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'76 Suzuki TM 400 Ignition

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Posted by: OldTimer---------------------

I'm fairly certain I've got a bad PEI (CDI). I don't even want to try finding the stock part. What I'd like to find out is how to determine what to replace it with. Could I just determine the magneto output and then match it to the requirements of the ignition of a more modern bike and then just buy the ignition system from the magneto on out?
You know, could I buy a new system for, say, a YZ 250, and then slap it on the old girl and take her out dancin'?


Posted by: SFO---------------------

try this

http://www.pentonimports.com/


BTW, '76 was an RM370, no?


Posted by: OldTimer---------------------

Well, I know it's a 400
Maybe I'd better go out to the shop and remind myself of the year. I haven't fooled with it in ten years.
It did puzzle me that my Clymer manual was for up to '74.
I may need a new ignition for my brain also!
BTW, thanks for the link I'll check it out.

Yup, says right there on the steering head,
MFG 10 - 1974
But would that make it a '75 model?


Posted by: BadgerMan---------------------

Quote:
Originally Posted by OldTimer
But would that make it a '75 model?


I think there was a '75 model but there were no changes (except graphics) from a '74.

1974 TM:
http://www.suzukicycles.org/photos/..._yellow_800.jpg

1975 TM:
http://www.suzukicycles.org/photos/...250_bw2_800.jpg


Posted by: OldTimer---------------------

Oh yeah, it's a '75 model. I just wish it still looked like that!
Some idiot went as far as to use vise-grips for a gearshift lever on the one I have!
Thanks for the pics. I'll save 'em.
Any thoughts on the ignition?


Posted by: AjayMike---------------------

I seriously doubt that you will be able to find an ignition black box and coil from a more modern bike to work with your TM400. Like SFO suggested, try the Penton people to see if PVL makes an aftermarket system for it.
FWIW: My older brother raced a TM400 back in the old days. What a handful that thing was, with its "all or nothing at all" powerband and the flexi-flyer frame. Someone knowledgeable told us the strange power curve was largely because of the advance curve built into the CDI. So he installed the (points type) magneto from a TS400 Apache (The enduro version of the TM400.) The difference was amazing. The motor still gave a good kick in the pants but it was smoother and much easier to ride. All I'm saying is the aftermarket system would probably be a big improvement and worth looking around for.
Mike


Posted by: VintageDirt---------------------

Here's a good read for all you TM400 fans

http://www.off-road.com/rick/tm400/


Posted by: ScottS---------------------

points would be a good idea and a fair bit cheaper if you can find a donor bike cheap enough


Posted by: OldTimer---------------------

I guess I shoulda put this part in from the jump...
The PEI or CDI or whatever went out several years ago, well, at least I wasn't getting any spark.
So I arbitrarily(sp) picked out a capacitor and resistor from the electronic tech's drawer at work and hooked 'em in parallel to the PEI unit (what did I have to lose?) and voila, back in buisness! Crazy ain't it? Okay the spark (still) is really weak, but it did the trick for awhile. I rode it to where it sets today. That was about 6 or 7 years ago. Didn't even try to start it again until my sons got thier little dirt bikes this spring, coincidentally the oldest is 7 years old.
My point is: If that worked, well sorta, then it seems like it wouldn't be too damn hard to get a real live ignition unit to work, right?
BTW I do get an arc, but ether in the air cleaner won't even make a sputter, so I figure it's gotta be that rig job I put on it.
Maybe I should just put up one of those candley shrines in my shop with a Roger DeCoster effigy in the center and sacrifice a quart of Castrol over the top of the 'ole girl?


Posted by: originaldirt---------------------

A guy I used to ride with years ago had a similar problem. He was an electronics wiz. So when his PEI/CDI or whatever quit he operated on it and figured he had nothing to lose. He ended up fixing Can-Am , Yam, and Honda CDI's for low $$. He had fun and if it worked he saved money or made a few bucks and he or the other rider got a cheap fix with no guarantee. He later showed me and a m/c tech that worked for me (who was in college to become and electrical engineer and is now an EE) what he was doing. :
He opened the "trigger box"(black box) by cutting around the bottom carefully with a box knife to expose the guts connected to the wiring harness. He then uncovered the pc board in the black box by digging into it's covering which ranged from a hard epoxy on some models to a silicone rubber on others. This exposed the soldered joints on the pc board. First look for a broken solder joint (very common due to vibration), resolder it with a pencil tip iron. Plug it back in and kick to see if you have spark. If that didn't work the next most common problem was a fried capacitor which he checked for with a ohmmeter. If one is found, dig it out, unsolder it, and then it's off to Radio shack or an electronics store for a replacement. Solder in the replacement , again try for spark.
Broken solder joints were very common!!!! Broken connections from the wiring harness to the pc board were the next most likely culprit. The capacitors usually crapped out because of kicking over the bike without a grounded spark plug attached to the plug wire.
If you make a shade tree fix re-seal the unit with an silicone sealer that is safe for use around electrical components. (That stuff smells like alcohol rather than the sour vinegar smell that is common with silicone sealers) DO NOT USE a sour smelling sealer!!!!! Or, use an epoxy to reseal the components if they were encased that way previously.
Good Luck !
OD
PS: Most of the fixes that worked, worked basically forever or were refixable in the same manner.


Posted by: KiwiBird---------------------

Do a search on Mototek ignitions, they were the hot setup back when I was riding TMs and RMs of that vintage.

Much better ignition (I think it's box and coil combined - can't be sure though) with no rev limiter.


Posted by: 2smoke---------------------

Man.....I remember some old Aussie riders and a Kiwi fella (Ivan someone or other) down here who were pretty good circa mid seventies. What I remember is towels wrapped around their mid section under the kidney belt such was the severity of the ride on a TM400. That and that mental powerband it produced. Good luck!!!!


Posted by: OldTimer---------------------

Actually, I think with the narrow profile and the wide bars it handles kinda nice! Sorta like a bicycle, suspension and all! Goes KLANK when you jump a mole hill. But it's really fun on the ground.


Posted by: AjayMike---------------------

I'll bet that old girl can humiliate quite a few modern bikes in a drag race. If you can keep the front end down, that is.

The reason you have an arc at the plug bit it won't fire is probably the spark is too weak and "blows out " under compression.

Original Dirt's idea is sure worth a shot. Probably a lot more people around nowadays who would not be afraid to cut into that CDI box and nose around, what with these kids building their own computers and all. Like the man said, what have you got to lose?

Those CDI's had just come out when I worked at a dealership and I think half our mechanics thought a little dwarf was in that black box throwing a switch to make the spark. The Suzuki tech rep, who was no dummy, tried to give us a little class on the system but I don't think he really understood it either.

Mike


Posted by: OldTimer---------------------

When I first encountered this problem, years ago, the Mr. Fixit guy at the generic bike repair shop tossed me some unknown CDI unit he found lying around on the floor somewhere and told to "try this one". Well, I never did, but now I have one I can dissect for practice.
BTW I've discovered that the Clymer manual has all the test criteria for checking the unit with a standard multimeter. It's not as precise as the "PEI test machine", but I can determine whether or not I'm risking fouling up a GOOD unit.
Oh yeah, one more thing, I checked the Penton web site, and just like everybody else, they form a tight circle all around my model, but just don't quite hit home. I haven't been able to find much more than a fender for this bike so far. Oh well, first I've gotta get it running.



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