epoxy question

[idiotboy]

I recently got an old non-Penton dirtbike for free.It sat outside with water in the motor for a while, causing some corrosion in the crankcase.I glass beaded the area and cleaned it with acetone.I would like to put some kind of epoxy or sealer on there to try to prevent any future air leaks.What brand or type of product do you guys suggest ?

[dirtbike]

I suggest SYSTEM3 or WEST marine grade epoxy.
Just try to locate gasoline without alcohol
if you can. Modern gas often contain alcohol
and it will deteriorate the epoxy.

Do not buy epoxy at your gas station or
hardware shop in those two small tubes.
Doesn't matter what the name say, it's crap.

I have heard that JB weld which infact is
epoxy have worked pretty good inside the engines.
Have no experience though.

It might be a good idea to buy a epoxy based
gelcoat. It has a more resistant surface and
could possibly withstand the gas better.

By the way. Both magnesium and aluminium will form an oxide layer within fractions of a second after sanding. That layer will prevent the epoxy from binding. You need to sand the surface with epoxy saturated grit paper and leave the resin there for curing. On top of that you can add another coat of either plain epoxy or gelcoat (epoxy type).

Do not build up a too thick layer. Pieces that might come off could damage your engine.

[DKWRACER]

Kip Kern has been thru some of the same adventures with badly pitted Mag cases. He has had success with Red Glyptal paint which is impervious to oil and gas etc...I think his method is to bead blast then clean and then brush on the magic...I just bought a quart and would be willing to split 50/50 with you....Interested??

[tomale]

I am not so sure about JB being all that bad. I cracked the clutch case on the KTM motor soon after I bought the bike. The shift lever was pushed into the case. I cleaned it up and filled it in with JB weld, allowed it to dry and then painted it. After all these years (28 to be exact) it is still holding just fine. I forgot all about it until last year when someone else in the group had the same problem and it reminded me of what I had done years before. I am sure that there are better product on the market now and would probably work better in the crank case area but for somethings JB has worked just fine. I would have thought that if corrosion was that big of a problem then the JB stuff should have let go years ago. Just my thoughts, Probably a good Idea to use something that holds up better against gas, etc. I hope things go well in your efforts to get it runing again.

Thom Green,I own and ride a 76 250 MC5 MX which I bought new.

[herman]

I had bought a 74 250 and had the same problem with the water making the cases look like swiss cheese,I had a retired penton machanic and owner of the Buss.split my cases and do the rebuild he said that in all the years hes been seeing this happen he would check behind the bearings if you have it behind there most of the time it will not hold the bearing any more.Just hate to see a person put money into a bottom end and have a bigger problem.So i ended up buying so good cases from Barry Higgens Hope yours are better than mine where. Herm

[farmer58za]

Devcon F aluminium epoxy.
Good luck
David

[hrbay]

Sandblast not bead blast, glass beads close the grain of the metal you want to open the grain up(increase surface area) to hold the adhesive. Loctite Hysol EA934na, good stuff and has good temp. resistance. I have it in several motors for same reason and others.

GC