Engine Number vs Color

[Keith Meatyard]

I have an unusual combination that I would like to explain.  My 74 Jackpiner, 54-40271535 frame number has an engine number of 4-5205605 stamped into the right case below the cylinder fins,  Therefore both 74 assembly dates.  Now here's the problem.  I thought the 74 175 engines were silver instead of black like the 72/73 bikes, yet my engine date clock cast into the right case below the sprocket is 11 - 72.  The cases are painted with semi-gloss black, and I think they are original because all of the machined off surfaces are bare magnesium just like the factory.  The clutch cover is the later one and where paint is rubbed away, I don't see any evidence of silver paint under the black.  The cylinder and head have obviously been painted with some gloss black.
Could this bike have been built using the left over 72 cast cases, and the factory left them black, but the cylinder and head bare aluminum?  On bikes with the silver painted 175's, were the cylinders and heads bare aluminum, or painted silver?

Keith Meatyard

[brian kirby]

What forks are on the bike, 32 or 35mm? What tank, toaster or watermelon? This would not be the first Penton that defied the conventional wisdom of what they were supposed to come with by their build date.

The silver engines have painted cases and bare cylinder and head.

Brian

[chicagojerry]

hi keith. the date clock stampings are pretty inconsenquential. i have seen matched cases where the date clocks are almost a year apart. thats just a date that those cases were cast, not necessarily machined and put together with a serial number. as many motors as i have worked on, i see something new and unexplained all the time.
chi jer

[brian kirby]

At one of the Reunion Rides Jack said many times they would open a crate of new bikes from KTM and all four of them would be different.

Brian

[454MRW]

When Gary Ellis rebuilt the engine for my early 74 250 HareScrambler, he thought that the lower engine was originally painted black, since some of the 250 engines between the black 73's and the silver 74's had the bottom end painted black with the cylinder and head aluminum. I had actually painted the bottom end black myself when I worked on the top end, because I wanted to take advantage of the flat blacks ability to shed heat, and I thought it looked cool, but it was silver when I got it, still on standard bore. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
1975 Can Am 175 TNT & 77 250 Black Widow
1979 Husqvarna OR390
1976-78 RM & 77-79 PE Suzuki's
1974 CR250M 07 CR125R 79 CR250R

[Keith Meatyard]

Hi Brian.  The forks are 35's, not 32's like my 73 JP's.  It also has the small MX tank.  Also, I did look carefully at the paint on the cases and they definitely look to be the original black with all machined surfaces free of paint.  It sure looks like the cases may have been in inventory since they were cast in Nov 72.  They probably just used up what they had and stamped the engine assembly date as 74, but the cases would have already been painted black.  Thanks for the answer on the bare cylinder and head.

Thanks everybody for the info and comments.

Keith Meatyard

[rob w]

Originally the cylinder is not painted, but the head is painted.

[Dennis Jones]

A friend of mine has a stone stock early 74 Jackpiner that looks like new and it's motor has that color combination. Maybe he'll come on here and tell about it.

Dennis Jones