Did I ruin my engine?

[kcasser]

OS 50 Hyper, one year old.

I was replacing the bearings and the hammer slipped ever so slightly while drifting out the front bearing. I grazed the edge of the back of the crankcase where it mates with the backplate. After putting it back together, now when I turn the crank by hand, a couple of drops of oil squeeze out at that spot where the backplate mates flush with the back of the crankcase. Am I screwed? I'm presuming a new body will cost as much as a new engine, and my weekend is shot. And it was turning so smoothly with the new bearings...

Any suggestions? Sorry - no time for photos.

[TheBum]

Maybe some JB Weld to fill the gouge? I used some to fix a crack in my crankcase after a crash, but it wasn't in an area where it would really impact operation of the engine.

[kcasser]

It's a thought. I just don't want to glue the backplate to the crankcase!

[TheBum]

It's a thought. I just don't want to glue the backplate to the crankcase!
I was thinking more of the JB Weld as a filler.

[kcasser]

I think that if I fill the void without the backplate tightened on, I'll have other problems. But if I fill with JB Weld and then install the backplate, it will probably be stuck for good.

I'll try to post a photo: The spot is just to the right of the center joint in the crankcase

[Wrench]

Next time you want to change the front bearing heat it a bit with a torch or monokote gun. Take an ball allen or small screw driver that is long enough for the handle to reach from the bearing past the end of the crank case with the bit through the bearing. Turn the eng on it's back and smack it against the work bench. Hitting the handle of the driver against the workbench will drive the bearing out and not damage the crank case. Doing the rear bearing just heat the case around the bearing then tap the crankcase against a block of wood and the breaing will fall out. Place the new bearing on the crankshaft and slide it back into the crankcase while it's still warm. You can freeze the new bearings before hand to make it a bit easier. Leave the hammer alone.

I have a saying for my DIY customers that tried to fix their car before bringing it to me which ends up always costing them more in the long run.


" Drop the tools and step away from the car" :YeaBaby:

[kcasser]

Lesson learned! I've ordered a new crankcase and will do it right this time, I hope.

[JimLerch]

Find a flat piece of glass, like an old table top or fish tank. Get some valve grinding compound from the auto parts store (loose abrasive in thick oil paste). Place grinding compound on table and spread it around. Place engine block on top of glass plate, and with short back and forth motions, re-grind the back of the engine flat until your dent is no longer visible. The trick is to keep the engine flat against the glass at all times, this will re-grind the back of the block into one smooth surface again.

You'll know when to stop when all of the surface has a uniform texture. You can also clean and dry the surface of the case and rub "Sharpie" permanent marker all over it, then do a short session of grinding. Inspect back of motor for evidence of the Sharpie ink. Done properly, the ink should erode in a smooth progression all about the contact area of the case.

Clean up with mineral spirits or other thinners. Just make sure you wash the case well to get rid of all the loose grit.

If you don't have glass, you could use a large flat piece of steel or alluminum.

[Bigron]

Hi ,


You might try to face off the damaged surface by placing the dinked piece on some 320 sandpaper and rub up and down carefully to try and re surface the part?


Bigron.

[DavidH]

Just curious. If he machines off the back of the crankcase or uses the sandpaper as suggested to smooth out the dent. Then how is he going to prevent the crankshaft and crank pin from rubbing the back plate? Sometimes the crank will run the back plate when crankcase that has no material removed from it. That is if the crank is not pulled into the bearings enough when tightening the fan hub.
The crankcase and back plate are machined to certain tolerances. Changing those dimensions and tolerances and the crank shaft is going to rub on the back plate.

David

[forjer]

Just clean it good, put a light bead of silicon gasket maker (RTV) on and then put the cover on, let it cure and fly. You'll have to do this every time you remove the cover, but how often is that.

[kcasser]

I RTV'd the backplate and viola! no leaks! Thank you all for your help. Engine runs great.