spock58

Those carb parts I mentioned won't be in most aftermarket rebuild kits but you can get oem ones separately from a Yamaha shop. I used to wrench for the local dealership so I've run into this issue before. It's common on older single cylinder bikes since they vibrate and some spend a lot of time idling, therefore they wear the needle out in that spot. The tolerance between the needle and the tube it runs in has to be quite tight at closed throttle especially.

I wouldn't sweat the resistance test on the coil - anytime a spec is less than an ohm this is normal. It's very difficult to get an accurate reading that low - if the coil was bad it sure wouldn't produce as rpm increases.

Unless you see a misfire using a spark tester I doubt that there's an ignition issue - still sounds carb related. One thing that comes to mind is the pilot screw, is the little o-ring & spring properly in place? Usually this results in a lean condition at low rpm which makes for rough idle & bogging or hesitation. Since your symptoms indicate richness (ie. black plug) there could be wear on the needle in the slide, was this replaced already? You also have to replace the piece that it slides into, at the top of the needle jet. This is a likely reason why it over fuels and is really noticed at the closed throttle position. I will see if I can show a parts diagram of this. You should try needle set #2 & nozzle #16. Pilot screw o-ring is #9 https://www.ronniesmailorder.com/oemparts/a/yam/50038fb7f870021f60a0ca5f/carburetor

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Wow, great photo Frank! That boat looks awfully far away from you, haha. Looks like the weather is decent, unlike up here in central BC. Nothing but rain, so that's good for keeping the forest fires away! Still going riding today unless there's too much lightning - last night was epic.

It couldn't hurt to pull the air filter and see if anything changes - take it for a short ride and report back.

If they're not leaking, just keep running them! The hubs run a small amount of ATF in them for lube.

Sounds like the front diff needs help alright but the rear is normal - both axles are "locked up" together at all times. It really isn't a differential on the rear, usually called a gearcase btw.

Oh wow, that's crazy! I wish we'd get more snow here for sledding, instead of the constant cold. By next weekend they forecast for it to start melting, then the dreaded spring breakup.

What part of the (cold) world are you in?

You're not kidding Frank, it hit -34C at my place this morning!! Coldest it has been all winter I think....(interior of BC here)

That's true, they called it a Quest up until 2004 then changed the name. They also had the 5 speed Traxter that year which I believe was a 500 (and also sold by JDeere as well)

I recall the 650 being a different model than the Traxter built by BRP. It had a CVT (belt drive) which is what the Quest 650 had. The Traxter was a 500 with a multi-speed gear transmission. Hope this helps.

Better look closely for a bent tie-rod or something like that. Usually bad alignment is caused by some kind of impact.

Don't forget to examine the valves closely, this may be where the loss of compression comes from.

Does the neutral light work ok? Most Honda quads need it working for the electric starter to function.

Next test is to see if any power is getting to the starter motor when the button is pressed. Best to use a test light, connect it to a good ground and probe the positive wire at the motor.

When the key is on, do you get any power to the gauge? Neutral light coming on or any other sign of life?

Did you test for spark when you had the switch disconnected from the module?

Did you ever redo any tests on the stator? What kind of resistance was there....seems more likely to see a bad stator than a cdi problem.

I see no reason why you couldn't run it without the cable connected. Usually the hour meter is separate and gets its reading from the ecm/ignition system.

It's just called a flywheel puller - they're different sizes and you need one that's specific for your motor. They shouldn't be that expensive to buy, or else you can take it to your local shop that services these brands and get them to pull it for you.

My vote is for the Yamaha 700 - they work great!

Sounds to me like you have a starter clutch that has failed. To repair this requires removal of the ignition side case cover and pulling the flywheel off which needs a special tool to do so. There is a one-way bearing likely attached to the back side of the flywheel. If this has failed there may be other parts involved that are worn. Not the easiest of jobs but it's usually possible to do without engine removal. I've done this fix on a newer 300 Suzuki quad but I believe the older ones also used this style of starter system. Hope this helps.