oMG, what have I gotten into.

[Curseduth]

So I picked up two xs400s in a trade, a 1978 mostly complete and kinda running, and a 1980 parts bike with a crate of parts.

Previous owner said the 78 needed a battery and a carb cleaning. He replaced or repaired the stator and after this was done it just didnt run right.

I haven't been wrenching on a motorcycle in 15+years but am a fairly good mechanic. So on to the issue.

First after I got the bike home and got a little fresh gas in it and jumpers it to a small auto battery I was able to get it running, it obviously had synch issues with the carbs or timing as the left cylinder heated up quite rapidly vs the right cylinder. So I pulled the carbs and proceeded to clean them. I thought...they were stock carbs for the bike but after looking at them it was apparent there was a homemade bracket on the bottom and the top bracket was only held on by one side. (I can only assume they put the 1980 carbs on the 78).

So after cleaning I shoved them back on, checked for leaks, and turned it over...no fire. Plugs aren't great but they had weak spark so I figured it should at least attempt to fire. Then I noticed the right side was barely sparking regardless of coil change or plug. So I opened up the timing cover.
Very apparent someone had been working in there with a heavy hand. Hours later after trying to get the points set correctly I give up....

So long story short, is there a good write up for wiring in a TCI from a 1980 into a 78? All the schematics I see do not have the same colors I see on my tci box. Did I mention there is no fuse box on this thing and I cannot find where it used to be or where the PO hot wired what should have been fused. Also, is there much effort involved in putting slide carbs on(I was given two slide carbs that appear to be in good condition). Better to run a single Y cable or a dual cable?

I have spent hours trying to find a TCI swap with adequate pictures and the only thing I could find was either for the 650( which carries different colors and no identification of what is what on the box) or a simple "just swap the whole harness" answers.

 

[Curseduth]

Uploading more than one pic isn't working..

 

[Curseduth]

...........help with carb ID?

Also why is it rotating all my images...

 

[xschris]

Carbs look to be off a 70's Suzuki gs400. There was a member a while back that had just picked a bike up with a set also. Not sure how it turned out. I would rewire the entire bike. Or find a factory 80-82 sohc xs400 wire harness to put on the bike.

 

[Sesty]

if you are taking the photos in portrait mode on an iphone when you email them to a computer they are turned... taking the photos in Landscape is better

 

[Curseduth]

Well the were taken in landscape on an iPad.

Xschris, I wouldn't doubt this was the same bike as that previous problem. Funny, I was at the bike store looking for a rebuild kit and I accidentally told the guy "I need a carb kit for a gs400". Mabye I knew before I knew? Unless of course you are mentioning my mistake of typing gs400 instead of xs400 in the hello from the desert thread.

 

[xschris]

They used a few different styles of carbs for the gs400. Not knowing the exact year they came off of it will be hard to get the right ones. Or even how well they will work on a xs400

 

[Curseduth]

Yeah, I am going to take them down to the local real bike shop and see if they can id them and give me some specs. All I know is I cleaned them, tuned them rich, then tuned them lean and it didn't like either. Now I am chasing an ignition gremlin and can't figure out the wiring to swap the tci over to the 78. ( none of the colors match). Had power to the coils(which seem to be 3ohm instead of the 4 that should have been on a points bike) but the crank signal wasn't firing or the tci box is dead....hopefully they have a new points set at the bike shop..

 

[Curseduth]

Finally...using the simplified "start damnit" or whatever it was called I was able to get the tci fired up and started. Carbs need to be tuned but it started..so on the pickup itself am I to assume one is power and the other two are trigger sensors? Because one way just backfired so I switched coil outputs and it fired right up. Does the manual have part numbers for the coils? Because I check mine and they were around 2.76ohm but like I said this was on a rigged together points bike? One is a CM11-54 and the other is physically different, 029700. Btw thanks for the help.

 

[Curseduth]

Here's a pic of the "different" coil.

 

[xschris]

The beige coils are 4 ohm points coils and the black ones and 3 ohm TCI coils.

 

[Curseduth]

They both checked out the same, ohm wise.

 

[xschris]

The beige ones could be bad and test low. All those style I have seen should be 4 ohm or there about. Check the secondaries also to see what they come out to. The tests and numbers are in the manual for each type of coils.

 

[Curseduth]

Instrumentation error...I have five seperate coils, 4 blacks and a beige. An what was the chance they all check out the same? None..so I grabbed another multimeter ohm out the leads...huh...same again? So I grab another meter..wtf same again..so I grab a 1kohm resistor it reads 2.7ohms.. So I break out the fluke(instead of the ever so plentiful harbor freight ones) 3 of the blacks check out to 2.76 ohm the beige checked out to 4.3 ohm. 1 black failed on secondary but there was corrosion on the coil side contact.
I cannot fathom how three separate Chinese built meters all failed the same way (other than low batteries) as they are all varied in time of service...

Long story short I have at least two good coils.

Thanks again. . Getting closer and closer to a running bike, so I can start modding it..

 

[Wolfe_11B]

I've mentioned a while ago that investing in a quality meter is one of the best investments you can make. Flukes are the bees knees.

 

[Curseduth]

I was of all things..an instrumentation technician in the Air Force, calibrated and tested all things electric and electronic. The fluke of all these generally accurate enough meters failing the exact same way was strange. Just glad I worked it out.

Can I just replace the plug wire on these bikes as long as it falls into the set range? Or..?

 

[rshutchinson]

Yes you can replace the plug wire.

I personally use non-resistor caps with resistor plugs as that way you don't have to worry about a resistor cap failing later.

 

[xschris]

Use copper core wire.

 

[Curseduth]

Use copper core wire.

Well I had some MSD 8mm helical super duper wires hanging around. Took a little trimming but got the, on the coils and caps. I had just bought new non resistor plugs so I reused the resister cap. Overall ohm with the cap was about 15k on one and 16k on he other. I think this is about what the stock ones were? Caps ohmed out at around 6k. these coils are meant to be between 7200-8800k without a cap. So this should be OK right? They produce a hot spark, doesn't look as hot as before but that's expected raising ohm value. Or is my thought way off?

 

[xschris]

7mm copper core wire is what you should use with a 5k ohm cap if you have non-resistor plugs. If you want better than go with a non-resistor cap and a iridium resistor plug. NGK BPR7EIX is what I use in all three of my xs400's.