1mm over Bore Size

[etemplet]

Hello All,
Boring my cylinder 1mm over. Piston size at the skirt is 2.266" I have the Clymer's Repair Manual (it was free and it is all I have )but it doesn't give a tolerance for the overbore size. I have a cylinder that is 2.272" ID and I hope this is within tolerance. Can anyone hook me up with the max tolerance bore size and the OK range. I am off to a party and will do research when I get home. I actually asked WSF for a size range and of course they would not give me anything Ha ha. Help is appreciated.

Currently the bore is at 2.257"

 

[mikidymac]

The factory manual is available for free online. Just google it. It will list setup clearance for new bore. So basically for example your pistons are 2.266” and setup clearance is 0.05 your bore should be 2.316”

 

[etemplet]

2.271" Thanks mikidymac. That is good news because my other cylinder is 2.271" and I was worried it was at the upper limit. I need to hone it and am glad I have the room.

 

[mikidymac]

I am not saying.05 is the number. Just giving it as an example.

 

[etemplet]

I am not saying.05 is the number. Just giving it as an example.

I did some research and didn't find specific sizes for the 1mm bore. What I found surprised me as far as size range is concerned. I am still looking.

 

[NoRdO]

Yea, you don't want 0.050 clearance....lol that motor would blow up real quick. I believe anywhere under 0.008" is acceptable for a rebuild. I would think 0.0045 would be optimal... You are probably fine with 0.006" clearance... Has the cylinder already been honed?

 

[etemplet]

.002" - ,0043" is new. .008 is Max wore out. for the cylinders on the 787. Now that I machined a mandrel for the cylinders it is a snap. What do people charge to machine cylinders ?

 

[IDoSeaDoo]

If you haven't had the cylinders bored yet, just give them your pistons. They're supposed to bore to tolerance based on the piston anyway. That's how I've done it every time I've had cylinders bored. Also, if it's a RAVE motor, be sure to shave your raves so they don't make contact with the pistons.

 

[etemplet]

Yea, you don't want 0.050 clearance....lol that motor would blow up real quick. I believe anywhere under 0.008" is acceptable for a rebuild. I would think 0.0045 would be optimal... You are probably fine with 0.006" clearance... Has the cylinder already been honed?

Thanks for the response. I really value practical experience. I have not honed the cylinder in question and it is in good shape. The bore is straight and not out of round so it should clean up with a minimum of effort and metal removal. The cylinder I bored is at .003" before honing. I don't know why I love working on this stuff but I do.

 

[NoRdO]

Sounds like you are right on target