[taz69]

Ok as some of you know from helping me i had a OLD style superhead bought a new 124cc piston and crank for it but things were not going together correct. HERE is what I finally found out.. First there is a difference in the +R piston deck height and the OLD style piston deck height by about a millimeter and a half.. 17.5 to 19 on the +R piston.. Second there is only 1 crankshaft for both of these pistons just 1 and it has a 92mm rod on it not a 94.. So if you try to use and old style piston on a new crank its in the cylinder 2mm.. You HAVE to buy the piston for the +R and either turn it down a little to work with the old head or get a +R head... Or Change the rods but I didnt know where a 94mm rod that would work was.. So IF you have the OLD style superhead and its a 124 now DONT loose the crank or damage it cause you cant buy a new one exactly the same... You can turn down a +R piston though to work with the older head I did it and it was good to go.. Hope this might help anyone with an older style superhead thats looking for some new parts you might end up in this same situation.. Got the crank from CHP they just got a new batch in this christmas and im sure they all have the small rod on it.... The cranks are made to match the +R piston now its the one with the 19mm deck height.

 

[taz69]

Bump...

 

[bat999]

Way to go Tazzie, glad to see ya got it figured out.....Now I'll have to build one....lol

 

[Adam z50+R]

this doesn't make much sense to me



ie



my motor was crf50 base 124cc old super head 54 x 54mm ( 4 years ago)



i then upgraded cylinder,piston and head to twinspark +R still using the original crankshaft which i bought about 4 years ago



after running for a while the crank bearings wore out again so i replaced with the new style crank 3-point bearing pick up with polished side cover



never was there an issue with deck height???

 

[taz69]

Hey Adam im not sure what to tell ya.. I know the deck height on the old 115 piston was 17mm And on the +R piston its 19mm Thats 2mm the +R piston is WAY taller... So if you use the same crank for both pistons the OLD style piston is 1.5mm farther down in the cylinder.. The compressinon was way low.. Maybe all those pistons had the same deck height. But if you keep the same crank and cylinder and have to different deck height pistons by 2mm thats almost too far in the cylinder to run...

 

[Adam z50+R]

it does seem to be faster now

maybe it was not reaching the top of the cylinder before i changed to the new crank hmmm.

sometimes you can be confused by this due to the cylinder not being clamped down