Engine cases

Does anyone know if 1982 250 cases are the same as a 430 set ? In other words I'm trying to build a 430 out of a 250 ? cheers

No they aren't. Crank dia is smaller and the cylinder sleeve cut out in the cases is smaller.the castings are slightly different in that respect.

you can machine 250 cases to work with a 400/430 crank and cylinder.

correct. the only difference is the extra webbing to shrink the crank case.

And save the web for weld material when you need to have a magnesium case welded. The expensive part of magnesium welding is having to buy a minimum order of the correct rod(once you find what it is).

Yes, there nothing better for fill/rod material than the same exact material that you are welding when it comes to magnesium.

I would think the material in the case is designed to be cast easily, and in a manner that can be done with the emission requirements and methods available at the time. Generic rod for cast magnesium probably would be better than pieces of case. You would be dealing with impurities in both parent material and "rod". The magnesium rod I have must be the stuff for cast not the stuff for extruded. The rod corrodes in air while the concrete screeds and floats are in humid conditions and do not seem to corrode.

As to the original post is it the 82 where the intermediate kickstart shaft does not have the two 6mm reinforcing bolts. Folks have made 250 cases work with the 430 stuff, crank, cylinder, primary gearing, etc.

i have one of those early cases, i was able to extract that intermediate mount, drill/tap, and fit it. i had a blown out case i could get the donor mount out of.

When I was working I asked my welding supplier for a sample of the magnesium TIG rod. I took a cardboard box and turned up the argon gas and welded. I had no problem storing the rod.

My sons first date with this babe was a riding date at the thomaston dam. She rode a Suzuki TS 250. My Son had his 125cr Honda. Two days before the date a guy at the dam tee boned his bike and broke the clutch cover. I took it to work and welded it right away. The kid had his date. She was awesome.

The cardboard box approximates chamber welding. I can only imaging how a modern inverter welder is to what I have used. Whether or not a cr 125 Honda clutch cover has more or less impurities bubble out than one from a bike in this section I can not say.

Magnesium burns so to weld it, it must be surrounded by gas. I had a droplet of magnesium fall on the cement floor burning in flames so I made the mistake of stepping on it to put it out and had ten Richard Pryors running across the floor in flames. I just laughed.

I had a Hobart cyber wave 500amp TIG WELDER. I'd like to get a inverted TIG WELDER for doing bike parts.

I can get magnesium file shavings to burn. That is about it with atmospheric oxygen 20% or so. Yes race cars are not made of it because one caught fire and went into the spectators. If the shielding gas doesn't cover the weld area all I get is contamination not fire. Magnesium can be torch welded with flux can't it? Same kind of thing the flame has carbon monoxide shielding but the work doesn't just burn up if the welder makes a wrong move.

That was the 1955 LeMans race and I recall more than one Mercedes rolled through the spectators in fierce flames. Do you remember the code for that magnesium rod?

I think it was certainium alloys & research TIG rod.

Just from a Bing search
"Another problem is high zinc content. Magnesium alloys that have a zinc content of 5-6% are crack sensitive and dont weld nearly as good as the ones that have about 10% aluminum content along with lower zinc.
AZ101 magnesium filler rod is considered the most forgiving and the reason why is that it fits the description I just gave....about 10% aluminum with a maximum zinc content of 1.25 %." http://www.weldingtipsandtricks.com/welding-magnesium.html

I bought 5 little rods once perhaps 25 years ago was lead to believe there was one rod for cast and another for extruded. I got a pile of quite similar later. I thought aluminum/magnesium were only like 3% soluble in each other (each other's crystal structure) at room temperature at least without other stuff in there. Try and weld a worn mono shock brake backing plate, I think those have lots of zinc I have failed.

Interesting but not sure if this is correct as I have a 430 cylinder and it fits perfectly into the 250 cases ?. Crank web size yet to determine as I don't have a 430 crank to check with.

crank cheek halves bigger on a 400 or 430. otherwises cases same dimensions. Base gaskets same too

you ask and we answer. Ye of little faith. look at the 250 cases....remove the inner web and it is a 400/430 viola!

I must be looking at something different as none of my 2089 cases have inner webs ? have 3 sets of these and none have webs - all smooth on the inside ?

its not..the cylinder cutout is the same. the 250 has an extra web in the crank case to shrink volume. post a picture of your case