Same part ? or can they be interchanged at least

[Freakshow]

Are the 73/74/74 TM 400 CDI the same as the 74/75 250 ?

Do these things have advances in them , and if so do they map up near enough ?  the plugs all seem the same so im sure it will run but run right ?  i know the Sc500 electrics on the MX 250 gives you a better bottom end rather than wieghting the fly wheel.  so can i assume the suzukis are the same ?

Back to the question CDI Tm 400 --> Tm250 ? worky worky ?  assume the coils are interchangable.

me think me have found me problem :O)

[Doc]

All my info sources refer to the same CDI unit part number for all TM400's '71-'74.

no info if the 250 units work on the 400 but I believe the stator test figures are quite different which indicates to me the CDI may not be compatable. Not gospel though 

[Lozza]

The 400 cdi probably won't have the same amount of advance as the 250.The 400 runs around 22 deg advance IIRC the 250 is a bit more anyway less advance on the 250 for dirt track would be beneficial anyway.
In the finest traditions Freaky just suck it and see.
I thought your ignition had been tested?

[Freakshow]

yep took the whole lot to betta bikes last month and he told me it worked 

anyway i replaced everything last night with a 75M, carBies, plates, ign, coil, cdi spark plugs, loom and after a lot of combinations it seems the spark is a differant colour than when with the 74.

backing out all the combinations to all the original stuff and just patching in the 75 CDi you get an idle but when for some reason under load over say 3/4000 revs she cuts out.  like it has a high dishcarge circuit in the CDi that is flacky.  You run the 75 cdi and it leaves the shed on one wheel, so now i now where it is, ill give it back to steve to find out what it is.   Quick solution is grabing the Tm 400 CDi and running that cost wise its cheaper, but only if it works.   if your saying itll run ill grab one and get bbusy with it.    unless anyone can tell me it will fry something else ill grab one of those 

[Freakshow]

The 400 cdi probably won't have the same amount of advance as the 250.The 400 runs around 22 deg advance IIRC the 250 is a bit more anyway less advance on the 250 for dirt track would be beneficial anyway.
In the finest traditions Freaky just suck it and see.
I thought your ignition had been tested?

Magic book says :
TM 400 19.5 @3000
Tm250  21.5@ 6000

does that it yes still?

[Lozza]

Looks fine to me, just keep 4 fingers on the clutch and go 1 or 2 jets up first time out.Just in case.
Hmm steve said the cdi was fine..........hmmm now you know why I'm going to Eastern Bloc/Chinese combos for ignitions  .

[Quicksilver]

I was looking at 400 CDI for my bike too. Seem to come up on ebay USA more often. I emailed one seller about your very question 'will it work well in TM250' blokes answer was no.  He said he'd like to say YES because he wanted to sell it. He went on to say he tried in his 250 to correct his problems however it made matters worst and thats why he had it back on ebay from where he himself purchased it.

[Freakshow]

fToo late he cried for $24us im willing to ship it and see what happens.

NOw i no where the problem is, and have confirm its $220 trade to fix the little box, im happy to try it and see, if not im sure there is a 400 ridder out there who would buy it for there spares kit.

Did he say it wouldnt work with the 250 coil and pulsee or just flar out wont work.  maybe the high speed  or pulse is a differant shaped window so maybe you need that rotor to get things lined up ?  If thats the case does anyone now if the plate and the coils bolt straight up down below ? if they do a complete swap out and it should all run like a tasty sadwich.\

Can someone give me the correct printed numbers on a TM 250 CDI 74L, i want to know if the one thats not working here is actually the right model for the 250 and not a 125 etc swap made a few years back.  THEn i can confirm which pile it goes in .  the save for desperate pile, or the no fricken good to me sell of pile.

cheers freeky.

[oldfart]

Extracts from the Zook  Service manual  TM 400
If the engine fails to start or misfire,check the following points with suzuki pocket tester

Exciter  coil and palser coil
measure the resistance between the exciter coil leadwire  (black/red ) pulse  coil wire  (red/white ) and coil plate.

normal exciter coil resistance     315 ohms
normal pulser coil  resistance       80 ohms

Ignition coil

measure the resistance of the primary ( white / blue and black/white wire ) and secoundary ( blackand black/white wire ) windings

normal primary coil resistance      1.5 ohms
normal secoundary coil resistance 20 k ohms

It shows a picture on how to test the PEI unit

PEI unit circuit check chart using suzuki pocket tester

connect to - terminal                  connect to + terminal            consequence

black/yellow ( black )                   black/white                        no continuity
black/yellow ( black )                   black/red                        approx 2m ohms
black/yellow (black )                    white/blue                  pointer diflects once
                                                                               and returns immediat

red/white                                   black/white                       no continuity
black/white                                 red /white                   100-500 ohm indica
black/red                                  black/yellow ( black )         continuity
black/white                               black/yellow ( black )         continuity



Hope this may be of some help

[Freakshow]

yes Olddy, i seen them numbers, but reality is under load and heat - strange things a happen.   

BAsically this thing was working when it felt like it so a Static test would have confused the issue really.

Static tests i feel only get you to say it has a chance at working, but as to finding a fault they are a little flacky, most good autolecs would tell you to not waste you time.

Although thanks you for taking the time to find the info and post it for us all.

'suzuki pocket tester" - does they means a rebadged mulitmeter 

[Lozza]

You would be correct with the 'pocket tester' bit Freaky.Must be anologue ($30 from JayCar) as a digital just won't read right.
I got a Peak Voltage Adaptor just recently allows you to read voltage of source and trigger coils under load.
Next is the ignition dyno

[Freakshow]

You would be correct with the 'pocket tester' bit Freaky.Must be anologue ($30 from JayCar) as a digital just won't read right.
I got a Peak Voltage Adaptor just recently allows you to read voltage of source and trigger coils under load.
Next is the ignition dyno

well thats it isnt it if you cant load it up and get it under heat and presure your only half reading.  if you can bench race it for 20 mins i;d like to see how much these old electrics move off the boil so to speak and how far the curves move.

[Tim754]

Hey Freaky from experience I would not put TM400 ignitions on anything................ TM400 =  genuine twisted evil nasty killers but lovable in a frighteningly perverse way. Yes I did own and ride a Terrible Mother 400. Cheers Tim

[Freakshow]

surely just a little bit wont hurt anyone ?