Workshop: Top-End Check Up

Skill level: Intermediate Mechanic

If you purchased your Banshee used or have more than 80 hours on it, chances are it needs to come apart for a top-end inspection. The Banshee, like most other two-stroke sport quads, will perform well right up to the point of catastrophic failure. Checking out the condition of your Banshee’s top end is a fairly simple project requiring little more than basic metric hand tools. You will need a set of box end wrenches, 3/8 drive socket set, Phillips and flat blade screw drivers, and a pick (you can purchase the tools cheaper than you would pay to have the work done at a shop). And as we have stated in the past, buy good tools–the bottom of the barrel stuff can sometimes be hard on the fasteners. Note: you’ll also need a container for your coolant. Dispose of old coolant properly–don’t dump it down the drain. Most auto parts stores will accept it.

Step 1
Clean the quad well–particularly the motor. After a good scrubbing, dry the machine completely, then drain the coolant. Draining the coolant is done by removing the lower radiator hose from the motor followed by removing the drain bolts from the side of both cylinders. Take care not to lose the sealing washers. The reason for draining the cylinder is so that coolant will not spill into the crankcase during removal. Remove the front plastic and the gas tank. (Easy)

Step 2
Remove the exhaust system, silencers first, followed by the expansion chambers (a good idea when disassembling is to bag and label all the hardware to help when reassembling everything). Loosen the hose clamps and remove the carbs–they can be hung out of the way while leaving the cables attached. Remove the nuts and the head, and then remove the base nuts and the cylinders. Never pry on the cylinders! If needed, you can tap them with a rubber or plastic mallet to break the gaskets loose. (Easy)

Step 3
Mark the pistons left and right, using a marking pen on the inside of the piston. This is so if they are reused, the pistons will go back into the same cylinders. Take a shop towel or clean rag and stuff it around the rods covering the crankcase opening, ensuring that you can’t drop the wrist pin clips or anything else into the bottom end. Use a pick to remove the outside wrist pin clip from each piston (these should be thrown away and never reused). Press the wrist pins out. If they won’t come out easily by hand, you can press them out with a properly sized socket and short extension. (Easy)

Step 4
The piston-to-cylinder clearance must be measured using the proper equipment. We recommend taking them to a shop capable of measuring, boring, and honing in-house. This measurement must be taken with inside and outside micrometers or a dial bore gauge–don’t use calipers or feeler gauges, as they are inaccurate. If the pistons are within spec, you can have the cylinders honed and all you’ll need to do is install new rings. If the piston to cylinder wall clearance is out of spec, it must be bored to the next piston size, and then you’ll need new pistons, as well. (Advanced)

Step 5
Once the cylinders have been honed, it is very important to scrub them inside and out with dish soap and hot water. The honing process leaves tons of tiny metal particles throughout the cylinders, so clean thoroughly. Once clean, be sure to dry completely and coat with WD40 immediately to inhibit rust and lubricate. Dry with compressed air or paper towels, because cloth rags will leave fibers. This is now also a good time to make sure that all of the gasket surfaces are clean and free of old gasket material. You will probably need a gasket scraper or a razor blade, as base gaskets have a tendency to bake onto either the cylinders or the case. Never reuse any gasket or wrist pin clip! (Easy)

Step 6
Install the rings onto the pistons (either your old ones or the new pistons) with any lettering or numbers facing up (the markings are usually found at the ring end gap). Install the pistons back onto the rods, making sure to lube the wrist pin bearings with two-stroke oil. If you’re using new pistons, you need to install a new circlip into the inside of each piston prior to putting them on the rods. If you’re using your old pistons, they should already have one left in them. Make sure that you are installing the correct piston in its corresponding side, as they can measure slightly differently (you do not want to swap them). Once you have pressed the pins through, install a new circlip to the other side of each piston–install them by pushing one side of the clip in with your finger and chasing the rest in with a small flat blade screwdriver. Now you can remove the rags covering the crankcase. (Intermediate)

Step 7
Install new base gaskets onto the cylinder studs. Line the rings up on their alignment pins and compress with your fingers. Use your free hand to carefully slide the cylinder onto the piston. Be sure to install it straight so that you won’t have to spin the cylinder on the piston (having to turn the cylinder excessively can allow the rings to catch on a transfer port). Repeat this process with the other side, then install and torque all of the base nuts. Install a new head gasket, and then the head. Torque all of the head nuts to 10 ft/lb. following the order that is marked for you on the head, then set your torque wrench to the recommended torque (you’ll need your Banshee’s shop manual for the specs) and repeat this order. Install new spark plugs and reinstall the reed-cage assemblies with new gaskets. (Intermediate)

Step 8
Install the carbs back into the boots, making sure that they are on the correct sides and that the rubber choke crossover tube is still connected between the two carburetors. This part is commonly overlooked and has to be hooked up, or the quad will not run properly (and is only applicable on stock carbs). Reinstall the cylinder drain bolts with washers and the radiator hoses. Tighten the hose clamps, making sure that the ends of the hoses are in good shape. If a hose end is damaged, you can usually cut off a half inch and still stretch the hose to fit. Install your exhaust, making sure to use new O-rings on the header flange and copper RTV silicone on all pipe connections. Copper silicone is common at all automotive supply companies and holds up well to heat. Refill the radiator with a 50/50 antifreeze and distilled water mixture and then reinstall the tank and front plastic. You are now ready for a break-in session and the next couple of riding seasons. (Easy)