K9B help.

[Pete Schaible]

I’m in the process of rebuilding a K9B and when removing the main bearings I noticed this.  There is a crack in the case between where the bearing sits and the area for the connecting rod.  How big an issue is this?

[Pete Schaible]

Walt, the crack runs around the perimeter of the pocket itself.  I don’t know about ‘re-pocketing or how to recognize it.  In the picture it looks like a shadow but it’s a split that runs from 11 o clock -1 o clock of the pocket with the picture’s orientation.  I really just don’t want to blow it up.

 

[Pete Schaible]

It’s not visible from the outside so there shouldn’t be any vacuum leak.  It’s more the strength that concerns me.  I’m going to have it looked at by a welding shop to see what they think can be done.  Autocross shouldn’t put too much of  a strain on it as a season of autocross is probably the equivalent of 1 race weekend.  However fixing it now would be much cheaper than letting it fail and it’s already all apart.

 

[Steen Carstensen]

What you have there is a separation between the steel sleeve and the aluminum case. If the sleeve hasn’t spun in the case, you should be OK. I would heat up the case in the oven to the point where the bearing drops into the pocket, then let it cool and check if the the gap has closed up. If all looks good with the bearing in place, you should be good to go. Always heat the case to remove or install the bearings, they should fall out or drop in. :-))

If the gap is still there, I would send the case to someone like Swedetech for a sleeve replacement.

[Pete Schaible]

Thank you so much Steen,  I didn’t realize they were dissimilar metals.  I did not heat the case to remove the bearing and just tapped it out gently with hammer and bearing remover,  could that have caused this?  It is a SwedeTech motor and I emailed them about what happened and what to do but I am currently waiting on a response from them.  Would heating just the sleeve area with a torch work, or does it have to be an oven?  I was only replacing the Main bearing and don’t want to cook the current bearings for the trans shafts.  One company I spoke with recommended just replacing the case but the $1000 for a case is my entire yearly racing budget so I need to keep things affordable.

[Steen Carstensen]

Do NOT localize the heat using a torch, you need to heat the whole case, it’s very easy to do, just don’t let your wife see you using her oven :-)) The other bearings will not be affected, just don’t go overboard with the heat. You may have a problem dropping the bearing in because the sleeve look to be out of round, so you may have to help it with light tapping of hammer and soft drift.

[Pete Schaible]

Thank you again.  I’ve been freaking out over this for days.  I’ll let you know how it goes

 

[Pete Schaible]

Steen,  It didn’t really take much to remove the bearing… I was quite cautious removing it.  SwedeTech has asked that I send them the case to look  at and go from there.  I am trying to heat the case now and put in an old bearing.  I will probably just send it to SwedeTech and see what they say.

 

[Pete Schaible]

Old bearing installed, the gap is smaller but still there.  I hope SwedeTech can save me.  I’m not having any luck with motors this year.

 

[Steen Carstensen]

Yes, please let us know what Swedetech comes up with.

[Walt Gifford]

Not sure I can see it in that pic. Looks like the case was re-pocketed, maybe that’s why. If it’s just a small crack in a thick part of the case and it doesn’t go through to cause a leak it will be ok for a while longer. If the crack is into the bearing pocket I would think it might spin the bearing when it gets hot.

Gif

FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience

[Walt Gifford]

If it’s not deep you could ball grind the ends of the crack to help keep it from spreading. can you see it on the outside? hard to advise without seeing it.

FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience

[Walt Gifford]

Steen Carstensen wrote:

What you have there is a separation between the steel sleeve and the aluminum case.

Now I’m seeing what you’re saying but I can’t imagine how that would happen unless that bearing pocket is severely warped or the hole it’s in was totally out of round.

Did something move while the pocket for the liner was being machined but they put the liner in anyway. If that’s the case then it’s been that way since day one. Or, wow does the engine hammer the aluminum that bad?

I would say it has to have the pocket machined out and on center for a slightly bigger liner that will have to be custom made.

Anyway Pete, if you heat the case your other little bearings might want to float off their seats and if you’re thinking on it, removing the steel liner in the main bearing pocket will be very hard with just heat.

You need one of two people Muller Machine or me and (lol) I’m busy.

Gif

FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience

[Steen Carstensen]

Those sleeves are installed at the factory so I very much doubt that case made it past QC at TM, also the OP said the engine is a Swedetech, so again it would not have past his QC either. My guess is that something went wrong when the bearing was knocked out without preheating the case, they are in there pretty tight. In a perfect world, yes I agree the sleeve need to come out and the bore should be checked for round and if need be, rebored with new sleeve installed, but I would try to install an old bearing and have a look see and check for gap between the sleeve/case and the bearing/sleeve and if no gap is present, the case can be used as is.   JMHO

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