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General Category >> Rubber Side Down! >> Spark timing / CDI Unit
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Message started by metri on 11/15/08 at 06:31:32

Title: Spark timing / CDI Unit
Post by metri on 11/15/08 at 06:31:32

Hello,

I'm currently working on an Electrical Engineering project for school and have chosen to build a CDI unit. I found the plans online and ordered the parts and built the circuit. Now it runs on a bench, but it's designed for a different bike. I'm wondering a few things about the Savage spark system to figure out if it's possible to modify my current circuit to fire the savage (I'd get bonus marks :P ).

The questions are:
Does anyone know when the sensor sends the pulse to the CDI? and if there is one sensor or two. On some bikes there are 2 pickups for timing (12 and 36 degree's I think) and on other only 1.

The plans I'm following are on this page if anyone wants to have a look.
http://www.transmic.net/gb1684-V53.htm

Any thoughts on wether or not it's possible to make this work on a Savage would be much appreciated. Thanks again

Brian

Title: Re: Spark timing / CDI Unit
Post by verslagen1 on 11/15/08 at 07:54:31

Haven't been in there, but pretty sure there's only one pick up

http://verslagen.savageriders.com/images/wt_2085.jpg

not sure but this might be it.

I'm sure you can make it work but may take some doing, get a round one, it will help. You'll just need to add a pickup for the 36° sensor. Get yourself a alternator gasket or 2 cause there's oil in there.

Title: Re: Spark timing / CDI Unit
Post by verslagen1 on 11/15/08 at 07:55:54

BTW, is there a circuit for a single sensors for us that might need to replace the CDI?

Title: Re: Spark timing / CDI Unit
Post by mikestrikes on 11/15/08 at 08:23:23

Yes its a single setup... sure would be nice to be able to adjust it...

I'm use to motors with a rotor setup that you can modify or replace and get different timing.

The only way I see the Savage getting that is to have the pickup coils mounting holes slotted so you can move it ....

Also does the Savage have a rev limiter ? It should.

Title: Re: Spark timing / CDI Unit
Post by metri on 11/15/08 at 09:15:59

The circuit I'm using can work with one pickup. The biggest trouble will be to find out how many degrees before TDC the signal is fired. At the point, the circuit should be able to give any firing curve desired. I have a spare engine, I'll try taking out the sensor and figuring out when, with relation to TDC it signals...

Thanks for the help and schematic :)

Brian

Title: Re: Spark timing / CDI Unit
Post by DJM on 11/17/08 at 15:21:14

Hi Metri,
If you have access to an oscilloscope and a pressure sensor, here's how you measure the angle between sensor out put and TDC. You will need to us a dual trace scope, one input attached to the sensor coil.

You will need to unscrew the spark plug and screw in the a pressure sensor. Now, hook the other scope channel to the pressure sensor output and crank the engine. The pressure will peak at TDC.

Title: Re: Spark timing / CDI Unit
Post by smokin_blue on 11/20/08 at 03:21:11

According to the factory manual the timing spark is 5deg BTDC below 2000 rpm and 30deg BTDC above 4,000 rmp. my guess would be one of those should be straight up signal timing. Try degreeing the crank like you would for the cams and find TDC and see how far away the signal pickup is.