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Discussion Starter #1
right…after having a 'missing' issue and going through the whole carb thing i bought a 2nd hand CDI, fitted it to the bike, cured the problem…simple!!... bike ran fine, ticked over, revved out, i drove it and it seemed to be lacking acceleration a bit but i thought the 45t rear sprocket was the reason for this, as a guy wants to buy this bike i guessed that he can change that if he wants to…job done!

at the weekend i was repairing another Tw that a friend had so kindly trashed..somehow he had melted some wires…as i was checking out the damage i connected the battery n the CDI started to smoke..i quickly unplugged the battery and started cursing as i thought id just F$$ked a perfectly good cdi….to test this i fitted it to the bike i mentioned above, it started up first time so i thought..phew!..no damage done, i went to a quick drive to check it further…..the same bike that had low acceleration now was quick off the mark accelerated perfectly to the point i couldn't tell the difference in sprockets and just generally drove way better than previously….so I'm baffled as to what can fail on these things, both ran fine, no missing, just a noticeable difference on acceleration, i swapped them back n forth and its defiantly 1 cdi is better than the other but both work!!

any ideas? or solutions….i can get cheap parts from japan now but would rather not keep buying cdis to find another good one!!
 

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It sounds like one is going out unless one of the bikes pick ups and magnets isn't letting it advance with the rpms. ??
 

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Discussion Starter #3 (Edited)
both bikes run perfectly with the 1 cdi so can't be an issue with the bikes. the other cdi will run fine and will get to top speed with out missing..just not mid range/acceleration when you open the throttle
 

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Might I suggest a new oem CDI, but purchased from a more affordable source than dealer, i.e. Boats.Net? ( 2001 CDI @ $136.43 plus ~$12 shipping)
 

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Discussion Starter #5
buying another is easy, i would like to understand whats failing and why, just so i know. i have 4 cdis that came from perfectly good working bikes….all seem to have failed overnight which surely can't be coincidence ??
 

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It does sound as if something else is amiss to cause such re-accuring electrical gremlins. "Smoking CDIs" might make for a good garage band name, but in your bike that spells grief. From your past posts I think you have more CDI experience than any of us so I cannot presume to offer any true insights other than to confirm all wiring and connectors are in good original condition.
The ohm-meter tests of voltage regulator,CDI, coil and stator parts are indicative but not definitive diagnostics. All my similar readings were in spec but process of elimination with known good parts borrowed from Twilight's bike made me decide to order new source and primary coils which solved my problem. Wasn't really a process of illumination, more of speculation.:eek:

I feel your pain and frustration. Good Luck.
 

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Discussion Starter #7 (Edited)
thanks fred…the bike i mentioned above in this post has been cured with the 'good CDI', however i have another that has the same issue but far worse, i tried the 'good CDI' and it didn't make a difference..

I'm not too familiar with the primary & source coils so these are the things i will be looking at as soon as i get free time, but on that note...on this TW i have removed the fly wheel recently to repair the starter clutch bolts that had sheered, after drilling 1 bolt out i removed the magnets to clean everything properly…...i am starting to wonder if they have a certain way to fit?? i didn't notice any marks and they all lines up with the screws and fit, could this be affecting the sparking? i dont remember have this issue previously and have already been through the carb swapping/jetting thing, are the coils adjustable? any tips on what i should be looking for?

thanks
 

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Discussion Starter #8
It sounds like one is going out unless one of the bikes pick ups and magnets isn't letting it advance with the rpms. ??
i am having a clear out and this bike issue is still not solved, its now a spares bike, before i strip too much off id like to fix it and sell it as a running bike.....can you elaborate on this please littletommy, i removed the magnets from the flywheel when the starter clutch bolts sheered...do these magnets have a direction or order they fit in? also i noticed that there is current coming from the brown wire to the cdi, when i disconnect it it seemed to run a little better.

thanks
 

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It has been quite a while, but I seem to remember reading on the forum that placement is an issue and can affect timing. I am sure there are others here who can answer the question better. Sorry bro, I can't be of more help. :(

i am having a clear out and this bike issue is still not solved, its now a spares bike, before i strip too much off id like to fix it and sell it as a running bike.....can you elaborate on this please littletommy, i removed the magnets from the flywheel when the starter clutch bolts sheered...do these magnets have a direction or order they fit in? also i noticed that there is current coming from the brown wire to the cdi, when i disconnect it it seemed to run a little better.

thanks
 

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The magnets position and the source coil determine when the spark signal is initiated - you should have just the one magnet to send that "pulse" - so when you say "I removed and cleaned the magnets", (plural), this is a bit confusing.

However - if said magnet is loose or even slightly out of place - this will screw up your timing

My understanding (admittedly vague) of the advance, is that it is handled internally by the CDI unit - the parts numbers for the CDI's varied over the years - make absolutely sure you have the correct one for your year of bike - it is not a "one size fits everything" situation ........
 

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Discussion Starter #11
by removing the magnets, i mean the 4 magnets that are attached to the inside of the cdi magneto..as far as i was aware the difference between CDI's is 87, 88-00 and 01-present
 

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as far as i was aware the difference between CDI's is 87, 88-00 and 01-present
There were around 4 or 5 different ones - different prices too - it would help "a lot" if you were to come up with a specific year ......
 

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Discussion Starter #13 (Edited)
thanks purple...a specific year is almost impossible as these bike are all imported and paperwork has been lost over the time, this bike a i drum brake model, with small rectangular Cdi, so pre 01 but not 87, thats as narrow as i can get it.
i can't say i have had a problem interchanging them before and will go as far as to say its not the cdi. this bike didn't have this problem before, i think it is something to do with the cdi magneto and pick ups as little tommy mentioned, this is the only thing i messed with (and know nothing about) when i had to remove it to repair the starter clutch, i have a spare cdi magneto i could try, but would like to hear peoples thoughts here so i have all the info before tackling this bike again.

i realised this was on an old thread relation to cdi's, so i started a new one. thanks
 

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supachip1, I have read through your posts, and have a thought. I have had experience with many different forms of magnetos, and so I consulted the TW manual to have a look at the part that you removed the magnets from to clean.

Sure enough, Yamaha refers to this part as the CDI magneto. It does contain four magnets. Ideally, they should never be removed. IF there is ever a reason to remove them, the first thing one should do is to make careful notation as to exactly which magnet went where, & which direction / end / polarity the magnet was positioned in. This is VERY important, as for example, if the polarity of the magnets ran in series, ie +_- + _- +_- +_- and you were to get one of the magnets reversed resulting in +_- + _- -_+ +_- this would result in a problem!

IF you have a Yamaha CDI magneto that has not had the magnets tampered with, you can check to make sure they are the same with the use of an inexpensive compass. By moving the compass from the end of one magnet to the next & so forth, you can determine the direction of polarity & correct the CDI magneto you disassembled, if necessary. As you have removed the magnets, IMHO this possible issue should be ruled out to help save time.

This video goes into the subject way too far, but it will definitely give you the idea, & it's a cool vid.

Is this what your's looks like?
$(KGrHqUOKp!E24R8dt)kBN1S0ke-pg--_35.JPG

good luck, m.
 

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Nice info, might be just what he needed. Thanks for looking this up!! +1
 

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Discussion Starter #17
thanks mhomadness, i looked at the spare magneto, it has a continuous magnet. the one on the bike is the same as the picture you posted, i guess thats the difference between years??

i will google and youtube things tonight and see if i can find more info, and then try to fix it tomorrow.

thanks
again
 

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Yep! That's a difference... I was not able to find the correct polarity, or any mention to it while searching... I would get a compass and see what the polarity is at the moment...if one is out of step from the rest, try turning it & then check it again with the compass to see if that put it back in order. Worth a try? m.
 

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The difference in years I was on about was the OEM part numbers for the CDI – quite a difference in price too – so it’s likely there’s some sort of difference there or we’ll all be using the cheap ones from now on.

I did list them all once – but search as I might – no joy

Now I know it’s the drum brake model, this means “less” of a search through the parts catalogue (which I’ll do tomorrow) …….
 
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