No Spark

[geordabroad]

recently my TXT 300 Pro was stuck with full open throttle for around 10 seconds. Only way I could stop it was to turn off petrol.

It still kicks, but when I tested the spark plug there was no spark. It's a Kokusan system, so I got a new coil and Ignition control module and fitted them, but still no spark. Tested the ohms on the cables and the stator is 20.3 when the elecotronics diagram says 20.9. The pickup coil ohms reading is 91.6 when the diagram says 99.4 ( I tested this by bareing the wires - not sure if there's a need to turn the motor/ kick it to get a true reading)

My feeling is that I should check the gap on the pickup from the stator coil as this reading is low... and I was watching the video link on the 'stators and other mythical beasts' forum discussion submission that shows the pick up. Other than that, I can only think it's the coil itself in the stator, but the reading seems quite close.

1. Does anyone have any suggestions what I should do next?

and 2. can you confirm where I should be touching the end of the spark plug to check whether there's a spark or not.

Thanks, Ian

AKA, Clueless in the orient...

[husky]

Are you sure it hasn't just sheared the flywheel key,Ithink it would run longer than 10 seconds after turning the fuel off.Had a Beta that did this when it stuck open Seems odd that full revs for 10 secs f###d 2 black boxes

Edited February 3, 2009 by husky

[jse]

Are you sure it hasn't just sheared the flywheel key,Ithink it would run longer than 10 seconds after turning the fuel off.Had a Beta that did this when it stuck open Seems odd that full revs for 10 secs f###d 2 black boxes

That's a possibility but you should still get a spark, just at the wrong time. Like you, I'm also kinda suspicious about 10 sec at full chat frying any of the components. I'm also assuming that a new plug (BPR5ES or better at .024") was installed as that's a weak spot after a run-on. The readings do not seem to be too far off (I usually never get the exact numbers on my meters that are in the diagram spec.'s). I might want to check all connections and grounds just to be sure and inspect the air gap at the magnetic pick-up.

Probably the best way to stop a screaming Trials two-stroke is to use a gloved hand to plug up the exhaust and then the killswitch will work when the rev's drop down. They tend to auto-ignite when WFO unloaded.

Jon

[geordabroad]

Thanks guys, I'll have a look this weekend and give you an update.

Just as an aside, I am assuming that a spark plug held against the cylinder head or the frame of the bike will give a spark, or is there some magical place that you're supposed to hold it against?

Cheers

Ian

[rcgods]

Against anything that leads to earth. On my Sherpa I earth them to the engine, however that is bare metal. If possible earth to bare metal to get the best contact (head steady, engine brace, mounting point).

If you don't seem to get a good spark you can get an inline spark indicator something like Spark indicator on ebay, this will flash when the sparks are sent to the plug.

[peterb]

Hello Ian,

I have never known a kokusan ignition system to ever fail, since being introduced to GG in the late 90's. Best to check that all the electrical connections are intact and that all of the earth wires are tight. I did have a similar problem with a 300 some months back that would fire up intermittently then cut out, took ages to sort out. The fault was traced to the main harness plug/socket connection, the plug has pins that were just a little too loose inside their individual sockets, by slightly deforming the sockets, the pins could make a reasonable connection and the bike ran faltlessly afterwards. You need to carefully strip down the plastic casing of the main connector to get to this area.

Bye, PeterB.