jeepwm69

It is normal for the decompressor to flop like that. It is not normal for an engine to sound like that. @toodeep, any ideas? Sounds like valves or piston slap to me.

I don’t think so. I’ve had one of these with a bad fan control module so the sensor was taken out of the loop and it ran fine

Fuel pump Clicks on Battery shows 11.7 V at the coil, 12.41 V directly off the battery .26 V on the green yellow

Got a message from Rich last night. He bypassed the PS module, said it still dropped spark after a half hour of running, 25 degrees out. So OEM ECU, regulator, coil, stator have been installed. Still dropping spark when hot. @rich250rracer did you try cleaning up the grounds? I assume you’ve replaced the spark plug, but just to clarify, new NGK plug? @retro and other ideas? Ignition off/on/off switch on the handlebar maybe?

That’s my concern, when the coil wire melted onto the exhaust it blew the ignition fuse. I replaced the fuse and when I turned the key on the coil started smoking but the ignition fuse did not blow again. i’m wondering if that fried that ECU

Hooked up + to blue and yellow wire coming off of CKP, negative to green coming off of CKP. I took the measurement off of the round plug, engine side, so it was unplugged when I did that test. Is that correct? When cranking got 6.2 volts. got the same thing (6.2V) at the gray connector for the ECU when cranking, with stator/CKP plugged back into main harness

Gears under the shift motor look ok? The gears turn the shaft that the emergency shifter turns, so not really a linkage back there. If the emergency shifter goes through all the gears ok, I'd be closely examining the gears and bearings under the shift motor.

Looking at schematics, on the regular FM, the blue/yellow wire goes from CKP sensor directly to ECU. On the PS models, that blue/yellow goes to the power steering module, then a violet/white wire comes out of the power steering module and goes to the same spot on the ECU that the Blue/yellow wire goes on the non-PS model. The ECU is the same part for both machines. Engine (and thus CKP) is also the same on both models. So it is safe to say that if he bypasses the power steering module, running the blue/yellow wire straight from CKP to the ECU, that would reveal if the problem is in the power steering module? He tried his ECU with my regulator, my ECU with his regulator, my ECU with my regulator, and his ECU with his regulator. Same problem. Loses spark when it warms up.

So, good regulator (off my wife's Rubicon, don't tell her!) was sent and he still has same result. On a model with conventional steering, both wires from the stator pick up go to the ECU. On a power steering model, the blue and yellow wire from the stator goes to the power steering module. I wonder if I take that wire out of the plug and run it directly to the ECU if that will help with diagnosing the problem. Not sure if that’s going to bypass the PS correctly, since a lot it other stuff feeds into that PS module. @retro you have any ideas on this one? You know electrical isn't my forte

Got very little done this morning. Discovered the clutch nut is a weirdo and had to order a special tool for it. Dang JIS screws everywhere on this engine instead of regular hex head bolts! I also have discovered that there are no rings in stock anywhere for this machine. Plan was to hone the cylinder and put new rings on it while I had it apart.

Well this one is @basfnb's. I have two more just like it that I'm going to hopefully be able to build into one good one for the little princess. I'll practice on his crap just in case I mess it up! Had to order a flywheel puller this morning, and need to get a gasket kit ordered. These sideways engines are weird!

Tried the coil test. Got 10.3 volts at rest, when cranking voltage dropped to 9ish volts. so obviously that’s a problem. where is that ckp sensor? I got the airbox out but ran out of daylight

@basfnb bought this one a few years ago. Between his kid and the other neighborhood kids, it appears they've wrecked the transmission. It's stuck in gear and won't do anything. I took the sub-transmission off the side and didn't see anything there that looked out of place, so the next suspect will be a bent shift fork or similar. He's whined about how long I've had it, but I always tend to do stuff I know how to do before I dive off into an unfamiliar engine, but I finally pulled the engine in the fall and took it into the shop, and started tinkering on it the other day. First thing I found out was that it has JIS screws instead of usual 8mm or 10mm bolts, and my JIS bits don't fit my driver, so I had to order a set of JIS screwdriver bits to get this thing apart. I'll post pics moving forward, as much for myself as anything. I have two of these that are basket-case TRX125's, same year, with the hope of having one running one for the little one when she's ready.

Is it bad that even with you mentioning that, I have no recollection of it? I gotta lay off the beer........

I held the rockers up with my hand as I lowered the cover onto the engine, so the rods were hanging straight down out of the rocker arm cups, and using my other hand to make sure the push rods lined up with the cam followers. I'll be using OEM gaskets from now on though LOL

Big dollap of grease on top of the pushrods held the push-rods in place in the rocker cups so I could lower them into the cam lifter cups. OEM gaskets from now on for me. I ordered some but was too impatient to wait till they get here LOL

Motoalliance lists one for 00-03 Ranchers which is different part number than their 04-06 mount. No idea if it would be square though. They make good stuff though. Equal to KFI, just usually more expensive. https://www.motoalliance.com/atv-winch-mount-plate-rancher-350-400-2000-03-scratch-dent

You are correct that the ink blot is not repairable. However, post a pic of what you have to make sure. Best case scenario, AKATV can fix your meter and you can get Shade's for a spare.

Hey @rich250rracer, just to clarify, you've replaced now with OEM Coil ECU (from me) Stator Anything else you've done to it? I have a good regulator on the way, so we can eliminate that if it doesn't fix your problem.

Has the same sensor like the rest do, single wire on the bottom of the engine that kicks the fan on, and eventually will turn on the temp light on the dash. It's an air cooled 500 like that red one you sold to your mailman.

Are these the same in all the carbs? I have some trashed carbs in the shop, can send you one.

You sure it’s the screw and not the overflow tube?

Glad you found the place. I have a good voltage regulator as well if you want to try that, I can drop it in the mail. The TPS code I've had pop up before, and it was usually a poor connection from the main wiring harness to the ECU. Simply unplugging the ECU and plugging it back in a couple of times fixed the problem (guess the friction cleaned up the pins/sockets enough to make a good connection again). Anyhow, this one is a puzzle for sure. @retro and @Melatv are normally the electrical guys, although @toodeep @AKATV and @shadetree are pretty good at finding oddball issues like this too. All OEM parts have been used thus far, so I'll answer that question off the bat, as it's usually the first thing we look at here on electrical problems.

That would certainly be easier to check than pulling the top end.

If I recall correctly, I used OEM gaskets on the last one I went through. I think I might order an OEM gasket and see if that makes the process easier. I have at least two more of these that need to be gone through. Were this the only one I had I'd likely fish around and see if I could make the gasket I have work, but if it's a recurring problem that could be solved easily by using an OEM gasket I'd like to know that now and save myself some frustration.