TECH: Big Bore Install

MOD COST: $$199.99 from Scooterworks

MOD DIFFICULTY: Dificult. You should either be a mechanic or have your mechanic do this.

SPECIAL TOOLS: Regular socket set and some screwdrivers.

MOD BENCHMARK: HUGE increase across the board. Pulls HARD!

NEXT STEP: Replace the head.

The first thing I'll note is that after opening the box to inspect and verify all the parts that while there is a sheet with some tips you need to know about the kit, there are no installation instructions of any sort. This is not the sort of upgrade that you should try if you don't ALREADY know how to pull apart a motor.

The first thing I did was remove the petcarrier/seat assembly as well as the front panel (the one with the cooling vent behind where your feet sit)
to reveal the motor.

Next I removed the fan and flywheel cover to reveal the timing marks. This is important so you can get the motor timed properly for reassembly.
Note that when the "T" mark is aligned with the indicator arm, the crankshaft is at top dead center(TDC)

I then removed the vent return hose from the valve cover and the valve cover itself via the 4 bolts at the corners revealing the camshaft and rocker assembly.

The rockers are held in by 4 nuts with lock washers. These nuts are attached directly to the engine studs that hold the whole engine together.

After you remove those nuts the rockers should come off with some gentle pulling. Note the side labeled E X as this is the exhaust valve rocker and must end up on the same side of the head when re-installed.

After you remove the rockers, the camshaft will be mostly free of the head, though still held in place by the timing chain. Note that there is a line etched across the sproket on the end of the cam. When this line is parallel to the head and the hole in the sprocket is up, the cam is at top dead center(TDC). Gently pull up on the back of the camshaft to tilt it out of the timing chain and remove the cam.

Next I unbolted the two bolts holding the intake to the head and separated the intake from the head. Note that there is a tiny rubber O-ring on the end of the intake. Don't loose it!

Then I unbolted the two bolts that hold the exhaust to the head, and the two rear mounting bolts and removed the exhaust pipe from the bike.

Next you need to remove the plastic cover from the engine. It has two screws, one on each side of the motor, several tabs, and a bolt on the left side of the motor. Pull the top cover up and out(its a tight fit). You can leave the lower cover in place.

Now you can see the chain tensioner sticking out from the side of the cylinder. It looks like a tube sticking out of the top side of the cylinder with a bolt in the end and two bolts near the base. Remove the two bolts and the tensioner will come out of the cylinder.

After that I removed the two long gold bolts from the head that are on the left side of the engine. These bolts hold the head to the block directly.

The head should now be loose on the block, but you'll notice that the intake studs are too tall to clear the bike. There's a simple fix for this.
Unbolt the lower rear shock bolt and pull the shock out of the way of the motor. Now you can pull up on the rear tire to tilt the front of the motor forward so those bolts clear. This can be done by yourself, but would likely be easier with 2 people.

Remove the head now, being sure to pull it straight so as not to put any strain on the engine studs.

Now you should be able to remove the lower chain guide. It just pulls out now. The upper chain guide can stay in place.

At this point the cylinder should be free of the block, and you can pull it out and remove it. Again, be careful of the studs.

Now the piston should be free and open on the end of the rod. There are two C-Clips on the ends of the wrist pin on each side of the piston. Use a small flat blade screwdriver(Or a C-clip tool if you have one) and remove them, then push the wrist pin out of the piston with your finger. Now the piston will come off the end of the rod.

At this point its basically the whole process in reverse with one notable exception. The new cylinder comes with a different style chain tensioner that will not fit under the engine cover. You have to cut a chunk out of the cover to clear the new tensioner. DON'T opt to leave the cover off. Its needed for cooling.

If you've actually READ this far I'll just preface this again. You're replacing 1/2 of your motor to do this upgrade. If you've never done this before you probably shouldn't try now! THIS IS NOT A MOD FOR BEGINNERS!