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in this thread, I want to discuss how 4-cycle atv engines work- what the different types are... how they are set up and which you prefer. To start off, are the cams on ALL atv 4-strokes powered by a cam chain? I know that on say a lawn mower or logsplitter engine, the cam is turned by the tappet, pushrods, and valve rockers. Which is better and why? Chain-driven cams or pushrod-driven cams? Are the pushrods just an old version and everything is transforming to chains or the other way around...or not at all? Just looking for some explanation, history, and downsides/upsides...
Following on from the brief interlude in the "introducing myself" thread....
In a nutshell, I acquired a YFM250 Moto 4 (1991) for cheap recently with the previous owner citing "no spark, needs a new magneto coil and I don't have time to fix it"... anyway I am dubious that the magneto/generator is the issue and thinking more along the line of ignition coil as after a clean up of the magneto I was able to get a rather decent voltage reading off the magneto with pull start and resistence readings seem to check out that the magneto is all ok (all 3 x phases = 1.2 ohms and no run to ground)
None the less I ordered a new Ignition coil and Magneto/generator coil and am waiting for them to arrive.
In the mean time I cleaned up the current Magneto, popped in a new battery and sparkplug, checked out all the wiring harness, all seemed good except I came across the "neutral switch" wire was broken.
After wiring up a new neutral switch wire, the neutral light now comes on (small win) and the starter relay (attached to rectifier) now clicks. If I hit the starter switch on handle bar the starter motor spins and if I pull the cord starter I get a spark on pull....YAY!! I'll try and attach a video below if possible.
So onto the starter motor. Starter solenoid seems to work A-ok, even if it looks crappy and starter motor spins as it should when I hit the start switch....but here is my issue.
When the starter motor runs it turns Cog #1 and Cog #2 (see photo below)....but the chain in the back of the starter which I assume is the timing chain, does not move and there is no apparent movement of the piston in the cylinder.
If I turn it by hand (per photo) or with the pull starter however the chain moves and the engine turns. However cog #2 rotates but not fluidly with the "Crank" (part I turn by hand) for the lack of a better word to use if that makes sense?
Is there a grub screw or similar on Cog #2 that fixes it to the center shaft to make it all turn when the starter motor is run? Could there be a part missing? Previous owner had the starter apart so could be possible?
The outer/front part seems to be on a key-way so not sure how to remove this easily to check how Cog #2 is attached.
What am I missing here?
Hello, I have a 1990 Trail Boss 250 that is in very nice shape. I think it has been very well maintained from all indications. The problem I am having is that the four wheeler seems to take an inordinate amount of throttle to make it go. Once rolling, the second I take my thumb off of the throttle it slows down like it has engine breaking instead of just coasting. The brakes aren't binding, as it rolls easily in Neutral. I have changed belts to see if that would help. The belt also seems to have correct deflection. The transmission has the correct fluid, and is full. When I pulled the clutch cover and found a green spring so I replaced it with the blue/green that is recommended. The primary clutch seems to work correctly. I have not watched the secondary. The other thing that I am curious about is that the input shaft seems to be tied directly to the output shaft even in Neutral. If I put the ATV in neutral and rev it up the rear disc spins, which in itself may not be too unusual, but if I pull the brake lever it decreases the rpm like it is putting a load on the engine. So as it sits, it looks like I have an issue with either the secondary clutch or the transmission. My gut says transmission, but I hope not. I would appreciate any insight as to wether this is a normal condition or, if not, how to fix it. Thanks in advance, Dave
I am trying to help my son with a machine he recently bought. A Coleman Outfitters 400 4x4 UTV.(Ihsun 400) The problem is a big one and I'm trying to work through a step at a time. It's a 2014 that had a Kodiak 400 motor and CDI box put in it for some reason but don't know year. There was a fire and someone pulled out and messed up the old wiring harness. He got a new harness for the Utv but now we have to try to figure out how to wire everything together. Any help on wiring the Kodiak to it's own CDI and or into the Utv would be Greatly appreciated. If I get a Diagram for that motors wiring then I can go to work on the harness install for the machine. I do have pictures of some of the #s on the motor, CDI box and of the harness coming from the motor.
I know its asking for a lot to hope someone might be able and willing to help but it would be great if I could get some feed back. Now I have to see about uploading some manuals I have for older Linhai/Manco Atvs that I have.
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