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DOHC ignition timing adjustment?

Discussion in 'The Garage' started by 16VGTIDave, May 30, 2013.

  1. 16VGTIDave

    16VGTIDave XS400 Guru Top Contributor

    Ok, I've read the manual, and searched. :) As best as I can tell, the ignition timing on DOHC engines is either correct, or there is a problem, but there is no adjustment. :umm:

    Well, that is fine for a stock bike, but what if one needs a bit more advance due to mods like jetting? Based on what my sparkplugs are telling me, I should be advancing the timing a few degrees. And since I only run 92 octane gasoline, this should be quite safe. The only thing I can figure out is that I have to remove the plate that holds the pickups and elongate the holes for the 2 mounting screws.

    Am I missing an adjustment? What have others done?

  2. 16VGTIDave

    16VGTIDave XS400 Guru Top Contributor

    Well, being impatient and having a little time on my hands, I went ahead and slotted the screw holes. I installed the pickups what I thought was just 5 or 6 degrees advanced, but now that she is back together my timing light says I have 20 degrees advance at idle. :yikes: Stock is 10 degrees. I decided that since today is rather warm, I'd give her a brief run and listen for engine knock. There wasn't any. :thumbsup:

    The throttle response feels crisper and I had no problems wrapping the tachometer around to 10. Seems to start very easily, with no kick back when the cylinders fire. I think I will leave it for a tank of fuel and see what the plugs and mileage look like. Unless I hear knocking or notice other issues...
  3. ksqrly

    ksqrly XS400 Aficionado

    Good info dave
  4. Jeff0133

    Jeff0133 XS400 Junkie Top Contributor

    This is way old....but...
    -Did you leave it Advanced?
    -the crispness in the throttle at low rpm makes sense but by moving the torque curb, did you notice a little torque loss in higher Rpms.?
    -how did it affect fuel consumption?
    -did you have to change you fuel/air mix or change you RON to 98 on different temperature days to account for air density?
    ....I know that's a lot of questions, but i'm looking for low-end torque improvement without destroying my crank and or piston rods, building city bike and I don't want to be a " revving douche" at 11pm...
  5. 16VGTIDave

    16VGTIDave XS400 Guru Top Contributor

    I ended up going back to stock ignition timing after I replaced my TCI module in August of that year. As it turned out, my module was starting to fail and the symptoms were first evident at higher RPM's, which lead to my misdiagnosis. Advancing the timing helped mask the symptoms for a few months, until the TCI module failed completely and left me broken down at the side of a country road.

    I've wondered how the bike would run with a load sensitive ignition advance. Like the vacuum advance found on older cars, where the timing is advanced when the engine is under light load, for better economy and performance. But, I don't see an easy way to do it....
  6. BBS360

    BBS360 XS400 Guru Top Contributor

    I've been wondering lately if a power arc ignition could be adapted for our bikes.
    Each unit can have four different ignition curves programmed to 1° increments, actuated by vacuum switch.
  7. OldieOnWheels

    OldieOnWheels born on wheels

    Upppssss.... not even a hell of a lot of response :-o

    Please, before I open up a brandnew thread on this, let me try to go on with THIS thread.
    Might be helpful not only for me ;-)

    I just tried to get a helping hand from members of a German XS400 forum, now waiting for some replies.

    My problem/s is/are slightly different, but however, let's give us a try ;-)

    Here we go, that's what I posted in that German forum:

    Hello and good evening ! It's the weekend and bad weather for me, both of the existing strobes are causing problems, as well as poor throttle response due to a carburetor problem that has yet to be fixed. Without a garage, with a covered carport, it is no fun to fix the carburetor problems outside first in order to be able to determine the ignition values afterwards :-( Companies like IgniTech cannot be reached before Monday.

    Therefore, and because I have not yet achieved the desired success by keyword search, not even in the other sources, I would like to ask you here whether someone can come up with the advance values of the not freely programmable IgniTech-TCI [/ u] ??? [/ b] At the time, it came from the Czech Republic without any further information and should have been universally suitable for 27 or 45 hp engines. It was used for the 45 hp version, and the 27 hp version actually also ensures a good run.

    Now I would like to use one of the existing TCIs for a Honda CX500 because its Hitachi CDI was designed in a way too complicated. As long as it works, everything is fine, but as soon as one of the generator's high-voltage coils muck, it becomes unnecessarily expensive. The electronics are mostly intact, but without enough juice from the generator nothing goes clean anymore. ONE (of 2) broken coil means the replacement of the complete stator, although everything works fine in the 12-14V range! Until 1982 the CX used 4 + 2 pickups for 15 ° idle, advance ignition and maximum advance ignition. This is technically interesting, but stupid if the CDI is to calculate the advance ignition from the 6 pulses. Instead of purely mechanical by means of a centrifugal regulator (as used progress through stepping backwards, so to speak, Honda changed from 1982 on), i.e. electronically. But, although primitive enough for e-hobbyists, still 'repair-safe' cast in resin :-( Then you can also use a more complicated, but now cheaper electronics, like the TCIs, instead of a diode network.

    There are statements in the network that say that the pulse generators of the DOHC models are decisive for the calculation of the advance ignition; this contradicts the majority of the statements that state that the spark advance is calculated exclusively by the TCI. Which statement is true? [/ B]

    Since 2 functioning pulse generators from the Honda are sufficient, the conversion to the TCI is easy as long as you also take over the ignition coils that match the TCI, because there may be differences. This saves having to remove the motor, because only 4 cables are not required, if necessary 'load / ballast' should be used if one of the two high-voltage coils still produces a lot of oomph. If you want to keep the CX in its original condition, you have to go to the generator - and that does WORK! Unfortunately, it sits in such a way that the engine has to be out ... One tiny problem with the conversion is the pre-ignition/advance. You can do something with different idle speeds and ° before TDC, but the CX up to BJ 1981/82 comes to 40 ° early, the one from 1982 even up to 45 ° early. For the latter models, neither one nor the other of the 12E-TCIs should come into question, while the older models could definitely get along with the TDI12-07 or the IgniTech-TCI. At aliexpress I found alternative TCIs that can definitely replace the Hitachi TCIs if they are to be used in a 12E / 16M. Prices: from 37 USD including shipping to Germany to approx. 58 USD, sometimes 'even' from DENSO - if you should prefer so-called 'branded goods'. But you would like to use parts that you still have lying around ;-)

    Someone with you who can help out quickly with the IgniTech TCI values? In any case, I wish everyone a nice rest weekend, Greetings from Germany,


    P.S.: sorry for possibly wrong translation... ;-)

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