Partzilla Live Q&A with John Talley – January 07, 2022
John Talley is back for the first edition of Partzilla Live Q&A of 2022, answering your motorcycle and ATV repair questions.
The first Live Q&A of the new year brought in quite a few ATV repair questions. Check out some excerpts from Partzilla’s latest live Q&A session below, and tune into our YouTube and Facebook channels every Friday at 3pm Eastern for the next edition.
Partzilla Live Q&A Highlights – ATV Repair
I’m working on an 07 TRX 400EX and I adjusted the valves but there’s still a lot of click coming from the top end. Can I do anything else besides rebuild the top end??
John Talley: Well, it’s probably not your top end. I would bet that your cam timing chain and/or tensioner and/or guides are worn out. So you’re going to need to replace those because what you’re hearing is probably not so much ticking but more than likely a bunch of chain slap.
My Polaris Sportsman crank gear has a mark that says 15 BTDC by the TDC mark. What’s that for?
John Talley: What that does is show you a mark from top dead center that is 15 degrees before top dead center. And that’s probably going to be your ignition timing mark if you were using a timing light. That’s the part that you’re going to see where the strobe light will be lighting up that mark. So they’re advancing it probably at 1500 RPMs by 15 degrees.
My YFZ450 regulator-rectifier has two wires coming out of it, a red and a black one. No matter what OHM setting I put it on, the multimeter shows OL, but on the other wires that plug into the stator connection, it shows the 20 ohm setting. Could this be the cause of my no-spark condition? Keep in mind this bike doesn’t have a battery.
John Talley: If it doesn’t have a battery, it has a capacitor in there that temporarily stores electricity because it really doesn’t use much, and your black and red wires are pretty much representative of quote-quote “battery voltage”, although you can’t measure it because it’s just a capacitor and it charges and discharges very quickly. Now you’re looking into your stator and you’re seeing a 20 ohm. I can believe that as far as the resistance that you’re going to see because that’s reading back into the coil going around the stator. But is that causing your no-spark? I doubt it. On that particular machine it’s pretty easy to diagnose. … If you’ve got an OL on your red and black wires on the 20 ohm setting, that tells me your charging system should be ok and more than likely it’s going to be your ECU or CDI. Because there’s nothing else to go wrong. Are you sure your spark plug wires and your spark plugs are good to go? Take a look at those as well.
Want to see more live repair questions answered? See all of Partzilla’s Live Q&A sessions here.