crf450r 2010 won't start and backfiring

[Dezzi]

Hi all,

I have just finished the rebuild on my crf450r 2010 now it will not start, it started once but after about 50 or so kicks but now it backfires and won't start I rechecked- all connections, valves clearance, valve timing replaced spark plug, cleaned the air filter. need help.

Thanks Des

Edited July 8, 2013 by Dezzi

[Eddie8v]

Cam timing and/or valve clearances is my bet.

You said you rebuilt it, what, exactly, did you do? Piston/ring replacement only? Head and/or valve work done while it was apart? Use new OEM gaskets when you re-assembled it?

Edited July 8, 2013 by Eddie8v

[Dezzi]

I have rechecked the cam timing and the valve clearance both ok. I replaced the piston and rings the head was done last time around so I only checked the clearances. As for gaskets I used genuine Honda. Hope this helps.

[Qqqqqqqqqqqq]

Is it getting fuel ?

[gscx]

Turn your idle all the way down, then turn it up three clicks at a time as you attempt to stary it.

[Eddie8v]

I have rechecked the cam timing and the valve clearance both ok. I replaced the piston and rings the head was done last time around so I only checked the clearances. As for gaskets I used genuine Honda. Hope this helps.

How did you verify correct cam timing? What process did you use to verify it? And please check your valve clearances and post the results.

Edited July 9, 2013 by Eddie8v

[RUSVD]

Hopefully all your connectors are back on at the right locations. Did you tag the electrical plugs before you pulled them off. It's easy to reconnect a couple of them on the wrong sensor. The common ones are the MAP, TPS, and FI, those can get mixed up pretty easy.

[Dezzi]

Hi with checking the cam timing I removed the plug on the right crank case cover lined up the marks on the gear to the case and on the top cam gear lined up the mark on the gear to the base of the bearing cap where it bolts to(line or cut out). The valve clearances are exhaust 0.27mm and intake 0.17mm and I rechecked all the wiring connections just to make sure they are all in the right spot.

[Eddie8v]

You need to time it using the flywheel hash marks from the left side of the bike. There's a "sticky" thread about timing the motors at the top of this forum, I believe it explains the process fairly well. Line up the flywheel hash marks and let us know if you're off a tooth. It is very easy to be off 1 tooth if you're only using the right-side markings.

[nesc103y]

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Edited July 13, 2013 by nesc103y

[Dezzi]

checked the cam timing from the left side is was ok. tried to tow start it and it worked after giving it a run now it starts fine so thanks everyone for your help learnt a lot, just one thing which I didn't notice before the red light comes on for a couple of seconds on start up then goes out is this normal.

once again thanks Des

[Jon-D]

checked the cam timing from the left side is was ok. tried to tow start it and it worked after giving it a run now it starts fine so thanks everyone for your help learnt a lot, just one thing which I didn't notice before the red light comes on for a couple of seconds on start up then goes out is this normal.

once again thanks Des

yes, that is normal.