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XJ500 "Cafe" Build story :)

Discussion in 'XJ Modifications' started by zburke11, Feb 16, 2019.

  1. zburke11

    zburke11 Member

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    Good to know! Which model or year 750? I have a place over here in europe I can order them from for about the same price. Just want to make sure it's the same thing as what you are talking about.
     
  2. zburke11

    zburke11 Member

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    these are the two different coils I'm coming across for cb750's they have a crazy amount of models but all have one of these two it looks like. the site is wemoto.com
     

    Attached Files:

  3. Polock

    Polock Well-Known Member

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    electrically the honda coils are the same as yours, you want the mounting holes to be the same, horizontal / vertical
     
  4. Jetfixer

    Jetfixer Well-Known Member

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    Cycle Recycle part 2 sells these a kit these fit yamaha,honda,Kawasaki, but 80 to 83 are the ones to obtain , these have replaceable plug wires I have ran them for 3 years now runs great. If your in Europe realize shipping might be pricey . If your in the UK sure there are breakers that would have the coils.
     
  5. zburke11

    zburke11 Member

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    Ok guys, so today I got the Honda cb 750 coils in. The ones with replaceable cables. So I clipped the original connectors off the old coils to connect to the new ones. The the new ones had + and - posts. So I checked the voltage from the connector on the harness to make sure I got the positive and negative correct. Hooked them up. The ignition coil I had on the right side sparked just fine. The one on the left one would spark really strong, and the other not at all. So I took the one that had both sparking and hooked it up to the same connector that only had the one to see if it was something with the connection. Both still sparked. So I went and checked the resistances like I've seen in a few videos and read about. I've attached the pics.

    On 200 ohms the connectors on both read 2.5
    On 200k ohms putting both tester ends into the two spark plug caps, both coils read 24.6

    I even swapped the cable out with the one side of the coil that wasn't sparking and still nothing. So I don't think it's the cable. It's not the cap, because I swapped that too. No matter what I did that one side of the coil just wouldn't spark.

    Things to note. That coil also was warm to the touch after the first time trying to check for spark. The one that had both sparking was not. Also the one that only had one cable sparking was an extremely strong spark and after I would depress the start button after a few seconds it would let off a spark. I got shocked a couple times.

    Again this is all new stuff to me, so I'm trying to figure out some on my own, but legit have no clue about this kind of stuff. Is the coil just a bad one? Did I fry it somehow? Wouldn't the resistances be different if something was wrong internally with the coil? YpmgGiL0QCOrqfZbdyK1+w.jpg WYxBsgYBRwyJHGjF0me8Sw.jpg rV9C0nA3ScmR6bTyIx%a5g.jpg 9CfjwvYdTKiVygrseYhlZA.jpg
     
  6. Polock

    Polock Well-Known Member

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    https://www.hondatwins.net/forums/a...w-coil-works-dual-fire-ignition-coil_fig1.jpg
    swap the sparkplugs, it could be a bad plug.
    they can measure good with a meter but n0t work because a meter uses a little battery and when it's on the bike there's thousands of volts.
    if there's not enough insulation someplace inside the coil, the high voltage will jump it but the meter battery can't so it looks good to the meter.
    measure from the + and - to the mounting bars on the coil, should not be any connection
     
  7. zburke11

    zburke11 Member

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    So good news. They sent me a new coil just the other day. Put it on today, checked all the plugs and they all spark. So I put the tank back on and flipped the lever to prime, waited for fuel to stop flowing and then tried to fire it up. Nothing. Which I expected so then I used some starter spray, it got a few pops out of the exhaust, but also a few other pops that sounded more towards the engine. Also... occasionally when I would let off the starter button, I think I heard a small spark somewhere? Could that be a short somewhere? I took the voltmeter and put the negative on the battery negative and then was touching random spots on the bike. Some parts of the frame would give a .01 reading. Also the positive cable to the battery was super warm for some reason.

    So a couple questions. I'm guessing everywhere on the bike should read 0 on the voltmeter correct? Also any reasons why the positive cable would be warm?

    and super important, and probably stupid question. Do the spark plug cables need to be put on a certain order on the cylinders? I know sitting on the bike from left to right it's 1-4. From the parts list pictures it looks like the left coil should go to 1 and 4 and the right coil should go to 2 and 3. But even with that are out of those two for each do they need to be specific? like looking at the coil which goes on 1 and which goes on 4? and same with the second coil.

    Thanks again for all the help so far!
     
  8. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    The ignitionis a wasted-spark system. 1 and 4 are a pair and fire both plugs at the same time, twice per revolution. 2 and 3 are a pair and fire both plugs at the same time, twice per revolution.
     
  9. a100man

    a100man Well-Known Member

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    0.01 = 10mV = negligible.
     
  10. zburke11

    zburke11 Member

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    Thanks for the help guys! Went back out and realized I had them switched up. Got them on the correct plugs and coils and with some spray started up and ran. Sadly had to keep the choke pretty open or it would die off, so it seems I'll need to pull the carbs off again and check them for different things and check levels again. It has sat for 2 months while I was waiting on parts so who knows.
     
  11. a100man

    a100man Well-Known Member

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    The pilot circuit is easily blocked on these carbs - you need to get cleaner squirting you in the eye from the holes in the 'roof' of the venturi.
     
  12. zburke11

    zburke11 Member

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    Update! So I cleaned the carbs, got everything back on, checked levels and things also. All were in tolerance. Bike fired up, even sounded good. Took it out for about 2 miles and seemed good. Then took it for a little longer maybe 5 miles. Let it sit for a couple hours, and started up again just to move it and it seemed good. Let it sit a couple more ours, then went to start it up to drive home, and it sounded really rough. With the choke open it wouldn't really do anything until it sat for a little bit, then it would rev up like the choke was open. I was able to drive it back home the 5ish miles, but it was a struggle.

    So here are some things I noticed. If I have the petcock set to "run" it will work for about 30 seconds or so, then fuel will stop flowing.... I've replaced the diaphragm on it already, and also checked for leaks around the intake boots and found nothing. Also checked to make the vacuum hose isn't blocked. When I stop the bike, I usually put it to "run" just to make sure it isn't just flowing fuel into the engine freely, but seems like everytime I go back to it and flip it to "prime" some fuel flows into the carbs. I'm guessing I need to just set all the floats at -2mm just to be safe they don't over flow or something...

    Also I put an inline fuel filter on the bike while doing this whole rebuild, because there was a crappy one on it when I bought it. Could it be the filter is causing problems with the vacuum? Like maybe it is pulling the diaphragm out enough but with the filter there its not strong enough? I don't know I'm just kinda shooting around.

    The fact the bike ran awesome for a bit and then suddenly is running rough makes me think it has to be something with the carbs overflowing again and causing problems. Also... if they are overflowing into the crankcase... how big of a deal is it if some fuel is in the oil? Maybe thats a stupid question haha, but I might as well ask it instead of just assuming something. Thanks again guys. I should have recorded it when it was working well so you could hear it :)
     
  13. zburke11

    zburke11 Member

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    Ok, just a small update. Went back out to the bike and it wouldn't start up. Pulled the plugs, some were a little wet looking... Pulled off the carbs to check levels... 1 is at like +2mm, and the rest are all like -4mm... Is there something that happens that causes the floats to change? I haven't messed with adjusting them since I got them all about -2mm and one was right at the lvl. So now they are off.. and I wouldn't be surprised if the +2mm decides to overflow sometimes...

    IMPORTANT QUESTION. When I adjust floats, should I adjust one, then check them all? Or adjust them all and then check? Does the adjustment of one affect the other 3? Like if I adjust the one that is +2 to like 0, will it raise the others?
     
    Last edited: Sep 1, 2019
  14. XJ550H

    XJ550H Well-Known Member Premium Member

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    each carb works independantly from the other with the fuel level. are you saying your fuel level is even with carb/bowl joint (+2mm)
    fuel level.PNG in this photo 3mm is spec
    i do not know what the specs are for a 500
    xj550
    -Fuel level measured via the clear-tube gauge: 2mm +/- 1mm
    thats 2 mm below carb/bowl joint.

    make sure your carbs are level front to back and side to side. you can test this by using the tube and checking its "fuel level" to measure carb1 and 4 from same carb
    just like a carpenters water level. also check front and back of carb.



    Setting the fuel levels
     
  15. XJ550H

    XJ550H Well-Known Member Premium Member

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    plugs being wet after trying to start and failing to start is normal. I would look at ignition system and do a voltage drop test on battery when cranking starter.
    no less that 10 volts when cranking.
    my 550s are very fussy about the battery voltage when starting cold

    it is easier for me to set level of fuel on 1 carb at a time get it in spec and then set the next carb.
     
  16. zburke11

    zburke11 Member

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    Ok thanks so much for this info! I have been using my iPhone lvl to make sure carbs are level all around before checking the few levels. I always thought +2 meant 2mm above where the carb bowl meets the body. So really they should all be 2 below where the bowl meets the body?

    Mine are all like 4 below and then one is 1-2mm above that line. I guess I was just confused about what the +and - meant when measuring. I'll mess with them some more in a couple days. Thanks again!
     
  17. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    2mm below the join line +/- 1mm. This means that the fuel level can be anywhere between 1mm below the join and 3mm below for it to be in spec.

    Setting the fuel levels
     
  18. zburke11

    zburke11 Member

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    Hey guys... so I guess I only write when something goes wrong... That's too bad.

    So I did everything we've been talking about. Carbs were leveled correctly. Replaced the coil that I thought was just a bad coil. Everything worked awesome. Sounded great. Started up. Took it out for a few short drives 20 and 30 minutes. Ran wonderful. I even took a video to show you guys how it sounds, just never posted it.

    The bad news... as I was driving home, and I was about a half mile away, the engine sound changed completely, and I had to give it a lot of gas or it would just die immediately. So when I got to the garage I hopped off just to look, and one of my pod filters had fallen off (because I never tightened it I realized). So, I thought perhaps it was something with that carb. I pulled them off today cleaned it out, but it didn't have anything noticeable anyway. Put them back on. Started up with spray but sounded the same as before. I checked for spark, and both inner spark plugs weren't sparking. I immediately felt the coil powering those two, since I had a problem before, and it was warm... Did the same tests as before, swapping spark plugs, switching connectors, etc... no spark. So something went wrong with the coil. No idea how or why.

    What are your thoughts? It ran several days no problem, and then in the middle of a drive it just stops working? Everyone said the cb750 coils work with it, and the seemed to be. Maybe where I have the positive and negative wires that hook into the harness somehow touched the frame? I tried to wrap them in electrical tape so they wouldn't touch the frame. I'd hate to have to buy 2 more yamaha coils since they are about $110 a piece, but if it's an issue having the cb750 I don't want to keep putting out for them either...
     
  19. zburke11

    zburke11 Member

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    Also... it seems both of those spark plug openings are stripped on the frame now? No idea why. One I knew happened before I got the bike running well, so I would just tighten it with my hand until it was tight and it ran with that. But today when I checked the other one it also just kept turning. Perhaps that is why something happened with the coil?

    Has anyone ever rethreaded a spark plug socket on their bike? I've seen videos about kits and that it's possible. Just not sure.
     
  20. sybe

    sybe Active Member

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    To re-thread the spark plugs holes you have to pull the head off, so you might as well just replace it. if the coils are under warranty send them back. Check the connectors from the TCI to the coils and make sure they didn't come loose. If you didn't already try swapping the connectors from the TCI to coils to make sure its a bad coil vs bad TCI.
     

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