Hi did you ever solve this problem as I have the same problem with mine but with no head work doneI have an 04 crf450r and have gone through everything, still will not start. Engine occasionally backfires through intake after giving it too much gas.
The gentleman I got the bike from couldn't get it started either, after performing many needed repairs he decided to give up.
He had installed a new weisco piston and rings, had heads set up for S.S. kibble & white valves and springs, seats were all lapped in for new valves, new guides and seals. This work was done at a reputable machine shop familiar with this type of work. He performed his own work with the exception of the head work. He shimmed all the valves. Set cam timing and couldn't get it started.
I checked valves and had to reshim valves as they were set at .005" intake and .007" exhaust. I set intake at .007" and exhaust .011", w/ decompressor set at .014". I performed a compression check, getting 85 PSI w/ decompressor involved.
I have reset cam timing as he had it off by one tooth, set by second mark on flywheel aligned with mark on left crankcase cover and mark on cam and casting lined up w/ lobes facing rear of bike, TDC. I have checked this timing many times after rotating engine. Each time it comes right back to TDC. I have thoroughly disassembled and cleaned carburetor, put fresh fuel in, checked spark w/ spark tester, able to jump 8MM gap each kick. checked all static resistances of ignition coil, ignition pulse coil, and exciter coil. All readings were within listed specs in book. Peak voltage tests were performed on exciter coil, pulse coil and ignition coil, exciter coil and pulse coil failed, ignition coil passed, thus as the book directed I replaced the CDI box. still no start.
I'm thinking maybe next I should deactivate the decompressor and check full engine compression? maybe I should perform a leak down test? should I tear the engine down to the base and check all the work that has been done?
Should I go to the exciter coil and ignition pulse coil next, ( replace them) even though the troubleshooting section in manual stated the CDI as the culprit?
Good compression, adequate fuel, Great spark and engine timing all check good, what's up??? I'm at a loss. don't know where to go next, Could really use some input.
Thank you for reading this.
Welcome to the site !!ĺhi did you ever get to solve the problemHi did you ever solve this problem as I have the same problem with mine but with no head work doneI have an 04 crf450r and have gone through everything, still will not start. Engine occasionally backfires through intake after giving it too much gas.
The gentleman I got the bike from couldn't get it started either, after performing many needed repairs he decided to give up.
He had installed a new weisco piston and rings, had heads set up for S.S. kibble & white valves and springs, seats were all lapped in for new valves, new guides and seals. This work was done at a reputable machine shop familiar with this type of work. He performed his own work with the exception of the head work. He shimmed all the valves. Set cam timing and couldn't get it started.
I checked valves and had to reshim valves as they were set at .005" intake and .007" exhaust. I set intake at .007" and exhaust .011", w/ decompressor set at .014". I performed a compression check, getting 85 PSI w/ decompressor involved.
I have reset cam timing as he had it off by one tooth, set by second mark on flywheel aligned with mark on left crankcase cover and mark on cam and casting lined up w/ lobes facing rear of bike, TDC. I have checked this timing many times after rotating engine. Each time it comes right back to TDC. I have thoroughly disassembled and cleaned carburetor, put fresh fuel in, checked spark w/ spark tester, able to jump 8MM gap each kick. checked all static resistances of ignition coil, ignition pulse coil, and exciter coil. All readings were within listed specs in book. Peak voltage tests were performed on exciter coil, pulse coil and ignition coil, exciter coil and pulse coil failed, ignition coil passed, thus as the book directed I replaced the CDI box. still no start.
I'm thinking maybe next I should deactivate the decompressor and check full engine compression? maybe I should perform a leak down test? should I tear the engine down to the base and check all the work that has been done?
Should I go to the exciter coil and ignition pulse coil next, ( replace them) even though the troubleshooting section in manual stated the CDI as the culprit?
Good compression, adequate fuel, Great spark and engine timing all check good, what's up??? I'm at a loss. don't know where to go next, Could really use some input.
Thank you for reading this.
Thanks Steve
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