K&B sportsters

[chiefss]

Got a question for Randy,

I know the Sportsters made by K&B had no crankshaft bushing, just the steel crank running in the aluminum crankcase.

Now I see some guys claiming that Mecoa made Sportsters have a bronze bushing and some don't. I have yet to see ANY Sportster with a bronze bushing, either K&B or Mecoa.

Did Mecoa make them with a bronze bushing???

[MECOA]

Yes all the ones we made and the last ones made in Havasu have a bronze bushing in the very front of the case. Never on the .20 & .28. They didn't seam to need it.

The problem is the gyro torque on the crank from the prop in quick turns. That is the only thing that is hard on the plain aluminum case, beside lack of oil of course.

BTW all the Sportster castings were made from 17-19% silicon alloy 390 aluminum. Compared to 7.5-9.5% for standard 380 alloy material.

So when you say running straight in the aluminum it is not really true, it is running on nearly 20% silicon ant that is some really hard stuff that doesn't wear out fast. Believe me, all the castings are machined with diamond tipped cutters. Carbide wears out (at least looses its edge) in less than 50 parts. Imagine it's kinda like machining aluminum with sand impregnated in it.