Originally posted by spenzalii
I've read on the boards that some people will polish the piston and sleeve with a light polishing agent before break in to cut down on break in time signifigantly. I had my questions about this and never got a good definitive answer.
I tried breaking in my new SX12 yesterday. 2 hours and maybe a 1/4 tank, since I could not get it to start reliably for anything. So today, I grabbed my rotory tool and some Colgate. About 30 seconds with a rotary tool and a liberal cleaning, WD40ing and after run oil, and the engine starts up with no problem. I just finished heat cycling it for my first full tank.
Anybody else support/oppose this method? I really hope I didn't do irreperable damage to my new, worked engine.
On some brands of engines ( actualy most of them), to have engine running longer and better it is the best to lap it before initial start. I am always doing, regardless the brand.
Well I am against to use Cogate or other sustitute to real lapping compaund and using rotory tool ( any kind of power tool) is realy dangerouse because it is hard to control fitting condition.
am using old hand lapping method-lapping compaund 1500 grid from Clover ( oil based) and lapping tool for piston. I am sugesting to don't lap sleeve-only the piston.
I can give you my numbers for fitting piston to sleeve after lapping is done- for 12 Novas engines it is 3.1-3.0 mm ( initiay it is 4.3-4.5m) and for 21 engines it is 4.2-4.3 mm ( initial 5.7-5.8).
To mesure this fitting I do following- I clean piston and sleeve with denaturated alchol and fit piston inside sleeve with slight force till it got stock on the top and then mesure the distance from the top of the sleeve to the top of piston.
There is to thing needs to be taking care of-wash everything very good after lapping is done ( if any lapping compaund will stays there it will ruin intire engine within a second) and second thing is try to do everything possible to don't make ellips on piston.
Unfortunatelly I don't have digital camera to put pic of my lapping tool, but I made couple of them for my friends and may be they can put pics of it.
Good luck and be patient.
Edward