I am going to be buying a cylinder bore gauge to check the top end of my 250r. I am new to this rebuilding top ends, but from what I know so far, I will need this gauge to see what size to bore to (or re-sleeve).

What kind does everyone else have?
What should I look for in a good gauge?
About how much do they cost?
Who sells them? (Local Parts store, machine shops?)

 

I would buy a Sunnen, Starret, stay away from the "cheapos" A good one will last forever, unless you beat it.

 

Unless you actually have the boring machine and plan to do the boring you will not need one. If you do want one just to have around, stay with brand name units as previously stated. Here is some pricing:

el cheapo $80-$100
Mitutoyo 5 anvil $430
Federal 4 anvil $550
Starrett 4 anvil $525
Fowler 2 ring $2700

 

I agree with bpace that if you are only going to check a couple of cylinders take it to the machine shop and let them do it. If you really want to measure it your self I would get an outside mike and a telescoping gauge. If you get a bore gauge that is all it is good for. How are you going to measure the outside of your piston? You will need a micrometer any way. Staret, Brown&Sharp and Minitoia are all good brands. Industrial supply houses sell these and also check pawn shops. How are you going to check your piston pin, pin bore in piston, crank journals and case bores? Don't use dial calipars. They get you close but should not be used for precision machining.

Good luck
Dan D.

 

Here is my deliema….

I am rebuilding my new 89 250r. I did not get a chance to try out the motor before I brought it. Since I will not have it ready for the race this weekend, I was thinking about given it a new top end. But I am new to this piston and bore thing. The guy I brought it from said that it was bore 80 over. I think he said it was the largest bore that was allowed in the 250 class.

How do I know what the current size of the piston and bore is? From reading the forums, it sounds like you get the piston, then bring the piston and cylinder down to the machine shop to have them bore the cylinder to the proper specs. So you guys are saying that I should bring the cylinder down to the shop, have them measure it, then find out what size piston I should get, then order the piston?

I have heard that the piston should have some numbers on top, but I have not taken it apart to see. If there are numbers, what do they tell me? And how can I know if I need to put in a new sleeve or I can just have it bored?

Also, what should I look for when I pull the head off? You know the tell tale signs of needing a bore or just a hone, or leave it alone?