Diagnosing possible electrical issues

[simook]

So with less than 80 days till the 2015 OMRRA race season, I need to diagnose the root cause of my recent off track adventure.

1) Near the end of the front straight, I'm in 6th gear getting close to the rev limit and notice the (aftermarket) tach bouncing up and down from it's max range (~19k) to the current motor revs at roughly +-12,200.

2) At my brake marker I transitioned from throttle to braking into turn 1.

3) At the apex entry I transitioned from braking to maintenance throttle and felt no power in return. Bumped the throttle a couple times and still no power, pulled in clutch and immediately realized the engine was dead.

This was followed by checking my outside line and proceeded to move off the track, at this time my thinking was if I blew the motor I should get off the track. My speed was still probably in the 70s when I hit the grass and with my lack of skill with dirt biking on race slicks I did not stop the way I had hoped for.

Anyways, after picking the bike up and moving to the tire wall I attempted to start it. I could smell it was getting fuel and the battery was charged enough to turn it over but it would not fire. After roughly ~10minutes I tried again and it finally fired back to life.

So currently I'm tearing it down and doing a thorough inspection, cleaning the carbs, checking spark plugs, connections, etc... But how do I go about finding the root cause of the initial issue? Links to similar issues/guides would be nice.

[Alex]

The stock tach bounces around like crazy when it hits the redline normally; it comes back to normal once below redline. It sounds like your aftermarket was doing the same. There very well may be another electrical problem, but the symptom of the bouncing tach may or may not be indicative.

[simook]

Noted, Thanks Alex.

[alex.s]

care more about your own personal safety than how much the track workers are going to hate you for spilling oil. if you dont feel comfortable going off at the speed you're going, don't go off yet. spend 5 more seconds slowing down. if you're on the outside of the track it doesn't matter and if you really are spraying oil anywhere you'll probably go down anyway and slide off track so don't worry about saving the precious pavement so much as saving yourself.

about the power cut... maybe a fuel valve simply got stuck and after the drop it unstuck? maybe you have a bad ground connection? check the battery ground as well as the engine to chassis ground on the right side by the clutch.

[simook]

Originally Posted by alex.s

care more about your own personal safety than how much the track workers are going to hate you for spilling oil. if you dont feel comfortable going off at the speed you're going, don't go off yet. spend 5 more seconds slowing down. if you're on the outside of the track it doesn't matter and if you really are spraying oil anywhere you'll probably go down anyway and slide off track so don't worry about saving the precious pavement so much as saving yourself.

Yep, this is the exactly the lesson I learned afterwards. Every situation is different and we only have a split second to decide. Staying on the outside line for 3 more seconds would of allowed me to burn more speed and if I was leaking oil it wouldn't be on the race line.

Some things you just have to learn the hard way

[alex.s]

don't worry- we all learn the hard lessons the hard way.