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Benchtop Basics 101>Episode 2>

Benchtop BasicsNo. 2

Start me up

You'd be surprised just how few people really know how to start their bike correctly.  Don't pass on this tech tip just because you've read Benchtop Basics No. 1, or already owned your bike for a while.  You might actually learn something...


BEFORE YOU BEGIN:  A pocketbike has a centrifugal (RPM dependant) clutch.  When started, the rear tire may begin to turn immediately if the engine should rev up and engage the clutch, or the clutch should engage prematurely.   It is almost always best to start your bike on the stand to avoid having the bike "e;take off"e; immediately upon starting.  Make sure that the bike is started well away from others, and that no loose clothing becomes entangled in the bike's moving parts as you bend over to start it.  Always give your bike a "e;pre-flight"e; check for any unsafe conditions - check for loose fasteners, and damaged parts.


1) Fuel the bike.   I've actually had people call and say that the bike "e;just died, and won't restart"e;.  I ask if it has fuel in it, and there's a silent pause on the other end of the line...  "e;uh, hold on...lemme check"e; [another pause] "e;oh, sorry dude!..."e;


2) Turn on the fuel tap. Yeah...I know; stupid huh?   But it happens.  This is another one of my favorite "e;tech phonecalls"e; from new bike owners:

Customer :[perceivably frustrated] "e;I just got this bike, and I can't get it to start!!"e;
Me:"e;Uh, is the gas on?"e;
Customer:[long pause] "e;Whaddaya mean?"e;
Me:"e;The fuel it turned on?"e;
Customer:[long pause] "e;Fuel tap?? Where is that??"e;

That's when youKNOWthey haven't checked the bike over.

Even experienced guys have been known to occasionally forget that they had turned off their fuel tap, only to wonder why the bike won't start.  It's a knob or a lever, located just under the gas tank...either attached to the tank, or inline on the fuel line.


3) Turn on the choke. It may be a lever you depress on the intake side of the carb (SHA carbs),  or a black knob on the carb body you pull UP, then turn an 1/8th of a turn to set (PHBN or PHBG carbs).

Is a choke always required?  No, but until you get to know your bike well, it's always best to start with a choked carb first, when the bike is cold.

To release the choke on an SHA carb, just blip the throttle to maximum.   Obviously, you do thisvery quickly, and it's best done with the bike on the stand, or with the rear tire elevated off the ground, so as to not launch your pocketbike into the neighboring county.

PHBN and PHBG carbs must have their chokes manually released (turn the knob, and it will pop down).  Release the choke after your bike has warmed up for a minute or two.


4) Pre-lube the cylinder, and pre-charge the engine with fuel.   Pull the startervery slowly3 or 4 times.  You are not trying to start the bike, just merely fill the cylinder with the air/fuel/oil mixture.  Banging away at the starter on a "e;dry"e; motor is pointless, and abusive to both engine and starter parts.


5) Engage the starter pawls first.   Many people complain about the starter wheels on Polini engines failing prematurely.  I can get half a season, if not an entire season of racing out of one.  How?  Simple:  If the starter pawls are trying to grab a starter wheel's ratchet teeth that are whizzing by at 100 mph, they're gonna take a chip off each time they grab.

I am often asked why Polini makes these starter wheels from plastic, and not from metal; simple:  They are designed as a sacrificial part.  If anything should ever fail to retract or disengage in the starter, a $6 wheel will fail, and save a $100 flywheel, or a $100 crankshaft.

If you merely pull the starter cord up just a little first, to properly engage the starter pawls to the starter wheel before actually pull starting your bike, your starter wheels will lastmuchlonger.


6) Start with a light tug.   A Mini Moto is not a lawn mower!  It is an ultra-compact, fine quality racing engine.  Start it with a firm but short, brisk tug, and don't pull all the way out to the end, or you may break the rope.  Try to pull straight out, and not grind the rope against the starter's guide ferule.   This will help preserve the rope, and keep from wearing deep grooves in the ferule.   Get ready to give the bike a slight amount of throttle the moment it starts, and don't let the engine die.  Two stroke bikes aren't known for having great idle characteristics, and a little blipping may be required to keep it alive.


Starting Tips:

Always use fresh premium pump gas mixed with a good two-stroke lubricant at 50:1 (2.56 ounces to the gallon).  I use 2 3/4 ounces of oil to the gallon, as it's a little easier to measure, and it works out to approximately 47:1 (just a little more protection).   You can use up to 3 ounces of oil to the gallon of gas for initial break in (approximately 42:1), but using more oil may foul your plug, and make your bike hard to start.

If your bike runs a bit rich (as my red Carena does), it may refuse to hot-restart.   The way I get mine to hot-restart is by holding the throttle wide open (again, make sure the back tire IS NOT touching the ground!), and clearing it with about 5 good full pulls.  It will usually then start on about the 6th pull.  Bottom line?   Two strokes are extremely temperamental.  Some bikes ALWAYS need choke, some NEVER do.  You must learn the particular eccentricities of YOUR bike.

The 911 Polini and some others are very hard to access the choke on.  Sometimes you can get away with just pulling the back end of the bike way up, or standing the bike up on the back tire to slosh a bit of fuel into the intake, and obviate the need to engage choke the bike for starting.


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This information is provided in good faith as a guide. We are not responsible for any typographical or informational errors or omissions.  Due to the many mechanical and technical variables, this information is to be used only as a guide, and is in no way guaranteed to be accurate or applicable to your engine, your bike, or your world in any way.


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