A forum for owners of Yamaha TTR250 trail and enduro bikes!

Does the Yamaha original limit horsepower?
Does the Yamaha original have rpm or speed limiters?
How can a CDI reduce oil consumption?
How does this CDI break "the analogue control of the traditional method"?

Seems very expensive at £154.49 and very vague on actual benefits, methinks someone's been peeking through rose-tinted spectacles

Martyn

 ...methinks someone's been peeking through rose-tinted spectacles ....

Strikes me one could be peeking through a hole in the piston crown...

If the original CDI had a poorly developed advance map one could see room for improvement.  I would need a lot of convincing Yamaha's CDI was poorly developed.

Yes....
get a VERY small flt blade screw diver... theres a tag on the steel conecter you have to bend in... it will pull out
reach in from the plug end .....Then rebend it back out before you reinsert the connecter blade back into the plastic block.....

A bit of peeing around but it can be done...

This is the type of connector is used on the CDi.

They are all located in their housings by a sprung tab on the connector housing - not a spring tab on the terminal itself which is the usual scenario.

I just test released a terminal using a paper clip but a small flat bladed screwdriver would make it easier. 

If in the workshop, I use one of these to help take terminals apart:

 

Brian

Got that done today, used a paper clip to get the spade connector out
and fitted the shrink wrap. Should be ok.

I would have thought that if the CDi had packed up, the TTR wouldn't start at all 

Sounds more like a fuelling issue to me.

Have you a mate with a properly working  TTR so that you could try their carb on yours?

Brian

Hi Mark

Yep - most are like that. It is odd seeing some of the components where the resin is thin.

I think the "crystals" are just filler material put in with the resin presumably to save a few pence on resin.

Brian

there is these... for about $180US

www.aliexpress.com/item/New-product-Intelligent-digital-motorcycle-electronic-igniter-for-YAMAHA-TTR250-4GY/453231246.html


try Steve.. he's bound to have one or two....
...

-- Edited by petenz on Wednesday 19th of October 2016 08:22:08 AM

It is an expensive way to check your CDi! If you find the new CDi doesn't fix your problem it is unlikely that you would be able to return it - or at least that is my experience with electrical parts.

If you haven't got anyone nearby that you can try your CDi on then maybe go for a tested used one that you can easily sell on if it is not needed - see here for example.

Brian

Hi could any body please advise why (is it called the cdi) the black box under the seat would start smoking ,just started my bike one day and rode a 100m spark died and smoke was present tracked it down to Black box. The fuse didn't blow, Inam taking it the cdi is cactus ,I would rather find the cause before I replace it so I don't smoke 2 of them.Any help would be appreciated.

Welcome to the forum Bart!

I am afraid it will be a case of getting the seat and tank off and carefully going through the wiring and connectors. It is rare for the TTR CDi to give trouble unless provoked!

Brian

I have replaced the stator with an after market Celtic stator.maybe it wasn't compatible.

Have you run with the new stator before or was this the first time? (If first time out - suspect stator is the cause, but you're going to need a new cdi anyway by the sound of it)
Does the smoke leak even just with ignition on? (I understand the engine won't run) Unless there's a dead short somewhere it points away from the charging circuit, at least in my mind.
Is the smoke leaking from the wires or the cdi box itself? Poor connections can cause the plastic plugs to melt...
I hate electrical diagnostics, you have my sympathy. Best of luck,
Simon.

Not ignoring you Brian - just haven't got the faintest clue as to what goes on in the TTR's CDi and have never needed to know 

It is rare for a TTR CDi to go belly up and, if it did, it is cheap enough to buy a guaranteed  replacement unit such as Steve offers here

In all the TTR literature and online information I have read over the years I have not seen anything that would help you - sorry 

Brian

I was interested to know what each of the terminals on the TTR250 CDi does and think I have nailed it! If you think I have anything wrong please let me know 

 

This photo shows the wires going into the loom-side connector:

 

In order to time the spark (through the orange wire to the coil/spark plug), the CDI must know what speed the engine is rotating at. This seems to be from the feed from the White/Red wire connected to the pickup.  

 

I found the thread Simon - it's here http://ttr250.activeboard.com/t53088671/fitting-additional-lights-and-accessories-upgrading-electric/ 

But sadly the photos and diagrams are no longer there 

On a digital speedo model there is a 5V switched (no power when ignition switched off) supply (Yellow wire) that is blanked off on blue TTRs. The blank that is left on both models is a switched source of DC power at near 12v or as Jarrah says "A closed voltage circuit is what comes out from your CDi eg. 11.8V at 20 degrees Celcius" which can be used for 12v accessories. See diagram in my earlier post.

I was researching what CDis do because I am sadly ignorant about them  

I would have liked to have helped Elijah more (see here) but, to do that I would need to understand how the pickup works and how it relates to the CDi.

Is there a coil in the pickup and, if not, how does it trigger the CDi to discharge to the coil and fire a spark?

I would also like to understand if and how the CDi internally organises the advance/retard for the spark and acts as a rev limiter.

Brian

Watched that one this morning Simon and it was really helpful - but not the most exciting voice over 

Relating the TTR's set up to his diagram, am I right in thinking that the "Excitor Coil" in his diagram is one or more of the windings on the stator, (b) the flywheel acts as the "Pulse (or Pluse!) Rotor, and (c) the pickup is the "Trigger"?

As far as I can make out from the wiring diagram in the workshop manual (and looking at the external stator wires on my TTR), the two wires from the pickup coil are yellow and blue. The blue wire goes via a connector to a White/Blue wire in the loom which is an earth wire. The yellow wire from the pickup joins the White/Red wire on the loom that goes to the magneto.  These are the two wires that you found had continuity and read 192 ohms resistance. That is just within Yamaha's specification of 190-230 ohms.

Going back to Elijah's issue, assuming his pickup(s) check out OK then could he check the operation of the CDi by measuring the voltage coming out of the CDi on the orange (to HT coil) wire? I can't find anything in the manual to help with this test  It would have to be tested with the engine turning over so might be a tad difficult on your own!

Brian

PS I found this http://home.earthlink.net/~edstoller/id10.html which seems very good and also explains why we should always have the spark plug grounded when turning over the engine. I was told this by my biking mates back in the day but not why it was necessary!

 

HI Brian

no don't use them as power sources , 5v on control units are mostly switched outputs  to change the settings internally or supply a trigger to something else externally also can be used for factory testing  prior to fitment .not designed to provide any significant current.

i had a Yamaha scooter that was speed restricted to 40kph in the state i live due to its candle like headlight , once the correct wire was removed the restriction was removed and i could manage a frightening 80kph

 

ttboof wrote:

---

yes the magnet induces a voltage in the winding in the pick up coil  ( ive never had to check a TTR but ones i have are from .2v to 3v ) , once the  pre determined voltage is recognised the cdi unit does its thing switching  the primary coil in the ign coil causing a secondary voltage - spark

CDI -- capacitor discharge ignition  , capacitor in the unit charges to a high voltage , the pick up coil triggers the unit and the voltage is dumped through the ign coil simple and complicated at the same time 

---

Hi Les

Great to be getting feedback!

The more I think about it, I am not sure I understand how the pickup coil can both charge up the capacitor in the CDi as well act as a trigger.

I am now thinking that maybe the capacitor charges up from input from the battery and rectifier/regulator circuits through the Red/Black terminal. 

Looking at a loom cut down to the absolute minimum for a kick-started  TTR to run, the red wire from the regulator/rectifier feeds the red/black wire that goes into the CDi. Amended diagram below.

I recall test riding a newly rebuilt TTR that cut out once the battery went flat. I later discovered that I had forgotten to connect up the rec/reg  If the rec/reg had been connected the TTR would have kept running with a dead flat battery.  If the CDi was picking up power for the capacitor from the pickup it would have kept running without a connection to the rec/reg and/or battery.

The extract below from the wiring diagram seems to show this possibility?

Brian

 electrics are my thing but motorcycle electrics as much as they do the same thing as cars , some how bikes are a whole different can of worms . this discussion  with brians investigative skills is starting to put the pieces together

 

 

Hi Brian 

to Find the magnet run a screwdriver around the flywheel and you wil feel it attract the blade 

the timing is worked out by the unit  the timimg is retarded for starting that’s why the days of kick back are gone 

orange wire check ossiliscope is the best and you can see the output with a multimeter maybe a didgital voltmeter set on a high voltage scale if you have one with a bar graph across the bottom you may see the pulses when cranking  if I get a chance I will have a look soon 

the long strip may double as a balence strip as well 

-- Edited by ttboof on Friday 19th of January 2018 08:26:00 PM

Thanks for doing that Les. Another piece of the jigsaw!

I am a bit puzzled about how the flywheel triggers the pickup though 

Looking again at the flywheel, I think the metal strip may be a balance weight. However it seems to be positioned in about the right place in relation to the TDC mark and the position of the pickup in the generator cover.

I ran a paper clip around the outside of the flywheel and there is no discernible magnetism anywhere on its circumference - only on the inside.

Maybe it's not important enough to worry about but I would have liked to have understood the full story 

However, I think we have enough info now for an owner with a "lost spark" to check out the CDi 

Brian

Brian i have a bit of input here. It is as ttboof said, the pickup is the actual magnet. Nowhere on my flywheel is it magnetic, except inside for the stator.

My pickup reads almost exactly 200 ohms. Cranking the engine with the multi-meter set on AC auto voltage shows a variable reading but it is around the 0.5v mark.

Does that sound right? I tried it several times and the voltage reading was fairly consistent. I am assuming it was reading the spike of voltage as the pickup was triggered.

Brian