Is this main trashed?

tferrell · 09-24-2002, 12:51 PM

I finally pulled my engine to track down a major oil leak. Sure enough, the main seal (flywheel end) was trashed, but there were also remnants of 2 or more shims in there. It looks like they may have wiped out the end of the main bearing. My problem is that I don't know what the main bearing should look like. I assume that the end of the bearing should be a relatively flat surface. Mine has a lip around the outer edge. I've tried to attach a picture here. Can anyone offer advice? Thanks in advance.
Tracy

Steve F · 09-24-2002, 01:00 PM

Yep,trash,no good boat anchor

,I'm just up the street from you in Carlsbad,give me your address and I'll get that worthless mass of metal off your hands so you can look around for another engine

.........I really think you could be OK,I don't think holding oil is a function of that surface of the bearing,BUT,my offer still stands

tferrell · 09-24-2002, 01:10 PM

Steve,
I think I'll try rebuilding it first. I was just hoping that I could check end play, put in the right shims and seals, and drive it for a while. But, thanks for the offer

Tracy

Steve F · 09-24-2002, 01:34 PM

Hi Tracy,just messing with you

What you are planning to do is what I would do as well,Good call..,and good luck

Green 912 · 09-24-2002, 01:50 PM

Ouch! My vote is trash. The flat surface on the end of the main is where the endplay is set with the shim rings. I bet the crank was flopping back and forth pretty good and that can cause damage to the case in the middle mains area. Time to split the case.

Don't listen to those guys, sell it to me.

I love 912 motors and will sell you a nice Type 4 2.0 or a 2.5 to fill the motor hole with.

Efrain68912 · 09-24-2002, 09:41 PM

Shoo, vultures, shoo!

tferrell · 10-08-2002, 02:32 PM

Well, now I know the answer. That main is trash and the inner main bearing areas of the engine case are all munged up. I'm waiting word from the machine shop on whether it can be saved. Tearing that engine down was fun, though. Tracy

tferrell · 10-11-2002, 02:29 PM

The engine case and crankshaft can be saved, but
I'm having trouble locating under and over sized
main bearings. Does anyone have a secret source?
I will probably need .25mm inner/.50mm outer. Any
help would be appreciated. Thanks.

Green 912 · 10-12-2002, 04:39 AM

Non-standard bearings for 356/912 cases are almost imposable to find. Bearings for ground undersized cranks are common and same price as stock but oversized bearings for line bored cases are made from Unobtainum. If you are able to find any let us know, I myself have 2 cases that could use a line bore. I think that the company that used to make them stopped and they are now NLA type parts

There is another method for saving a case but it is almost as expensive as getting a used but good case. The case halves are machined down slightly on each of the 2 mating faces and then the case is reassembled and line bored, both crank and cam, to standard size. This is the same method for reboring rods but on a larger scale. Among other things you have to shim the jugs out or you will have something like 200 to 1 compression. As the cases are, due to the machining, closer together and smaller.

Is the damage to the middle main the little notch that keeps the bearing from moving? That is common when there is too much play in the crank. The crank punches the middle bearing and cracks the case at the notch. If so there is an easy, at home fix. Cut a new notch on the other case half mirror to the damaged one. Use a new bearing to mark and measure and cut very carefully with a Dremel tool using a thin disk.

If the damage is due to a ridge built up in the bearing seat portion of the case from the crank running against the case then you have more work to do. If it is not real bad you can shave it down using box knife type razor blades as a scraper. (Scrape holding it 90 deg to the ridge, don’t try and cut the ridge off, scrape!) Shave it down and use machinist marker ink on the case as you get close. Paint on a film of ink, press in a new bearing to see the high spots then shave very small amounts and check progress often as you go. You want to remove the high spot ridge without leaving any low spots. Don’t shave any material off the undamaged portion of the case/bearing seat, just the ridge! All is good when the bearing fits in and seats fully in the marker ink. This can be done but you MUST be slow and careful.

tferrell · 10-14-2002, 06:59 AM

Thanks for the reply. You are right on about all the damage to the case. The machinist that is working on the case says he knows someone who can make bearings, but they will cost about $400. That's beginnig to sound like my only option. Bummer! I'll post here if I'm able to track down a source of bearings, though. Thanks again. Tracy