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Discussion Starter · #1 ·
Hello everyone,

so I took my CB400t head to an engine shop to get my cylinders bored and honed and the guy behind the counter asked me what gap they should be leaving? He tells me there should be a number on the new piston box indicating manufacturers set gap for heat expansion.

I can see no such number on the box.

Do you guys know what this gap set by Honda should be?
 

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Dont know about a cb400T. The last one I had bored was a cb77.I took the new pistons in and asked for .0015 as per the info from the maker,but I think normal is .002. If you can contact the supplier of the piston and ask what they recommend . If Im wrong someone will be along to help us out.

Bill
 

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Ring end gap per page 7-1 of the factory service manual:


Top: 0.2-0.4mm (.008-.016 in) service limit 0.60mm (.024in)
Second 0.2-0.4mm (.008-.016in) service limit .060mm (.024in)
Oil (side rail) 0.2-0.9mm (.008-.035in) service limit 1.10mm (.043in)

PM sent
 

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Discussion Starter · #4 ·
Thanks for the help guys, I appreciate it!

What I was looking for was the cylinder to piston clearance. After diging through forum I have eventually found this posted by 66Sensei:

Standard piston to cylinder clearance is .001 to .002" Max is .004"
Ring gaps: Top and second std.. .012 to .020"... Max .031"
Oil ring std ... .008 to .016" max .031"
 

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What he needs to know is the piston to cylinder wall clearance. Probably in the neighborhood of .002" . Should be listed in the FSM for that model.
 

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I sent you a PM for the factory service manual. Specs are listed on page 7-1.
 
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