Hi guys,
Need some help from people smarter than me. Have a 2004 500ho that will not start.
Has fuel and spark, it is backfiring through the carb with the filter on. Just wondering if it could be ignition timing? I can't get tdc and timing mark on the flywheel to line up(out by about 3-4 degrees). Valves seem to be moving good so i don't think its a stuck valve. Tried swapping the ecm did not help.
Any help would be appreciated.
thanks.

 

think thats a good place to start

 

thanks for the response but do i adjust on the fly wheel or cam?

 

If it's never been messed with then no need of messing with timing now. The stator plate has a timing mark on it that lines up with the mark on the case. Cam timing is a different thing if it's been removed. You can pull the sprocket cover off the head,have the sprocket index pin dead center of the head.Remove the 14mm timing bolt on the recoil cover and you should see the inverted "T" on the flywheel for tdc. If it's popping back through the carb,even though you say the "valves are moving ok",best to check clearance at tdc. .006 intake and exhaust. Couple other reason for pop back can be problems in the carb itself,jets partially stopped up,float sticking,etc. Or could be in the stator area. Dirt or trash on the pick up coil face or flywheel tab or even the pick up coil air gap may need to be checked. Air gap between pick up coil and the tab on the flywheel is between .016-.040. Plus one way to test this is to see if it recoil starts. If it does and doesn't electric start,pick up coil gap is usually the problem. Plus don't over look obvious things like a partially fouled plug.Try it with a new one. IF cam timing is truly off,you have to remove the cam chain tensioner,the 3 cam sprocket bolts and while at tdc on the fywheel,wiggle the chain and sprocket around until the index pin is straight up and reinstall the sprocket and bolts(blue locktite on them) Push the cam chain tensioner plunger in and reinstall it. Once you turn the engine over the tensioner will self adjust to the chain.

 

Sorry guys should have given more info.
Bought the bike not running from a friend. Hopes of getting it running but if not for a parts bike Was told parked it last winter came spring would not start same symptoms . He sold the carb so it's got a new carb on it. Also new plug, new throttle cable, fuel filter and lines valve clearance has been done and compression test 88 psi. Swapped the ecm with my 01 to take that out of the equation made no difference.
No difference on pull or electric start.
So now my thought process had gone to timing.
When the cam sprocket marks are at TDC the flywheel mark isn't in the sight hole.
Friend is currently deployed so can't ask not sure if cam was touched.

 

Didn't have ecms on the 2001 model? Guess you're talking about the regulator as ONE model on the 2004 Sportsman 500 had one. Mounted up front by the radiator. Here's a post on how to really set cam timing the right way.This way is usually done when engines are rebuilt.https://atvconnection.com/forums/pol...ml#post3305250 Before you mess with the stator plate and timing get the manual,DON'T guess on anything. Here's one for 5 bucks that can help on electrical troubleshooting.Worth way more than the 5 bucks. 2004 Polaris Sportsman 500 Service Manual PDF Download

 

I have a clymer manual went through the process it told me to until it said if none of this works take it to a dealer.
This is part I switched from my 01 maybe I called it the wrong name I thought it was ecm




I won't be home till sunday but I'll check the spacing on the pick up coil before anything else.

 

sorry i think its called cdi not ecm. Anyway will check pick up coil spacing when i get chance and go from there and update.

 

Yes this is the Kokusan cdi. If it has spark,but still back firing I'd still download the 5 buck manual and do the electric troubleshooting checks,stator,pick up and ignition coil tests. No sense in swapping parts and guessing if mechanical timing isn't the problem.