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By Christopher Williams
i just rebuilt the top end of a 99 Bear Tracker 250 and it can’t get it to hit off of gasoline or starter fluid. Occasionally it will backfire. Right now I’m just trying to get it to fire off without the carburetor like I’ve done a thousand times before with other engines. Usually there is no response, but occasionally I get a backfire through the intake. ISeems like it’s out of time, but I don’t see how that could be possible.
Here’s what I know:
1. compression 120psi
2. all timing marks are lined up after numerous revolutions.
3. Strong spark.
4. Valves adjusted correctly.
Thanks in advance.
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?
ok help so according the service manual, Idle Air Mix Screw (aka Pilot screw) should be initially set to 2.5 turns out from fully seated.
If I do that the motor doesn't want to start or stay running...right now the pilot screw is probably somewhere near 5 turns out....I'll take the carb off tomorrow to count to know for sure.
mind you the carb got a new float seat,float needle and various other components in the kit.
To get the motor running I hard to turn the pilot screw out quite a bit, and turned the idle speed screw in quite a bit...I didn't hook up an inductive tach to know what it is idling at, but does sound about right.
What should the idle speed adjustment screw initially be set at (the one that has the black cable sheath with a knob you can twist easily)?
Is there a special tool to turn the idle/pilot mix screw whilst the carb is on the running motor? I am using a slotted screw driver bit (normally goes into a driver) by hand..makes it hard to turn the driver and hard to tell how many turns .
Hey so i have a 1990 bayou 220, and its missing the wiring harness so i went online and bought a bayou 300 wiring harness by mistake. Will it work if i use the 220’s cdi box and ignition coil?
Hi all, new to this forum so thanks in advance for the help.
I have recently brought a 2013 power steering fuel injected foreman 500.
It has a crack in the front casing and was running rough. I have since replaced the front engine casing and this has made no difference to the engine performance.
It starts and idles but bogs down and starts to die once throttle is applied.
It maybe be but it also sounds very load.
I have uploaded a video link of it.
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...
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