Need help with timing on a 98 sportsman 500
 

So I replaced the stator and flywheel due to a no spark condition. It idles perfect but at wide open throttle it sputters and backfires so a new carb and starter long story now same no change in thinking its a timing issue but kinda at a loss

check your cam

May look like this if really worn.Bad Cam Pic - ATVConnection.com ATV Enthusiast Community

I don't think it's a cam issue this problem started when the stator fried due to a water in the recoil housing

any water get in the oil?..
did you remove the stator plate? if so, did you mark it so its back in time?
if you havent looked at the cam, i wouldnt rule it out

No water in the oil and no I did not mark the stator in any way I put it back kinda just how it fit but not sure how to align to time it not much good instruction about it anywhere

if you took the whole stator plate off without marking it, then yeah, very possible its out of time

That's exactly my issue so to set timing from scratch I guess is the real question I guess tdc on piston verify cam marks then how do I set stator

if the manual doesnt cover it then opt would have to answer that, ive never had to do it on an atv...id first go back in and see if you can see where the bolts used to be on the plate, should be a cleaner circular looking spot if you didnt clean it....might give you an idea if its off or not

It had to be totally replaced the old stator was fried so no way to mark or read marks

Not my machine so excuse me if I'm incorrect.
Stators usually only fit one way because of wire routing. If the mounting holes are slotted for adjustment, it's only a small amount of movement. Shouldn't take much trial and error.

If the old stator was fried you could have left the old stator plate in place(or mark it as the manual calls for) and installed the new stator and pick up coil using the the three stator mounting bolts and it still would have been in time. Now you're going to have to use a timing light and preferably an accurate rpm gauge and trial and error in getting it to the 30 degree mark on the flywheel while maintaining 3500 rpms. You have to get the plate at least close enough to run(set the screws in the center of the slot and try that) check where the 30 degree mark is in relation to the recoil case pointer. Kill the engine,remove the flywheel and advance or retard the plate until you can get it to the 30 degree mark with the timing light.

Wow no fun sounds complicated crap funny thing is it idles great so I can't be far off

If it at least idles,you're fairly close.

That's what's I was thinking lol minor tweaking

So opt question clockwise rotation of the stator will advance timing and counter clock to retard?

Clockwise retards timing,counter clockwise on the plate advances timing.

Ok opt after rereading this thread and retracing my steps I realized I only removed the stator not the stator plate so timing probably not the issue. Having said that it idles perfectly and the trigger coil is actually at .025 by feeler gauge from the magnitude on flywheel should I be thinking about that cam and reconsidering it?

Timing shouldn't be an issue then..Just for grins and giggles,tap the pick up coil bracket lightly inward. Plus check resistance on the white and white/red pick up wires. Should be around 97 ohms. If the p/u coil is within resistance range and closing the gap further doesn't help,then go towards the cam. Ground down cams would usually idle,but spit,cough and back fire through the carb when you gave them any throttle.Very easy to tell if the lobe is the problem.

The trigger is fixed no room to adjust and can I test the resistance at the Cdi if so its 137

I know the bracket is fixed,but a light love tap with a hammer without breaking the p/u coil may help.. :) Have done that in the past. Plus the same thing that this guy did,but his rope broke earlier and bent the bracket away. no spark to plug when using electric starter - Page 3 - ATVConnection.com ATV Enthusiast Community Plus touch your meter leads together and see if they zero out or get close. 20% +/- is the allowable amount on the pickup and you show over that. If the meter is accurate the coil may be a little weak.

Ok interesting my meter does zero out and I did get the trigger closer about .15 instead of .25 what still bothers me is that it idles so well just bogs out and a little exhaust backfiring actually on throttle it seems to surge oddly but won't ramp up just mind boggling at this point

Look at the exhaust cam lobe and rocker arm.. Still sounds like what most of them do,backfire,won't take throttle.

Yah I suspect that's the next step just not sure how I will be able to tell without a side by side comparison

That's where cheap calipers can come into play if needed. 1.2884-1.2924" (32.726-32.826 mm) is the standard lobe height,1.2766 (32.426 mm) is the limit. But if worn bad enough to cause the back firing,wear should be noticeable.

Ok a little intimidated with this step but game to try it this machine owes me nothing and sooner scrap it than foot the bill to have the work done lol

Ain't no biggie on cam and rocker arm replacement. The manual can help you on this. Cheap cams are on ebay.

Random thought any other test like compression that will give any confirmation of cam probably not as it's an exhaust lobe issue huh

They book is good and cam is only like 100.00 just consequences of bad install are catastrophic lol

I gotta remember that quote.. :)

55-95 psi compression on average because of the decompression device. Some machines may show a little higher.

Trying to think about it in terms of the cam compression will test good even though exhaust lobe is worn is that accurate

a bad cam would have no effect on a compression check

Correct.. You can have a flattened lobe and still show within range because of the decompression device.

That's what I thought I am gonna bite the bullet and pull the cam and be done with this project lol details to follow

You don't have to pull it.. Just a visual check is sometimes all that's needed if it's ground down bad enough. If in doubt measure the lobes and look at the rocker arm for scarring. Here's a bad one up against a new one.

Sorry yah I meant pull the cam not the motor but I guess I could pull the rockers first and rotate the engine a couple time and see if I can ID the lobe or lack of a love

That's what I meant too.. Just examine the cam.If the cam needs to be replaced you can replace it with the engine still in the frame.

Absolutely thanks for all your excellent advice getting to this point

Well OPT so just went ahead bit the bullet and finally put a new cam in it to no avail still idles like a dream but when I give it throttle it bogs out with no gain in rpm as a matter of fact it almost stalls