Archive for January, 2010

Why Does A Two Stroke Engine Smoke So Much?

One question I’ve been asked many times by two stroke customers-bikes, sleds, or Atv’s.

“Why does my engine smoke so much when I first start it”.

Well going back to the last time you used it, the gas and oil going into the engine from the carb and oil pump are atomized into very small particles so they can burn and the engine can make power.  When you shut off the engine and it cools down these little particles will turn back into a liquid and settle to the bottom of the engine.

When you start the engine the next time, this puddle of gas and oil has no place to go but up and back into the combustrin chamber where this extra fuel will make it run very rich until it’s all gone. What also doesn’t help this is a cold engine will need the choke turned on to help start, this extra rich mixture adds to the averall rich mixture and makes the engine smoke a lot until it’s warmed up and blown out.

When you first take off the higher RPM will help blow out the liquid around the crank shaft and that’s what causes that rough running on on the first ride of the day.  This is normal and all two stroke engines do it, think of it as part of warm up.

Happy Trails

Ray

If you have any questions for me, please ask.  You will get a quick, accurate, answer and I don’t charge a dime!

After Market Belt Replacement On Your Sled

A common complaint I have received from many customers over the past 30 years is:

“I replaced the drive belt on my sled with a new one and now it bogs off the line or really doesn’t run right”.

What I’ve found is they bought an after market belt or tried to save money and bought a (cheesy) cheap belt.  The exact width, length and most important rubber compound is VERY important to how the clutch will grab off the line and shift.

I HIGHLY recommend that you run a stock factory drive belt on your sled, there are just too many variables with an aftermarket and your performance will likely suffer.

Ray

How To Read Your Spark Plugs, They Are Telling You What’s Going On in There

In a AIR COOLED ENGINE, the spark plug center electrode porcelain color can tell you how well your engine is running or can tell you how to get it right.

Basically the plug color is telling you the combustion chamber temperature at the time you shut the engine down.

If the engine is running well  and you pull the plugs while riding on the trail and you see a light chocolate brown color all is well—This would be an average of the throttle position and shut down at that time.

Stay with me,

If you are trying to jet your carbs after doing any type of mods—pipes, porting, heads, carbs, clutching or gearing, You are going to have to do this.

First lets get it down on how to do a PLUG CHOP

This is what you have to do on a test ride each time you want to test the particular  change you did to the carbs.

ALWAYS do only ONE change at a time or you won’t know which one is working

First get yourself a new box of NGK spark plugs of the correct type for your machine, this testing will take quite a few NEW plugs.

Now warm up the engine in a area that you can hold the throttle in one position for at least 1 mile ( a lake is great for this) with a set of usable not new spark plugs in it.

Doing a plug chop plug chop on a snowmobile can be dangerous, So you must have your head on straight (no beer or drugs)

Right now I’m not getting into carb jetting or systems, I’m assuming you know what change effects each system of the carb—I will be doing another article on carb jetting later—Right now I’m trying to get you to know if the adjustments you are doing are working.

Say you moved the needle  one clip position and your trying to get rid of a flat spot.

We want to get the engine RPM up to the throttle position that your testing (a neddle clip change works around ½ throttle)

So here we go, you have the engine all warmed up and cleaned out (from several test runs to make sure it’s safe). Replace the plugs with a set of new ones (they will be hot-use a rag to handle).

A plug chop is getting the engine to the test RPM as fast as possible and MAINTAINING that RPM  for at least 1 mile with out changing the throttle position AND shutting down the engine as fast as SAFELY possible.

With the warm engine with new plugs in it, Have all your gear on, Start the engine and go to half throttle as fast as you can and hold it for at least 1 mile-try not to move the throttle—after the 1 mile you need to be on a flat smooth spot and hit the kill switch on the handle bar and lock up the track with the brakes and CAREFULLY slide to a stop. If you start getting side ways, let up on the brakes a little—DON”T roll it and hurt your self.

So we got the engine up to speed, held it for 1 mile and stopped the engine as fast as possible.

Now reach into your pocket and get the spark plug wrench you put there and remove the very hot plugs.

Congratulations,  you just did a plug chop!!

Looking down the inside of the plug porcelain you are looking for a ring of color or a band about 1/8”to 3/16” wide. This is why you use a new set of plugs each time you do a plug chop, this ring will only show up one time.

If you went far enough on that plug chop ride you can get enough color to cover the whole electrode and it will look like a regular new plug with color—just go by the color—a great running engine will have a light chocolate brown color—darker is richer and a lighter color is leaner, You can adjust the jetting and try again.

I do this at low speeds to wide open, each a new set of plugs and test ride and it can take most of a day, After this you KNOW it’s running right!!!

I hope this makes sense and works for you-Remember your controlling the heat inside the engine, and that heat is coloring the plugs.

RIDE SAFE

Ray

Snowmobile Mid Season Check Up, Is Your Sled Running Like It Did Back In Nov.

Now that you have been riding your sled for part of the season

Is it running as good as when it first hit the snow?

There are things that you need to check that wear or get out of wack as you ride.

First lets take a look at the drive belt:

The clutching on a sled is the heart of it’s performance, it is what allows the engine to rev to it’s max horse power RPM. (shift rpm) more later.

An easy way to check the belt for burned or narrow spots is to ride your sled from a dead stop and very slowly accelerate to about 5 or 6 mph (this should only move you 20 to 30 feet). If you feel any jerking or pounding as you pick up speed you have a bad belt and it really should be replaced.

These narrow spots allow the sides of the clutch to move in and out each time the bad spot goes by and beat the heck out of it, after about 10 to 15 mph you won’t feel it any more, but the damage is still being done to your clutch.

The other thing to look for is normal wear (the belt will wear narrower) and sit lower in the secondary, If it gets too low the clutches will not shift correctly and it will be like taking off in your car in second gear. No power off the line!! If you want to maintain that like new performance this is also time for a new belt.

So how does the clutching mechanism work on a sled you ask, here is a simple explanation:
The primary clutch is the one on the engine and spins any time the engine is running and is the smaller diameter of the two. It controls the engine engagement rpm and most of the shift rpm. It’s the one that gets you moving from a dead stop.
The secondary clutch is the larger of the two and controls the back shifting and some of the shift rpm. Basically the two clutches work together to maintain the engine rpm verses the ground speed.
The way it SHOULD work is: From a dead stop, if you hit the throttle wide open (on a safe flat area) and watch the tac the rpm should go to your sleds shift rpm (found in your manual or call your dealer) and NOT change until you hit top speed. If the rpm drop or go over, you have clutch issues, I
will do an article on clutch tuning and set up soon. If you can’t wait and want to learn how to tune your clutch NOW I recommend OLAV AAEN’S CLUTCH TUNING HANDBOOK. It’s the best book on clutch tuning I’ve ever seen and I use it.

Next lets take a look at the spark plugs:

Pour or missing spark is one of the primary performance robbing problems. Start by removeing them and take a look at the center electrode, porcelain color-it should be a light chocolate brown Not black and shiny. If they don’t look great,

replace them—it’s an easy way to keep your sled starting easily and there cheap. On replacment spark plugs, I highly recommend the NGK brand. They have a wider heat range and just start better and last longer, just my opinion, after 40 years of experience.

A neat piece of information to know: If you are having a running problem and can’t seem to find it (everything you checked is ok) Remove the spark plug caps from the wires and connect an ohm meter to the screw sticking out from

inside the cap where the wire was and put the other test lead to where the spark plug goes, set the meter to the “K” ohms scale and tap the cap on something hard (your work bench) and see if the reading changes, make sure your making

good contact while your tapping it. Try it several times per cap, if the readings change you just found the problem. There’s a small resister inside the cap that looks like a small stick of carbon and it can bust up to a

powder and not allow the spark to pass through causing a misfire.

Way to go your a trouble shooting expert-Tell your friends.

Other things to look at:

The wear bars under the skis:

These wear down as you ride crossing a road or along a road with one ski on the road. They are designed to wear instead of your more expensive skis but do need to be replaced when worn.

Pick the tip of the ski up and look or feel the metal bar running down the center, if it’s flat or a short piece of carbide in the center of it is really dull you should replace them-the sled will steer much better on hard pack with new wear rods.

Hyfax:

These are the long black or colored pieces of plastic that the track is running against. Looking at the side of the sled, you can see the slide rails that the suspension connects to (they are aluminum and are curved up at the front) On the bottom of these are the hyfax, they rub against the metal clips on the inside of the track and when you are in snow the pressure and weight of the sled turns the snow into a thin film of water witch lubricates the hyfax and metal clips-this works very well as long as you are in enough snow to keep them wet.

If you ride long distances on a hard packed roads or on glare ice, they will dry out and melt ( it takes 425 degrees to melt hyfax) There is a wear indicator along the side of the hyfax (if you look at the curved part on the front where the track doesn’t touch you can see how thick they used to be) if they are down to the wear line they need to be replaced.

I will be doing a article with pictures and video on how to do this your self the EASY way.

Lights:

Check all lights each time you ride. The most important one is the brake light-You don’t want someone running into the back of your sled. You can easily tell when the headlight is burned out but you won’t see the tail or brake light unless you look.

Oil:

Make sure the oil tank is full of the correct type of oil for your machine each time you ride.  Check the oil level of the chain case. It can use a bolt you remove, a dip stick or a level window you look in, Just make sure there is enough and do change this oil at least once a year. It doesn’t hold much and it does work hard.

Brake pads:

Look down each side of the brake disk and check how much pad material is left, most pads have a slot to indicate a wear limit.

I hope this gives you something to check and keep both you and your sled HAPPY

Ray