squish with lead bars

[748R_bb155]

Using1.5 mm lead bars on top of my pistons to measure sqish,

the measurement is 1.2 at one side oft the piston and 1.07 on the other side of the piston. (inlett and exhast, have so ledbar at piston dome as well but these are not squashed).

I just tightend the headnuts to 40 NM at oposit sides, as per the 748RS manual.

Is it better to tigthen all 4 of the bolts ???

which measuremnet to use :

use the 1.07 mesurement or the average of the two(or all led bars).

(Meaured both barells and both are about the same).

(853 R pistal pistons).

I using the .40 mm cylinder base gasket,
is the 0.30 the best choise??

EO

EO

[Old Baldy]

I always tighten all head bolts. Not sure about the RS procedure, but I'd be concerned about warping the head if not tightening all bolts.

There should not be such a large variance, if the head is flat, fully torqued and rod and crank bearings are in good shape.

Use the minimum clearance to determine final squish clearance.
Personally, I prefer to err on the side of safety for a street/trackday bike which is not being stripped down every few thousand miles - so I use the 40 thou (no less than 1MM) clearance that Guy Martin suggested to me for this type if bike - unless you keep a close eye on clearances and rod stretch, etc.

[chris steedman]

Originally Posted by 748R_bb155

Using1.5 mm lead bars on top of my pistons to measure sqish,

the measurement is 1.2 at one side oft the piston and 1.07 on the other side of the piston. (inlett and exhast, have so ledbar at piston dome as well but these are not squashed).

I just tightend the headnuts to 40 NM at oposit sides, as per the 748RS manual.

Is it better to tigthen all 4 of the bolts ???

which measuremnet to use :

use the 1.07 mesurement or the average of the two(or all led bars).

(Meaured both barells and both are about the same).

(853 R pistal pistons).

I using the .40 mm cylinder base gasket,
is the 0.30 the best choise??

EO

EO

I use a flat steel plate after clamping the barrell down with no head on.. I then use feeler guages placed at the front and rear of the piton to determine squish.

The solder methord is fine. The piston will always have some rock (front to back) this is why you have one piece of solder at 1.20 and one at 1.07. The real figure is half that . Say one piece was 1.10 and the other was 0.90 this would calculate 1.00mm squish. With your calculation it seems you have approx 1.12mm squish so a 0.10mm drop in base gasket will be whats needed.

[748R_bb155]

Thanks for the replys.
First time setting squish.
Did an other measurement with all 4 of the headbolts attaced.
(Torqued to 40 nm for checking,748 rs manual states 30 NM)

it reads 1.05 and 1.15 Both heads are fairly consistent at this value.
(have done several measurements).
So I'm thinking to go with a 0.3 mm base gasket (stock 0.4mm) thish should set the squish at about 1.00 mm (or between 0.95-1.05)

Was going to order some new basegasket today, but the shop is closed untill tuesday.(Easter holiday)

(dail calipers accurate to 0.03 mm)

EO

[TrickLidz]

Info on setting squish is here-
http://knol.google.com/k/steve-methia/ducati-4-valve-notebook/2rk7csiieinrp/5#
and here-
http://www.ducatitech.com/2v/maint/rebuild/headwork.html