175 motors - differences through the years

[adrian_goold]

Could someone shed some light on what differences there were between the 175 motors from '73 on?
I have a '73 Black motor and would like to know whether i can use a barrel from later models on my bike. Also crankchafts and Rods, pistons - were there any changes to the specs with these?

Your help is greatly appreciated.
Regards,
Adrian

 

[john durrill]

adrian,
the only things i know are different between the black and silver motors ( up to 75) are the shifter shaft , and the cylinder. you can use a newer cylinder on the black motor and it looks like the shift shaft would work but you would have to plug the hole in the right side case. The silver engine shifter shaft exit's only on the left side. The sliver engine had a metal sheet plug in that hole in the cases.
 Best way to find out would be to get the parts book from a 73 and one for a 75 and look at the #'s. the crank is a different size on the mag side but can be use with a different bearing in either engine.
Maybe someone else knows of other differences?
Did you find a shifter lever for you bike?
John


 

[adrian_goold]

Thanks for the info on the motors. Need to know just in case anything bad happens to my motor. Have to keep my options open.
Yes i have found a lever locally.
Thanks for your help.
Adrian

 

[Mike Lenz]

I believe a 76 on jug,head,and piston should work on a 73-75 lower end. the crank and rods all have the same numbers. The 76 piston and cyl are shorter,but seems should bolt right on when used together. Anyone tried this?

 

[Larry Perkins]

Oh Yeah, that will work boys but I believe you have to change out cylinder studs and the headpipe on the pipe is alot different in angle because the exauhst manifold is a steeper angle on the 76-77.  You can bolt on the old manifold from a 72-75 and use the old pipe but the angled one is the stink.  I rode out of a shop that had a winning Penton 125 MC5 in 76 which was past the day of European 125's.  In reality it was one of these 175 motors converted on a KTM 125 bottom.  It was a real fast "125"  I think the 76-77 motor is a vast improvement over the previous ones in the case of the 175 Penton/KTM.  My opinion only no dyno proof, just seat of the pants observation.