So, I found a crack from my SXF250 07 crank case. Cant find any info about the alloy.. is it aluminium? magnesium? aluminum-magnesium? Is it possible to weld? I know a guy who is a specialist on tig welding. But what do you guys think about these pics. Can it be done? Or.. should I just scrap the engine? Is there any problems to install a 08 or 09 engine on 2007 frame?

Looks like an easy fix for a good tig welder. I believe the cases are cast aluminum.

If its cracked from the bore where the shaft goes through, I doubt welding would do much good.
Looks like metal fatigue, time and revs have taken their toll. 06 to 10 will go straight into the frame. EXC, SXF or XCF.

I'd try having welded. I've had some worn cases welded and they held fine. Sometimes for cracks, they will bore/grind into the crack and then weld it up. Take it in to a machine shop and just let them give you their opinion.

they make a aluminum brazing rod that works well just google aluminum brazing rod and check it out works well low heat and you can do it your self
www.aluminumrepair.com/

Edited by rmzbeast72, 30 May 2011 - 08:08 AM.
added a link

Im just in doubt because you can see that the crack goes to the crankshaft bearing. But I hope they can machine it again after welding so that the bearing goes like it should. The guy who I know. who knows TIG welding. Is a owner of a machine shop. He should know this type of stuff.

So the case is aluminum? Only the valve cover and side covers are magnesium? I think this could still be useful engine! Not just a intresting piece of junk at the garrage.

Im going to visit the machinist tomorrow.

There is no way the case is magnesium. It's aluminum.

Heh, just wanted to be sure. In speedway racing, there has been italian GM engines with magnesium crank cases.

The crankcase is aluminium, some other components are magnesium and dont respond too well to excessive heat......

Machine engineer said that get new engine case. TIG welding in that place would ruin the case. And would be a big job. ..and he has so much work that he could do it in August. But.. he told me to take the crankshaft to a other machine shop and see that it is ok and in balance. Change the crank bearings and try Techno Weld. It could work and stop the oil leak and fracture. Cant do any more damage any more. Now I have done some praciticing on the Techno Weld, and reading everything about welding of aluminum.

My possibilities at the moment: Make a big ashtray from the engine case. Pay some money to welder/machinist to try TIG-weld it and possibly ruin it. Or.. use this wierd Techno Weld and try it myself. I have done gas welding before and this is very much like welding colmonoy on a steel shoe. I shall take my chances on this! If I fail.. I still have a chance with TIG.

Considering you can get a used set of cases for under $200 (US) why bother welding, gluing or hoping something will fix it.

i have been a welder for 12 years,it is cast aluminum,it can be welded,tig welded by an experienced welder,the problem with welding cast is it is very impure and pours.to make it worse the oil gets impregnated in the material,which means you have to weld and grind it out multiple times.because all the impurities float to the top.and all that takes time.i would guess most shops would charge 100-150 bucks.i dont know what the machine shop would charge.if you can get one for 200 i would do that.

Machine engineer told me it would cost 150-200 euros because it is so complicated job to do. And.. I have been looking for used engine case. Yeap.. I have seen that I could get one from USA or UK by eBay. But in Finland where I am, no luck! Havent even found an engine or actualy one over 3000 euros. Every bikeshop starts to look from the books, 1100 euros thx! ..yeah right. There is few places where they buy old/crashed bikes and sell the parts but. They dont have any engine cases for RC4 engine. Almost everything else they have!