04 CRF450r won't start
  • this ole man
    Posts: 7
    Joined: Mon Nov 18, 2013 4:58 pm

    04 CRF450r won't start

    by this ole man » Tue Nov 19, 2013 9:13 am

    I 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.
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    124
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    by 124 » Wed Nov 20, 2013 7:34 am

    "Adequate fuel" ??
    If everything is correct, the engine will run.

    Your compression numbers are too high. 64psi at 600RPM is spec.

    There may be something also going on in the carb. Check to make sure the floating valve seal (the slide plate cover thing) is correct. Hole at the bottom.

    Have you tried bump starting it?
    70' Honda CT70 (Trail 70; Gold)
    16' KX450
    16' KX85
    12' YZ125
  • this ole man
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    Joined: Mon Nov 18, 2013 4:58 pm

    by this ole man » Wed Nov 20, 2013 9:49 am

    I have tried pouring a small amount of fuel into the spark plug hole, still does not begin to start, just backfired through intake once.
    I have also once tried starting fluid and it backfired through the intake as well.

    I did pay particular attention when servicing the carburetor that the diaphragm integrity was intack and in good shape as well as it was installed in the correct orientation. Hole down, sliding plate toward the cylinder.

    I have looked at the fuel delivery of the accelerator pump into the throat of the carburetor and see a nice solid stream going toward the intake. I assumed this would allow fuel enough should the pilot circuit not be working to at least fire intermittently. I did also ensure the pilot jet was nice and clean as well.

    Most times when trying to start it I put choke on full with no results, I have also tried to blip the throttle a couple times then put choke on full, this is when once again I would get a backfire through the intake.

    Could the compression numbers be higher than typical because maybe the decompressor is set a little high or low? I believe I read in my Clymer manual that the compression value with the decompressor should be around 78 PSI.I will have to check on this again.

    I have not tried to bump start the bike but that may be the next step.

    Thank you for your input, it is very much appreciated and it gets me some more things to look at.
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    JimDirt
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    by JimDirt » Wed Nov 20, 2013 11:20 am

    Its sounding more like either the timing is off for some reason , or you possibly have a bent valve as you mentioned he had the timing off and could have done internal damage and that is the whole issue , have you tried a Leak Down Test ?? to rule out any valve or broken ring issues , with a leak down , it will tell you where (if at all) any leakage is , and where its going , if the added fuel in the plug hole did nothing and your sure spark is good then it would narrow it down to what it could be , and your symptoms keep coming back to timing or a valve issue , at least that is what i would be looking at judging by the backfiring thru the intake every time it tries to fire

    Have you verified that the flywheel key has not sheared ?
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • this ole man
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    Joined: Mon Nov 18, 2013 4:58 pm

    by this ole man » Wed Nov 20, 2013 1:58 pm

    I guess I assumed that if I had good compression the cylinder and head sealing would most likely be adequate, I have contemplated removing the decompression from the picture and performing a full compression check.
    As far as the timing goes I have checked the 2nd timing mark on the flywheel when lined up with mating mark against a rod on top of the piston with an indicator showing top dead center at top of stroke I assumed this would be an accurate way of determining TDC timing.
    Further ensuring proper timing.
    I am thinking similar to you in that maybe it's timing or cylinder valve issues.

    Thank you for your input, I appreciate it very much, if you have any other input it is always welcome. Thanks again.
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    JimDirt
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    by JimDirt » Wed Nov 20, 2013 3:08 pm

    Like i mentioned before , if you have access to a Leak Down Tester , it would give you more info than a compression tester , the compression tester will not tell you where the issue is IF its a valve train issue , the Leak Down Tester will , basically the engine will be at TDC compression stroke , and you basically put 100 psi into the cylinder (via the spark plug hole just like the comp tester ,except without rotating the motor) , if there is a bent valve , air will leak in the direction of the carb and you will hear the air escaping there , same goes for rings (you will hear it inside the engine if you remove a Oil filler plug) , if its exhaust valve it will come out the pipe , if its a blown head gasket it can even blow air into the radiator and you will have bubbles in the radiator when you remove the cap , its fool proof testing procedure if there is a issue

    You have to eliminate everything , including the kill switch ,

    It needs fuel (is the plug damp but not wet ? ,

    It needs air (make sure the Hot Start in the carb is not stuck (make sure the lever moves freely and it snaps back when you release it , make sure it has tension on the lever (it should be about like the clutch lever is)

    It needs compression (make sure with a leak down tester that air is not escaping causing a change in fuel mixture and lack of compression)

    It needs spark (make sure the plug is firing under load *if you pull the plug directly after trying to fire it , and its saturated in gas , then i might either be too rich or weak spark
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • this ole man
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    Joined: Mon Nov 18, 2013 4:58 pm

    by this ole man » Wed Nov 20, 2013 3:50 pm

    Great feedback, I do have access to a leakdown tester. I will give that a try next. should I see any leakdown or none at all, what is acceptable?

    I have disconnected the kill switch and still no luck starting.

    I haven't checked the hot start, but I will set up according to manual. and check as you say. It does operate freely and does snap back when released quickly.

    I had previously checked the spark intensity with an adjustable gap spark tester.I was able to jump the gap at 8mm (.320").So I figured that the spark was nice and strong. Not completely sure it's firing in the cylinder.
    I don't remember seeing the spark plug being soaken wet, it was wet but not severely when pulled after trying to start.

    This is excellent feedback and helps tremendously. Thanks Jim Dirt.
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    124
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    by 124 » Mon Nov 25, 2013 5:49 am

    less than 8% is acceptable. 5-6% is good. >10% is poop.

    Did you check the sparkplug against the cylinder when you did the gap test?
    70' Honda CT70 (Trail 70; Gold)
    16' KX450
    16' KX85
    12' YZ125
  • this ole man
    Posts: 7
    Joined: Mon Nov 18, 2013 4:58 pm

    by this ole man » Mon Nov 25, 2013 4:32 pm

    I did try the plug grounded. it does spark, it appears to be adequate, but wasn't sure it was firing in the cylinder. That was why I checked with the spark tester.
    I borrowed a leak down tester from a friend at work,will test it this weekend. I hope this uncovers something.

    Thanks again,124
  • Spr crf
    Posts: 1
    Joined: Sun Mar 11, 2018 10:45 am

    Re: 04 CRF450r won't start

    by Spr crf » Tue Mar 20, 2018 11:19 pm

    ĺhi did you ever get to solve the problem
    I 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.
    Hi did you ever solve this problem as I have the same problem with mine but with no head work done
    Thanks Steve
  • User avatar
    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: 04 CRF450r won't start

    by JimDirt » Wed Mar 21, 2018 6:29 pm

    ĺhi did you ever get to solve the problem
    I 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.
    Hi did you ever solve this problem as I have the same problem with mine but with no head work done
    Thanks Steve
    Welcome to the site !! \:D/

    Can you give some specifics as to what took place (did the bike run fine , then suddenly not start ?? , etc)

    Generally your bike needs 3 things to run , FRESH (any gas over 3 months old should go in your Lawn Mower not your dirt bike) Premium gas ... Air , and Spark , with those 3 things (as long as the timing is on and the valves are within spec) the bike should run

    Can you give some specifics to what the events were that led up to it not running ?? (along with a time frame , like , did the bike sit for 3 or more months with the same gas ? , then it would not run , or you were riding and it quit and would not re-start , ?? etc..)
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • Tmbr
    Posts: 2
    Joined: Sat Apr 18, 2020 6:13 am

    Re: 04 CRF450r won't start

    by Tmbr » Sat Apr 18, 2020 6:18 am

    If the engine had issues and the previous owner had to repair the head, it is possible that the cam gear spun when the piston hit the valves so when you time it, the timing is actually off still. I struggled with this issue for weeks broke down and got a new cam. Fired up first kick.
    Good luck

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