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Old 09-16-2009, 04:02 PM
buzbikebklyn1 buzbikebklyn1 is offline
Join Date: Jun 2009
Location: Brooklyn N.Y.
Posts: 208
Default "why Wont This Thing Start?"

Greetings fellow buzz bikers... its been a few weeks since my last posting...
Sorry about that, but life's a ***** and then you marry one...Yeah... the little woman's on the war path again, but luckily its not me shes ticked off at this time.(for a change) i just count my blessings and slink off to the garage.

Since it seems I'm one of the few intrepid moto bike builders and riders in the area i get quite a few E-Mails like the following-

Hello Tom
Sorry to bother you I was wondering if you can help me out I live in Brooklyn ??st between ?rd and ?Th ave I just finish to install STEALTH JET BLACK 80CC BICYCLE MOTOR ENGINE on my bicycle but it don't start I really need some help please let me know if you are able to help me thank you my cell number ???-???-???? my name is Luis.

I know this information might seem kind of basic to our more experienced riders out there but i think it bares repeating.

Sure Luis... no problem-


1)- Spark and ignition.
First make sure all your control wires are OK, blue to blue, white to white and black to the kill switch.
I like to use barrel or spade connectors that are soldered to the wire ends and heat shrink tubing heat shrink tubing to make sure those vital connections are as water tight as possible and secure.
Then I protect the entire control wire bundle with wire armor and i secure it to the frame in a safe position with zip ties.

Take a few extra minutes to route you wires carefully, not only for reliability's sake but it looks better and makes the entire installation look more professional.

Be sure that the kill switch wire hasn't been pinched or grounded to the handle bars in some way.

Make sure the kill switch its self is functioning properly and in the "on" or "run" position.
(don't laugh, it happens!)

Next check the spark plug wire and boot, be sure its solidly connected to the module and the module is mounted securely to the frame, then be sure the boot and contact are holding the tip of the spark plug tightly.
If you can, put the bike in a stand or prop it up so you can turn the engine over with the rear wheel off the ground.
Use a long insulated grip screw driver to hold against the spark plug and engine, crank the engine over and check to see if you have spark. If you have no spark, recheck the wiring and plug wire and use a multi meeter to see if the ignition module is good... replace any parts as needed.
(leave the bike on the stand we aren't done yet)

Make sure the engine itself is properly grounded to the frame, -IE- that the brackets are contacting bare metal, some times paint and decals can keep the ignition system from working properly due to poor frame contact.

2)- Vacuum and compression leaks.

While the spark plug is still out from the last chapter, remove the spark plug from its boot and make sure the plug wire cant touch you- (ZAP! ouch !@#$%%^^& that hurt!)
Now put your thumb over the spark plug hole and turn the engine over again you should not be able to keep your thumb over the hole if the engine has compression, if it doesn't...
crate that puppy back up and call who ever you bought it from!
Just kidding...
Several things can cause no or poor compression, make sure the head studs are properly tightened, listen to the engine as its turning over... some times you can hear were its leaking from. If you think its the head gasket, remove the head, and check the gasket, *replace it if needed, I use a thin layer of gasket sealer painted on the gasket surface at this point.
Re install the head and torque down the head in sequence to the proper torque value. Do the thumb check again... if you now have compression your golden... if not...
crate that puppy back up and call who ever you bought it from!
Just kidding...
I don't like to rag on the engine or parts manufacturers but some of this stuff is junk.
Be sure to use only the best parts you can... its cheaper in the long run and it keeps our State side aftermarket manufacturers in business.
Piston rings, base gaskets and crank case leaks-
These can be trickier to spot and diagnose with out specialized tools, but here are a few tricks Ive used over the years.
re install the spark plug but make sure its disconnected.
Now turn the engine over slowly, you should get a decent amount of resistance, this means the piston rings themselves are sealing well.
if not...crate that puppy back up and contact who ever you bought it from...
I'm NOT kidding this time, poor piston ring seal is not acceptable in a brand new engine.
Some times the castings of the crank cases are so poor that there are vacuum leaks in the cases its self... this will interfere with proper cylinder filling.
use a soap and water solution on the seams of the case halves... if theirs any kind of leak it will become apparent as you turn the engine over.
if so... crate that puppy back up and call who ever you got it from.
I'm NOT kidding this time,

OK... say we have compression, both head and base gaskets are good.
Now its time to check the intake and exhaust and fuel flow.
Remove the muffler/head pipe and set it aside for now.
Remove the carburetor and secure it so it doesn't hang buy its cable.
Check the intake manifold interface, make sure the intake gasket is in place and its bolted to the cylinder properly.
they will strip out on you easily.

Just like the spark plug hole test, cover the intake manifold opening with your finger or hand and crank the engine should get a decent amount of vacuum, if the piston rings were good, you will.
if not...crate that puppy back up and call who ever you bought it from!
Just kidding...
Now reinstall the carb, make sure the rubber boot is oriented correctly before slipping on the carb and screw clamp. if your kit did not come with a carb to manifold rubber boot skip this step.Be sure to set the carb as close to level as you can.
Now look down the carbs throat with a flashlight and work the throttle and check it for smooth operation of the slide, if the slide doesn't open correctly the engine wont start no matter what you do!
Adjust the throttle cable for proper action.
Reinstall the air cleaner... i suggest an after market cone shaped air filter if you have room for it.
Now check the exhaust side.
You should hear a pronounced "puff" of air from the exhaust port as you turn over the engine, set the exhaust gasket in place, and reinstall the head pipe/muffler and re secure it to the frame.
Take the time to make a secondary exhaust mount out of perforated strap or any other sturdy type of stock.

Check the muffler and head pipe, be sure its clear for all obstructions.
>take this next step out doors!< be sure to have a fire extinguisher at the ready.
Have a coffee can or other receptacle ready to catch the excess fuel.
Now check the fuel valve, be sure its turned to the "on" position (dont laugh, it happens)
make sure you have a good quality fuel filter installed... disconnect the fuel line from the carb and see to it you have good flow, it the flow is bad you might want to check and make sure the gas cap on the tank is venting properly.If all is well reattach the fuel line to the carb and make sure there are no kinks in the line.

Make sure you try this in an open area, were there is little chance of hitting any body if something goes wrong (and no one will see you if you screw up)
WEAR SAFETY GEAR! a helmet, gloves and stout foot wear.
1) Set the bikes derailleur in first gear.
2) Make sure the fuel valve is in the "on" position.
3) Make sure the kill switch is in the "on" position.
4) Pull in the clutch and lock it open.
5) Now mount up and peddle the bike to get up to speed, I usually use 3rd gear.
6) Now pop the clutch and peddle through the first compression stroke, it SHOULD start right up.
if it doesn't... crate that puppy back up and call whoever you got it from.

Luis, i hope this little tutorial helps... keep trying!
now, let me go see if the little woman is still ticked off!

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