Squish Clearance - How to ?, Got 2 top end's - ready, Please school me ?

[ceaserthethird]

I got 2 build's going on, I just recently installed the piston's & cylinder's with head's ( cooper washer's on both )

The Cylinder Base & head nut's are not Torqued yet.

Stock Cylinder - Re~sleeved 295cc Big Bore, With LRD 300cc Head ( Cometic Stainless steel Head Gasket .010 )


This is my First Top End Build, x 2.

I would like to be Schooled on How To Check Squish Clearance & what tool's i need to buy?

Thank You for all the Help & Tip's

http://i72.photobucket.com/albums/i167/ceaserthethird/ATC%20250R%20Build%201985/100_2453.jpg

[MTS]

All you need is a couple piece's of 2mm Rosin core solder and a good Set of vernier calipers, Need to make a C or L shape out of the solder and put it down the plug hole So it reach's the edge's of the cylinder On the intake and exhaust side... its a bit tricky...but works, another set of hands makes it easier. So once you have the piston on the up stroke and the exhaust port closed Hold the solder and give it a good kick, Should Flatten the ends of the solder, Remove and measure with calipers at thinnest point...normally the end. May take a few tries (use a new piece each time) This is the most effective way short of using clay on the piston..i like the Kicking method becuse if there is any play in the bearings..it will come out..so to speak. Works well and is cheap and easy..Will give you a ball park on how the motor is set up...CC'ing the Chamber is the next step..to figure out compression ratio's.
Just a note i forgot to add...the 2 piece's of solder front and back is to take up any slack from the piston rocking back/forth in the bore you might get just using one piece
Just Re-red your post..thought i would mention...It all needs to be torqued down before you do this.

[ceaserthethird]

Will this work?

- Forney, 1/8" dia.

- acid core metal repair solder

[cr480r]

too fat.. look for something closer to your target squish for most accuracy

[Billy Golightly]

Thats a little bit thick, but it should work. There are a TON of variables on head dome design, but generally speaking with a good normal dome design your target is anywhere between .035 (Bare minimum) to the upper .040's. MTS's description and instructions on doing the test are spot on. Make sure you've got all your gaskets in, everythings torqued down, etc. etc.

[cr480r]

if you cant kick it through easily with one hand the solder is too thick. 062" would be much more accurate.. the conecting rod deflects easier than you may think. i usually remove the head and place the solder inline with the wrist pin. making sure it reaches all the way to the edge of the bore. i usually test with a pre-torqued old gasket and then put the new one in when i am finished altering the dome.

[ceaserthethird]

UP-Date with Number's, Is this OK ?

exhuast side ~ 0.38mm

Intake side ~ 0.30 - 33mm

[cr480r]

piston rock.. measure inline with the wrist pin... and .38mm is wayyyyyy tooo tight... i would look for closer to 1mm

[Billy Golightly]

Wow! Thats like close enough that just with heat expansion you might see some contact. That converts over to about .015, WAY too tight! you sure that caliper was zero'd out when you started?

[MTS]

Yes...much too tight...Need to be in the 0.8- 1.2 mm range, ..like billy mentioned the calipers....i would double check that again...Could have a milled down jug with a cut down head...Something is fishy :beer

[cr480r]

Maybe a stupid question, but is the head gasket for a big-bore?

[ceaserthethird]

YES the Gasket for a Big Bore but it's the High Compression kind, Papper Thin.

[ceaserthethird]

Dam thing Started but has Bone Breaking Compression!

[cr480r]

YES the Gasket for a Big Bore but it's the High Compression kind, Papper Thin.
Ok just wondered cuz i've seen that situation before.. looks like you will need a thicker head and/or base gasket.. cyl probably has been decked in the past


Dam thing Started but has Bone Breaking Compression!

you joking right?

[ceaserthethird]

NOT Joking

[ceaserthethird]

would a gasket Solve this issue ?

[Billy Golightly]

do NOT run the motor with squish clearance that tight! You will have the top of the piston slapping into the bottom of the head and subsequently flattening needle bearings in both ends of the connecting rod and if you do.

A base gasket is like .011, if I recall off the top of my head. Thats still like .026 which isn't nearly enough.

[cr480r]

sounds like a thick gasket or dome recess is in order.