cylinder head problem

[draku]

haynes repair manual said:
piston ring end gap:
- top and second rings:  -standard 0.2 to 0.35 mm
                                - maximum 0.6 mm (mine is about 0.53-0.54 mm so....)
- oil ring: 0.2 to 0.8 mm (din't check mine yet)

I will order no.1 piston ring set, and I will adjust the end to a 0.25-0.30 mm gap

about the paint...it is really tough. cannot remove by a sponge, need a chemical (or scratch by screwdriver or something...)

[andyb]

What DR means is when you install new rings, aim for .35mm gap rather than .2mm gap.  You can go a little outside that, it does look like yours is on the leaky side. 

Guessing that the bigger problem is in the head though.  While you've got it apart, go ahead and rering the the engine.

To get the paint off, the fast/easy way is sandblasting.  You may want to send it out to have it done.

[draku]

I understand (I hope)
because this engine usualy work in high temperature, it's better to be a bigger gap

[andyb]

Pretty much.  Too big of a gap means more leakage past the ring pack, and a little lost power.  Too tight of a gap means that the ring ends touch and tear the cylinder liner all up, can freeze a piston in also!  Very bad news.

[draku]

yes, but too big gap, mean also oil consumption.... 

[VMS]

I'd rather have a little oil consumption then tear up your cylinder walls. If you're concerned with a little loss of power, degree the cams.
The little amount of oil you would use is a non issue,  and remember you're using 2 rings, with the gaps opposite eachother

[draku]

my problem it is not loss of power (my other bike is Yamaha XJ600 Diversion with 60 HP, so...)
I don't like oil consumption at all

[SlowOldGuy]

Then worry more about the other 245mm of ring surface seating properly and not the 0.5mm gap. 

Seriously, the difference in any oil consumption between a .3 and .5mm ring gap would be unmeasureable.  Just make sure you clock the gaps correctly.  Most FJ oil consumption probably comes from the valve stem seals.  At least that's what made my FJ smoke on startup.

DavidR.

[draku]

yes, you are right
I will make sure of that when put back new piston rings
anyway, I will change all the valve stems seal