Hello. I have a 09 rancher with a little under 4000Km on it. Since last year it has had some weird problems such as draining the battery when off and that includes dual batteries in parallel after sitting for a couple days. The fact of the matter is that either by them selves or in dual the same batteries (jumper cabled) to my 700 diesel atv are able to start the diesel rather easily and this is when the 420 rancher is doing it's relay click click low power. This also happens if when boosted from my pickup and it's always two turns of the 420 engine then it gets sluggish to almost stopped then levels out at a low winter like turning over. After being idle for a few days even when boosting it will drain most of the battery power when starting then you left it rest for about 30 seconds and try again and it back fires and i do mean high power rifle level of sound back fire.
Considering this happens when boosted off a running truck i'm at a loss as to what could be pulling that kind of power in a 420, especially when those same batteries start a diesel engine at near 0 Deg C. I'm including a couple videos, not the best quality but what i can tell you is that even with dual batteries the VA drain was down to 9.46vDC.
Secondly last year that 420 rancher gave out on me in the middle of no where and there wasn't any where near over heated. I did notice that once it reaches about 1/3 of a tank of fuel the engine just stops even on reserve in place running idle. I did disassemble the fuel system and there are no blockages anywhere and no vapor lock. I changed the petcock (oem). No improvement, fuel filter change, no improvement and yet the 420 gets up to about 82KM/h with my bulk on it. It did drop suddenly on the return test run on the road and i let it settle to around 40km/h then it came back but that was on a full of fuel so that wasn't the problem. Lastly this 420 rancher does eat a-lot of gas even just sitting there on idle charging the battery it eats about 1/2 tank of fuel per hour at idle. Always did since out of the box.
When i was stuck in the woods last year i decided to take a nap for an hour or so and try the start the 420 again and i was able to... Barely. There was no over heat warning the rad was working,
Another detail is that the spark plug is new, it has a new oil and oil filter all oem. Also the fact that this starting power drain happens with no oil in that atv so it's not a oil pressure/compression resistance issue.
Air box seems fine and he air filter is new and yes i did try starting it without the air filter. No real difference except that it tended to backfire more on idle if that makes any sense particularly for an efi.
That should about cover it.
Any ideas?
Video 1

Video 2: The day after, also have further description of the problems in the video description on YT.

 

This morning i uncovered the atv and it's humid outside again and the batteries are dead in the 420 rancher. It even triggered the "battery save" on the Optimate 3 charger. What in blazes is wrong with this machine?

 

Regarding the battery drain, this is almost certain to be a faulty voltage regulator as nothing else is switched on when ignition is off, though the 420s crazy complex wiring system does have one half of the ignition switch click a relay, which sends positive from the other half of the ignition switch, to power the bike. There is also a capacitor which is still charged with ignition off. Anyway, with ignition off, put a 10 amp ammeter between one battery terminal and the battery, you may get a slight ampage at first (charging the capacitor) but it should then read zero. If it reads anything, pull the black plug from the voltage regulator and the ammeter will read zero if the voltage regulator has had it. Regarding starting, the bike should start instantly, no churning over before firing up, though a good fully charged battery may alter that. All I can think of with the backfiring and stopping is fuel pump low pressure, usually filter, but filter in injector, or faulty pump, or pressure release valve, could cause problems, also breather pipe in filler cap.

 

Thank you Merryman. I appreciate the assistance.
Yes i did notice they random click off (no sound) reading on the multi meter and that did solve the problem until the atv was started. There is indeed some form of short or intermittent electrical contact since it gets worse when it's humid out. Full battery, booster pack or not. There is an improvement if you put the charger on even for a few seconds with or without the battery connected. Not to mention that fact that i can start another atv with the drained honda battery.
Thanks again.
Btw the fuel pump filter in new and it's the vertical oriented one and the filler cap breather hose was never blocked an i ran an air compressor on both ends of the filler cap air exchange just in case. No blockages.

 

Edit update:
I found the problem, at least somewhat. The grey octagonal ignition connector to the right of the + of the battery once unplugged stops the drain and i did work the wiring a little and after a tine the drain stopped. However it had nothing to do with the black rectangular connector or the larger grey one beside it (the ones with the green orientation paint markings) that are further down the line towards the ignition switch. There is what looks like a parallel in line fuse wrapped up in some tape that holds the harness bundle together. Also on the greay rectangular connector there is a small red something that has three wires in it. It doesnt' appear in the service manual so i have no clue what it is. I does have green yellow and black red wires along with what looks like a n Neg ground.

 

The red connector is in the service manual, it is the port for the diagnostic computer, but was at the back of the battery box on early 420s. It would seem a main wire from fuse box (30 amp) to ignition switch may be shorting to earth, trouble is, part of the relay system may also be permanently live. You don't mention pulling the regulator plugs, though those may be the black and the grey you referred to.

 

Yes i did pull those black and grey plugs in the side. It didn't change anything except the black disconnected the ignition but the power drain still happens. The only time when i have any control over the power drain is when i disconnect the octagonal plug on the+ battery terminal side for a few seconds and replug, then the atv starts as normal for a time but as the past few days have proven as soon as it gets humid out the power drain comes back and this is is a shed not in the rain. I agree that it does sound like a short to ground since something starts to send power to a capacitor.
It will take a while to find that short and i did check the frame ground points near the starter motor.
For the time being i have installed a 30amp heavy duty switch to the negative of the battery. If i use the rancher during the day it usually works fine so i'l only switch it off when not in use and leave the optimate charger on it. For the time being it's back to a conventional single 14-bs battery rig for the 420. Also went and got a regular li-po jump starter to carry with me until i can find that short.

Thanks again.

 

The plugs you are on about are not the voltage regulator ones. I repeat pull the black voltage reg plug, it is on the voltage regulator under the RH wheelarch next to the header tank.

 

Yes i had already done the VR, the one beside the reserve anti-freeze bottle. The charge was still there when unplugged.

 

I fixed the problem.
I replaced one harness with a new one and each wire pair is isolated with it's own loom this time.
The battery now holds stable between 12.86 an 13.06 vDC.

What i think happened is that in the fall when the atv is put away in the shed. The humidity in the wire bundles turned to ice and corrosion got in and caused random shorts. On the original wire harness there are some cracks and traces of oxides. Since this rancher never saw deep water there wasn't much of any explanation left since disconnecting the VR still left random current it had to be something else. Even if you dry out the atv first and if it's not in a heated garage all year round it will still collect humidity afterwards and at -40c even for a snowmobile things like this happen.

I hope this whole mess helps some one out in the future.