'77 Liquifire CDI question

[guitardude081]

My Uncle brought his '77 Liquifire in for a preseason and a CDI replacement. I've ohmed out the ign. system and checked voltage and all switches. The CDI is for sure the defective component. I ordered a replacement CDI box for the sled. It will have the "style B" square connectors. His is "style A" with round connectors. I know that people have spliced these in. What all is required to do it. The wire colors will no doubt be wrong on the aftermarket CDI so I'll have to rely on pin location. If someone has done this can you give me a detailed description on which wire connects to what? It does have the commonly found Black CDI wire soldered to the white ignition wire as well. I'm trying to get this thing ready for Waconia.....and the CDI box won't be here until Thursday afternoon.

[harleysportster]

Jack,
Here is a sketch of the retangle and round types, side by side for you.

[guitardude081]

Harley,
So if I get this right, the connector on the top is the only connector that I'll have on the new CDI. If so then I take it that I solder the wires from the New CDI to the proper ones on the old round connectors. This one already has the White wire splice done which from what I took from your post in FAQs was something commonly done as a fix. Other than that, the 2 coil wires and the ground loops should connect as they originally did right? I'm not too familiar with the older generation ignitions. The few times that I've had to work on the "S" chassis sleds, I never really paid much attention to the ignition system. Thanks for the help. It looks to me like a good splice job won't be that bad.

I've got 'er all detailed, pressure tested, greased and she's got a pair of nice clean carbs and a rodent free airbox. It's nice starting with a sled that 5 years ago was possibly the most beautiful original machine I'd ever seen. There wasn't a scratch and speck of rust to be found. 5 years in "corrosion corner" in the garage at the cabin took its toll. Plus the seat is cracked on the back and the hood has its share of scratches and scuffs now. It looked horrendous when it got dropped off on Saturday. I spent most of the day doing the ign. diag, cleaning the carbs and detailing. She's still one of the nicest originals out there. If all goes well my Uncle will be in the saddle at Waconia.
~Jack

[harleysportster]

Jack,
If my memory is correct, the rectangle plug CDI will have a seperate set of leads which go to the external coils plus an external ground wire.
Pat

[guitardude081]

Alright, well everything is spliced and working properly except for one huge problem. All I can get out of this thing is a backfire out the pipe. The carbs are set correctly and this is not fuel system issue. I ordered an aftermarket CDI made by SPI. I have spark on both sides but like I said, all I get after 3 or 4 pulls with choke or no choke is a backfire. It doesn't kick back like it's out of time. The stator and trigger assys. are both set correctly...and neither has ever moved from their original positions. I'm thinking about reversing the coil wires but, I really hate doing that on ignitions that aren't meant to fire both cylinders at once. Is there a chance that SPI accidentally got the wire colors wrong for the coil leads? If I reverse the connections (white wire PTO and Red wire MAG) and it's wrong I'll also get a backfire but the engine should kick back as well.

Before the CDI failed, this sled would notoriously start on the first pull and run perfectly. My readings from the stator and coils are all within 1 ohm of the readings in your FAQ post....talk about consistency! I'm going to try switching the leads (reluctantly) What else could be wrong if this doesn't cure it? Compression is at 135 in each cylinder, the carbs are set to factory and have the correct jets, all switches work, the exhaust is clear of debris, the reed petals are in good shape and the slides are synchronized. This style of ignition is foreign to me. I really appreciate how simple snowmobile ignitions are today after dealing with this thing for the last few days.
~Jack

[harleysportster]

Glad to here you figured it out from your other post.