Very Strange Engine Trouble

creede55

New Member
Local time
6:48 PM
Joined
Oct 17, 2014
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Howdy, I bought an engine kit, assembled it, and got it to run for about a week solid with no problems. Starting 3 days ago the engine started to get harder and harder to start but once I got it running it worked fine. Today the engine would not start at all. I drained and refilled the carburetor, check the spark plug for spark (tried a new spark plug to make sure there was enough spark), checked the timing on the magneto, checked the wiring, tightened down all the gaskets, tried starting with a lot of fuel in the carb, and fiddled with the choke. Still it will not run. The piston turns without effort and I can hear the engine turn over but no matter how hard I pedal it will not start.

Has anyone else encountered a problem like this?
 
If you're using the stock ignition coil, they have a reputation for being a garbage part.
Mine went bad. Though it was allowing voltage to pass to the plug (thus showing spark) the spark was too weak to fire the motor.
I upgraded to the aftermarket coil and seperate ignition box from sickbikeparts.com

Original coil lasted about 200miles spread over four years. The upgrade/replacement has 600+miles on it this summer.
The only time I've had trouble starting it now have been issues with installing the motor in a new bike and adusting to new gear ratio at or behind the chainring(s).

On a weird note: take apart your muffler to check for obstruction. Mud wasps started a hive in my tail pipe and blocked it off. The motor is too low compression to have blown it out.
 
Another issue I've heard mentioned is the main jet in the carb can come loose and fall into the fuel bowl. With an NT carb, the nut that holds the throttle cable to the carb can loosen too. Do you have a rubber washer in this fitting? It is another source for an intake leak. Though it is more likely to cause a high idle issue vs hard start.

Hope this helps...
 
I went out this morning and took the carb apart, everything was still tight and screwed in. I tried tightening the metal collar that connects the carb to the engine since I noticed the collar slid forward a bit leaving 4 1mm holes which could have been the problem all along. Got it all tightened and sealed up, still though, the engine wont start.
 
You definitely have an ignition problem. Are you running the stock plug and plug wire? The end cap on the stock wire is notorious for failing. Get a good quality wire, they screw onto the cdi box, while you're there, get an NGK B6HS plug and install. I think this will solve your problem. If not, check your wiring connections, you're not using the stock cheapazz connectors, right? Could also be the kill switch, the have a poor reputation for failure.
 
how's the compression? could be head gasket or case gasket leaking, could be a seal leaking

are you sure the carb is seated so that you feel it hit metal when you push it onto the intake?
 
I went out this morning and took the carb apart, everything was still tight and screwed in. I tried tightening the metal collar that connects the carb to the engine since I noticed the collar slid forward a bit leaving 4 1mm holes which could have been the problem all along. Got it all tightened and sealed up, still though, the engine wont start.



Do you have a multimeter? Check the magneto loop and ignition coil for resistance values.
If the black to blue reads less than 33ohms, your coil is bad. Its letting voltage pass through which will show spark. But its no building a charge to actually fire the motor.
Remove the spark plug and connect the volt meter to the loop. Turn the motor using the back wheel. Volt reading should be about 6volts.

These tests will confirm which part is bad and needs to be replaced, short of the plug being broken inside the porcelan...
 
Thanks for the replies and advice. I put in an order for a new CDI and hopefully that will fix the problem, if it does then when I get the money I'll invest in better parts so my bike doesn't crap out on me again.
 
Thanks for the replies and advice. I put in an order for a new CDI and hopefully that will fix the problem, if it does then when I get the money I'll invest in better parts so my bike doesn't crap out on me again.

Did you test the loop and the CDI with an ohms meter?
I've forgotten the exact specs you should get but if you shoot an email to sickbikeparts.com or try looking for a vid on youtube, you'll get the info you need to confirm or dispell those components as the source of your problem.
Replacing the loop or stock CDI are relatively inexpensive but why throw good money after bad chasing a ghost...
 
Thanks for the replies and advice. I put in an order for a new CDI and hopefully that will fix the problem, if it does then when I get the money I'll invest in better parts so my bike doesn't crap out on me again.

The Jaguar CDI and coil is a "must have item" on any motorised bicycle engine.
If the bike still misfires after installing the Jaguar CDI and coil, you will most likely find that you have a bad stator coil, otherwise known as a magneto coil. Having said that, i have only had one stator coil fail on me in 5 years.
 
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