I bought a fl250 a couple weeks ago. Traded a 300 dollar trailer it. At first I couldn't get it to fire. Pulled the flywheel and found the drift key had sheered. Replaced it and still no spark. Installed a CDI (Capacitor Discharge Ignition) from an atc 110 0n it and it started but runs like crap. Checked the coil and resistance was off so I purchased a new one but no change. I checked the timing and I have an erratic spark until it starts to warm up but then its almost but not quite 180 out. Would the CDI (Capacitor Discharge Ignition) cause the timing issue? The odyssey needs help but I have wanted one since I was a kid. (got the kids a manco in the deal so I've been riding it around)

Replaced the CDI (Capacitor Discharge Ignition) ??? Didn't they have points??
I don't know if you have a manual so I will try to attach the pdf file of this manual here for you.
Hope it comes through for you. Looks like it won't work file to big. Only allowed 4mb and the file is 12.4mb. If you type in the search box here for the fl250 manual I am sure you will find it. I think that's where I got mine.

If you need the manual and can't find the link for it here, I can email it to you.

looks like his is a 83 so no points its a 12v CDI (Capacitor Discharge Ignition) system

Yes it is an 83 and thank you for the manual. I checked the CDI (Capacitor Discharge Ignition) and one side has nothing. I only have a reg voltmeter/ohm meter but it should still show resistance. I think.

i can check my CDI (Capacitor Discharge Ignition) if you want to know resistances mate, don't know if the manual shows them or not. Check that the wires going into the CDI (Capacitor Discharge Ignition) plug are not frayed as well.

I ordered a CDI (Capacitor Discharge Ignition) and the motor (( Internal Combustion Engine ? )) ran rich but better for a minute then it backfired hard enough through the exaust so hard it blew the exaust off. I have a chance to get a skii do for 150 with a running 380 rotax and reverse transmission

see if the exhaust is not full of mouse nest or something, IMO keep the 250 in it, there is no suspension in the rear and these can be rough enough, they can do good donuts as is, slid through corners, and are well balanced as they are, a lot of work for a lot of heartache, less work and $$ to get this running good.

I you want to go the sled ay have a look in projects in bigheads world, he has a good write-up on it

I decided to stay with the stock motor (( Internal Combustion Engine ? )). Im not sure if its a timing issue now. The motor (( Internal Combustion Engine ? )) idles okay,comes idle OK but sputters and surges. I think I'm starving in top end. I adjusted the floats and now I have gas dripping at idle from carb . I put stock main jet in when I was trying to get it running cause the one that as in there and been soldered and redrilled

How did you go with this mate?

Been waiting for the cycle shop to open. Bought the next 2 size jets smaller. 115 and 118. Going to change them tonight and see what happens.

The position of the C clip can make a difference also.

I need smaller jets? I can get a higher rev with the 115 but its still got that blap blap blap sound. Loud and slow coming back to idle. I have messed around with the needle but it doesn't seem to do anything on the high end. Sunday I was checking for leaks an I found out the Engine has been ported both sides. Looking through the exhaust port there is honing marks where the piston rings ride. That Engine hasn't been run much at all since the cylinder was done. The pipe has no guts in it at all, spark arrestor was in 4 pieces sitting in there.

Thank you all for your help.

Backfire strong enough to blow the exhaust off could damage the key again and affect the timing, been their done that on a 250, it all depends on the fit between the crankshaft taper and the flywheel if its really good a key will never shear if its not that great it will shear easily, the KEY is only designed to set the correct timing its NOT designed to keep the flywheel from spinning, you don't even need a key racers use to throw them away and use NO KEY so they could set the timing to what ever they wanted for their Engine design, they would how ever take lapping compound and lap the flywheel to the crank to ensure it matched perfect.

You change the plug to a known good plug I have seen bad plugs cause a Engine to backfire right before they foul out completely have even seen new looking plugs do this.

Best way to test a plug is to install it into another cold 2 stroke Engine see if it starts and runs ok in a known good running Engine then their is no doubts its also good practice to test new plugs the same way when your trouble shooting to ensure the new one is good.

Ok thank you. Rmesser gave me a digestion that worked. The Engine bottom end has been flooded

Oh hell that is even easier lol Good job Rmesser!

You had that 250 long? They are such a blast every time I ride one and I am bouncing along the trail I am giggling the whole way

I've had the odyssey about a month but only got to ride for first time last night. I know what you mean about the giggle lol