Does this sound like a battery problem?

[Tom Halverson]

I'm a road racer and am having a heck of a time diagnosing a problem with my RMax. At last weekends race I spent my entry fee and most of the weekend driving around Portland International Raceway listening to what sounded like a 1984 Yugo diesel conversion experiment. Here is what happened. I warmed the kart up in the pits, went out for a practice session, took one easy lap (everything OK), on second lap I smashed the throttle coming on to the back straight, everything was fine up until about 10,500 rpm and then "POP!" went the engine, followed by 3-4 seconds of nothing (coasting) and then it would catch on again sputtering a bit and at a slower rpm until it ran up to the 10,500 range again. At first I thought it was too small a main jet (read the book, book said "lean condition") so I put a 178 jet in it (I had a 170 in originally which is what others were running and it seemed fine for many of them). Didn't make any difference it still did the same thing e.g., run, run, run, POP! coast for 3-4 seconds, and then putt/putt/putt, run, run, run. I tried pulling the choke up when it did this and it seemed to make a little difference for a second or two, and then after about thre or four times of trying this it didn't seemed to make any difference if I choked it or not (and believe me, I REALLY wanted to choke the dang thing at this point ) My battery is about 9 months/6 race weekends old, could it be going bad this soon? Or is this soon for an RMax battery to go out? Could it be the fuel pump? Could it be the ignition system? Could it be that I've run out of ideas!!!!

[Chris Bradley]

I dont know about the popping sound, but when my battery went, it would not fire above a particular RPM (it would coast until RPMs fell below a particular point). As the day went on, that RPM ceiling got lower & lower.

[Nick Weil]

This sounds like a bad battery to me. When you get to that peak RPM your battery can support the system shuts down(electrically from a voltage drop and then a spike). The spike reactivates your ignition coil, combusting the built up fuel in the chamber and produces your 'POP!'.

It only takes one time of leaving your power button in the ON position for an extended period of time to do real damage to your battery. Unfortunately, the battery may not show the signs of a problem for weeks or months afterward, but killing it once like that is not good for it.

Hope this helps...

Nick Weil
SpeedQuest Online Store

[David Leflang]

Always check the battery first, it's usually the culprit. They are relatively cheap, so if you can find one get a spare.
If that's not the problem, check the entire fuel circuit, from pickup tube in the fuel tank, pinholes in the fuel line, plastic bits in the fuel pump, remove all the jets in the carb and blow clean with compressed air, as well as the carb screen, and see if the motor will then reach a higher rpm.
Good luck
Dave
Team Perfect LapsPerfect Laps Racing Team/Racing School