Engine Understanding?

Contribution: Scott Collier

Previous posts have talked about some of the aftermarket pieces and accessories that are needed to go fast.  But, the real heart of going fast is the engine.  Pushing the limits of your engine requires skills and knowledge and a lot of maintenance.    More then most, it requires much knowledge.  Just adding parts and not making proper changes to accommodate these aftermarket parts can hinder engine performance.  This is not our goal!  I thought a general overview of the 4 cycle engine would help the inexperienced mechanic and provide a refresher to some with a little education.

Before getting into the heart of this there are a few things that need to be covered.

TDC: Top Dead Center

This is a point where the piston has reached its maximum height and briefly tops out before it swings downward.  On a degree wheel 0/360 degrees.  General basic terms - On a clock think of it as 12:00

BDC: Bottom Dead Center

This is the point where the piston has reached its maximum downward swing and briefly bottoms out before it starts to swing upward.  On a degree wheel 180 degrees.  General basic terms – on a clock 6:00

There is also…

BTDC – Before top dead center – an area prior to 360 degrees

ATDC – After Top dead center and area after 0 degree 

Ok, let's get into it.

The basics of a four stroke 

A four cycle or four stroke engine requires 4 distinguished steps that allow it to operate.  They are as follows:

1. Intake
2. Ignition
3. Combustion
4. Exhaust
   

First thing to discuss is the carburetors position in this mix (pardon the pun).  A carburetors job is to provide a mixture of fuel and air in the proper amounts to promote a strong burn or ignition.  Too much air and not enough fuel creates a condition called a lean mixture.  This condition leads to excessive heat and will break down the engine quickly.  Too much fuel creates a condition know as a rich mixture.  This condition will run cooler and burn or ignition may not be complete causing a lack of power.  The goal of the carburetor is to provide a balanced mixture (to be discussed in a later post). 

Now we have a fuel air mixture...lets move on to how this gives us power.  We know the piston travels up and down in the cylinder turning the crank giving us a rotational output for power.  The up and down of the piston is governed by many things..

Intake

On the intake stroke, the piston is on its way down.  This movement creates a vacuum that draws the fuel/air mixture into the cylinder.  Of course the valve timing plays a part in this as it determines how long the valve (door) is open allowing the flow of this mixture from the carburetor.  If valve timing is off, you are restricting or lengthening the amount of time that valve is open allowing a condition of too much or not enough fuel into the cylinder.  Therefore check you valve clearances regularly! 

Compression

Fuel and its properties are the basics of this stroke.  The fuel and air will burn very well under atmospheric pressure.  But, place that same concentration of fuel and air under pressure and it will burn much quicker.  Hence, the compression of the fuel air mixture allows an explosive burn producing the punch to push that piston back down allowing power to be created.  Yes...power is only created on one of those four strokes… make it count!  So the compression stroke is the upward movement of the piston, with both valves closed, that allows the fuel air mixture to be compressed.

Combustion

This is where the power is created.  After the spark plug ignites the compressed fuel air mixture, the piston is driven downwards with help from the explosion.  Again, the valves will maintain a closed position when this occurs.

Exhaust

After the power stroke travel downwards, it must return to the top to start again.  However, the cylinder is now charged with vapors and exhaust gases that do not promote good combustion.  So during the upward movement of the piston, the exhaust valve opens, and bad air is forced out of the cylinder allowing for a good clean return to the intake stroke.  Hence, it is called the Exhaust cycle.

At this point the exhaust valve has allowed the bad air out and the cylinder is ready to accept a new clean mixture into the cylinder as the four cycle process starts again.

So keeping that piston going up and down and the valves opening and closing at the correct time will provide a good ride.

Other areas of future focus…and future articles will include:

Valve timing

This all seems easy to understand but the real performance comes with the valve timing and knowing how to push the limits of a specific engine.  Valve timing is all related to position of the piston.  Timing is based on the 360 degree circle. 

Valves open and close before and after top dead center and at a time, there is an overlap of the opening of the intake and exhaust valves!

Carburetion

Getting the proper mixture is almost the one key factor that will allow a smooth trouble free run.  Too lean or too rich leads to a lack of power and poor performance, not optimum for a race machine.  Finding the balance is a matter of learning your machine and watching your plug. 

Follow the flow

An important piece of information besides the timing and correct mixture is the flow.  This is the flow of the fuel/air mixture into the cylinder and the exhaust out of the cylinder.  Better flow means better performance.  There are various ways to create better performance.  Topic to be discussed later

Aftermarket parts

In some cases, aftermarket parts are just a simple bolt on procedure.  However, when it comes to disturbing the flow to create more horsepower, usually there is more to it then the required wrench and the single part.

Canadian Speedway Track Gearing

Contribution:Philip Small

Paris gearing for a newcomer:
try 16 crank, 16 countershaft , 72 rear wheel

Generally the countershaft gear (gear behind the clutch) is standard at 16 tooth. It can be changed but this is unusual.

So when you hear speedway riders say 16:72 it means they assume the countershaft is 16 but they have specified the crank as 16 and the rear wheel as 72.

A rule of thumb is one tooth on the crank is equal to 3 or 4 teeth on the rear wheel.

So 16:72 would be very similar as 15:68

This Paris gearing is a good starting point for a newcomer, but as you get quicker, the gearing should be raised.

For instance in Division 1, I will sometimes will 17:72. This would be similar to 16:68.

If it's your first time at Welland, try 18:60.

Paris Speedway

Contribution: Aaron Hesmer

D1 guys try staying at least with 68 or 69 on the back. Anywhere from 67 - 70 works good on that track. Any higher will be to inconsistent for you. Lower isn't enough.

Tire pressure depends on weight of rider. Between 7 - 8 pounds is premium. Too little is a waste, you lose speed and bite (trust me it's weird)... Too much no control of course. You have to able to feel the tire.

Jetting 220 for both tracks is good

If you go up in jetting it'll bog the motor and make the bike want to hook up. If you go up in jetting you'll make the bike want to spin.

Newbies try a 210 jet. and keep lower tire pressure THIS IS ULTIMATE TIP... It will give you more control because the back tire wont be so inconsistent. Most newbies get on the gas hard to turn the bike. Most times will spin the bike right around. Lowering your jet will tend to give you the ability to go over bumps and turn the bike while maintaining full control that your tire should give you.

Welland

18 on the front works best!

57 - 60 on the rear no secret and if there is I don't know it!!!

Go Fast????

Contribution: Scott Collier

Although this is not technical stuff, it is good novice rider info. As a beginner, I was told "get good before you go get fast." These were good words to live by. Many get fast before they get good. Riding in control WILL prevent you from hitting the boards or someone else.

To get good, you must have the fundamentals in order. The first thing to comprehend is steering. For most, turning right to go left, is not natural. As most bike operators we usually turn in the direction we want to go. But while ‘sliding' or ‘drifting' many things are opposite. As an example: you are turning right to go left and more throttle (rear wheel spin) actually slows you down.

There are three things that control where you will go. First, the way you steer will control where you go. The right to left thing will be controlled by the amount of gas you give. Also, with the amount of gas you give, less throttle will allow you to drift wide on the apex and coming out of the corner. Giving more throttle will allow you to keep the front wheel down on the inside. The third thing you must consider is where you look. Look ahead. Just as you are driving a car, if you follow and watch someone that crosses the line while going around a bend, chances are you are going to also. If you look ahead of that car, you can keep centered in the lane. If someone goes down in front of you, DON'T look at them. Look inside and focus on your line. Same principle while racing, look ahead, don't follow.

So, three things to consider: direction of steering, amount of gas, and where you look.

The Melting Pot!

Contribution:Philip Small

Setting up a speedway bike is a lot more than just a few factors individually addressed. It's a whole "melting pot" of things, all combined and inter-twined to provide a massive combination of bike handling and performance characteristics.

So, how does one convey all that information to a newcomer?
Well you have to start with a few "key" things that really make a difference, and explain them one by one.

Some of these important factors have been well documented in the posts above, especially by Aaron. Some of the things I've had to say have been mostly correct too (although I'm far too modest to admit it)!

Certainly gearing, jetting, tire pressure, ignition timing etc are major factors. Only years of plugging away and trying different combinations for different track conditions will really show you what works for you.

Another major factor (and one more piece of the complex puzzle) which is well worth mentioning is rear wheel position.
We've all seen the "slots" in the rear frame loop where the rear wheel axle or "spindle" goes through. These slots are not just for achieving the correct final drive chain tension. They play a major role (again, in conjunction with all the other factors) in the rear tire grip or "hook-up" one can expect to get. In other words, the back tire's ability to grip on the track and drive the bike forward.
Of course, it is very important to insure the final drive chain tension and alignment is correct, but if that results in the rear wheel of the bike being positioned too far forwards or too far backwards in the slots, then that's a big "no-no"!
The chain length will have to be adjusted by adding or removing a small number of links, to achieve optimum rear wheel position.
General rule of thumb is the further forward the rear wheel in the slots, the more grip will be gained. This makes the bike much more difficult to slide in the turns for a newcomer, but gives a more experienced rider much more drive and speed.

Conversely, if the wheel is near the back of the slots, it will make the bike "longer" and breaking the back wheel free to slide will be easier. The end result, a slower lap time, but an easier bike to ride as a beginner.

Newcomers, try to follow the general guidelines in previous posts. In conjunction with that, insure your back wheel ends up about three quarters of the way back in the slots. At the very least, definitely behind center! Don't dare go in the front half of the slots, or you may not be around to read my next posting! LOL!
Of course, don't loose sight of achieving correct final drive chain tension (about 1/2" play up and down on the "top" run of the chain at a point half way between the top of the countershaft sprocket and top of the rear wheel sprocket).
Also, last but not least, insure correct final drive chain alignment. Unlike lots of street bikes, speedway bikes do not have "markings" on the rear adjusters to help with wheel alignment.
During rear wheel adjustment, walk behind the bike while it is on a bike stand and look straight down the top chain run from the rear sprocket to the countershaft sprocket. Everything should be dead straight and in alignment. (If necessary, get an assistant to hold the clutch lever in and spin the rear wheel so you can see it moving.
Don't listen to some advice that a "slightly" misaligned wheel will help you slide the bike easier.
This is BS. Make sure alignment is dead nuts!
A **** up here will almost certainly result in a "thrown" chain in the middle of a race. Not a good experience!!!!

Starting By the Referee's Rules

Contribution: Ian March

It is therefore necessary for the referee to pay a great deal of attention to obtaining a start that is deemed fair to all riders.

The following is what is expected and needed for that to happen.

1, All riders should come to the start area in their assigned gate positions and depending on the starters method, either wait to be brought to the start position (front wheel on a line-a distance back or whatever has been discussed at the riders meeting) or bring their wheels straight to the designated position. Once there the bike should be kept still (it may be put on the foot rest to keep the clutch cool) while the starter checks with the riders that all is well. If all is satisfactory the starter checks with the referee,-all OK- then the starter will indicate, usually by a hand gesture, that he is handing over to the referee at which point bikes and riders should be ready for the start with bikes on 2 wheels and clutches disengaged. The starter will walk to the rear of the bikes during which the engines can be spun up to the desired speed. The starting lights and gate will then be operated as discussed at the riders meeting and a perfect start will have been executed.

2. Problems however do seem to appear at the most inconvenient times. Should a rider need a legitimate moment for correction after the start has been handed to the referee the accepted procedure is to “raise his right or left hand” BEFORE the gate is raised.

The rider will then be allowed a maximum of 2 minutes before either he will be eliminated from the heat or the start handed back to the starter for his procedure to be commenced again.

Routine Maintenance

Contribution: Philip Small

With our Canadian Speedway season fast approaching, I thought it may be of help to some people if I were to run throughout the things we should all be doing to our bikes in between meetings. As stated in a previous article, our off season rebuilds are important, but perhaps more so is the work we must do to keep our machines reliable and safe throughout the season. This is how I approach my routine maintenance. I'm not saying this is how we all have to do it, some of us have our own regimes but this can be used as a guideline for those less familiar with maintaining and preparing a race bike.

1. Drain Oil.

For those with recirculating oil systems (most machines after about 1987) the engine oil must be drained. To do this the motor must be hot, so the best time to do this is immediately after your last race of the night. If, like me you're too tired or more interested in the after meeting socializing, then you'll have to warm the bike up at home and dump the oil there, much to the delight of the neighbours no doubt! Just as a side note, some people say always drain the tank and carburetor of methanol. During mid season, I never do this. Corrosion will only set in once the methanol has dried off. So I leave fuel in my tank and in the float bowl of the carb. If the bike has been running well, I leave the carburetor alone. If the carburetor requires cleaning, it will be because the bike has been running poorly. If it ain 't broke, don't fix it! I will assume the carb is clean in my example here as an article on cleaning the carburetor could easily take up a whole evening alone!

2. Hose Off Bike.

Firstly remove the excess dirt from the bike covers and then remove them. Then, remove the air filter and place a small plastic bag over the carburetor (a sandwich bag usually works) and seal it on in a watertight fashion with a rubber band. Continue to hose off the rest of the bike including chains. Agitate stubborn dirt with a hard brush if necessary. For those lucky enough to own a pressure washer, go for it!

3. Remove Chains and Soak.

Remove both chains from the machine and make sure they are clean. Wash in a container of gas if necessary. No Smoking! Then, I have a container full of used Castrol R engine oil and I dump the chains in there. Forget about them for an hour or so. After this time period, hang them from a nail in the wall over a container on the floor and allow them to drip. I just have to mention, no matter how well they drip dry and even if you wipe excess oil off before re-fitting, when the bike is fired up for the first time it will spit black Castrol R everywhere! Yes, my method is messy, but I have never broken a chain and each one lasts me a whole season. Please, do feel free to try something different if you get fed up of ruining white tee shirts whilst warming the bike up!

4. Strip Clutch.

The clutch is one of the most important things on a speedway bike and must be maintained in optimum condition. Remove the springs and pull out all the plates. Wipe the plates clean and dry with a shop towel, nothing else. If the fiber plates are blackened or glazed (shiny), then they will require scuffing. Lay a piece of 80 grit sandpaper face up on a piece of glass and with a circular motion, rub each plate lightly until all glazed areas are gone. This usually results in deglazed fingertips too! Never remove too much material from the plates and always be careful not to inhale the dust. Inspect the metal plates (aluminum or steel) and ensure they are flat and corrosion free. Pull the clutch actuation push rod (and bearing if applicable) from the clutch center and wipe off dry. LIGHTLY grease and re-insert through the center of the countershaft.

5.Clean Remainder of Machine and Inspect.

Continue with the cleaning process, paying special attention to the grunge that will be left around the sprocket teeth. If you've got time to polish and shine then do so. A super clean machine not only shows professionalism and care, but presents the image we wish to convey to our paying spectators. Use this cleaning as an opportunity to inspect the rolling chassis. Check the frame for any hairline cracks, check wheel bearing play, front forks for correct actuation and all nuts and bolts for tightness (in particular engine plates and motor mounts, seat brackets, exhaust system and rear frame loop bolts).

6.Check Cable Actuation.

I usually feel this as I'm riding the bike but if either the clutch or throttle cables feel sticky or gritty, then they should be cleaned and lightly oiled. A good tool to own is a cable oiler. It's like a small screw clamp with a rubber insert which clamps around both inner and outer cables on one end. It has an orifice where WD40 or similar lubricant can be squirted in under pressure from the aerosol can. These can be found at any good motorcycle store. This makes a huge difference in friction reduction.

7. Clean Air Filter.

Essential. Follow manufacturers instructions carefully here as some types differ from others. Use the recommended filter oil if specified, lightly applied to the filter before replacing.

8. Re-Fit.

Once all the above has been accomplished, re-fit everything back to the bike. Lightly grease any nuts and bolt you have removed as this always makes for easy removal at a later date. Ensure she's looking as good as you can get her in the time available and hopefully you'll enjoy a trouble-free night of racing the next time you visit the track.

As a guideline, the above tasks usually take between three to four hours.

I would strongly recommend following a maintenance and machine preparation schedule that fits with your lifestyle but does not cut too many corners. In other words, spend as much time working on the bike as possible.

Rider Tips

Contribution: Philip Small

Section 1. Really Want To Go Quicker

Section 2. Make Sure Your Equipment Is In Good Order

Section 3. Get Yourself Physically Fit

Section 4. Stay Focused On Race Nights

Section 5. Have The Support Of People Around You

1. Really Want To Go Quicker

I found there was a certain point in my racing career that I stopped going to speedway meetings to enjoy the riding, and started going to enjoy the results. Of course, it's important to enjoy being involved in speedway in any capacity, but I found myself going home disappointed if I had not gotten a good result. I had been concentrating for so long on trying to ride and slide the bike well, I had forgotten it was a race and the idea was to try to win. What I'm trying to say is you won't go any quicker if you don't want to pass that rider in front of you. Once you get the mind set to cross the finish line ahead of the guy in front, you will find your speed picks up naturally. It's also a blast trying to win a race from the back. I should know, my gating is lousy! Be warned however, taking this attitude can result in frustration at times and there's a fine line between hard enjoyable racing and finding yourself, and everyone around you totally p****d off!

2. Make Sure Your Equipment Is In Good Order

So now we've gotten the mind set we want to win. We can't possible give ourselves a

chance of doing well if our bikes are no good. I'm not saying we all need the latest, most expensive equipment. Just make sure the things are well enough maintained and prepared so they start reliably, run smooth and are safe. It is impossible to enjoy a nights racing if our machine typically takes a lap of the track pushing before it splutters into life. And equally important, it is impossible to ride a speedway bike well if it does not run smooth with good throttle response. No misfiring is A MUST! If you can't figure it out yourself, find a friend in the know in the speedway fraternity and get them to look at it. Have confidence when you unload the machine on race night that it will work well. And don't forget to check those brakes!

3. Get Yourself Physically Fit

It is SUPER important that speedway riders are fit. "The race only lasts a minute", you may hear people say. Then I ask you this, "Is a 100 meter sprint athlete any less fit than a marathon runner?" The answer is no. Anyone involved in sport should keep themselves as fit as their daily schedule allows. This becomes even more important when you reach the twilight of your speedway racing career. Joints and muscles are typically less flexible when the body ages and so the chances of injury rises dramatically with age. The other factor here in Canada is the heat and humidity. It's unusual if we are not racing in 90 Degrees of heat and 95% relative humidity. With wearing leathers and all the other protective equipment, the heat itself can be a major drain on the body's energy levels on race night. Building muscle is not the correct type of fitness regime for speedway. Cardiovascular fitness and suppleness are the important factors. During the off season I work out 40 minutes per day on an elliptical trainer in my basement (excellent low impact workout for my old injury-ridden body) and then do some push-ups and sit-ups every night. I also do a lot of stretching exercises to give myself a chance of bending rather than breaking when I crash. During the racing season, riding the bike is training enough. Actually there is absolutely no substitute for practice and becoming "bike fit". Give yourself a chance to win by being fit enough to hang on without becoming dangerously tired.

4. Stay Focused On Race Nights

Difficult to comment on this as I'm sure it's different for everyone. All I know is that if I'm not totally focused before each race, then my result usually suffers accordingly. We all have our own mental preparation before a race. Make sure you take time out to go through your routines and get in the right frame of mind. However, that word of caution again, the people around you are your friends and loved ones and they are usually there to help. Don't become so selfish that it upsets them. Again, I am speaking from personal experience here and it's still something I need to concentrate on. It's that fine balance again. Make sure everyone enjoys their speedway experience, but get your racing head on!

5. Have The Support Of People Around You

This is incredibly important for me as I try to go quicker and quicker, and by doing so take more risks. We all have responsibilities to our families and friends. I am the first one to accept that speedway is probably not the ideal sport to be doing whilst trying to contribute to a family, pay the mortgage etc. It is therefore very important (to me anyway) that I have the support of my family to go and try harder in my racing. It's not just the risk of injury either. It's all the money that gets poured into the sport for little or no return. It represents a huge financial commitment, one which many of us can ill afford. I am very thankful I have the support of two sponsors for this season which has certainly made the financial side of things easier. But knowing that your family are at the sidelines cheering you on and wanting you to win is the greatest help of all to me.

Thanks for taking time out to read this and thanks go out to 'Tiger' Tom Marriott #13 for prompting me to write it.