2010 YZ450F 157 Hours now hard to start after rebuild

Just to let people know that i have done 157 hours on orignal piston and is still in good condition and i have never had to adjust valves

i only had to do a rebuild beacause i had a clunking noise when pushing bike in neuteral it ending up being third gear was chiped on dog where it pushes on to 5th gear

after rebuild new gears new stock piston rings it is nearly imposiblle to get it started by kicking(maybe 20-30kicks) i can get it started by rolling down a small hill and bump starting

i get no software error codes and when i get it started it goes like a brand new bike i have done a hour on it and still no better may i need more hours ?

thanks david

Double check your work...especially in the carb area. All hoses connected, all lines routed, good spark. I would replace the plug with a new one,,,an absolute must for me.

Air filter clean and re-oiled. Check the HT lead and coil are all connected tight. Was every thing a success in the cam dept when you assembled? Is the fuel flow okay..has a bit of crap sneaked into the carb when it was being rebuilt. Were you working from an after market manual or an manual for that matter i.e can you check all the specs.

Certainly try a new plug first off.

I would double check your cam timing and valve clearances to be sure.

has a bit of crap sneaked into the carb when it was being rebuilt?

Something makes me doubt that's the problem. :cry:

Something makes me doubt that's the problem. :cry:

I don't know much about this model.....just trying to offer some areas to check. I am guessing by what you have said above that this is an EFI model? :cry:

I don't know much about this model.....just trying to offer some areas to check. I am guessing by what you have said above that this is an EFI model? :cry:

Yes sir. :cry:

Dirt could still be involved, but they way EFI works, dirt that would make it hard to start would normally cause the bike to run very poorly. The OP might want to check the flywheel for being properly keyed, check the voltage to the fuel pump while cranking, things along those lines. A mis-keyed flywheel wouldn't show up as a fault code, either.

Yes sir. :cry:

Dirt could still be involved, but they way EFI works, dirt that would make it hard to start would normally cause the bike to run very poorly. The OP might want to check the flywheel for being properly keyed, check the voltage to the fuel pump while cranking, things along those lines. A mis-keyed flywheel wouldn't show up as a fault code, either.

Cheer thanks. This will be interesting to follow. Always keen to learn new things as this is a whole new ball game for me....The EFI.

I would double check your cam timing and valve clearances to be sure.

I'd start here first

mine does the same thing , and I have not found why , once the bike have start once in the day it will start in 1 crank start every time but cold ..... I was suspecting coil but not sure and my key is in there at the flywheel , maybe not enough charge (electricity ) but how to find it ?

Just to let people know that i have done 157 hours on orignal piston and is still in good condition and i have never had to adjust valves

i only had to do a rebuild beacause i had a clunking noise when pushing bike in neuteral it ending up being third gear was chiped on dog where it pushes on to 5th gear

after rebuild new gears new stock piston rings it is nearly imposiblle to get it started by kicking(maybe 20-30kicks) i can get it started by rolling down a small hill and bump starting

i get no software error codes and when i get it started it goes like a brand new bike i have done a hour on it and still no better may i need more hours ?

thanks david

the bike run really well when i get it started i have been bump starting by rolling down a hill normaly starts no problems doing that way i suspect that i am not getting enough speed when i kick it and the efi is not working properly

Your timing is probably off by one tooth.

Your timing is probably off by one tooth.

your right both intake and exhaust where out by 1 tooth i do top end rebuilds but this time i paid someone to do the gearbox repair and topend rebuild i am superised it was out as the guy is very good mechanic

it now starts easley now

thank to all that helped

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