Vintage Dirt Bike Q & A

Hey guys, brand new to the forums and dirtbiking in general, and I've got a dirtbike that needs some fixing. I'm really new to riding, bought my first bike a couple months ago, an old 79 suzuki 125 trail bike. I've since sold that and bought an 88 Honda CR 250, with a 300cc big bore kit, and a FMF Gold Series pipe on it. I bought the bike not running, planning on fixing it. (I have alot of mechanical knowledge, done a ton of car work, and wasnt too concerned with getting a 2 stroke running) However, I'm out of ideas on this thing.

Kicking the bike over, or even bump-starting it, it will backfire every 10 kicks or so, but I cannot get the bike to start.

The bike was used last season, and the previous owner said it ran great. I have the receipts for the engine rebuild, which was done in late 02. The last owner said it had very few hours on the rebuild. The bike is very clean and overall seems to be in excellent shape. He thought it was an electrical problem, probly the coil. I have checked out the whole electrical system (I'm an electrical engineering major @ SDSU), and done all of the electrical tests in the Clymer repair manual. The coil is within specs, but on the low side for a resistance test. I'm assuming its ok. The kill switch is fine too. From looking over many internet motorcycle forums, it seems like the stator is the problem. I tested the stator with the electrical tests defined in the manual, and it seems to be bad. However, I don't have a flywheel puller, so I cant take off the flywheel and check out the stator more closely. I have also taken apart and adjusted and cleaned the carb. The bike seems to have very good compression although it hasnt been tested for an exact value. The spark seems to be very weak and inconsistent when grounded agains the cylinder and kicked over. I'm assuming the internals of the engine are in good shape from info from the previous owner.

So I think I've narrowed down the problem quite a bit, I just dont have alot of experience in this part of bike repair.

Please help guys, do you think this is the problem? Any other ideas of what to do?

Thanks in advance for the help!
Evan

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88 CR 250