Click on the pictures to enlarge them
To restore engine pinch/compression of your model car engine you can use the Sizemaster tool.
The Sizemaster tool from CTECK is a tool that can restore the pinch/compression of non ringed model car engines.
Sizemaster is designed and comes in various sizes to suite most engines types and brands.
For review and testing we at TEAM TWF8 received from Jim Couch from CTECK
19.5 mm Sizemaster that works on all Nova Rossi based and OS 3.5 ccm engines.
The Sizemaster comes as a tool with a simple written user manual without pictures.
The extra hexagon tools needed to operate this tool are not supplied with it!
How does the Sizemaster works in simple terms?
Put the sleeve in the size master and wrenching the hexagon screw so the sleeve is made smaller by the mechanical pressure provided by the tool.
Ok that is the easy version or is it really that simple in real life.
As test we will pinch a few test engines at TEAM TWF8 but also provide some other persons this tool to be tested.
There are generally 3 steps needed to pinch your worn out piston sleeve set.
Read this sequence first fully!
Step 1 Cleaning and disassembling the engine
Step 2 Pinching the sleeve
Step 3 Reassemble and break in the engine
|Clean the engine from the outside and disassemble the piston
The conrod does not need to be taken of the piston.
Check for the play of the conrod and the big end (conrod pin)
If this is to much replace either the conrod and/-or the crankshaft .
Check the piston and sleeve for severe scratches/cracks or other optical
If there is to much damaged on the surface of either piston or sleeve using the Sizemaster is of no use and a new piston/sleeve set must be installed.
Watch the mark of the anti rotation slid in the sleeve.
If there is no slid mark with a felt pen the top of the sleeve pointing to the exhaust port as we need this point later.
|Check the way (orientation) how the piston normally fits in the sleeve before completely disassembling the engine.|
|Check for the spot where the TOP DEAD CENTER (TDC) of the
piston in the sleeve is.
Normally clearly visible.
Take a ruler and measure the TDC point in the sleeve.
|More about engine disassembling/cleaning can be found here!|
|And this is the Sizemaster!|
|The two screws on the Sizemaster both are USA inch sizes.
The large 1/4-20 hexagon head screw for the pinching.
The small 8-32 hexagon setscrew for opening the Sizemaster.
|According to the manual we have to slide the sleeve into the
Turn the 1/4-20 hexagon screw 2 turns anti clockwise.
If the sleeve can not be slide into the Sizemaster use the hexagon 8-32 set screw to open up the Sizemaster to fit the sleeve by turning the hexagon 8-32 set screw a few turns clock wise.
Try to align the anti rotation slid in the sleeve with the slid in the
When the sleeve is at its place turn the hexagon 8-32 set screw 1 full turn anti clock wise.
# Now use a 1/4-20 hexagon tool with the long tip and turn it clockwise until little force is felt.
# Turn the 1/4-20 hexagon tool 1/8 turn clockwise with the short tip.
# Turn the 1/4-20 hexagon tool 1 turn anti clockwise with the short tip.
|We now have to rotate the sleeve 90 degrees (1/4 turn) in the
Sizemaster clock wise.
If the sleeve can not be rotated use the 8-32 hexagon set screw to open up the Sizemaster to turn the sleeve, by turning the hexagon set screw a few turns clock wise.
When the sleeve is turned reset the 8-32 hexagon set screw.
# Now use a 1/4-20 hexagon tool with the long tip and turn it clockwise until
little force is felt.
Take the sleeve out of Sizemaster.
|Fit the piston in the sleeve in the same way (orientation)
as the piston normally fits in the sleeve and check if the pinch is OK.
If not repeat the steps above ONE BY ONE until you have achieved the required pinch.
For getting the required usable pinch you might need to gain some experience.
Use the previous measured TDC of the piston to gain experience in pinching with this tool.
|Remember that the sleeve is
resized by mechanical force with some tolerances and it is hard to say how
much each resize will do.
Never overdo the resize the first time as this will stress the conrod extra making the engine to fail.
It is better to do less resize and run the engine and then perform an extra resize if needed..
Reassemble the engine and lube the moving parts with after run oil and mount the engine in the car
|Break in the engine for 2 or 3 tanks of fuel while driving
it at moderate speed on a smooth surface with a 90-100 degrees Celsius
More about break in of new engines can be found here.
What we think of it so far ?
|J||The device looks well made.|
|J||Short break-inn period|
|L||No correct hexagon tools with Sizemaster|
TWF8 rating **** stars
five stars is maximum
Paco Raap 06-09-2004
OK during a race we showed the drivers the Sizemaster and everyone was
curious if it worked.
I had brought along with me the correct hexagon tools and a 3 port Nova Rossi piston and sleeve where the piston could be put beyond the top of the sleeve! :-)
Everyone gathered around to see what was happening. We placed the sleeve in the Sizemaster and gave it the 1/8 turn as the manual suggested.
Tried the piston but no pinch so we tried and other set of 1/8 turns with same result.
To tight and loosen the large hexagon screw you need a lot of force and we suggest to put the Sizemaster in a small bench wrench.
As we thought it could not harm we did a 1/4 turn instead of the advised 1/8 turn.
Still no pinch. All watchers were eager to see if we got a pinch eventually.
So we hit it an other 1/4 turn and tried the piston in the sleeve.
We went to far with this last 1/4 turn. The piston now had to much pinch and can not be used anymore!
So although it can take some time use only 1/8 turns as 1/4 turns can pinch it to much.
Also use a small bench wrench to clamp the size master into to ease up thigh ting and loosen the turning of the large hexagon screw.
Currently one of our TEAM TWF8 members is trying this tool for some of his worn out piston sleeves.
Paco Raap 13-09-2004
The manual explains everything very clear although no pictures are used.