Bought this project with top end removed due to scarred piston & cylinder found bad crank bearing roller cage. So have rebuilt entire engine well bad luck was I dropped flywheel and shattered magnets!! Got used flywheel off eBay with same numbers. Now it kicks back when it fires. Have marked several lines around flywheel and found it is firing about 3 inches in advance of timing mark which is about the length of a magnet. Is this a reversed polarity problem??? How can I change polarity? Or can I cut and switch wires to cdi without damaging cdi or other parts? Thanks

 

Check the basics first. Check the exciter coil resistance. Black/Red wire to Brown/White wire should be 120 ohms. Coil primary to ground .3 ohms Coil secondary 6300k ohms. Check that the plug cap resistance is around 5k ohms. Make sure the flywheel woodruff key hasn't split allowing the flywheel to move on the crank shaft. Normally stator plate timing is close when you have the mounting screws in the center of the slots. That is "IF" you didn't make marks on the engine case and stator plate before you removed it to rebuild the engine. Timing is 25 degrees at 3000 rpms, 20 degree at 6000 rpm.

 

Thanks opt exciter 119.5 primary .4 secondary 6.37k cap5.97k. Woodruff key is straight and intact. Using automotive inductive timing light with stator plate fully clockwise it's firing about 3 inches in advance of timing marks I put a series of lines about 1/2 inch apart to find where it fired at. Thanks. Danny

 

With the stator plate turned fully clock wise timing is retarded. You should end up with the plate screws pretty well centered in the plate slots if you set the timing correctly at 3000 rpm with the timing light and rpm/dwell meter. At least that's where I usually ended up. Once you have the timing set make a mark on the plate and engine case if you ever have to remove it for any reason.The newer engines have the marks on the case and on stator for easy realiging.

 

Yes sir but will not start, only kicks back while cranking, like a backfire, as I stated timing light shows firing way advanced as you look at flywheel timing marks I find the fire to happen about 3 inches to the right by marks I added to determine where spark happens moving stator plate alters this but no where near timing marks thanks

 

Ok,all this happened when you say you changed the flywheel? If the stator specs check out as you say,then it's entirely possible the flywheel is the problem. According to the manual the center mark on the flywheel(25 degrees) should line up with the case pointer at 3000 rpm while the engine is cold. If you can't get it right at any position on the stator plate,quite possible it's the flywheel even if it does have the same numbers stamped on it. You could have one for a 300 engine? . Again the manual shows flywheel timing marks on the early EC25PF01 through early -03 engine models. Then the later engine flywheel that includes the EC25PF03,05,07,08,09 engine models and also includes the EC28PF(E) 01 which is the 300 2 stroke engine. Oem part # for a 250 is 3083939,the 300 flywheel is #3084813. It's the only thing I can think of causing it to pop back and timing can't be adjusted ,unless you have a piston or crank seal problem you might be over looking ?? What does the compression read also,plus have you had a chance to do a leak down test? Plus pull the black reverse limiter wire as the limiter can cause all sorts of problems.

 

That's what i was worried about short of spending bigger bucks for new one I guess it's hard to know what model your getting one from. Best I recall mine was the 25 with an 08 following it. Am out of town right now so tomorrow will check compression and leak down. Even though all new top end and seals. Will check motor number to verify also. Thanks for all your knowledge and time spent answering mine and other questions here.

 

motor #93-12452 ec25 08 compression test shows 105 lbs. these are new rings & piston, don't have enough fittings to do leak down. pulled black wire from limiter no change. used straight edge to check magnet locations in relation to keyway I know this is not exact but they are very close to the same. but using a small magnet to check polarity the 2 flywheels are just opposite of each other.

 

105 psi sounds like the main problem!!Plus the flywheel could be from a 300 engine? A fresh top end bore job on a 250 or 300 engine should have at least 135-140psi or more!!. If you just honed the cylinder and dropped in a new stock,or matched up an over size piston that was already in it,it probably has too much ring to cylinder sidewall clearance.A new piston to cylinder clearance should be between .0015 to .002 max!This measures from the bottom of the piston skirt to the bottom of the cylinder sleeve.Plus the crank seals need to be replaced if you haven't already done so.

 

well back to magnet polarity!!! using flywheel with no ring pull started had a few issues but got it to idle timing is right on. was sent another flywheel by seller who sent one with reverse polarity and it is exactly same. how can my old flywheel have different polarity as well as another one but 2 others are identical but reversed north-south polarity,only difference I see my old one has a symbol that looks like a tree cast on the inside that the others dont