I have a 1973 Penton 125 Six Days. I've read on here about a hole in the piston. Does the hole in the piston apply to my year and model? I did the top end last winter and have a little over 2 hours on the top end. I took my cylinder off to get vapor blasted and realized mine has no hole. Just want the best for the old girl.
(http://i567.photobucket.com/albums/ss113/ebarth6/Mobile%20Uploads/image_zpstwxho6ls.jpg) (http://s567.photobucket.com/user/ebarth6/media/Mobile%20Uploads/image_zpstwxho6ls.jpg.html)
(http://i567.photobucket.com/albums/ss113/ebarth6/Mobile%20Uploads/image_zpsjru55dhi.jpg) (http://s567.photobucket.com/user/ebarth6/media/Mobile%20Uploads/image_zpsjru55dhi.jpg.html)
(http://i567.photobucket.com/albums/ss113/ebarth6/Mobile%20Uploads/image_zpskbys2j9m.jpg) (http://s567.photobucket.com/user/ebarth6/media/Mobile%20Uploads/image_zpskbys2j9m.jpg.html)
Ed Barth
'73 Penton 125 Six Days
'73 Yamaha DT3 250
'04 KTM 125 SX
'06 KTM 250 SX
'13 KTM 250 XC
no hole is needed
Exhaust bridge in KTM cylinders(and all other makes)require the holes to be drilled for lubrication in the exhaust side of the pistons. As mentioned, none in Sachs.
ED, looks like you might have some barreling on/in your liner.
Thank you guys. The cylinder was bored to the new piston's (54.5 mm) spec by point view cycle last winter. What exactly is barreling gooddirt?
Ed Barth
'73 Penton 125 Six Days
'73 Yamaha DT3 250
'04 KTM 125 SX
'06 KTM 250 SX
'13 KTM 250 XC
Barreling is wear in and around the center of the liner .... seeing some ring imprints below the ports a bit to early for 2 hours on a ( maybe they did just a hone) new bore , could be hard rings and hard rider. Is that at thumb print at 4 o'clock in the liner? ports edges need to be rounded a bit to be safe.
It was an incredibly hard ride at the VMD Hare Scrambles on the old girl. I pretty much had to keep her wide open the whole time to go anywhere on that tough track and to keep her from bogging (going to try a new need new needle & needle jet). I did do a few warm up rides before the hare scrambles on the new top end and motocross. So it is probably more towards 4-5 hours. I am pretty sure that is a thumb print. I will double check when the cylinder comes back from vapor blasting and port the cylinder. The help is much appreciated!
Ed Barth
'73 Penton 125 Six Days
'73 Yamaha DT3 250
'04 KTM 125 SX
'06 KTM 250 SX
'13 KTM 250 XC