Tuesday, January 25, 2011

Snowmobile Tow Hitch

In the winter our primary means of transportation is by snowmobile.  Most of the time when you are snowmobiling here you are pulling a sled.  All of this sled pulling puts a lot of wear and tear on the tow hitch.

The factory made tow hitches that come with snowmobiles are never tough enough.  I replace a lot of them for people.  Here is a collection of broken and wore out hitches.  Many of these are the type that fit into a tube on the rear bumper and they are held in place by some type of pin.  The pin is never strong enough, it eventually bends.  Frequently the hitches are made from metal that is too thin or they have inadequate welds.  Another source of trouble is the latch that keeps the sled connected, the springs fall out or the latch bends.

Over the years I have come up with a replacement that solves all of these problems.  I build my tow hitches with a 1/2" clevis, a 3/4" bolt and a nyloc nut.  If you use a quality clevis they are made with an alloy steel that seems to wear better than the typical mild steel factory units.  The shape of the clevis also makes for a better tow hook than the usual "J" hook.  The clevis is narrow at the top and keeps the sled draw bar from coming out.  The shape works so well that I often don't screw the clevis pin in the top.

After grinding the galvanizing off the clevis I clamp them together for welding.

This is a very important weld that must be done carefully.  These are the tools that I use to clean the slag off between weld passes.  The top three are typical welding tools, but the bottom one is one of my favorites.  It is a standard Stanley awl.  If you hold it loosely with one hand and tap on the end of it rapidly with the wire brush of the side of the chipping hammer it acts like a mini needle scaler.

Here is a close up of the completed weld.  An old well driller that I used to work with would say that a good weld "looked like a stack of dimes."

This is the completed hitch.  The nyloc nut holds it much more secure than a little pin through a hole.

Here is the new hitch on the back of a Polaris.

Tuesday, January 18, 2011

Battery Safety

This photo shows the contents of one of my pockets.  I went out on a service call for a furnace yesterday and on my way out of the shop I grabbed a couple AA batteries for my flash light.  I was in a hurry so I just tossed them in my pocket. 

A few hours later I felt something hot on my leg.  At first I thought maybe I had been leaning against one of the hot pipes in the boiler room.  Then I looked down at my leg thinking that maybe I had spilled some of the hot glycol from the boiler onto myself.  When I saw that my pants were dry I realized that the heat was coming from my pocket.

When I reached into my pocket one of the batteries was very hot.  Not hot enough to burn my fingers, but hot enough to make me think about it.  Apparently the battery was shorting out on all the metal stuff in my pocket.  From now on I am going to be more careful with batteries.  I don't know if they could get hot enough to start a fire, but I don't want to find out.

Monday, January 17, 2011

Kawasaki Prairie 700

Today I have a Kawasaki Prairie 700 in the shop.  I think this machine is about 10 years old now.  When it was new it was the flagship of the Kawasaki line with a big 700cc V twin engine with 4 valves per cylinder and overhead camshafts.  The owner of the machine thought that the pistons were "wore out", so he changed them but could not get the engine started after putting it back together.  I asked a few questions about the rebuild job and discovered that he did not know about setting the cam timing or adjusting the valve lash.

Setting the cam timing is pretty straight forward.  Take the valve covers off, loosen the cam chain tensioner and turn the crank to the timing mark for that cylinder.  Then simply rotate the cam shaft to where the timing marks line up with the top of the head.  Put the chain back on the cam and reinstall the chain tensioner.  Repeat for the other cylinder.  

The next step is setting the valve lash.  This involves inserting a feeler gauge between the rocker arm and the top of the valve stem and turning the threaded adjusting stud until there is a slight drag on the feeler gauge.  On most machine it is a quick and simple process, unfortunately on this Kawasaki the access is very limited.  The access cover on top of the head is very small and it is hard to get a feeler gauge into the correct spot, also the exhaust valves on the front cylinder are impossible to see, and hard to get your hands to.  This photo shows the screw driver on the adjuster and the feeler gauge set on the right.  That is as good a view as I could get.  I basically had to make the adjustments entirely by feel.  On the lower part of the photo you can see the small access opening for the intake valves.

Now I need to put the carbs back on fill up the fluids and see if it will start?  Hopefully the rest of the rebuld was done ok.


Thursday, January 13, 2011

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.

Sunday, January 9, 2011

Polaris Sportsman 500 ATV

I have my own vehicle in the shop today, a 2008 Polaris Sportsman ATV.  My wife was driving it a few weeks ago and she called me and said "something exploded, there is oil everywhere!"  This first photo shows what I found when I went to get her.  The oil reservoir had actually exploded.

These Polaris ATVs have a 4 stroke engine with a dry sump oil system.  Unlike a typical engine with an oil pan or sump on the bottom of the engine, these engine have a separate reservoir to hold the oil.  This allows the engine to be more compact and probably makes it easier to increase the ground clearance under the engine.  I think that it also helps with cooling the engine,  the oil reservoir has a large surface area to dissipate the heat in the oil. (There are probably more reasons than this to use a dry sump, but these seem like the obvious ones.)

I have seen this problem several times before on other peoples machines.  ATVs in the village make a lot of short trips in cold weather.  They do not get run long enough or hard enough for the oil to heat up.  This allows moisture to build up in the oil and the vent line on the reservoir gets plugged with frost and ice.  Once the vent is plugged the pressure builds up and blows the side of the tank off.  Polaris is aware of the problem and has tried to prevent this by putting a small slit in the vent line.  This slit in the rubber hose is supposed to stay closed during normal operation and open up if pressure builds in the line.  Unfortunately it seems like the blockage happens right at the tank and the pressure can not be relieved. 

Another potential problem with the moisture build up is the possibility of ice forming in the bottom of the tank when the vehicle is parked in the cold.  If enough ice forms it can block off the oil supply line to the engine.  This of coarse leads to an oil starved engine and all kinds of problems if the operator is not aware of the situation.

This photo shows the new tank and the original.  It is interesting how the whole side of the tank exploded.  This is the same way that I have seen other ones fail.  I am surprised that the tank doesn't simply split open?

To try and avoid future problems I have decided to insulate the tank to help the oil heat up better in cold weather. 

I cut up an old camping type sleep pad to cover the sides.  I am using DOW 732 silicone to glue the closed cell foam to the tank.  732 is great stuff, I use it for everything.

 Here is the completed tank ready to install. 

Monday, January 3, 2011

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?

Sunday, January 2, 2011

Piano Repair

This afternoon I spent a few hours at the local church working on the piano.  The piano is a 1950s or 60s Baldwin upright.  It looks like a basic piano that you might see in an elementary school class room.  AnnMarie plays it on during Sunday church services and it gets used once in while when we have regional conferences at the church. 

Over the years I have gotten to know this piano rather well.  When the church burned a few years back the piano survived, but barely.  The piano got hot enough to melt the plastic tops ("ivories") off the keys.  After the scorching heat it then sat outside for a few weeks in the rain and wind while the church reconstruction was being organized.   It was in pretty rough shape, but I decided to try and rescue it.

I moved it to our house and spent the next few years slowly learning about pianos and restoring it.  I had to take apart the entire action to clean the rust out and readjust all the linkages.  I then figured out how to tune it and finally finished the project by giving it a new paint job.

This afternoon I was gluing a few of the key tops back on.  The glue that I used in the restoration did not stick to the plastic very well.  Every year a few of the tops pop off and I have to stick them back on.  I think the glue that I am using now will hold better.