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Thread: 500 motor hard starts

  1. #1
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    500 motor hard starts

    I realize this is a bike motor but its in an ATC frame so i figure trikesylvania is fine for this post. if not please move it, i just need some help here. I have had this motor in my ATC500 project running and riding around tuesday night. Ran great! was able to pull start the bike and make it run too, fires up quick. Yesterday I go to kick it over and it wont start for anything. I kick and kick and kick. I got the trick down finally too with where to kick it the hardest. Anyways, last night after pulling the reeds for inspection and rebuilding the carb again it will fire up for just over one second and then die. Like it runs on its own and then dies quickly. I gapped the stator and pick up coil to 8 thousandths, pulled the plug to check spark 3 times, said a few prayers. nothing Starting to get frustrated, I was able to kick it over tuesday night after I got the trick down for kicking it; rode it around tuesday night a little bit and was able to fire it over first kick after that on tuesday. Yesterday i go to start it up and nothing. after tinkering for 2 hours it starts for like 20 rotations of firing on its own (about one second) and dies right away.



    88 motor with decomp head
    39pwk with 55 pilot and 175 main and dgn needle, middle clip on needle. airscrew was a 1.5 turns but ran it in to 1/4 turn out right now for starting.
    40:1 klotz premix, 93+ octane
    br8es plug at .020
    500 ft elevation

    what would cause this to fire over and then die right away?
    TrikeFest 07,08,09,10,11,12,13,14 SandPuppie's Ride 07,08,09 Imperial Invasion 09, 13

  2. #2
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    You said you got it running and it ran fine, then the next morning it started on the first kick. If it was running good one day then the next it won't fire up it sounds like an issue with the ignition system. If it was a fuel problem it probably would not have run good the day earlier. I could be wrong but that is my guess

  3. #3
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    ya im baffled. I pull the plug out and flip the motor with the kicker and it makes a nice blue spark when i spin the motor as fast as I kick it. I just dont get why it will fire over and run for a solid second and shut right off. no sense i tell ya!
    TrikeFest 07,08,09,10,11,12,13,14 SandPuppie's Ride 07,08,09 Imperial Invasion 09, 13

  4. #4
    Dave8338's Avatar
    Dave8338 is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    Plugged passage in the idle circuit? If it were a coil issue, it should take longer than 20sec for the problem to show up and then wouldn't create spark until the coil cooled down again.

    Have you traced your fuel system all the way from the petcock and through the carb? My thought is that it may just be the float is either stuck in the up position OR possibly in upside down. I've done it myself so I know it can happen.

    Is there a drain screw on the float bowl? If so, pull the screw and see what if anything runs out. Other than that or an inline filter in backwards, it sure sounds fuel related to me.
    The Goal... All I Need Is The Time...

  5. #5
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    check the decomp thing on the head too... maybe do a compression test... something could be sticking or keeping it open after your first few rides
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  6. #6
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    would the coil be hot after it ran if it was bad? like real hot?

    I am considering looking at the woodruff key now; several people suggested that. now i need to source a flywheel puller
    TrikeFest 07,08,09,10,11,12,13,14 SandPuppie's Ride 07,08,09 Imperial Invasion 09, 13

  7. #7
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    Quote Originally Posted by LastFoolerInVA View Post
    check the decomp thing on the head too... maybe do a compression test... something could be sticking or keeping it open after your first few rides
    even after a SOLID kick and good rotation of the motor it shuts itself and i have to reach down to open it again before another kick. This bike has some serious compression to it as well, i can barely roll it over without the decomp on.
    TrikeFest 07,08,09,10,11,12,13,14 SandPuppie's Ride 07,08,09 Imperial Invasion 09, 13

  8. #8
    Dave8338's Avatar
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    Quote Originally Posted by JasonB View Post
    would the coil be hot after it ran if it was bad? like real hot?

    I am considering looking at the woodruff key now; several people suggested that. now i need to source a flywheel puller
    Jason... the coil should not get HOT. It may be slightly warm to the touch but NOT hot.
    The Goal... All I Need Is The Time...

  9. #9
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    i havent felt it to know if its warm/hot. I assumed it would be warm from use, but i havent touched it or anything so far to know if its malfunctioning lol

    Petcock is flowing great, tank lid is not clogged at all, tank is now full of 40:1. I swapped back over to a 45 pilot from the 55 per the people on cr500 websites suggestions. I am planning to pick up a flywheel puller tomorrow from a local shop to check the woodruff key next. Tonight i am setting the float level in the carb to make sure that's not the issue im having here. Really odd!

    I got it to fire up on my lunch break for about 2 seconds multiple times. I mean i kick it just right and it will fire up and right back off. Like it wants to run but its not getting spark or fuel just right to keep it going. I think I can rule out spark, i have tested that 3 times. Maybe just the timing if the key is sheared on the flywheel, or maybe the float flange is bent and its only letting enough fuel in to start the bike not keep it running. GRRRRRRRRRRRR
    TrikeFest 07,08,09,10,11,12,13,14 SandPuppie's Ride 07,08,09 Imperial Invasion 09, 13

  10. #10
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    Hekllo JasonB


    You have lot's of good input so far.


    I apologize in advance if these questions seem dumb because I realize you already know a bit about bikes. 500’s are ”bleepin” finicky. You can try the following.

    Do you leave the gas on after riding? The float might be high or the needle/seat might weep slowly filling engine after a while and subsequently flooding it.

    INSPECT CARB BOWL GAS - Drain float bowl as dave8338 suggested but drain it into a narrow clear glass. What color is the gas, any sediment, is there a small clear bubble in the bottom of the glass? You can get sediment and water from the gas at the station.

    GAS LEVEL TEST – Take a clear 10” plastic tube, connect it to the bottom of bowl drain. Hold it next to carb with open end even with carb top. Open drain valve. Gas level should be from even with bottom edge of carb body to 1/8” below it.

    PRELIMINARY TIMING CHECK – Even it does not run you can hook a timing lite to it check timing. Mark the flywheel timing mark and the timing mark on eng case with white out. This makes marks highly visible. Remove spark plug and ground it somewhere. Some victim kicks it over while some lucky person gets to hold the button down on the lite and check the timing. Do this in a dimly lit area. Obviously if it’s on the mark your flywheel did not spin on the crank so that’s ok but retighten nut anyway.

    COIL AND STATOR CHECK – Ohm coil and stator per manual. See manual link below. If they ohm in range then they are 99% going to be good. If it’s the 500 cc stator then the stator spec should be near the same.

    http://www.kb0nly.info/ATC/index.php?dir=ATC250R%2F

    STATOR VOLTAGE OUTPUT – Put volt meter on 50, disconnect stator wire, connect red lead to stator and ground the black lead to eng. If stator has 2 wires connect one lead to one wire and the other lead to the other. Voltage should be 30 – 50 while kicking. A digital volt meter that has a peak reading setting is best otherwise it may or may not work. Watch meter while kicking if it does not have this feature.

    SPARK PLUG COLOR – It should be a strong pale to bright blue as it is now on that set up. Check it AFTER trying to start it.

    PLUG WET OR DRY - Remove after kicking 4 times and see if it is bone dry, damp or dripping wet. Bone dry speaks for itself.

    IGNITION PARTS – What exactly is the CDI, Coil and stator off of?

    HOT COIL – Try your other bike and see how hot it gets then compare it to your other bike[unless this is your other bike, lol]. It MAY be remotely possible the stator in the 500 eng is putting out too much voltage for your system therefore causing you coil to get hot. I actually don’t know if this is possible with your particular system, perhaps someone else will. Guessing won’t help.

    COMPRESSION RELEASE - Does your compression release take a cable or is it designed to be manually operated? If it’s factory or your compression is higher than stock then it MUST work properly to start this pig. If it is closing while you are kicking it, it will likely never start.

    COMPRESSION TEST – Do one if you want as lastfooler in VA suggested, but it has no effect on your problem [providing your compression release is working properly] since it ran fine once already but it won’t hurt to know what it is. You might need race gas to reduce detonation potential if you don’t use it already.

  11. #11
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    Quote Originally Posted by barnett468 View Post
    Hekllo JasonB


    You have lot's of good input so far.


    I apologize in advance if these questions seem dumb because I realize you already know a bit about bikes. 500’s are ”bleepin” finicky. You can try the following.

    Do you leave the gas on after riding? The float might be high or the needle/seat might weep slowly filling engine after a while and subsequently flooding it.

    INSPECT CARB BOWL GAS - Drain float bowl as dave8338 suggested but drain it into a narrow clear glass. What color is the gas, any sediment, is there a small clear bubble in the bottom of the glass? You can get sediment and water from the gas at the station.

    GAS LEVEL TEST – Take a clear 10” plastic tube, connect it to the bottom of bowl drain. Hold it next to carb with open end even with carb top. Open drain valve. Gas level should be from even with bottom edge of carb body to 1/8” below it.

    PRELIMINARY TIMING CHECK – Even it does not run you can hook a timing lite to it check timing. Mark the flywheel timing mark and the timing mark on eng case with white out. This makes marks highly visible. Remove spark plug and ground it somewhere. Some victim kicks it over while some lucky person gets to hold the button down on the lite and check the timing. Do this in a dimly lit area. Obviously if it’s on the mark your flywheel did not spin on the crank so that’s ok but retighten nut anyway.

    COIL AND STATOR CHECK – Ohm coil and stator per manual. See manual link below. If they ohm in range then they are 99% going to be good. If it’s the 500 cc stator then the stator spec should be near the same.

    http://www.kb0nly.info/ATC/index.php?dir=ATC250R%2F

    STATOR VOLTAGE OUTPUT – Put volt meter on 50, disconnect stator wire, connect red lead to stator and ground the black lead to eng. If stator has 2 wires connect one lead to one wire and the other lead to the other. Voltage should be 30 – 50 while kicking. A digital volt meter that has a peak reading setting is best otherwise it may or may not work. Watch meter while kicking if it does not have this feature.

    SPARK PLUG COLOR – It should be a strong pale to bright blue as it is now on that set up. Check it AFTER trying to start it.

    PLUG WET OR DRY - Remove after kicking 4 times and see if it is bone dry, damp or dripping wet. Bone dry speaks for itself.

    IGNITION PARTS – What exactly is the CDI, Coil and stator off of?

    HOT COIL – Try your other bike and see how hot it gets then compare it to your other bike[unless this is your other bike, lol]. It MAY be remotely possible the stator in the 500 eng is putting out too much voltage for your system therefore causing you coil to get hot. I actually don’t know if this is possible with your particular system, perhaps someone else will. Guessing won’t help.

    COMPRESSION RELEASE - Does your compression release take a cable or is it designed to be manually operated? If it’s factory or your compression is higher than stock then it MUST work properly to start this pig. If it is closing while you are kicking it, it will likely never start.

    COMPRESSION TEST – Do one if you want as lastfooler in VA suggested, but it has no effect on your problem [providing your compression release is working properly] since it ran fine once already but it won’t hurt to know what it is. You might need race gas to reduce detonation potential if you don’t use it already.

    First off thanks for the lengthy response! Wish more people had this volume of input lmao! OK first things first. I usually shut the petcock when done riding, but this bike hasn’t been out really so far since i put the motor in the frame 3 or so weeks ago. I have had the carb off just over a dozen times as of my lunch break today, I keep pulling pilot jets and playing with the floats. I will get the float level correct tonight I just learned online how to set it! Seems easy enough. But the fuel is clean and i do run an inline filter. I removed it Tuesday night to eliminate it as a blockage. Gas has come out clean and clear every time though. Gas flow freely cfrom the carb to; I tip the bike over to let a little gas flow out the overflow lines before trying to start; its part of the procedure outlined everywhere by cr5 riders.

    Timing is on my list for tomorrow night; if a fresh plug doesn’t fix this tonight than I plan to grab a flywheel puller tomorrow and check the woodruff key isn’t sheared etc and check timing too. I will also check specs on the cdi and coil tomorrow.

    Spark plug doesn’t really have a color to it yet lol, bike has been around the neighborhood twice now and shut off. I don’t think it has a consecutive 5 minutes of run time yet in my hands. Plug still looks new! I am replacing it tonight as someone suggested it may be bad. It has been consistently wet though so I know gas is flowing.

    All ignition parts on this bike belonged to the cr500 dirtbike that was torn apart for this build.

    Coil wasn’t hot, It was mentioned and I don’t know if its an item that gets warm or hot lol or anything.

    Compression release is manual, I have to reach down to open it. As soon as the bike kicks over and gets any kind of fire, even a solid kick that should have made it fire up, the valve closes itself. When the bike has started in the past it has shut itself too. I reached down to play with it after getting the bike started the first time and it makes farting noises but takes a little bit of pressure to keep it open while the motor is firing normally so it is working right.

    Head has a custom cut squish band to raise compression and allow me to run 93 octane. I just put 3 gallons of 93 in the tank on my lunch break at 40:1 klotz techniplate. I have been kicking it with the left over race gas 110 mix from the 310 that was in the tank from the last ride a few weeks ago.

    I am hoping that a fresh plug will do the trick now, start cheap and smiple I guess!
    TrikeFest 07,08,09,10,11,12,13,14 SandPuppie's Ride 07,08,09 Imperial Invasion 09, 13

  12. #12
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    Hello JasonB


    Quote Originally Posted by JasonB View Post
    First oFirst off thanks for the lengthy response! Wish more people had this volume of input lmao!
    Thanks for the compliment but you’ve seen my posts before another similar one shouldn’t surprise you, lol.



    I raced big bore pigs in MX for many years including the second hardest bike in the world to start which is a 450 Maico. My friends 501 “square” bore might have been a bit harder, lol.

    I just have a minute so this may be sloppy.



    SPARK PLUG – Yes a new one is a good idea, if you are running a fancy narrow electrode one I would buy a regular electrode one too and try that. If you are running a 9 buy an 8 but not in Champion. It will start easier for now. Once it's running you may need a 9 if your compression is too high and/or you ride it where it is over 70 degrees outside etc. Big bores do NOT like to start with a 9, lol.

    TIMING - Check the timing with lite irregardless but again I would do this first. Why pull the flywheel if you do not need to.

    COMPRESSION RELEASE – Original or no. On an original one or on a big bore with high compression it is common to run the bike for a few seconds with it OPEN. If it is closing half way thru the stroke or right after it fires it is not functioning the way one should and is either faulty or a less than practical design.

    COIL HEAT – Yes dave already answered that. It should get fairly warm at best but the engine heat may heat it above it’s normal operating level while riding, giving you a “false” reading.

    GAS LEVEL IN FLOAT BOWL – The ONLY way to know positively 100% guaranteed whether your float/gas level is correct is to do the test I mentioned. I can’t stress the importance of this enough.

    KICK 4 TIMES AND CHECK PLUG – I also can’t stress the importance of doing this enough. Try it before and after checking timing.

    TIPPING BIKE TO START – I would NOT do that in your case. It’s a long explanation. I don’t care what the cr5 guys say at the moment. It depends on the set up, even if it is ultimately helpful to use this technique on yours [which I think is highly unlikely] don’t you think it is prudent and practical to eliminate the possibility that you are simply flooding your engine doing this and that’s why it won’t start? You yourself said that every time you pull your plug out it is wet. If it is wet after only 4 kicks you certainly don’t need to flood it with more gas. There is a rhyme and reason [sometimes, lol] I do things the way I do.

  13. #13
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    Did I mention, factory big bores are pigs, yes PIGS...LOL?

  14. #14
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    One way I’ve found to check ignition problems when the carb is unproven is to run it on WD-40.

    Pull the air filter, open the throttle and give it decent shot of WD and kick it, should fire right up. You can work the choke and try to keep it running on the carb, but if it won’t run on its own have a buddy on hand to give it a little more WD-40 once it fires and if all is well electrically it should keep running on a little spray and you will have eliminated an electrical problem.

    If it runs on WD-40 you need to take a good look at that carb and beside that float height make sure that all your vent lines are open.

  15. #15
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    Hello JasonB


    We used to sit on the starting line and when we got the 2 minute sign, TRY and start our bikes. Most would start, but there was ALWAYS at least 1 guy whose PIG wouldn’t start so one of us would help him push it or change the plug and go back to our bike, then someone else’s PIG would die and had to be pushed etc. This went on EVERY start of every race without fail, lol. PIG’S.

    If you watch an old 2 stroke big bore AMA National or World Championship MX race on youtube, you will see many mechanics starting the PIG'S for the riders so the rider wouldn’t get tired or hurt trying to start his PIG. I saw a PIG actually snap a guy’s ankle when it kicked back on him.

    Oh I like PIG’S, they’re fast and fun if you can get one started and not be to tired or ambulatory to ride it afterwards, lol. P...I...G...S

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