 62t/64X top cases. I'll buy them from you and run them for years to come.