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TCI box - a successful repair, electronic ignition, ignitor

Discussion in 'The Garage' started by xjwmx, Sep 6, 2010.

  1. Wharfcreek

    Wharfcreek Near 50 Yrs of Experience

    Hello Leo,

    Just to clarify...... I had done a substitution of a known good box for my 'old' box, and with the known good box, the engine ran 'ok'. I say 'ok' because it still need further tuning.....but, from idle to about 5K it runs well. Over 5K it breaks up, but I've narrowed that down to 'carb' issues. So, given that the known 'good' unit does work properly on the bike...... my inclination is that the magnet/pickup combo is fine. But, I may stick the RatShack magnet on there just for good measure.....and I appreciate the advice!! Thanks!!

    As to repairing the old unit, thanks to TwoMany for posting the schematic! I don't know if all those parts are available today.....and I'm not sure that 'exactly' the same diagram for my unit. In looking at it.......I see 5 transistors.....and my unit only has 4 on it's board....though I do have an '81. Odd discrepancy....and may be my error; I may have missed on on my board. I just wonder if that IC chip is available? My guess is not.....but hopefully I'm wrong. I would guess the transistors can be sourced......if not 'exactly'....then there are probably suitable replacements available.

    Thanks guys!! Most helpful!

    Tom D.
  2. gggGary

    gggGary When a whole one is just too much. XS650.com Supporter Top Contributor

    The TCI's were "black box" components, Yamaha specced the inputs and outputs, the venders were free to design the internal wiring, it varied a LOT unit to unit depending on vendor and production date.

    I still use TCIs and your over 5 grand issue sounds very much like a weak magnet. Had one like that this summer, a fresh rotor (coil was reading low anyways) cured the high speed miss.

    My take is TCI's systems are fine when they are working, but internal repair much beyond looking for bad solder connections, blown output diodes or the power transistor is probably not economic, replace with a known good unit or change to PAMCO with E-advance is my drill.
  3. Wharfcreek

    Wharfcreek Near 50 Yrs of Experience


    I think you're spot-on with the 'fix' prognosis.

    Just to clarify, I'm pretty confident my over 5K problem is carb related. When I pulled my 'junk' Chinese pods OFF the carbs......I can run to 7K with barely a hiccup, and the engine pulls so well that it breaks the clutch loose. With the crap pods back on, it breaks up over 5K! This is NOT the original problem that caused me to diagnose the bad control module issue. Originally the engine would barely start......though I did get a near idle from it. But, a turn of the throttle and it wouldn't hit 2K without misfiring badly. Changing to a known GOOD IM cured that problem...but revealed the over 5K problem. This is where it switched from being ignition to being carb related.....particularly considering that I swapped out the old BS34s for a set of un-tuned BS38s. This is further complicated by my lack of knowledge of just how much prior 'tampering' was done with the new carbs. I have a feeling that there have been some inappropriate changes made to them in the past that I may have to sort out as well. I think I've already found that they have the wrong needles in them......but..... I'll get that figured out eventually.

    Anyway..........thanks for the comments...... I think I'm going to do the magnet thing just for good measure!!

    Tom D.
  4. Wharfcreek

    Wharfcreek Near 50 Yrs of Experience

    Correction...... I DO have 5 transistors! I forgot that the power transistor (or regulator unit?) is also shown on the schematic similarly to the other NPNs or PNPs. I do a LOT of 'Tube' Audio Amplifier repair and re-furbishing...... and I'm not used to seeing semi-conductors in a circuit. My Bad!! Sorry........ TSD
  5. kopcicle

    kopcicle antidisestablishmentarian


    I have near 20 good years of experience . The other 30 were only so so .

    First the MoPar thingy


    These things are dirt simple and the internal diagram is out there I just didn't bother , They are the second most common spark box made save for the briggs and stratton thing .


    Rivals the briggs and stratton for availability and with a proper coil you can weld with it . Needs a bit of a heatsink and really isn't that picky about input signal . If it is just leaking a little B+ into the pickup side through a 3.1v zener diode is acceptable and common .
    For those of you that actually paid attention in basic semi conductor elements it biases the input signal above the noise floor to prevent false triggers .
    Try this link then you're on your own
    Two ! Two for the price of one ! I'm sure there are others and I once sussed out the timing plate diameters and coil ohms but again I'm old lazy and like to make other people do my dirty work .

    It really is simple . get a piece of metal to pass by a coil producing a positive voltage bump that is applied to the base of a NPN power transistor that turns the coil of and on . Do this with out false triggers and you're golden . Ignore the fact that there is considerable electrical noise in and through the bike at your own peril . While on that subject , the stock charging system is marginal at best , will rarely charge at idle , and is surprisingly quiet electrically . A PMA on the other hand stuffs three phase alternating current into six junctions for rectification and shunts all excess to ground causing considerable noise in the system . It's actually the SCR's creating the bulk of the noise with the rectifiers a close second . You can try a small DC oil filled capacitor on the positive side of the battery but it rarely helps and actually confuses the regulator . Using a high MFD electrolytic cap with a a battery may sound like belt and suspenders but I'll save you the trouble . Just don't .

    Okay , I have personally used all of this junk to create spark at one time or another . It really isn't rocket surgery . This isn't meant to be a howto or instructions of any kind it's just putting the possibilities out there to confuse you all . Now I'm going back to my regularly scheduled programming .
    Last edited: Oct 23, 2014
  6. kopcicle

    kopcicle antidisestablishmentarian

    Just in case someone was asleep during basic semi conductor principals :)
  7. Wharfcreek

    Wharfcreek Near 50 Yrs of Experience

    Kopcicle, Many thanks! Got a couple questions though: Actually, this first question applies to both the GM and Chrysler units. I'm pretty familiar with the Chrysler unit, having had 33 years in the field for Chrysler and 3 of those were in the '70s as Chrysler Field Service Rep. I've often wondered about 'converting' an automotive ECU to motorcycle use......as they are pretty reliable 'switching' devices. But, I know for a fact that there are NO advance curves built in to the Chrysler unit. The Chrysler distributor, much like the OE Crank-Based unit, simply derived it's trigger signal from a 'star' shaped device (Reluctor) having points that equaled the number of cylinders.....and as each star tip passed over the pick-up coil a signal was induced that then triggered the ECU. BUT.....the old style EI systems still relied on a mechanical/vacuum advance built into the distributor.....much like I believe the Pamco unit does using the original Yamaha Points system centrifugal advance unit. So, in adapting either the GM or Chrysler unit for use...and assuming you're still using the crank-based pick-up system....how do you account for an 'advance' program? Or, if using a different pickup with the automotive ECUs.......aside from the Pamco unit.....do you have a different method that DOES supply an advance?

    I guess the other question is simply; What about other motorcycle ECUs that might be applicable......like an adaptation of a 400 or 750 2-cylinder with electronic ignition......or even a Honda, Kawasaki, or Suzuki unit that might have some similar engineering?

    You mentioned Briggs & Straton; I have wondered about those myself. But, again, not sure how the programming works......and what kind of advance system is employed on some of the Briggs units. Also, wondered about the HD systems. Harley's been using 2-cylinder electronic ignitions for decades, and the number of after-market units available to 'upgrade' a HD is amazing. My HD has a unit made by Daytona called a Twin-Tec. It's quite programmable......had a cost of about $60 when I purchased it.......and it works with HD's single wind / dual fire coil.......which is a similar design to Yamaha's coil. I gotta believe that there's some potential there for adaptation.......but have heard of no one ever giving it a try. Just seems to me those are better options than attempting to re-purpose the automotive units that have the 'no-advance programming' associated with them. But.............hey, I'm a rookie at all this......so that's why I'm asking the questions. There's probably good reasons....and I'd just like to know what they are.

    Tom D....... (2 cats by the tails.......lol)
  8. kopcicle

    kopcicle antidisestablishmentarian

    Never considered a crank trigger other than the Kawasaki which already has one . All the suggested hardware and methods rely on a stock , points type ATU / centrifugal / mechanical advance .

    While on the subject I always found it erroneous to call it an automatic advance unit of any kind using any words . Far from an automatic advance it is an automatic retard mechanism . The only reason an ICU spark ignition engine has advance capabilities is to improve efficiency at working rpm and allow a reasonably retarded setting for starting . A good example of this is my alcohol engines running between 36 and 42 degrees fixed advance . They get started goofy rich with a spot of high test petrol and have no issues .
    The TCI supplied on late 79 and up XS's has no advance curve to speak of . It has separate start and run pickups . any "advance curve" that you see with a timing light is your imagination and a bit of diode leak electrolytic within the TCI .
    All from that era are similar in several ways . connections for power , ground , pickup in and out and , tach (one or two wires) . later models had bells and whistles like the clutch/neutral safety , kill switch w/o cutting main power and in rare cases a vacuum port . Simply by chasing colors on a wiring diagram and physically on the bike should determine their functions . I know I've done it to several but the details have been lost to time .
    You really are over thinking this from a one off standpoint . The automotive parts are available everywhere . The GM , FoMoCo , and MoPar "igniters" are under $20 in most places and the pickups sometimes as low as $10 . Add the possibility of roadside scavenging or junkyard acquisition and the availability increases and the price drops substantially . in the case of the GM for sure a bit of forward bias allows you to use points at greatly reduced voltage and current leaving the rubbing block as the only wear item . The size of the stock points setup and the HEI parts is low allowing you to carry both a spare HEI or even an extra coil with little weight , volume or complexity penalty .In short i don't know the alternatives because I never looked . I didn't have to , need to or have any desire to .

    A better mouse trap ? sure I've done that . A better hammer ? Why bother ? Just get a bigger one . I'm not about to re-invent the wheel , build a bridge to throw a rope across , design , adapt an electronic ignition , or fix the national trade deficit just in the name of a programmable advance curve for a 50 year old design (century if you want to include Kettering) 40 year old motorcycle just to say "mine is bigger , better than yours AND shoots around corners" NOT gonna happen . :)

    Two cats indeed

    Last edited: Oct 23, 2014
  9. Wharfcreek

    Wharfcreek Near 50 Yrs of Experience


    This is my first go-round with Yamaha's EI system, other than an '81 Special that I got running and gave to my younger son a few years ago. I didn't do any significant 'tuning' to that bike. It ran well....and he liked it 'as is'....and it was born the same year he was......so he felt some kinship to it. It now resides up in Michigan where my '79 'Standard' keeps it company. Just for the record, my other son lives only a few miles away from the youngest one.....and the older one absconded with my '75 'Standard' as well. So, at least when I go back to Michigan from Maryland, I have a bike to ride up there....and my two sons to keep me company!

    But, back to the EI systems: I did not know that there were two pickups in the one 'unit' that is on the Yamaha. I call it 'crank' sensed only because the magnet on the rotor is affixed to the crank shaft.....vs being 'cam' sensed like the Pamco unit.......or as in my 2000 HD Dyna Glide. My '01 Fatboy is 'crank sensed'..... and while the magnet on the Yamaha is not directly affixed to the crankshaft itself, since it is directly related to crank position at all times...... I'm just used to using that terminology. I'd also mention that the same terminology is often used in the automotive world when a pickup signal is following crankshaft speed and position....even if the actual signal is generated off a harmonic balancer, a flywheel, or starter ring gear. Anyway.....just a 'vernacular' discrepancy..... not a big deal.

    I might also clarify my take on the 'advance' terminology. While the term 'automatic' is something that may be used by a designer or manufacturer...... I think the simple concept there is that happens by itself rather than having to do it manually. Recall that the early years of motorcycle technology included mechanisms where the rider had to use one hand on the throttle, while the other actually controlled spark 'timing'. This was also true in early automobiles, and even machinery like tractors and mill engines. So, if the operator does not have to 'manually' adjust spark timing......I think that qualifies as being 'automatic'. As to the comment about 'Advance' actually being a 'retard' function...... while I understand how one could look at it that way and even be 'correct' in so doing, the reality is that the term was 'defined' by the folks in the field probably long before you and I were even a glimmer in our parent's eyes...... So, simply got to go with the commonly accepted definition on that one. But, I do see your point.

    Final comment: I had read somewhere that the Yamaha Electronic Ignition Module DID have some advance curves programmed in to it. And, like I mentioned, I'm pretty familiar with the types of EI units used in the Harley Davidson field (not to mention those 'auto' related units). HD has some pretty sophisticated parameters built into their ECUs......not to mention those available for HDs on the after-market. I had the privilege of working for Zipper's Performance Products for a short time......and if you know a bit about HD units, then you may be aware of the ThunderMax.....a fully user-friendly EFI control unit that is WAY more sophisticated than most people can even comprehend. Interestingly enough, I also worked for Magnetti Marelli for about 18 months. MM is a HUGE supplier of fuel management EFI systems used in race systems. They also supplied HD with their first EFI system back in the late '80s. But, EFI is a far cry from simple EI systems still associated with carburetors. BUT....the concept of Electronic Spark Control is what evolved to Electronic Fuel Control.....and was definitely the chicken that came before the egg. So, as advanced as these units have now become, it still seems to me that someone would have addressed incorporating some of the more sophisticated units into the current Yamaha XS market. Oh well......... For what it's worth......

  10. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    TCI info extracted from the XS650G supplemental manual:

    Attached Files:

  11. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    TCI info extracted from the XS650H supplemental manual:

    Attached Files:

  12. Wharfcreek

    Wharfcreek Near 50 Yrs of Experience

    Two Many, thanks for the additional info. While I've not looked at the info on the 650G/SG until now, I have reviewed the information in the H/SH supplement. I find it supports that there's not 'timing' to be done if the thing is running. But, it's unclear about 'advance' issues. In reading the info on the S/SG unit.....it too doesn't seem to discuss the matter of 'advance'.....or the specifics of how that is accomplished. I have a Haynes manual here.......and it's even worse. Seems to me there's GOT to be some level of advance between what happens when the engine is started and running at idle.....and where the spark takes place with some additional RPMs. I don't recall the 'points' bike's set up exactly.....but just going from past 'points' type experience, I see basic timing set at anywhere from a degree or two BTDC to upwards of ten to twelve degrees BDTC....at idle! Then, with rpms moving upward to 2, 3, 4, and even 5K......advance can go upwards of thirty degrees BTDC and even higher. So, with one stationary pickup coil.....even if it had two sections to it........those two sections aren't spaced twenty or thirty degrees apart. So, I'm thinking there's got to be some level of advance built in to that Ignition Module. Of course......I'm probably wrong......but jut looking at the way it's built......it's pretty complex to be 'just' a spark controller. If that's all it did, it wouldn't need to have all that circuitry.....and certainly not an 18-point Integrated Circuit. I sure wish the factory literature gave some more detail. TSD
  13. kopcicle

    kopcicle antidisestablishmentarian

    You're not alone on that one .


    P.S. i hope you have some decent pipe otherwise checking you're mail is going to be painfully slow :)
  14. kopcicle

    kopcicle antidisestablishmentarian

    Okay , back to work


    good thread but I already had and engine stand (automotive four arm) and adapted . I welded four tabs on a plate corresponding to the outside of the four rear mounting bosses and welded a round (3" ?? ) to the back that socketed into the existing pipe on the stand . I have two other sockets . One is vice mounted and the other is bench mounted . Now back on topic ...

    What was the question ? Oh yeah Bikini or Brazilian ...



    Tom as far as I ever bothered to "look" at the circuitry in the YaMoCo black box was attempt to reheat every solder joint to prove a point to my Inde manager . It was a waste of time . Replace or replace with a common auto parts available thingy . (Anything Ken didn't understand was a "thingy") . In the fhoto I'm with mike and the rest . That is a start and run pickup(s) . Looking at it on a few (okay if I say hundreds I'd be guessing and likely called out but keep in mind most of my early experience was indeed with YaMoCo and the xs was a very popular bike .) I discovered that yup one half could go bad , intermittent , intermittent with heat , intermittent with vibration , Depending on which half went bad it could act possessed , be dangerous to kick start for the unwary or break up on top like a dying coil or equally possessed BS carb set . Even when working correctly there was no rhyme or reason why they or when they would come off the start pickup and advance . On some it was as if the white sense wire off the dyno that goes to the lighting circuit (the one that allows you to start the bike with the light off and turns the head light on as soon as it sees current over drain. On others it happened as late as 2800 . In either case it depended on battery charge and health . And again , the "curve" data you see in any manual is related to the ATU and NOT the 80 1/2 TCI magic box . All I can tell you for sure is that working correctly it starts retarded and runs advanced . I actually think that the support circuitry points more at analog support for a standard 7400 TTL IC with the discrete components inside used as switches gates and amps . The rest of the parts count looked like RCL drains and buffers . ie; Charge it and discharge via delay or charge via delay or ...

    Those that did pay attention during basic electronic principals get it the rest of you don't need to . You just replace stock with stock , $19 junkyard ignition (HEI), Pamco ,Wells (MoPar) FoMoCo , Brandson , Marelli , Dyna. not like you don't have choices . I'll spend my $80 on wine women and song , oh and source my parts from the junkyard . You can (and will ) do whatever the hell you want.

    Here's a test for ya . find the common of the three wires coming out of the pickup . (Blk/Wht common Red/Wht one side Grn/Wht the other~ from memory so check .)Measure both sides . Heat and beat both sides . infinity ? well yeah obvious . intermittent ? well fsckit replace . ohms climb to off scale while in diode check mode ? broken in the middle of the windings and it's acting as a capacitor and causing very indiscriminate starting and idle OR breaking up on top like a diseased ignition coil . I have seen ONE with the start and run pickups reversed .

    Last edited: Oct 25, 2014
  15. Wharfcreek

    Wharfcreek Near 50 Yrs of Experience

    Hey, just wanting to thank everyone for the responses to my questions on this. I'm actually in Michigan now......a good 600 miles from home, and from my '81 project bike. But, the good news is that I got a chance to ride my '79 yesterday with my son on his bike. Though a short ride, it was great to get ANY time riding around with my son here in Michigan......so, I appreciated it. The '79 ran OK....for not being ridden much in the past 2 years. But, I'm anxious to get back to Maryland and back into the '81 project bike. I've also ordered up some special tools in order to go through the top ends on a couple of 'spare' engines I have around my garage and shed. So, time for me to 'exit' this thread....having learned a LOT from everyone.... and move back into the 'mechanical' side of things in attempting to get one good motor from 3 'bad' motors. All 'valve' related issues.....or so I hope. Guess I'll find out soon. Tom D.
  16. mugpug

    mugpug XS650 New Member

    Has anyone ever seen or know of an electrical schematic layout drawing for the Hithaci 4M4-10 TCI unit?
  17. Wharfcreek

    Wharfcreek Near 50 Yrs of Experience

    Mug, just so you know someone saw your post, I'll acknowledge by saying 'sorry, but not me!.' Regarding my '81, my 'fix' of the 'used' OE box gave me a successful ride all last summer. That bike became the subject of some modifications, though nothing too dramatic. I ended up with a nice set of '79 model carbs on the engine and exhausting out through a 2-into-1 header. I stripped some weight off, put a set of aluminum rim '78 wheels on it, and when done, I figured I had just enough change in HP to weight that I might be able to run a gear change......so swapped the 34 rear sprocket for a 32. Completed the drive-train change with a nice gold-link 'O' ring chain. All tuned up and running smoothly, powerfully, and I think even a bit more 'economically'...... as I think I averaged about 60 mpg with it. I compare the use of the bike in the summer with NOT driving my pickup.....and figure that for every 100 miles I drive the motorcycle, I save about $20 in fuel costs over NOT driving the pickup. If current gas prices continue, that will drop significantly, as the price of gas is now under $1.80 / gallon around here, for regular. This is also 'winter' blend fuel, which contains 10% alcohol. Anyway, as to ignition issues, I'm pretty convinced that some better 'retail' options are needed here. These are simply GREAT motorcycles....... and a 'cheap' replacement for the factory black box that is also a 'plug-in' version would REALLY be helpful!! FWIW. WC

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