Patching a crankcase cover.

10 replies to this topic
  • Geomyster

Posted April 12, 2012 - 01:15 PM


Needless introduction: I crashed and put a small gouge in my crankcase cover (LH).

I searched the forums a bit to see if anyone has had much luck repairing rather than replacing the crankcase cover. (Why drop $100 bucks on a new one and wait for it to get shipped here if I can fix the old one). -But didn't see a lot regarding repairing the cover (Although sounds like plenty of folks have also punched a hole in their cover.)
The hole is about 3/4 inch long and not wider than 1/4 of an inch.
Has anyone had luck welding these up using a welder? Or has anyone had success with JB Weld on filling a gap that size? -I've also heard rumors of a "tape" that you can put over small holes in metal with low pressure.

Any suggestions?

Edited by Geomyster, April 12, 2012 - 01:15 PM.

  • Lumberjack450

Posted April 12, 2012 - 09:05 PM


Are you referring to the flywheel cover or the actual side of the case? If the first, yes. If the latter, I am not sure, however I did JB weld a hole/crack on my clutch cover about an inch long with success. I assume as long as it does not rub on any internal moving part you should be fine. Many people on here will tell you to do it right but I know what it's like to ride on a budget.

  • jsantapau

Posted April 13, 2012 - 05:37 AM


The problem with epoxy is that it will eventually fall out could be 6 hours or 6 years. proper material selection and care when applying is the key. The ignition cover may be magnesium and you might have difficulty finding someone to weld it.

I would epoxy it for now and stop eating out and drinking beer for a month to save up money to buy a new one. By replacing worn out/broken items in a timely manner with a proper fiitting part will prevent your bike from becoming a roached out rat before its time and ensure you a happier existence with your bike with a better resale value when you are done with it

  • Zombatar

Posted April 13, 2012 - 07:22 AM


I successfully patched a cracked clutch cover with JB Weld many moons ago. It lasted for at least two years until I got rid of ths bike.

  • zlathim

Posted April 13, 2012 - 07:30 AM


I successfully patched a cracked clutch cover with JB Weld many moons ago. It lasted for at least two years until I got rid of ths bike.

You and me both. Mine was on a 1980 YZ 400.

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  • Zombatar

Posted April 13, 2012 - 07:35 AM


You and me both. Mine was on a 1980 YZ 400.

Nice! Mine was a 1978 YZ100.

  • freeriders98

Posted April 13, 2012 - 03:40 PM


I JB welded the clutch cover on my 98 WR400, and had no problems with it. Just clean it up REALLY good, sand it with something like a 60 grit to give the JB weld something to really grab onto and you should be good. I then took high temp engine paint and painted it black, you could hardly tell there was anything there.


Posted April 17, 2012 - 05:32 AM


Is this the stuff you talking about?

  • BajaFool

Posted April 18, 2012 - 01:26 PM


Yes, that is what you can use to repair your little hole. That EBay price is ridiculous. The seller should at least wear a black mask and point a gun at you. There are other companies that sell similar products. Duro, 3M, Devcon and Loctite are some that come to mind. You can find these products at home improvement stores, hardware stores and auto parts stores for the do it yourself mechanic. The JB Weld product that you referenced is two part epoxy adhesive/sealant. It will work just fine. Let it dry thoroughly after application and then CAREFULLY blend the repair so it doesn't stand out too much. Don't grind off so much material that the repair will fall out of the cover. Paint the cover and go riding.

  • Geomyster

Posted April 22, 2012 - 11:18 AM


Thanks for all the input everyone!
Just a follow up:
I went ahead with the JB Weld, it seems like it worked, just a couple notes:

I had a big enough hole (dim sized) and the JB weld was fluid enough that I couldn't seal it. I taped a latex glove to the outside of the cover to dam the JB Weld so it wouldn't just run out. After doing that it went smoothly.
JB Weld says it's dry after a couple hours and cured after 24. But it was still a lil bit soft after 24 hours so I let it sit a couple more days before putting it back on the bike.

I took it out for a ride yesterday and it did not leak any oil. -Now maybe I'll address the cosmetic issue and paint it up a bit.

- freeriders98 Thanks for the tip on hitting it with 60 grit sand paper before applying the epoxy. Definitely a good thing to do.

Another note for anyone that decides to do this kind of epoxy patch: I suggest making sure that the inside of the cover is VERY clean before putting it back on the bike. I would also suggest that you do an oil and filter change after an hour or so of riding in case any lil grit was left floating around in there after reassembly. -At least that's what I did.


  • allterra

Posted April 22, 2012 - 04:08 PM


On the JB subject......If you have the 2 tube style and need to patch a larger hole then what I do to increase the tensile strength in to add fileings fom my saw or course grinder to it. The idea behind it is alot like that of concrete. The epoxy is an excellent binder (cement) and the cuttings (stone) provide the strength. Do a couple test strips on a piece of paper to find the right mix for the applications strength and flexiablity. The larger the hole the longer the suttings I use. and of course the cleaner and rougher the area the better adheasion.


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