Measureing deck height.

[YAMLAM]

how do i go about measuring the deck height . got a ts1 with recessed head to suit yam piston,using rd400 rod (115mm).have bolted the barrell to the casing with crank and piston fitted. what with ,and how do i measure the deck height?
thanks in advance.

[sean brady scooters]

deck height should be height of base gasket surface above
centre of shafts...........
but once barrel is fitted (assuming they are all 101mm) then your piston would be either flush with top of barrel /above /or below..............
if its below for eg ,then simply use feeler gauges to find the difference.........this will be negative deck.........

[YAMLAM]

thanks for your reply Sean, it has a negative deck height of 1mm (measured with feeler gauges) which, going by the conrod length (115mm) and piston height (22mm) is what i expected.
do i have it removed from the base or top of the cylinder.

[byron]

how come the barrel needs to be shortened if there is negative deck height ? or am i getting my terminology confused ?

[YAMLAM]

perhaps im explaining it wrong,but at TDC the piston edge (not crown )is 1mm short of the top of the cylinder.

[byron]

perhaps im explaining it wrong,but at TDC the piston edge (not crown )is 1mm short of the top of the cylinder.

ah, got it. then that's not what i understood negative deck height to be. I thought deck height was the distance between edge of piston and top of barrel [without any gasket], so the 1mm in your case. And that negative deck height was when the piston "side" extended beyond the top of the barrel...

[sean brady scooters]

your explaining things quite right matey.............
you have as you say a deck height of minus 1mm..............
.......1mm negative deck..........
SO ..........when your piston is at the bottom of its stroke.......BDC..........is it flush with bottom of ex/trans............or above or below............?

[YAMLAM]

at BDC ,it looks flush with the exhaust and about 1mm below transfers.

[sean brady scooters]

ok matey..
moving on...........
you also said your head was recessed ..........?
do you just mean re profiled to suit piston or recessed as in it fits down into barrel by an amount.........?
some pics would be helpfull if poss.............
but anyway............when head is fitted.............what squish clearance do you have........?
and what head gasket thickness are you using if any...........?

[YAMLAM]

the head was reprofiled by harry barlow to suit the piston (yam it175) it doesn`t sit in the barrell, the recess is in the actual head,will try to do a picture later.brand new casing.no base gasket. was told to bolt barrel on without,then measure deck height(hence original question) .many thanks for your help sean.