There comes a time in every tired motor’s life when it’s time for a new set of rings. Ours came a little prematurely, but that was due to unfair riding practices. One of our tester LTZ’s, which had a Curtis Sparks 440cc race build, lost nearly all compression through a huge ring leak. We could smell gas in the oil, and it would only start if we pulled it behind another quad. So, while we were rebuilding it, we thought we would show you how to do it. The kit we ordered was Maxpower’s 455cc Ice Cube kit, that comes with a piston, rings, cylinder, wristpin, and all the required gaskets. The kit retails for $1250, and sports a hefty 12-horse increase at the wheels on our L&L Motorsports Dyno, (661) 944-9043. Maxpower has many options, too, so give them a call at (608) 224-2524. As for the rebuild, here’s how it goes.
We started off by taking our LTZ down to Maxpower’s Dennis McAdam, a well-known engine builder in the MX circuit. He stripped the entire machine down so we could pull the motor out, because we found an interesting turn of events lying our motor.
After removing the gas tank and shrouds, you can start to see the whole motor. We had to pull ours, because it ended up being a little more than worn rings. We had a hot spot in the cylinder, caused by lack of coolant flow. The motor overheated and cooked the aluminum piston and the forged cylinder!
Right off the bat, when we removed our intake, we saw bad signs. Metal shavings and water means that you’ve got some engine problems!
We started off our teardown by pulling the radiator hoses, electrical wires and spark plug, and removed the head. You have to take the cam chain off the cams first, so be careful. The cams on the LTZ are removed by unbolting four bolts on each cam cover, then removing the cam chain tensioner. You can see the hole where the tensioner sits right above our engine builder’s index finger.
Our head was pretty cooked, as you can see by the large circular ring worn into the cylinder from the extreme heat. We will have to take the head to a machine shop to get it milled flat and polished. The valves are cooked, too, and you can see chunks of aluminum and Nikasil coating stuck to the faces of the valves.
This is our piston. Not good! It suffered from a blowout due to extreme heat and predetonation, and it blew chunks of piston all over the motor. A good tip when you’re rebuilding your motor is that if there are metal chips in the oil filter, you better split the cases and clean out the bottom end. If you just throw a new piston in, chances are you’ll lose a rod bearing or cook the motor due to clogged oil passages.
This is our cylinder wall. There was a hole that went completely through to the coolant passages, thus flooding the motor with boiling coolant! This one is junk, so it’s time for a new cylinder. That’s where Maxpower comes in. Their Ice Cube cylinder blocks have on average 80 percent more coolant capacity than a stock cylinder, making them extremely difficult to overheat.
Since we had metal shavings everywhere, we had to split the cases and clean out the bottom end. If you have no experience with building bottom ends, take it to someone who does. Trust us, it’s worth the price. This is a shot of the oil pump housing; we took the pump out to clean the passages and gears.
These are the oil pump drive gears. Make sure to clean any metal shavings off with a Scotchbrite pad, or the pump won’t work correctly.
Check out the color of the oil—it’s black. That’s a sign that the motor reached temperatures upwards of 400 degrees! Better check for heat damage! We had to rebuild the head, because the valves were cooked pretty badly.
Here’s the head after a fresh mill and polish, with new valves. It’s ready to be installed!
While we had the head off, we sent it out for a mild port and polish at L&L Motorsports, (661) 944-9043. This will let us extract a few extra ponies when it comes time to run it.
The cam on the left is the stocker, the one on the right is from Hot Cams. Swapping for high performance cams gives the motor a whole new attitude, as well as an extra 3-5 horsepower at the wheels!
The sprockets on the Hot Cams (right) are adjustable, allowing tuning of the powerband. If you don’t know how to degree in cams, don’t even attempt it. Take it to a pro.
Hot Cams also sent us out a full shim kit. These shims are used to adjust valve clearances in overhead cam engines. The shim sits between the valve and the follower, which looks like a small bucket. A thicker shim will make the valve close tighter, and a smaller shim leaves more slack.
Make sure the piston fits in the cylinder before you ring it. Be careful not to gouge any metal!
Carefully install the rings onto the piston, and don’t bend or break them. A bent or broken ring means that you have to order a whole new ring set, because you can’t use a piston with a broken ring.
Install the ringed piston onto the rod, carefully sliding a lightly-oiled wristpin into the piston. Use circlip pliers to install the retaining rings, but don’t drop anything down inside the motor! We use a clean rag to block the hole, so you can’t lose any parts.
Carefully slide the cylinder onto the piston, taking note not to jam any piston rings. Carefully compress the rings by hand or with a ring compressor tool, and don’t use anything more than light force. The piston should slide in easily, with no drama; otherwise, start over.
Make sure you pull the cam chain through the cylinder, otherwise you’ll be fishing it out with a long hook. Also, make sure the cam chain guide isn’t binding. The cam chain guide is the large black plastic piece alongside the chain.
Slip the head onto the cylinder, once again pulling the cam chain through. Bolt it down gently, making sure nothing is bound or stuck. We recommend buying a repair manual for your machine, so you can torque the bolts to the correct specifications. Also, don’t forget the gaskets!
Place the cams into their guides one at a time, looping the cam chain around the sprockets. Make sure you don’t mix up the cams! The intake cam goes towards the rear of the motor, the exhaust cam towards the front. To time the cams correctly, the engine must be at top dead center, and the cams lined up to the manufacturer’s specifications.
Here’s a shot of the cams from the top. You can see the cam guides and the spark plug hole in the middle. Note how the exhaust cam has a centrifugally-actuated automatic decompressor that allows the motor to turn over easier during starting.
After you install the cam caps and cam chain guide, install the cam chain tensioner back into the head. Adjust the chain to the manufacturer’s specs. A useful tip is to have the engine at top dead center, and run the bolt in on the tensioner (if you have the manual type) until the chain is snug, but not too tight.
Reinstall all of the engine’s parts, like this clutch basket. Once you’ve completed reassembly, it’s time to put the motor back in the quad! Follow the break-in specs listed with the cams, which in Hot Cam’s case says to run the motor at approximately 3000 rpm for about 20 minutes, without letting the motor idle for long and with no excessive rpm. After the initial break-in, check your valve lash to make sure it’s still in spec. After that, go rip it up!