xj650rj no spark/ ignition questions

i have a xj650 seca i bought to fix up. bike came semi disassembled but when i first got it i put it back together and in trying to start it. i found it had a bad rectifier and that the main fuse was blown. replaced it, bike ran for about 15 seconds then died. no spark after that. tried new ignition coils but returned them because that didnt work. (found out the specifications too late on how to test the old ones via ohm). but they old coils are good.

took apart the tci/cdi and found some bad solder cracks and a couple of the printed circuit board runs were broken. fixed those hoping to salvage the tci.

previous owner had semi modified the wiring harness in a way that does not make sense to me. so i decided screw it, the motor has great compression and i had it start once so i ended up doing a full teardown and building it back up with minimal wiring diagram to rule out all the bad sensors, relays and switches. this is going to be a minimal bike anyway.

bike is torn apart and cleaned and im in the process of building it back up. motor was just put back in the frame, so i decided to wire it up minimal to make sure i can get spark without all the extra wires that werent connected to anything, etc.

still no spark even with minimal wiring. used a car battery. starter turns over fine, 13v on red/white wire going to ignition coils. but ive noticed that the voltage drops on the red/white to 10v when i plug in the tci. then cranking it drops to 6-8v.

i noticed one the tci is connected i also get voltage on the grey and orange wires on the ignition coils even when not cranking. is this normal? the ground bolt/where the ignition coils bolt to the frame also got really hot when trying to test for spark. idk what the hell that would happen for.

im going to pick up a new tci on ebay, just wondering if anyone has any input before i spend money to throw a new one in there and accidentally fry it.

engine is a 5v2-000XXX, but the hitachi cdi on it has no identifying marks. can i use a cdi from an 82 maxim without timing curve problems?

 

The ground should not get hot. Sounds like the whole harness may not be grounded well enough.

 

From one of your earlier post.
"I tested the transistors, one was iffy and the other was definitely bad. So i ordered some replacements from digikey. The rest of the wiring through the bike was a hack job from the previous owner."

What transistors did you order from Digikey? Here is an interesting write-up on what works:

http://www.xjcd.org/TCI_transistors

I think you mentioned broken etch earlier also, so likely best to just replace the TCI. They can be pricey, but if you can be patient Ebay listings will show up with reasonable prices. As for the correct TCI these are listed as compatible per Partzilla:

This Yamaha 5V2-82305-10-00 IGNITOR UNIT ASSEMBLY 1 Not Available fits the following models and components:

Yamaha Motorcycle 1980 XJ650 - XJ650G ELECTRICAL - 1

Yamaha Motorcycle 1981 XJ650 - XJ650H ELECTRICAL - 1

Yamaha Motorcycle 1981 XJ650LH ELECTRICAL - 1

Yamaha Motorcycle 1982 XJ650RJ ELECTRICAL - 1

See below on checking the overheating ground wire. If the wiring scheme is not correct the high current starter could be causing losses resulting in the lower voltage. Go ahead and check the battery voltage also at the attachment point (not the battery terminals) just to be sure whatever jumper cables you are using are providing an adequate connection.

Yes it is normal. The orange and grey wires are pulled to ground for a very short duration (dwell) when the bike is running. The only exception to that is when the key is first turned on either the gray or orange will go low momentarily (about 2 seconds) and then go back high to protect the coils. The TCI will remain in this standby state until the engine is cranked and voltage from the ignition pick-up coils will activate the TCI.

That should not get hot. It would only heat up if:

The large cable from the battery negative to engine (starter) is not properly connected or undersized.
Improper gauge wire was used - note that wire should be sized for the entire electrical system (excepting starter) as all circuits return to battery through this ground.
A corroded or resistive connection at that point
A shorted or miswired device adding excessive current to return through the ground.

 

so the hot coil grounds are probably from resistive ground connection then. after painting, i sanded the coil grounds connections and where they bolt to on the frame to bare metal. but i forgot to do that on the engine motor mounts, im guessing the motor mount help ground the engine to the frame? or is the frame mainly grounded from the 6 guage ish wire that is bolted directly to the engine block. i have 2 thick black ground wires that are bolted to the engine block and i just connected both of those to the negative jumper cable. i guess one of those needs to go to the frame.

just never seen a ground get hot from lack of ground, only from shorted wires. i tripple checked everything was right with the diagram wiring. and nothing was touching. i also used the wires from the old harness so gauge should be fine.

anyone have a minimal wiring diagram that they labeled with what each wires is supposed to be by chance? voltage wise? would make it alot easier to understand exactly how everything works, and if the currents on those wires are correct. for example when initially looking at it, i would have figured the red/wire wire supplied the voltage, not that it needed to be supplied by the goldish/brown wire. kinda thew me when the silinoid that already has a 12v main, needed 12v supplied to it via the red/white to work.

i found 81 xj650 cdis on ebay for alot cheaper than the 82 . but if it wont work right, i guess ill have to spend the extra money.

Thanks for the replies

 

Yes, the smaller one should go to the frame and the larger one directly to the battery negative. That way you won't have to worry about the painted frame at the engine mounts.

So that was the Rect/Reg that was replaced along with the main fuse?

Do you notice any sparking when connecting the cable with the key off?

And maybe some more specifics on the heating ground. Does it heat only when cranking the motor? Can you turn the key on and just let it sit will it heat up? Are you sure the coil itself is not hot?

According to Partzilla the 81 650 is the same P/N. Hopefully one of the 650 Seca members can publish the number on their TCI so you can use that to purchase one. Most also have the matching P/N stamped on the reluctor plate for the pick-up coils.

XJ750 MaximJ

 

I don't have seca's in the garage but I have an 81 and 82 maxim in there which have different tci's. I suspect this has to do with the 81 being non-yics and the 82 being a yics motor. If I get a chance tomorrow I can take some pics and see which matches the OP's tci. I'd venture to guess it would more likely match the 81. Not a bad idea to make sure they match the reluctor plate either

 

good, was gonna be anoyying to take the motor back out without scratching the paint

yeah the reg/rectifier was the first thing i replaced because of the blown fuse and it was rusted to hell, so i figured it was prolly bad. if not, just preventative

ill check that when i get home from work tomorrow. the coils were a little warm but i couldnt tell if that was because of how hot the bolts/gounds got. literally could only hold my finger on the bolt for 2-3 seconds . so prolly 140 ish degrees( about the same running temp of a 77 Johnson outboard i rebuilt)

i ended up ordering a tci from a 82 xj650 maxim for 50$. 5V2-10 TID14-08 1982 and my engine is a 5v2 sooo that seems solid. everything i read has me believe the 82 maxim and seca non turbo had the same motor, just difference in sport look. so well see, for that price and i can send it back if needed. so i pulled the trigger.

someone had a tid14-05 4u8-10 listed as a xj650 maxim 81 for 30$ which is why i asked about 81-82 difference but looking up that part number it supposedly goes to a 550xj

 

5v2 tci came in so i went and hooked it up, and now i have spark. seemed a little weak but spark now non the less, could be from the painted headcover i was holding it against. used a car spark plug test light and its a little dull but i dont know if thats from it being designed to work on car spark plugs/ bigger ended sparkplugs. not the best connection having to hold it in place with one hand but all 4 are getting spark.

i also had to create a spot and bolted the shorter/ braid style wire to the frame. ignition coils/ground bolts no longer getting warm at all.

i did notice the coils have 12volts, but when running the starter drop down to 9-9.2 volts. could that cause the weak spark or is it supposed to drop a little.

atleast im at the point now where i can start building it back up. and getting the wiring more permanent. i used the old connectors to make things a little easier but they are pretty old and a little grimmy. is it worth cleaning them and using them, or just hardwire/solder everything for a better connection

 

so i got everything hooked up and tried starting it, it sputters like its trying to start but never fully runs. im also getting backfires constantly. will these bikes not even idle without the airbox on and just running open carbs? airbox that came with the bike has a big crack and is also missing the top so i cant really use it.
bike also loudly backfired a couple times even like 10-15 seconds after i had stopped pressing the starter, any idead why it would do that?

 

first bike will run/start with out airbox.
the backfire after 10 seconds of not pressing starter button is normal it is the tci firing as desinged.

did you clean the carbs?

 

oh yeah, have run through the carbs about 3-4 times now. i initially bought the bike for so cheap because i thought it was just the carbs that needed cleaning instead of it being an electrical issue. first time i took them apart they looked brand new like someone had just cleaned and threw in a rebuild kit. floats and everything are new. still went through it with a fine wire,compressed air and carb cleaner. ive rebuilt many a carburetors and im pretty positive they re spotless.

i still do have somewhat of a weak spark, ive read thats kind of how these bikes run, but not igniting the gas is almost what it seems like. even misting some carb cleaner into the intakes didnt get it to start better.

spark plugs are also new, bought them about a year ago when i first got the bike. bike has never ran in that time. so they've basically never been used.

 

That's too low to really trigger the TCI - fire the coils, battery is probably bad / undercharged. Charge battery or hook-up jumper cables and try again.

 

ive been using a car battery via jumper cables to try and start it, easily cranks my truck

 

Welp, got it figured out. it ended up being................................. The spark plugs... was ohming out the coils and ignition and checked them just to see, and sure enough 3 out of 4 were open resistance and the 4th was about 40 ohms.. literally cant understand how brand new plugs that have never run the bike were bad after sitting for 1.5-2 years. picked up 4 new bp7es for 9$ and instantly fired up



the star idle adjustment didnt really seem to do anything, but got her to idle with the throttle line screw.
i also noticed a little bit of gas mist coming out of carb 2 and 3 back towards the air filter side. 1 and 4 were fine. anyone know what could cause this?

update: 2-3 werent firing, wire came disconnected, now they are firing and it actually sounds like a sports bike when revd.

gas mist/sputter still remains and is now on all 4, just 1 &4 are alot less than 2-3