Cracked Motorbike Engine Block - Repairable?

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Ok, I'm here to ask the experts (you guys)  I cracked my motorbike engine block and was wondering if it can be welded up.I was told by a motorbike mechanic that using a putty metal to cover up the crack would be sufficient but i don't really belive that..Any thoughts??
Reply:I've repaired these using TIG and 4043 wire.  I would insert a bolt in the threads to insure they remain there when welding is completed.  This will require more heat than normal as the bolt will act as a heat sink.  By welding without a bolt, if  "burn through" occurs it could require machining and re-threading.  Good luck.
Reply:Not knowing much about welding myself, are there any issues with the block being a composite of metals and the weld holding?
Reply:Where exactly is that boss at, is it into a water or oil jacket and what attaches to it? I've repaired similar breaks and depending on the situation I'd grind the boss off completely so you can get to the base of it, build it up and the drill and tap a new hole. As I said tho, it depends on the place it's at and so long as it's accessable.Usually it's the exhaust mounting boss that has been mangled by the stud seizing in and then further mangled by trying to get it out.....Mike
Reply:Originally Posted by mrmikeyWhere exactly is that boss at, is it into a water or oil jacket and what attaches to it?
Reply:If it's for an accessory that isn't used and under no pressure I'd go the epoxy route. It's hard to get something that's been soaked in oil clean enough to weld. If there's no pressure or anything mounted to it and unless you want to take it off to get is really clean epoxy is the easiest way out. I don't often say that but there are occasions where welding just isn't the best or necessarily the easiest option, just my 2 cents worth (probably only 1 cent now with the economy ) .....Mike
Reply:Mr. Dave--apparently you're saying that the bolt hole keeps oil from leaking out ofthe crankcase and the presence of the crack--thus leaks oil?   IOW---the crack needs to be sealed to prevent oil leakage?If this is the case:-epoxy is not satisfactory. Epoxy doesn't bond worth squat to oil--let alone tolerating the vibration, heat expansion and contraction that occurs with aluminum cases.This can be tigged, by some folks.I normally use 5356--there's been all manner of discussion that 4043 is the way to go...however as Zapster, myself and others have noted--from real world experience, that 5000 series aluminum rod, sees good subsequent service life.The thread hole is washed, blown, cleaned a few times. All oil is drained from engine. The dummy bolt is cleaned dry, sprayed with graphite anti-seize spray, then installed finger tight--if it is used--at all.     A new tap for the correct thread size is on hand--probably a bottoming style tap. The tap is test-fit in the hole prior to welding.Using a higher end TIG machine with balance and especially frequency control isneeded to minimize heat input, effective cleaning action and puddle control.During welding, max. interpass temp. does not got over 150-180 degrees F. Intermittentwater spray cooling, then blow off with air. Minimizing localized heat expansion and subsequent contraction is critical to not distorting the assembled case, which is also under assembly torque loading. This cooling is done multiple times during the welding. If one wants further, dramatic case cracking and distortion--don't do this cooling.The bolt hole is carefully chased with the new tap, cleaned then gaged with a new bolt. The presence of this crack, may allow the tapped threads to be a loose fit on the new bolt. The new bolt's threads are then coated with a thread sealant to prevent capillary leakage.I've done at least 150 case repairs entailing all manner of destruction. Just did a 1000 cc Suzuki, fully assembled race engine--on 10-1-08. It was way more jacked-up than this job.Blackbird
Reply:Can you it be welded HELL YES.Clean it like crazy,It might need to be drilled and tapped.http://weldingweb.com/vbb/showthread.php?t=21936David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Can it be welded, of course, preheating and very, very slow cooling, Do you have to completely dismantle the engine engine, Not nessessarily.. JB weld will do the same thing, make sure it's real clean. Done it before after sliding my race bike. Been 2 years, ZERO poroblems. After curing, you can shape it, paint it and and tap it.Cast Aluminum likes to spiderweb if you don't weld it just right, and cool it real slow. How you would do that on a engine thats still in the bike, I don't know, and thats a bad thingLast edited by Cruizer; 10-04-2008 at 08:18 PM.
Reply:Thanks chaps   Ok all I need now is to find someone to weld it for me.... any idea of how much I should be paying?? & Anyone know of someone in the Midlands (UK) who could do this for me
Reply:I charged the guy $120.00 for the job in the link.  He brought it to my shop though.  Shipping would kill you.  DavidReal world weldin.  When I grow up I want to be a tig weldor.