Running in a new piston on a 1956 ajs 16

[Jez H]

I have just fitted a new piston and rings, I decided not to rebore as there was only a few marks,

How long would people think I should run this in for? 1000miles under 30mph seems a bit excessiveEdited by - Jez H on 02 Jun 2010 10:45:14 AM

[Eric]

Speed is not the important thing in fact slow maybe completely wrong. Keep the engine spinning freely and lightly loaded although this more for bearings rather than bores. Slow down and speed up regularly to induce oil into the bore. Stop frequently in the first stages to let things cool down just in case there is a chance of nipping up. You don't say what make the old piston was and why you changed it new rings maybe all that was needed.

[Jez H]

It was a standard club piston +20, I am not sure what make the old one was +20 as well. The old piston was U/S but failed very gracefullyEdited by - Jez H on 02 Jun 2010 11:05:45 AM

[pto]

Did you hone the cylinder or make any attempted at " glaze busting" before you fitted the new piston, if not it will never run in!.if you did follow Eric's advice

[Eric]

Club pistons may need more clearance than original pistons ask back at JSL they should know. pto is correct you should have removed any existing glaze from the bore but if you need more clearance after talking to JSL you will have to get it honed anyway to open the bore a little.Edited by - Eric on 02 Jun 2010 11:39:40 AM

[Jez H]

Interesting replies, I had best dig out the old de-glazing tool from the back off the garage.

if it miss behaves it will get a full rebore and go up a size over the winter anyway.

[iandusud]

Jez, did you measure the piston skirt to bore clearance with the new psiton?

Ian

[Jez H]

To be honest I did not worry to much as I was putting a +20 piston in an already worn bore. The bike was puffing alot out the breather anyway previous to the fail. When I have had rebores done in the past on jap stuff the engineering firm has supplied the piston as part of the cost

What clearence should I look for and do i just measure the bore with a DTI and the piston with vernier calipers

[Eric]

JSL should be able to tell you what size the bore needs to be. Whats a DTI? Digital calipers are OK vernier calipers are also OK if they are good ones and you have good eyesight

[orbinrangle]

dti=dial test indicator.