crankcase welding

[stuart1981]

what would be the bestmethod for welding a cracked crankcase off a motocross bike? it is all stripped down, cast alloy, any tips? i heard it is bad to weld iff contaminated with oil, best cleaning product? all help welcome!

 

[Pete.]

Have you stripped the engine down to the cases? If you have I'd suggest starting with cleaning it first by scraping off any heavy dirt then cleaning with Gunk or Jizer, then hot water & truck clean then blowing it dry. You can then use something more aggressive like thinners to clean the area to be welded & a new stainless steel toothbrush-sized wire brush.

If you haven't you're gonna have to do the above the best you can by cleaning locally. Clean up the engine as a whole then go over the area to be welded meticulously. What's broken is it an engine mount or the clutch arm housing or a lump out of the case from a rock strike?

 

[stuart1981]

yes all stripped down, its the flange around the drain blot on the gearbox, hald f it got snapped off, will try and upload a pic, i have been told there is a lot of magnesium in cast alloy, is this a problem for welding?

 

[Pete.]

The couple I've had welded were no problem at all, except one was near impossible to clean perfectly and kept cratering.

 

[aametalmaster]

I just welded a Harley Davidson engine case and it mig welded perfect. I don't know what the guy soaked it in but it was spotless inside and out...Bob

 

[Sam]

Try cleaning with a caustic soda solution and use a 10/15% silicone filler rod should help stop honeycombing have found the higher silicone good for Jap motors any of the above methods of cleaning will be ok.

 

[BChild]

Dishwasher - hotest cycle is a very good way of cleaning engine parts - make sure she's out mind and use one of those cleaning/deodorisiers things after to get rid of the oily smell

 

[stuart1981]

thanks for that, did try jb weld at first, but never held up bouncing over rocls and drop offs ect! i take it tig welding will be the best option then? hopefully you can see from the pics what the problem is!

 

[wyn]

From your pics stuart, it looks like it could do with the whole threaded bit drilling out to a much bigger size and welding in a new lump, then drilling and threading it. Or get it totaly welded up then redrill and thread.

 

[Weldingartisan]

As it's only a drain and not dimensionally critical, I'd make a threaded boss cut all the crap out and weld it on. W/A

 

[stuart1981]

yes was going to get it totally filled then drilled out and retapped, thanks for all the help! by the way, it cracked off while i was un screwing the drain bolt! so if anyone else has a motocross bike, i reccomend a tourqe wrench! even if it dont seem that important on the drain bolt!