1. Some members were not receiving emails sent from XJbikes.com. For example: "Forgot your password?" function to reset your password would not send email to some members. I believe this has been resolved now. Please use "Contact Us" form (see page footer link) if you still have email issues. SnoSheriff

    Hello Guest. You have limited privileges and you can't "SEARCH" the forums. Please "Log In" or "Sign Up" for additional functionality. Click HERE to proceed.

**UPDATE** My Seca Woes :( Need Advice guys.

Discussion in 'XJ Technical Chat' started by KrS14, Aug 17, 2010.

  1. Ground-Hugger

    Ground-Hugger Member

    Messages:
    801
    Likes Received:
    0
    Trophy Points:
    16
    Location:
    Near Port Dover Ontario
    "However, contaminate the plug with fuel (even just a little) and a high value resistor will cause the plug not to fire. 10K plugs as are used on some motorcycles now are about maximum I would guess." He is guessing.
    I'm also in Electrical Engineering and his test are not done in actual operating conditions. In the air or on bike on a road.

    Weaker sparks foul easy thats why we don't run them in our bikes, they are not designed to run with them. Easy fouling results in engine misfire, poor gas mileage, not starting and so on. If you want your bike to run right either get rid of the resistive plugs or the resistive caps. But the bottom line is you have to ADD the resistance of the plug to the equation if you don't you just fooling yourself into thinking everything is to spec when its not. Check with chacal on this matter.
     
  2. KrS14

    KrS14 Active Member

    Messages:
    1,642
    Likes Received:
    9
    Trophy Points:
    38
    Location:
    St Marys, Ontario
    Ya i hear what yer saying, i guess the issue i've always had with it, think of the resistance of the air gap... plus the V the coils produce (it's what 20-40KV)

    In the grand scheme of things, an extra 5kohms shouldn't matter when we're talking about multiple Mohms on air.

    I definitely do agree with the fact that fouling can suppress spark tho.

    I'll have 12 new plugs to play with after today tho lol so i'll get it figured out.
     
  3. Ground-Hugger

    Ground-Hugger Member

    Messages:
    801
    Likes Received:
    0
    Trophy Points:
    16
    Location:
    Near Port Dover Ontario
    Well I have learned the hard way with these bikes is that it takes very little to stop them from running. The coils don't put out as much of a spark as do the older cars/trucks which used a coil for spark. As a result fouling occurs very easily. That is why it is so important you get the air fuel mixture just so. I had the same problem you are having. I checked my coils and they where border line so I said the h*ll with it and replaced everything coils wires, plugs and caps best move I made, everything just fell in place after that.
    My next move is to install E3 plugs on the bike. They ignite faster then a regular plug and have a larger spark which results in burning more of the fuel that is in the combustion chamber. The result is less gas used and a little more power. I'm running them in my 03 Grand Am and it has made a world of difference. She seems to accelerate better, but the big difference is gas mileage. Big improvement. They are resistor plugs so when I get them I'm going to try them with and with out the caps. They do make E3 plugs for the XJ750.
    A question for you how is the Royal Purple working for you? And where did you get it? How much is it?
    And let me know how things work out. I really want to know.
     
  4. waldo

    waldo Member

    Messages:
    871
    Likes Received:
    1
    Trophy Points:
    18
    Location:
    San Jose, Ca. 95125
    Your comment, on the things I was trying to point out to you was,"@Waldo, thanks for your input but theres this: Posts: 667 under my name the common stuff has all been done, of course new plugs are in it. "
    Really . Your right you do ask allot of questions. Anyhow read Lens bible on carbs lots of info pay particular attention to the section on jetting when you do mods Ol Supertrap. By the way what color are your exhaust pipes where they exit the head kind of blue maybe? As far as having too much resistance not affecting spark as I remember it those things are proportional. That means if one goes up ( that would be the resistance) the other goes down (that would be the amperage) more amps = ________you can fill in the blank. The coil voltage pretty much stays the same its determined by the primary Maybe Ground Hugger could put some real numbers to it so we can see how much difference it really makes. Whats the formula I=E/C or something like that.
     
  5. waldo

    waldo Member

    Messages:
    871
    Likes Received:
    1
    Trophy Points:
    18
    Location:
    San Jose, Ca. 95125
    Now I have 5 posts how many more till i become a RED LINER like you. Just bustin your chops good luck .
     
  6. Polock

    Polock Well-Known Member

    Messages:
    9,751
    Likes Received:
    2,097
    Trophy Points:
    113
    Location:
    Beaver Falls, PA
    waldo, a few things in there just don't fly, the supertrapp doesn't count in chacals formula because the restriction is variable by the # of disks
    the idea is the same but not the #'s. exhaust pipe color don't count because 1, stock pipes are double wall, rarely do they turn blue 2, black pipes don't turn blue, 3 once a pipe is orange/blue from leanness
    all the richness in the world won't make it chrome again
    amperage doesn't make the spark, voltage does
     
  7. waldo

    waldo Member

    Messages:
    871
    Likes Received:
    1
    Trophy Points:
    18
    Location:
    San Jose, Ca. 95125
    Are you sure? Heres my thinking if the pilots have to be turned way out to get a proper idle and everything else is good then it might be that you need to step up the pilot jet but probably not the case here. How does the number of disks in the Supertrap not make it a mod that might need to be accounted for if it does not affect the performance then whats the point of putting it on the bike to begin with? Why does the pipe color not fly its a good indicator that a cylinder is or has run lean and way too hot . Amperage doesnt make spark voltage does. Lets ponder that one take a 12 volt battery say out of an xj fully charged connect wires to the leads now touch the other ends of the wires together it will spark (dont really do this) not take the battery from say a car, again 12volts do the same thing with the wires which one had the best spark? Thats the way im thinking maybe im wrong.
     
  8. KrS14

    KrS14 Active Member

    Messages:
    1,642
    Likes Received:
    9
    Trophy Points:
    38
    Location:
    St Marys, Ontario
    The formula is V=IR or better known as this:

    __V__
    I | R

    "V over IR"

    So, if you have 12V lets say, and you have 5Mohms (just pulled a number out of thin air ;) lol With NON resistive caps that means you have 12/5M = 2.4 uA

    Now if you add 5K resistive caps you get this:

    12V/5.005M = 2.397uA

    2.4 ~= 2.397 So basically the resistive caps do nothing to the current that flows, which is VERY small. It just makes the current flow last a touch longer.

    Keep in mind, the resistance value of the air in the gap of a cylinder will be MUCH higher than that, I read somewhere in the ballpark of 4x10 to the 13th ohms. or 40 000 000 000 000 or 4x10E13 Ohms.

    5K won't do jack. The issue i think it that 12V isn't always gunna be 12V.. it can drop to 10V if the bikes electrical system isn't up to snuff. that would be a big issue.
     
  9. KrS14

    KrS14 Active Member

    Messages:
    1,642
    Likes Received:
    9
    Trophy Points:
    38
    Location:
    St Marys, Ontario
    Oh btw, my pipes are a rusted mess lol no chrome left on them.

    EDIT: They're rusted right at the cylinder heads, but the rest of them are painted black, i'm assuming that the Supertrapp headers are black new.

    BUT

    After getting 12 Spark plugs (lol) it's a little easier to see what the mixtures are doing, and i got it sorted out i believe.

    Went for a nice short ride, and she performed great, starts right back up when hot. The next couple days will be the test tho, i THINK i may have a bad choke seal on #4 carb, i'm pretty sure it dumps gas like crazy if it's on, it fouled a brand new plug in 10 seconds or running with choke.

    With choke off it's fine, but the pilots turns from 1-4 are VASTLY different from eachother. Anywhere from 2 to 5 turns out. As long as i get it looking right tho, and it stays that way i'm happy :)

    Starting from cold will be the tell tale over the next few days.
     
  10. KrS14

    KrS14 Active Member

    Messages:
    1,642
    Likes Received:
    9
    Trophy Points:
    38
    Location:
    St Marys, Ontario
    Hey Hugger forgot to comment on the Royal Purple :)

    After a bit of running i actually really noticed a difference on the 400, it shifted smoother, felt like it had a bit more power, generally ran better, AND you can do double the mileage per oil change If you wish.

    It is a bit pricey, i think 12 bux or so a litre. I got mine from Napa, but i'm sure you can get it at other places. I Put it in the 750 too, not sure how it's changed it, cause i never ran it with regular oil at all to compare. But the reason i did that was because of how well it made the 400 run.

    I had a '94 GrandAM SE 4 cyl, that would get 700 km/tank if i really babied it :) I miss that car.

    To bad some ass had to brake late in the winter. ABS don't do shit when there's 4 inches of slush and the sun hasn't hit it yet in the morning :(
     
  11. Polock

    Polock Well-Known Member

    Messages:
    9,751
    Likes Received:
    2,097
    Trophy Points:
    113
    Location:
    Beaver Falls, PA
    waldo, your maken me think now,the idle circuit needing a bigger jet is true IF the pilot air circuit is right
    suppertrapp mufflers are tunable with 1 disk there's so much restriction it probably wouldn't do much more than idle, 12 disks would be about like a open header, or anywhere in between, so to say +2 or +3 jet sizes don't work anymore. a guess is 4 disks and keep the stock jet size
    what your seeing in a small battery and a big battery is the current available once the air is ionized, both batteries start and stop the spark at the same distance BUT in a coil the current and voltage in the secondary is determined by the physical make-up of the coil and the voltage applied to the the primary, so the current available in the primary has no effect on the spark in the secondary, within reason, lets not get into dwell angle
     
  12. Polock

    Polock Well-Known Member

    Messages:
    9,751
    Likes Received:
    2,097
    Trophy Points:
    113
    Location:
    Beaver Falls, PA
    "Why does the pipe color not fly its a good indicator that a cylinder is or has run lean and way too hot "
    what's it matter what happened in the past the here and now is what counts
    what temperature does chrome turn blue ? is that too hot ? is all chrome the same ?
     
  13. RickCoMatic

    RickCoMatic Well-Known Member

    Messages:
    13,843
    Likes Received:
    66
    Trophy Points:
    48
    Location:
    Massachusetts, Billerica
    Take a Jardine System right out of the box.
    Get it on the Bike.
    When you Start the Bike; watch the Pipes.

    They turn blue right before your eyes!
     
  14. padre

    padre Member

    Messages:
    233
    Likes Received:
    0
    Trophy Points:
    16
    Location:
    Lawton, Oklahoma
    Chrome turns blue at about 500* (550 for tripple plated) farenheight, but chrome is also a heat conductor. Many (most stock) systems actually have the pipes insulated with a chrome plated sleeve around the outside. Headers usually don't (except some of the more expensive Harley systems) so stock pipes need to be alot hotter to turn blue than chrome plated than moderately priced (read cheap) racing headers. So they turn blue alot faster, and they allow heat transfer from the exhaust fumes to the ambient atmospheric air temperature so the fumes tend to cool faster becaust the thin chrome plated pipes pass the heat from the flow to the atmosphere through the walls of the pipes it can effect the jetting too. That's why they sell exhaust insulation wrap. It'll actually make the bike run leaner because it slows the transfer of heat it also allows you to run a little bigger jets. Heat means horse power, it can also mean engine detonation. So if you can keep the exhaust hotter on the inside, you can richen the jets and increase the Volumetric efficency at the same time(more bang tor the buck). If you can't afford to put it on a dyno or install an O2 sensors in the exhaust collector with a mointor or gauge, the best ally you have is the combination of a well trained ear, the seat of your pants and color tuning. Chrome be damned! I know the chrome plated pipes look better and cost more but they don't make the bike any faster or quicker than black ones, probably a sliver slower It's Rustoleum BBQ black for me. I'd wrap them but then they'll get too dirty too fast.
     
  15. waldo

    waldo Member

    Messages:
    871
    Likes Received:
    1
    Trophy Points:
    18
    Location:
    San Jose, Ca. 95125
    Glad to hear your bike is starting to run better, no you can start to tune her out. As far as your formula for the coil lets just say the secondary voltage is determined by the primary voltage of the coil that is 12v gets you 20000 volts ( i am not sure what the real voltage is supposed to be so I am just using this as an example) of spark and all is well with this side of the circuit. So for an example lets say that would be a formula of I= E/r I= amps e=voltage and r =resistance so 200000 v / 21000 ohms = 0.95 amps now take 20000 v/ 10000 ohms and that = 2 amps heres the deal no matter what happens on the secondary side of the coil it will still produce the same voltage thats determined in the windings of the coil no ifs ands or buts as long as the input voltage is correct and thats a given . Which reminds me when you tune out your bike make sure the battery has a full charge on it. damhikt Oh air gap ya well that might be the case if you sitting in the garage playing with the spark gap what ever that number was but add 150 psi to your formula and the fact that someone spewed a little octane in there and your air gap resistance dont mean squat . im just sayin. All this reminds me of the banter me and my bud used to do. It would actually cost a beer in the end, of course loser pays. I drink alone.
     
  16. waldo

    waldo Member

    Messages:
    871
    Likes Received:
    1
    Trophy Points:
    18
    Location:
    San Jose, Ca. 95125
    I ride alone Iam just sayin
     
  17. KrS14

    KrS14 Active Member

    Messages:
    1,642
    Likes Received:
    9
    Trophy Points:
    38
    Location:
    St Marys, Ontario
    LOL ya this could be argued at length, and my brain ain't what it used to be :)
     
  18. mdee

    mdee Member

    Messages:
    108
    Likes Received:
    1
    Trophy Points:
    18
    Location:
    Billerica
    The current is the quotient of the resistance and voltage in the circuit.
    Per formula ‘Ohm’s law’ I = V/R
    (Don’t even try to break this law without moving to another Universe)

    If you change either voltage or resistance the current will change per Ohm’s law.
    The voltage out of the coils secondary (to the spark plugs) is high voltage. I don’t know where the exact spec would be found for these XJ’s, but in general, ignition coils put out voltage in the kilovolts. (High voltage is the reason for such thick spark plug wire insulation – the conducting wire is small diameter in relation because the wire carries a small amount of current.) The coils produce that voltage from the 12volts on the primary circuit side (via voltage fly-back, too complex for this discussion).

    Unless you alter the coils internals, you are not going to change the voltage produced by the coils. When you alter the resistance in the circuit you change the amount of current flow thru the circuit. More resistance = less current.

    The Yamaha engineers designed the ignition system to operate most properly at it’s designed specifications. Randomly altering or substituting the components will have consequences. You may guess wrong on what all those consequences might be. When chasing a difficult issue, targeting your actions towards the baseline (factory specs) is a good place to start.

    Put in the spark plugs spec’d for the bike at least until you get the bike running correctly. Then if you what to mess up a good running bike with modifications, you would have a clue as to what went wrong.
     
  19. KrS14

    KrS14 Active Member

    Messages:
    1,642
    Likes Received:
    9
    Trophy Points:
    38
    Location:
    St Marys, Ontario
    Hahahahah, i dunno why i'm so dumb sometimes. I have NO idea why i was using 12V in my equations lol i knew it was prolly around 20KV.

    AND i don't know why i thought my service manual said BPR7ES as plugs to use instead of the actual BP7ES it states.

    Sometimes i have blonde moments lol. Needless to say tho, this winter i'll be doing a FULL and COMPLETE rewire of the entire bike. I feel like it's just absorbing WAY too much voltage in the wiring than it should.
     
  20. waldo

    waldo Member

    Messages:
    871
    Likes Received:
    1
    Trophy Points:
    18
    Location:
    San Jose, Ca. 95125
    Polock are your pipes blue?
    KrS14 good to hear things are starting to come together for you
     
  21. padre

    padre Member

    Messages:
    233
    Likes Received:
    0
    Trophy Points:
    16
    Location:
    Lawton, Oklahoma
    I'm not exactly sure why, but resistor plugs can alter the spark curve, 20,000 volts may be the maximum out put of the coils but if the spark can arc at 10,000 volts, it will. As soon as the spark arcs it shorts out the coils and the magnetic fields of the windings colapse. Usually coils don't opperate at maximum output and if they do they don't last long. The factory put differerent resistors in #1&4 plug wires than in 2&3 for a reason, probably because #2&3 cylinders run a little hotter (leaner) due to having less airflow around the cooling fins and being closer to the air inlet
    . so #1&4 plugs most probably foul quicker without them. If you have access to a scope you'll see that the leaner running cylinders dudally draw more voltage than their cooler running neighbors but gapping the plugs too wide draws an unnessary amount of current through the coils, and I'd most probably upgrade the coils before I would go far from specs.
     
  22. mdee

    mdee Member

    Messages:
    108
    Likes Received:
    1
    Trophy Points:
    18
    Location:
    Billerica
    Padre – Thanks for providing me the clue as to why the plug caps on #1 & 4 have different resistance specs than the plug caps on #2 & 3.
    The plug caps on the outside cylinders will be cooler than the two inside cylinders.
    Resistance of a component increases as the component gets hotter.

    Interestingly, my genuine Yamaha XJ750RH Service Manual has specs:
    #1 & 4 = 5Kohm #2 & 3 = 10Kohm
    yet I measure:
    #1 & 4 = 8Kohm #2 & 3 = 6Kohm

    My measurements coincide with the principle of the inside caps resistance increasing due to getting hotter than the outside caps. (Meaning the books spec’s are backwards)

    Since the book has a mistake on the inside vs outside caps difference, stands to reason the book may also be inaccurate on the resistance values.


    More electronics education:
    The voltage present at each component in the circuit will be a percentage of the circuit’s total voltage. The coils put out a given (unchangeable) voltage. Those volts will be shared / distributed (the term is ‘voltage drop’) to each component. The sum of voltage drops across each component equals the circuit’s total voltage (the output from the coil). (This is a simplified description of a circuit in series. The high voltage circuit is in series per spark plug – no parallel components). The design of the ignition system is such to have the proper voltage drops across the proper components, such as the spark plug. Modifying the components (wires, caps, plugs) to other resistance values will redistribute the voltage values (voltage drop) to each component in the system.

    Since you have a given unchangeable total circuit voltage, you want to stay with the designed specifications per component so as to have proper distribution of voltage drops.
    Altering the voltage drop on the components can have consequences, especially to the individual components performance.
    If other components in the circuit have resistance values higher than they should have (including resistor plugs), the voltage at the spark plug gap will be lower than spec voltage *. Lower voltage at spark plug gap will make it harder for the voltage to jump the gap. Alternatively, a higher voltage at the spark plug is not necessarily advantageous and can have consequences like shorten plug life. Lowering the total circuit resistance will increase the circuits current. Increased circuit current could have consequences, because the components were not designed to carry the higher current.

    * Actually the voltage present at the gap (an open circuit due to the air gap) is the full circuit voltage until the instant spark jumps the gap completing the circuit.
    (The principles of electricity can be difficult to comprehend)
     
  23. Polock

    Polock Well-Known Member

    Messages:
    9,751
    Likes Received:
    2,097
    Trophy Points:
    113
    Location:
    Beaver Falls, PA
    exactly, and THAT'S why it's so important to index your plugs
     
  24. mdee

    mdee Member

    Messages:
    108
    Likes Received:
    1
    Trophy Points:
    18
    Location:
    Billerica
    Polock – I’ve been meaning to ask you that.
    Where do you index your plugs?
    I usually index my spares to the tool compartment.
     
  25. Polock

    Polock Well-Known Member

    Messages:
    9,751
    Likes Received:
    2,097
    Trophy Points:
    113
    Location:
    Beaver Falls, PA
    someone explain indexing plugs, i have to go change the air freshener
    in the seca air box, i think i'll go with spring bouquet this time
     
  26. mdee

    mdee Member

    Messages:
    108
    Likes Received:
    1
    Trophy Points:
    18
    Location:
    Billerica
    My air box always smells of gas no matter what air freshener I’ve tried.
     
  27. iwingameover

    iwingameover Active Member

    Messages:
    2,145
    Likes Received:
    4
    Trophy Points:
    38
    Location:
    Maryland
  28. mdee

    mdee Member

    Messages:
    108
    Likes Received:
    1
    Trophy Points:
    18
    Location:
    Billerica
    Thanks iwingameover.
    I was looking for a task I could waste my time on instead of focusing on the real issues on an aging 30 year old motorcycle !
     
  29. pillowmaster50

    pillowmaster50 Member

    Messages:
    105
    Likes Received:
    3
    Trophy Points:
    18
    haha
    im pretty sure that a spark plug can be installed two ways. so theres no need to buy a bunch of extra plugs and hope one ends up "indexed". if it's oriented backwards from the way you want it, pull it out... right when its completely unthreaded, turn it 180 degrees and put it back in. it should end up with the ground electrode on the other side...

    EDIT: oops just checked. turns out im wrong :oops:
     
  30. mdee

    mdee Member

    Messages:
    108
    Likes Received:
    1
    Trophy Points:
    18
    Location:
    Billerica
    pillowmaster50 –
    Screw threads start at only one place on the spiral, whether internal or external treads. The same spark plug will start and stop in the same orientation every time assuming the stop is at same length on threads. Indexing a plug can be done by using washers to space the stop to a shorter length.

    Indexing spark plugs is, as Betty White would say ‘ a colossal waste of time’.
    Unless you are tuning something on the order of a formula 1 car.
     
  31. Polock

    Polock Well-Known Member

    Messages:
    9,751
    Likes Received:
    2,097
    Trophy Points:
    113
    Location:
    Beaver Falls, PA
    pillow, your thinking of a double lead thread, two sets of threads 180 form each other, start two places
    our plugs have one set, single lead
     
  32. waldo

    waldo Member

    Messages:
    871
    Likes Received:
    1
    Trophy Points:
    18
    Location:
    San Jose, Ca. 95125
    And I was beginning to think you guys didnt have a sense of humor
     
  33. padre

    padre Member

    Messages:
    233
    Likes Received:
    0
    Trophy Points:
    16
    Location:
    Lawton, Oklahoma
    the most common is to mark a place on the insulator that you can see is in line with the ground arch of the plugs so each plug is nearly exactly in the same posisition in relationship to the combustion chamber, I also notice that bacause the arch shrowds the plug slightly, the area of the insulator , behind the ground electrode runs a little cooler so it looks a little darker there.

    One more base to cover about the available voltage of the coils. although the coils are rated at 20k dosn't mean the plugs fire at 20k that is a variable depending on air gap and conducitivity of the insulator, a fouled plug dosn't fire at all so its an almost deat short. ON an ocilliscope it would look like a flat line, and since 2 cylinders share each coil I always change the plugs at least two at a time, because I believe one can short out the other. On a scope, if you loosen a wire and create an air gap between the positive tip of the plug and the wire terminal end the current peak will increase, it's like 'sort an' old hillbilly trick to unfoul a slightly fuel fouled sparkplug should you forget to push the choke back in. So the gaps between matched pairs of cylinders, and resistance should be equal, don't put a resistor plug in #1 cylinder to compensate for an over lean condition such as a clogged jet and not do likewise in #4, the power will follow the path of least resistance and the techniques used in vehicles with distributors for spark, like autos. Won't work! Resistor plugs change the timing by changing the spart attenuation, or the ammount of time the power actually spends arcing since the charge has to build up in the resistor more before the arc can take place. This results in a sharper albiet shorter duration of time the plug has to foul out. All new cars come equiped with resistor plugs because they will fire the newer leaner contitions that lower air polution. As far back as the late 80's autos made in this contry had 60-80 kv coil capacity and gaps to match .060-.080" If you widen the gap too much not only will you overload the coils, and make the engine run leaner, you may create the problem of the gap horizontally lesser than the gap across the electrodes vertically, heating the ground electrode like a arc welding rod and blowing nice big holes in our tiny little pistons!!

    Now ask me about HC, CO & NOx. Lol, it cost somebody alot of money so I could learn all of that stuff. Basicly I don't suggest you experiment too much with a proven ignition system. If you upgrade the coils they still won't fire much differently than stock ones do with the stock spark plugs and same air gaps. Gap the plugs that share the same coils the same and don't mix resistor, and non resistor plugs on the same coils.

    Spark plugs made to be set wider than .035" usually have a suffix at the end like b7es would be made for up to .035, b7es11 would be for gaps up to .045, Bosch too hr10 .035, hr10bx .045, hr10by .065" etc.

    I understand you didn't ask for all of that but there's more going on in the combustion chamber than Ohms law, Air cooled automoblies are only history because we can't make them run lean enough to meet epa regulations without burning up. Motorcycles are next. And you'r welcome.
     
  34. padre

    padre Member

    Messages:
    233
    Likes Received:
    0
    Trophy Points:
    16
    Location:
    Lawton, Oklahoma
    Ps, the airbox allways smell of fuel because the blowby return line, ak crankcase vent is right between #2 & 3 cyl in the log connecting the four carbs behind the filter element.
     

Share This Page