Starting problems.

Hey guys, lately we have had alot of trouble starting my dads bike. For one, the bike will not start with the choke in, and will barely start without it. The only real way that we can get the bike to start is to open the throttle all the way and kick 5-6 times before it will finnally fire up. What is causing this? Is it a jetting issue? Or possibly a valve issue? Where would you guys start? The 450 is new to me, but this is what my guesses would be for why it isnt starting based on my knowledge from 250f's.

Thanks alot.

PS, alot of the time it will backfire more than once while trying to start it.

Sounds really lean. Check the AP too, it could be preventing you from priming the bike prior to starting. Back the fuel screw out a bit, and see if it helps. I'm betting you will need to go up a size or two on the pilot jet.

Myself on a YZ400 and my buddy on a WR450 had the same issues until we increased the pilot jet, 50 for me and 48 for the WR450.


start with simple things first compression, timing, these can be checked easily. more than likely your cylinder is worn allowing blow by. holding the throttle open eventually you get enough to help seal the piston raising the compression. anyway i would start there because if it ran fine at one time and you havent changed anything the it is probably normal wear items.

Its not the compression for sure, and I dont think its the timing (it runs great once started). The cylinder is a posibility since the bike was raced before we bought it and it maybe a little overdue for a topend. I will definately look into the jetting, because that is what we are hoping it is. Would you recomend a JD jetting kit to solve the issues? or just work with what we have (whatever came on the bike). Thanks again.

Have you done anything to the bike between it starting fin and not starting? New bars? Changed something else Hows the air filter look? Change oil type for the air filter? Try a new plug? Have you checked valve clearances in a while? :applause:

Did try a new plug (by the way, is it a CR9E or CR8E or neither, I have tried both and it wont start well with either, but im not sure which one is right). I put a new stock airfilter on it (it had a twin air filter) and I started using motorex filter oil (im not sure what the previous owner used). Could this have caused a jetting issue? Maybe the filter I put is stopping the bike up compared to the twin air... If so what adjustments would you recomend on the carb. Also would you happen to know an online link for a owners manual because the bike didnt come with one.


So did the problem start right after the change of air filter? If so, I would say you may have answered your own question! I would say you over oiled the filter.......Plug is a CR8E...

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