I just bought a used Polaris Preadtor 50 and installed a new top end (cylinder + piston + rings + gaskets) after market from eBay, installed new battery, made sure all connection are right; the engine turns over, but will start, I sprayed starting liquid in the carb and in the cylinder, but nothing so far. I do have spark though.
What could be the problem? any ideas or help is appreciated. Thanks.

 

What amount of torque on the head bolts? Should only be around 10-12 foot pounds I believe? Plus have some one hold throttle wide open when cranking and check that you at least feel pressure from the exhaust pipe,if not it could be stopped up(had a few do this) Also when you start the engine place your thumb over the air box inlet tube(allows more fuel, this little engine is hard to pull in fuel at times) we even a had a "tech" bulletin on this for electric and manual choke models. Hope this helps. OPT

 

Thanks, I'm not sure of the torque but can measure it and advise the value. Usually I just do it by feel (I have done so many Polaris 50s and 90s top ends). Yes I do feel air coming out of the exhaust (I had this problem in the past with a polaris 50, it turned out that it had mud in the exhaust!). I tried placing my thumb on the tube of the intake tube with the choke open/closed no luck; held the throttle wide open when starting and no luck. sprayed starting fluid in carb and in cylinder and no luck; as I said I have spark though. I have worked and fixed many of this ATVs but I'm stomped on this one. Do you have specs for the stator, CDI and coil, a manual will really help.
Any other ideas will really help. Thanks for your help.

 

Don't have the specs on the stator,but will say stators were what I replaced the most on the 50s and 90s! If you have a flywheel puller,you can try to clean up the stator and inside the flywheel and see if this helps as they do get muddy and I got a few back running by just doing this.But most of the time they would short out from the water and dirt and have no spark.Didn't have many cdi or coil problems. I still remember the stator #s off the top of my head 0450998 for the 50 and 0451000 for the 90! But still strange though if you have a new top end and have spark,that it won't at least try to crank on starter fluid?? Good compression?? OPT

 

Thanks, I did pull the flywheel and of course the stator had mud so I cleaned it and measured the resistance, if I remeber two were low ( 5 to 7 Ohms) and the pick up was around 570s Ohms.
I ordered one of the aftermarket stator on eBay and it didn't spark at all; it had the same plugs and same holes for attachment, and the seller confirmed that it work for my bike. I put back my old stator and it sparks, go figure!!!
I don't want to buy an OEM and find out that it was not the problem and get stuck with it. the strange thing that it has spark!!!
Any other tests you can think of will help solve this mystery? thanks.

 

Fuel,air,compression,and ignition,ONLY thing I can think of is how much compression you have? The little brass/tin head gasket can leak if torqued too much! I found this out myself! Don't know if this helps or not. Plus I heard about some of the aftermarket stator problems from people before I retired,even though they show to be a perfect match! See if a local dealer can be persuaded to give you the electrical resistance specs! I did on numerous occasions for people! Keep us updated. OPT

 

Well I measured the compression and found around 92 psi, and I think this engine needs around 120 psi to work correctly, so the culprit would be the crankshaft seals since the the whole top end is new.
So I took the engine apart and split the crankcase, the seals dont have that tight fit around the crankshaft, so I'm almost sure that's my problem.
I will order them today and when receive them and install them I'll let you know. By the way the exhaust was full of all the gas and starting fluid that I sprayed in the carb, so I emptied it and run the blower through it, air comes out from the other side fine. Air was also coming out when I was cranking it.
Let me know what is the normal compression for this engine. Thanks for your help.

 

Your 115-120 psi is a good figure on compression! Sure the main culprit isn't the head gasket? This is from my own experience! Make sure when you do put back together DON'T over tighten the 10 mm head bolts! I've ruined a couple gaskets by not torquing properly! Off top of my head 10-12 foot pounds,but best to get the specs! Good luck OPT

 

I'm overdue for an update!
I borrowed my friend's Predator 50 and swapped every every electrical part you can think of including the flywheel and no luck. Again the only think that is different was the new aftermarket cylinder that I installed.
So I decided to buy a used Predator cylinder on ebay; once I got, cleaned it a little bit and installed it, after few kick strat the thing started!!!
After few adjustements on the carb, the little monster runs like a champ.
It looks like the scrambler cylinder is a bit bigger (1 or 2 mm)than the predator cylinder!
Anyway, put it back together and sold it.
Thanks for everyone's help in this forum.

 

04 predator 50 had issues with spark. Tore it down. Had same issue with horn not working. So I held horn button and wiggles wires. Over by the coil wiggling wires caused horn to work! So I proceeded. Brake on, both safety buttons on, key on, turned over got spark still no fire. Mine has no headlights. Stator blk/red stripe to stator white/red stripe had 988 ohms. White/red stripe to ground was 113 ohms and blk/red stripe was 875 ohms. Come to find out the exhaust bolts were loose, and gasket wasn't sealing. Could tell by gas running down pipe. Tightened up and it fired!! My issue now is I broke the head off the exhaust bolt. Time for the easy outs. Finally, my starter rely, got hot, and all 4 wires fell out the harness. So I been hot wiring it to start. Can someone send a pic of the 4 pin start solonid wiring harness so I can figure out where the wires go? Thanks hope this helps others