300/440/550 pistons and crank questions

[On the fly NY]

Noob here..hello to all...1987 JS 550 teardown and rebuild, crank seals are shot, bearings are freewheeling nicely...

question #1, is there supposed to be any space between the middle spacer and the 2 bearings on the crank between the connecting rods?

question #2, looking at new pistons and I am seeing sizes in the plus .25mm to .75mm, even +1 mm...so my question is do the cylinders need to be bored out for anything larger than the std 75mm pistons....sorry if this sounds like a silly question.

Thank you

 

[WFO Speedracer]

Std pistons are 75mm so add whatever dimension your cylinder is bored to , lets say it is now 75.75 mm and it needs to be bored again , you would need 76mm pistons or 1.00mm O/S .

Your best bet is to take it to the machine shop and let them tell you what size pistons you need , as far as the first question goes I am not following you on that one.

 

[On the fly NY]

thanks for your response SR...this is my 3rd time posting back to you here, last 2 just disappeared or were deleted ....want to reach out to administrator for some help but the "contact us" button doesn't seem to be active, so no help there....am hoping this post sticks around unless I am doing something wrong here on my end, which is quite possible

thanks for your input on the pistons, mine measure 75mm so I ordered accordingly.

as for the crankshaft, I was asking about the black striped between the 2 orange striped bearings in the middle but I have that figured out now