Hi gang,
I dabble in a bit of Go Karting with a bunch of mates we all run Yamaha KT100s (100cc) 2 stroke motors. The crank bearing journals are a bit soft and tend to wear as the bearing inside race is much harder. The usual repair is to split the crank and send the 2 halves off to be hard chromed. The journals are either machined or ground under size and then hard chromed and ground back to size, 20mm. This is not a cheap fix. In the US they fit crank savers to new cranks these are a hardened and ground sleeve, ID is an interference fit on the 20mm and take the OD upto 25mm, you then run 6205 C4 bearings in the case, the sleeve only covers the bearing width and the standard 36x20x7 seal is run in the case. I have fitted a set of these to the crank which is in my current engine. The sleeves are what could almost be off the shelf needle bearing inners but I believe the crank savers are specifically made ground to give the interference fit on the crank.
The attached pics show one of my other cranks that need repair, I was thinking if I can source needle inners in 25 OD with the ID in any range from 19.5 to 18 mm I could machine/grind (SHER tool post grinder ) down the crank journals for an interference fit with the sleeve. The length would need to go to 25mm which covers the seal section of the journal but 36 x 25 x 7 seals are available so no problem.
I have googled high and low but can not source the required size. If any of the group could point me in the right direction that would be appreciated.
Cheers
Bruce
I dabble in a bit of Go Karting with a bunch of mates we all run Yamaha KT100s (100cc) 2 stroke motors. The crank bearing journals are a bit soft and tend to wear as the bearing inside race is much harder. The usual repair is to split the crank and send the 2 halves off to be hard chromed. The journals are either machined or ground under size and then hard chromed and ground back to size, 20mm. This is not a cheap fix. In the US they fit crank savers to new cranks these are a hardened and ground sleeve, ID is an interference fit on the 20mm and take the OD upto 25mm, you then run 6205 C4 bearings in the case, the sleeve only covers the bearing width and the standard 36x20x7 seal is run in the case. I have fitted a set of these to the crank which is in my current engine. The sleeves are what could almost be off the shelf needle bearing inners but I believe the crank savers are specifically made ground to give the interference fit on the crank.
The attached pics show one of my other cranks that need repair, I was thinking if I can source needle inners in 25 OD with the ID in any range from 19.5 to 18 mm I could machine/grind (SHER tool post grinder ) down the crank journals for an interference fit with the sleeve. The length would need to go to 25mm which covers the seal section of the journal but 36 x 25 x 7 seals are available so no problem.
I have googled high and low but can not source the required size. If any of the group could point me in the right direction that would be appreciated.
Cheers
Bruce
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