430 or 420 pistons

[fran...k.]

I was taking some pictures the other day and maybe someone could add something to some of my queries. Even if no one can add much it most likely will be informative to some.

so here we have left to right
420 auto which I have been lead to believe is also an air cooled 430
430 water pumper mahle
cagiva replacement piston
not sure perhaps seizeco
Also you will see the original and the cagiva replacement wristpin bearing, not as much different as I thought.

Here we have them base to base the two mahle or stock ones on top have the same transfer port cut out. As you can see the seizeco has a gap much larger and the cagiva one slightly smaller. You can also see the three wristpins the short, too short waterpumper one the 420 auto one and the new cagiva one in the wrapper.

Here I am showing that the cagiva piston seems designed for the air cooled 430 cylinder and the gap in the mahle pistons lines up with the water cooled cylinder which might be a 500 but the cut out is the same I got somewhat confused. I got the cagiva piston and had a water cooled cylinder bored for it but noticed the issue of blocking off part of this transfer area. I am not showing how these skirts and the lands between the holes in the cylinder work out but the seizco one obviously will miss some land to rub on/slide by.

Here is the packing reverse side and the cagiva piston.

Maybe someone can help me out here.

Any idea what entity made the cagiva piston or the one I am calling the cagiva piston? It is a very nice piston, my boring guy was impressed with it, the wristpin isn't super short but it doesn't fit in the water cooled cylinder well if you want maximum transfer.

Can someone take one of those Woosner or what other brand names they are marketed under in other parts of the world and put them up against any of these options for a comparison?

Is the seizco the brand I think it is?

Fran

 

[fran...k.]

I believe Oldhuskychuck dropped a link to Wossner on line shopping in a recent post. Since I have seen places to buy these for 430 bikes made from 1946 to present but won't answer questions I was suspicious. I kept the communication simple as they most likely are in the business of selling an engine's worth of pistons to the BMW car folks. I could return it if I didn't like it and it was still in new saleable condition. So I got one, a hundred dollars less than I was offered a NOS one which the wristpin hammers itself loose by a member on here. I am not really sure what to make of it, Probably the best thing is to get one of the earlier Mahle ones and lighten it up as much as you dare. The sides don't have any raised portions so I don't see any reason not to carve on it. I don't have a scale to actually weigh it but do see quite a mass of aluminum which could be whittled on if one felt like it. They take credit cards the payment goes to Tennessee and the shipping goes ground from California at least in my case.

Mahle one in the cylinder, note evidence of hammering loose wristpin. These have a stop so the top of piston is even with bottom of exhaust port. Even this one doesn't line up perfect.

Wossner one

I might also note it seems the Mahle ones I examined in this instance for the 500 seem to keep the same internal size and get thicker walled as the over bore from origional increases. The wristpin is a little longer (perhaps a fat quarter inch longer just going from where the clip grooves are) than the one I don't like and the space at the wristpin bearing is just a little tighter. Pretty crude casting (cylinder) isn't it.

Added 10-22-2010
I was talking with a guy who bought these kind of bikes new and sold them or traded them in at the dealer back when they were what folks rode at events chasing for trophies and jackets at the end of the year. If cast vs forged and placement of the skirts aren't enough you also have the offset of the pin in the piston. I was told and I think he was talking of the 500 ,but he had both 430 and 500 back then, Upon going to a Wiseco piston it rattled more than the stock one because the stock one the pin for the connecting rod was offset and hence didn't rattle as much as the Wiseco one. It appears to me the Wossner one of these two is offset and the Mahle is not, Just using an adjustable wrench as a caliper and measuring off the lightening cut out, can't say about the others in the first post at this time.