In the last issue of STREET CHOPPER we gave our readers a look at the frame, forks and wheels that will be used as the platform for the rigid chopper we're building at V-twin City's new facility in nearby Santa Ana, California.
With the chassis underway, it was time to decide on what motor we were going to use to power our project. As you can imagine, there were a few different ideas on the subject, as each member of the staff seems to have a favorite size and configuration when it comes to their dream motor. Well, we're here to tell you that performance won out once again.
We gave Don Sekora at Merch Performance in St. Louis, Missouri, a call to help us with our final decision. Merch builds 120 and 131-inch motors and with Don's help we finally agreed that since we're all lovers of big inch motors, why not go really big-131 cubic inches of big! Don recommended going with Merch's 131ci Stage II package with the addition of Stage III heads that were decked an additional .050" to bump up the compression, and running a Merch .650-lift cam to maximize resuts. Don told us told us that dyno runs on this configuration typically show about 135 horsepower and 145 ft/lbs of torque-at that moment, more than a few smiles appeared in the office!
To ensure consistent quality, Merch builds each motor in four sub-assemblies; cylinders, heads, cases and crankshaft, before they are assembled into a finished product. Each step is carefully inspected, with measurements taken to .0005" and logged on a build sheet for tracking purposes. Here's a look at how it's done.
Our tour begins with a look...
Our tour begins with a look at the cylinders being honed to size.
Once the cylinder is the correct...
Once the cylinder is the correct size, the rings are ground...
...before being slipped into...
...before being slipped into the cylinder, using a special Merch tool that sets each ring to the correct depth...
...so that the end-play can...
...so that the end-play can be checked with a feeler gauge.
Important information is logged...
Important information is logged at every step of production, to ensure quality is consistent.
Our next stop was at the grinding...
Our next stop was at the grinding room where each head is ported for maximum flow.
Once the porting is completed,...
Once the porting is completed, the valve guides are pressed into the heads...
...before the valve seats...
...before the valve seats are treated to a three-angle valve job.
The valves are then inserted...
The valves are then inserted into the guides and the stem-protrusion length is measured so valve spring pressure can be set accurately.
To finish the heads, a spring...
To finish the heads, a spring compressor is used to allow the spring keepers to be installed.
After measuring the weight...
After measuring the weight of the pistons and rods and doing a little math, the flywheels are balanced to a 55% factor on a knife-edge stand. The wheels, with a bob-weight in place, must stay stationary in four quadrants to ensure a smooth running motor.
A Sunnen hone is then used...
A Sunnen hone is then used to size the connecting rod bearing surfaces.
The rods are then placed in...
The rods are then placed in a special fixture to check that they are straight.
After installing the crankpin...
After installing the crankpin and rods, the flywheel assembly gets torqued to spec and is then trued to perfection.
Drive-side Timken bearing...
Drive-side Timken bearing races are then pressed into the left hand case.
The pinion bearing race is...
The pinion bearing race is then honed to size and trued by using this Merch fixture mounted on a Sunnen hone.
A dial indicator is mounted...
A dial indicator is mounted to the crank bearing race so that flywheel-to-scraper clearance can be checked before installing the crank. Merch builds their flywheels 1/4" smaller in diameter than most on the market, which allows them to use a longer piston skirt for greater piston stability.
Since we are running a .650...
Since we are running a .650 lift cam, the inside of the cam chest must be clearanced due to the lobe height.
Cylinder studs are installed...
Cylinder studs are installed using LocTite and this special Merch fixture. The threads on the studs are rolled for added strength...
...and are anchored into stainless...
...and are anchored into stainless steel "bullet" inserts in the cases.
The cases are meticulously...
The cases are meticulously washed before final assembly begins.
Now it is time for the inner...
Now it is time for the inner drive-side Timken bearing to get installed, followed by the case and outer bearing, using a threaded bearing press.
After applying a little Permatex...
After applying a little Permatex Ultimate sealant to the case halves, the bottom end is bolted together. Note: Merch uses blind holes for their case hardware, which provides a cleaner appearance.
Pinion runout is checked after...
Pinion runout is checked after the cases are torqued, using this special tool developed by Merch.
Next, a JIMS oil pump is bolted...
Next, a JIMS oil pump is bolted in place and spun by Baisley 2:1 drive gears.
The cam gets well-lubed before...
The cam gets well-lubed before being slipped in place. End play is then set and documented on the build sheet.
Once the cone is in place,...
Once the cone is in place, pinion gear lash is checked using yet another innovative Merch tool. This keeps gear noise to a minimum.
Before being installed, the...
Before being installed, the lifter blocks are clearanced to make room for the .650-lift cam, using Merch tool #80-0014...
...and are then bolted in...
...and are then bolted in after the lifters are lubed and slid in place.
After the pistons are placed...
After the pistons are placed on the rods, the cylinders get slipped on with the aid of a ring compressor.
Before the heads are bolted...
Before the heads are bolted on, cylinder squish is measured with another special tool from the Merch arsenal.
Once the heads and rockers...
Once the heads and rockers boxes are in place. The lifters get adjusted...
...and then the motor gets...
...and then the motor gets bolted into the test stand. Each motor is pre-run and the ignition timing is set before being shipped.