Engine Trouble Engine wont start? TROUBLESHOOTING GUIDE

Skyhawk GT 2B. Has a brand new magneto, and CDI. Disconnected Kill switch. Spun tire and plug sparked. Flushed fuel tank, and put straight gas in. pistons move freely, and exhaust has been cleaned. new air fliter, yet no fire. What am I missing? I tightened all the bolts on the crankcase, even put silicone over all the seals
 
Your Engine Won't Start? Replace the cheap factory plug with an NGK B6HS. Do it NOW!

I spent three hours trying to get my just-completed bike to start. It had fuel and compression. The spark was very weak, but there was a spark. All I could get it to do was to "pop" every now and then with furious pedaling.

Out of desperation I read through this thread and went out and bought an NGK B6HS plug at my local O'Reilly's Auto Parts store.

I installed the new plug, cranked the bike down the driveway and it started up and ran perfectly.

LESSON LEARNED. THROW AWAY THE FACTORY SPARK PLUG AND BUY AN NGK B6HS.

If the B6HS runs too cold (carbon deposits or dark electrode insulator) use a slightly hotter NGK B5HS instead.
If the B6HS runs too hot (electrode insulator is white, not tan, after hard running) use a slightly colder NGK B7HS plug.

Use which ever plug gives you a light tan colored electrode insulator when run hard.
 
Thanks for the tip. I will try that plug next time.
It's the same size and extra length as the HS, but you don't gap them, they come with a protective sleeve over the end and the last plug you'll ever need to buy for that engine because of the better material making the spark gap.

SickBikeParts has 3 heat ranges for them for a good price.
http://www.sickbikeparts.com/catalo...n=1&osCsid=51m288d30g603tk9vj1jrtj9u3&x=0&y=0

The middle number (6-7-8) is the plugs heat index.

Look at the size difference in the white insulator length where the plug threads are.

chartheatratingflowpath-2.gif


The more white you have in contact where the threads are, the more heat is transferred to the cooling fins, and the pink is just providing an air gap to keep heat in.

----
Engine Speed and Load

* If the engine is to be operated at high RPM, under a heavy load, or at high temperatures for long periods a colder heat range may be needed.
* Conversely, if the engine is to be operated at low speeds or at low temperatures for long periods, a hotter heat range might be needed to prevent fouling.
----

Bottom line is run as cold (higher number) as you can until you see plug fouling.
 
burned 3 cdi s and 2 magnetos

I got a brand new 66 cc jet. Motor wouldn't fire, so when I pulled off the magneto it was wired all wrong. The blue and white were soldered together off one side and the black was soldered to the other and then ground. Np, replaced it. The motor still wouldn't fire. New ngk spark plug and iTried three different cdi s, One new two used. It fired for the last one, and went around the block before it just died. The magneto coils and spark plugs have all been put in my other motor. Runs great, never a problem. New motor just keeps burning up electrical parts.
 
I got a brand new 66 cc jet.
Motor wouldn't fire, so when I pulled off the magneto it was wired all wrong.

The blue and white were soldered together off one side and the black was soldered to the other and then ground. Np, replaced it. .
It was not wired wrong.

All the magnetos on the motors I sell are wired that way but I cut the white wire off.

These are improved magnetos and I have not had one failure since they have been coming
like that.
 
same here - folks were unsure of 2-wire mags, so factory added a dummy white wire in parallel with blue (go figure)
 
burning out cdi s

same here - folks were unsure of 2-wire mags, so factory added a dummy white wire in parallel with blue (go figure)

That's okay. I replaced it. The magneto I got with the motor must have been bad then, because the readings I got off it were all funky. The new magneto reads good. Now I have also burned up 3 cdi s. Two with the old magneto and one with the new. The last one ran for about five minutes yesterday before it died, so at least I know I nailed the problem down. The question I have is why do I keep burning up cdi s?
 
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new mags read about 480ohm rather than the old, reliable 350ohm - I get lots of dead CDI units now where they'll only spark at high speed after running for just a few minutes (they'll run the engine fine if you can get it up to 20mph before trying to start it) - I suspect the new mags are putting too much power into the CDI causing some to fail very quickly (since I see no increase in failures on bikes with 350ohm mags)
 
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