Arctic Cat Sno Pro 800

Someone brought a new Arctic Cat Sno Pro 800 by the shop recently.  It was only running on one cylinder and needed the spark plugs changed.  I think that they have a habit of warming it up for a very long time before driving it and then hardly getting above idle speed when they do drive it.  This leads to fouled plugs. This machine was built to run fast, not go across town to get groceries.

This second photo show about the best view you can get of the spark plugs.   Like a lot of newer machines this one has part of the chassis structure over the top of the engine.  It may make for a great light weight and stiff chassis, but it sure is a pain to service anything on the engine.  There really isn't a hood to lift up, just two little side covers that give you a peek at the engine.  To make the job a little more time consuming there is 4 plugs for this 2 cylinder engine.

With 4 new plugs in it it ran great.  The power delivery on this machins reminded me of an old 2 stroke moto cross bike from back before they had power valves.  There is a little rumble at low speed and then when you hit the right RPM the thing takes off screaming and stretches your arms out. 

Polaris 120 Snowmobile Rebuild

I have an older Polaris 120 snowmobile that I am rebuilding.  The engine had been neglected, so I decided to tear it down and inspect everything. While I had it apart I also removed the governor.  This is the first step to making these machines run faster.

With no governor to control engine speed the motor will rev up until the valves float.  To increase the RPM that this happens at I decided to install a set of "high performance" springs from Recreational Motorsports.  These springs are little bit longer and stiffer than the stock springs.  After the governor elimination this is the simplest way to make more power. The spring on the right is the new one, the original spring is to the left.

Whenever you are assembling internal engine components be sure to coat all the moving surfaces with some kind of assembly lube.  I normally use Lubriplate.

On these tiny motors I use my simple homemade valve spring tool.  You can see this tool and a manufactured one in these old posts here and here.

These small motors motors have a splash lube oil system.  There is no oil pump to distribute the oil around the engine.  The bottom of the connecting rod cap has a long thin "dipper" that sticks down into the oil reservoir.  As the crank spins this dipper splashes oil up onto the cam shaft and around the crankcase. 

Make sure the timing marks are lined up when the cam shaft is installed.  The small punch marks on the edge of the gears are the timing marks.

This photo shows the main parts of the governor assembly.  The governor can be bypassed by messing around with the springs on the throttle linkage, but this puts a higher load on this plastic gear that will eventually lead to it breaking and making a big mess.  If the governor is not being used it is best to remove this gear.  This photo also shows the governor control rod.  I cut it in half and remove the part that goes inside the crankcase.

When installing the spark coil it must be mounted as close as possible to the flywheel.  I have found that the easiest way to do this is place a piece of paper between the coil and the flywheel when tightening the bolts.  When you turn the flywheel you are left with a paper thin space between the parts.

This covers some of the high lights of small engine rebuilding.  When I get the rest of the machine together I will have more photos of chassis work.

Coolant Tank Repair

A friend brought me the coolant tank (reservoir) off of his Arctic Cat F6 Sno Pro.  One of the small plastic nipples for a hose was broken off.  The red arrows point to the nipple and the location that it is supposed to be connected.   A new tank is probably not to expensive, but would take several weeks to get here.

The plastic that these things are made from seems to be impossible to glue.  Luckily the area on the tank where the nipple was located was thick.  I decided to drill out the old hole and tap threads for a new brass fitting.  When tapping threads you must be sure to use the correct size bit, normally the size is printed on the side of the tap.  In this case I am tapping for a 1/8" pipe thread and the correct drill is 21/64.

Make sure that the tap gets started straight in the hole.  Pipe threads are tapered, don't run the tap in too far or the hole will end up oversize.  Stop and check the fit often.  A good rule of thumb is - 3 loose, 3 tight, 3 showing.  This means that you should be able to turn the fitting in three turns by hand, three turns with a wrench, and have three threads still showing when finished.

I applied a little bit of Leak Lock to the threads before assembling the parts.  Most standard water plumbing thread compounds are Teflon based and are not supposed to be used with petroleum products.  On anything involving oil or gas I use Leak Lock.

Here is the finished repair, a $3.00 brass fitting and 15 minutes.

Taiwnese ATV

On of the ATVs that I own is an Arctic Cat 366.  I purchased it used this past fall, and it is now a few years old.  It has been an OK machine, it mostly gets used for running errands around town.  It is has independent suspension in the front and rear, a CVT (belt) type drive train with high low and reverse gear.  It is powered with a basic air cooled engine with a carburetor.  Overall I would rate it's performance high.  The only negatives with this machine are it's small size and the lack of EFI (fuel injection).

Recently I was reading an article in an ATV magazine about some of the new Taiwanese and Chinese machines that are starting to be sold in the US.  In on of the photos I notice that the machine offered by Kymeco looked very similar to my machine.  I looked underneath my machine and found this label on the frame.  It turns out that my machine was not made by Arctic Cat in Thief River Falls Minnesota, but was actually produced by Kwang Yang Motors in Taiwan (that is the parent company for Kymeco).

I knew that Arctic Cat has sourced engines from Suzuki for years (and Polaris has used engines from Fuji), but I was surprised to see that they sourced the whole vehicle from overseas.  It looks to me like the smaller basic machines offered by Arctic Cat come from Kymeco, but the larger machines in their line up are produced here.  I wonder how many of the other big manufacturers are getting machines from China?

Mini Snowmobile Chain Repair

I recently had a Polaris 120 in the shop.  This is a mini snowmobile designed for kids.  It uses a 120 cc "industrial" engine.  This is a "Briggs and Stratton" type engine like you would see on a lawn mower or other outdoor power equipment.  Arctic Cat and Skidoo also make 120 cc sleds and they are all put together the same way.  There is a simple centrifugal clutch and a chain drive to the track.  The chain drive is the biggest source of trouble on these machines, it needs to be lubricated and tensioned regularly. 

When installing the chain a master link is often used.  They come in a few different styles, but they all work the same.  There is a chain link with a removable side plate and some type of clip to hold it together.  These are quick and easy to install, but are also prone to failing.  Over the years I have had several of them come off on different vehicles.   

A more secure way to connect the chain is with a chain rivet tool.  This tool is used to press the pins in and out of a regular link in the chain link.  It takes a little longer to use than a master link, but will produce a more secure chain.

Arctic Cat 366 ATV

I have an Arctic Cat 366 ATV that had a faulty ignition switch.  For the last few month I have had to wiggle the key around to make the machine turn on.  It gradually got worse, until it would not work at all.  I assumed that there was a bad electrical connection in the switch.

I removed the large plastic nut from the switch, unplugged it from the wiring harness and brought it to the workbench.

Before I took the switch apart I marked both pieces in case there was any confusion about how they go back together.  I have found that a silver Sharpie works great for marking things like this.

When I pulled the switch apart the corrosion was obvious.

I used a small wire brush to scrub the corrosion off the copper contacts.  Some of it was very hard and required a little scraping with a dental pick type of tool.

Before reassembling the parts I coated the contacts with a little silicone dielectric grease.  This stuff is great for preventing corrosion, I put it on almost every electrical connection.

Once I reinstalled the switch the machine worked fine.



Arctic Cat 1000 TRV H2

A friend brought over an Arctic Cat 1000 TRV H2 with a broken drive belt.  This is Cat's big top of the line ATV, with a twin cylinder 1000 cc motor, two up seating and all the fancy extras.  He had already purchased a spare belt and I thought that it would be a quick easy job.

When I pulled the belt cover off and removed the debris from the old belt I found a small piece of plastic and a metal key for a shaft.  Obviously there was more trouble than just a broken belt.  I removed the secondary clutch and discovered that the helix was cracked.

This first photo shows the clutch on the work bench with an improvised setup to compress the spring.  I used a piece of all thread and a few metal scraps to compress the spring enough to remove the snap ring.

Here is the broken helix.  You can see that the part cracked right at the corner of the groove for the keyway.  This is a classic example of a failure at a stress concentration.

This machine has a powerful engine on a large and heavy chassis, I wonder if the Arctic Cat engineers did not design a drive system that is tough enough to handle it?

Arctic Cat Sno Pro - Finished

I have been working on this Arctic Cat Sno Pro 600 on and off for a while now.  Today I was finally able to wrap up the project.  I will give you a quick recap of the situation.  The machine quite running last spring, the owners then left it sitting on the beach where it stopped.  After a whole summer of being very close to the salty ocean they brought it to me.  I figured out that the initial problem was a faulty fuel pump.  After changing the very expensive ($447!) fuel pump I started to fix all the rusted and corroded parts.

The worst corrosion was on the brake system.  The brake is made from aluminium and steel, that is a bad combination in a salt water environment.  When I first pulled the machine in the shop the brake was locked up solid.  After a liberal soaking in Deep Creep penetrating oil and a lot of pounding I was able to get it to turn by hand.  I thought that it would loosen up with use, but when I test drove the machine it was dragging and heating up the rotor.

After a lot more oil and pounding I was finally able to remove the rotor.  Once I had the rotor removed I put the caliper back together and used the brake pressure to push the pistons out of the calipers. The top photo shows the back half of the disassembled caliper in place on the machine.  The caliper is actually part of the same casting that holds the bearing for the drive shaft.  The rotor goes on the end of hollow splined shaft.

This second photo shows the other half of the caliper, the piston, and the seal.  Despite being made of stainless steel the pistons were corroded and pitted where they were in contact with the aluminum caliper.  This corrosion caused them to bind or stick in the caliper and prevent the brake from releasing.  At first I thought they may need to be replaced, but I was able to clean them with fine sand paper.  I reassembled everything with a little bit of silicone grease on the parts and  the brake now works fine.

Arctic Cat SnoPro - Update

I have replaced the fuel pump on this machine and took care of a few minor corrosion related issues.  Everything is running fine except the brake.  When I first put this machine in the shop the brake was locked up tight.  I took the outer half of the caliper off and cleaned things up.  It seems to turn free, but when I test run the machine it quickly heats up and seems to grab like crazy.  I drove it up and down the beach for two minutes and the rotor was glowing red!

I'm not sure what the problem is, but I guess I'll have to take it apart and inspect everything?

Arctic Cat F6 Sno Pro

Today I worked on a 2010 Arctic Cat F6 Sno Pro.  The owner brought me the machine because it would not start.  He suspected a fuel problem (normally I don't listen to what the owner says, but this time he got it right).  I pulled the rope a few times and the engine did not fire.  I pulled the spark plugs and checked for spark, then squirted a little fuel in the cylinders.  This time when I pulled the rope it fired up for a couple of seconds.  Definitely a fuel problem.

This machine has a modern engine with a battery less fuel injection system.  When you pull the rope the stator makes enough electricity to charge a capacitor and run the injection system.  I pulled the fuel line off the injector rack and checked for fuel pressure when pulling the engine over.  There was no fuel pressure so I decided to check the voltage to the fuel pump.  I found the wires going to the pump and checked for voltage when cranking.  I saw spike of 15 volts when pulling hard on the rope and it then gradually dropped off.   All these signs point to a bad fuel pump.

The pump is mounted inside the tank very much like a typical automotive system.  Just like working on cars, it is a pain to get to the pump.  I decide that I would like to do one more test to make sure it was the pump before I pulled everything apart.  In the photo you can see my temporary fuel system that I rigged up to run the engine.  I have a "Hudson" type garden sprayer filled with gas, I pumped this up to 15 psi (thanks Dave for the help) and connected it to the fuel rail using a few plumbing fittings and tubing.  With this setup supplying the fuel pressure the engine ran OK.  I later learned that the system is supposed to run at 40 psi, but 15 was enough for testing in the shop. 

Once I was sure that it was a bad pump I pulled everything apart and took the pump out of the tank.  Now I just need to find a replacement.  The Arctic Cat dealer only sells the complete pump assembly with the mounting bracket and fuel level sensor attachment for $450!  The pump itself is a basic Walbro like automobiles have, normal price $80 -$100.  Hopefully I can find a source that will sell me just the pump.  Any one have any ideas where to look?

C.O.