Why won't it run!

Hi guys, first post here, I wish it wasn't this type of post... Just bought a 1982 Yamaha xj650 (model RJ) with 46000 km for a upgrade from my 1982 Suzuki gs400 .
Bought the bike decently cheap and go two! One is supposed to run, the other for parts buuuut... The main bike doesn't wanna run.
Long story short, went through the typical, try it to start procedure and I think I can narrow this down to an electric issue.
Basically I feel like there is a safety circuit stopping the coil from firing properly. When I try to start the bike and check voltage at coils I get 8-9V which looking at other posts is not enough. To me, it sounds like something is up with the voltage available for the coils, when I turn the ignition on, I can hear the ignition cut off relay click, but when I look at the voltage at the coils I see 8-9V and after a second or two I can hear another click (coming from left coil as far as I can tell) a bit quieter and then I get the 12V at the coils.
Then I try starting the bike and it falls to 8-9V and back to 12V a second or two after letting go of the start button.
If I unplug the left coil, I don't get the second click, only one with 12V at right coil. Also tried to change the coil with the parts bike, same problem. Tried to change the ignition cutoff relay, same problem.

Running out of things to try other then testing the whole wiring which I feel will be a pain. **Also for your information, the headlight doesn't light up, and I get a on/off neutral light if this can lead you somewhere

 

A great battery is needed when you fist start to trouble shoot our bikes. The TCI will provide spark if you don't have a really good battery. As far as the headlight goes, it is engineered to stay off until the engine is running. Once the bike is running the headlight should start to work. Engineers knew they needed all the power to go to the starting system so the light is removed from the starting process.

 

Wasn't sure if there was supposed to have some amount of life in the headlight or none! I will let the battery charge fully before doing the test again, but it is brand new so should not be a problem imo.

 

I'd hook up jumpers to a known good battery, (or running car) and see if it will crank over. You didn't mention but does it crank? Does it do anything when you hit the starter button? Do you have any lights in the instrument cluster? A crap battery will show 12 volts, but when load is applied will drop down, showing the symptoms you are describing... It is just a little challenging to give specific advice without knowing a few more details!

 

Sure, gave the info I had in mind on the first post, but was sure to get more specific questions!

The bike cranks good, and almost want's to start if I give it choke, but the closest I got was 1-2 second of running but dying instantly.
Tried starting fluid with no success.

The voltage at the battery doesn't go down a lot when cranking, only at the coils.

 

You haven't cleaned the carbs, have you? If it's been sat for anything over a year you will need to give them a thorough clean.

Also you've not mentioned if you can get a spark with all plugs removed (reduces strain on starter motor) and resting (to make contact) on the head.

 

The change in voltage is reflection of the TCI doing its job.

When the ignition key is first turned on one channel of the TCI will power up low, which means a full 12V across a 2.5 ohm ignition coil. To protect the coil the TCI will wait about two seconds and if no pickup pulses are detected it will switch to standby mode, which sends that low channel high and removes the load.

When you press the start button and the pick-up coils send a signal to the TCI it is activated and the load of the ignition coils is alternately applied if the bike is running or cranking. When you stop cranking without a successful start the one channel that remained low will once again switch high after a couple of seconds removing the load.

So, a voltage of 8 to 9V at the coils is not far from normal, as normal for what is considered a good battery is above 10V when measured at the battery during cranking. The voltage you are measuring has the potential to drop through the ignition switch, the main fuse, the ignition fuse, the kill switch, and various connectors. Note that the original fuse boxes are often an issue as the fuse terminals corrode and break causing loss of voltage or poor voltage supply

A bike that almost starts, particularly if it fires at the moment you let go of the start button is a good indicator of a low voltage issue. So doing a load check on the battery while cranking is still a good idea. As mentioned above it needs to stay above 10V

And what about history on the bike that you may have gotten. The biggest issues for not starting or running poorly usually point to the carbs. Do you know if they have been serviced? In particular poor starting is a result of clogged enrichment jets in the carburetor float bowls

 

Yes, got them all disassemble and cleaned with brake clean and metal wire. Bought a rebuild kit to replace de needle valve also.

I can see spark when going one at the time, but to me looks like a weak spark (if I compare the spark I get off my Suzuki GS) but might just be because of the paint?

Thanks Rooster for the info on the TCI function!
I'll definitely check the other parts that can reduce the voltage like the ignition switch and fuse box that are not original!

I'll do to make sure with a full battery!

Like mention I did try to rebuild the carb to the best of my ability (check float heigh, check for cracks in diaphragm, clean with carb cleaner, etc.) and yes I did change the butterfly valve seals (with the oring option since I can't get the original!). Enrichment circuit pickup was checked and cleaned, I can see my flashlight through the little hole.

Like I said, I think it is more related to an electrical issue, but again might be wrong! I'll keep you guys updated!

 

So it doesnt pop off with starting fluid? That means it isnt a "too little fuel issue". To cover the rest of your bases here is what you can do. First, try cranking it for around 5 seconds then take the plugs out, what color are they/ what do they look like? Also go ahead and run a compression test for us, no point trying to get an engine to run if it has 8psi on all four cylinders..... Theres posts around here on how to do it correctly, main points are hold the throttle wide open and only take out one plug at a time (taking out them all for easy cranking can damage the electronics). Let us know what those two results are

 

You can take out all the plugs to compression test - just disconnect the TCI to avoid damaging it.

 

So tested the compression, I get around 60 psi on each cylinder, but I don't trust the compression tester that I got, so decided to take the head cover off to check valves.
Each one is in spec, but when I try to align the TDC mark, the timing dots don't seem to align... Could it be out of timing this whole time?
And would this do damage to the engine (like bent valves?).... Don't like where this is going

 

You have a few things going on there. How long has the XJ been sitting? Wondering if the rings are stuck and not giving you a good compression reading. I would get another loaner gauge and try again. You are doing the test with the throttle at wide open?

As far as the timing goes, I can't tell from the pics. If you have a manual you will just have to read up on that part of it and correct the timing.

You have any history on the bike why the timing would be off or why it has low compression?

 

Yes, the bike sat for 2 years so I guess it can be the rings not fully seating. The guy told me.it was running before putting it in storage (also go a proof of inspection on the bike so makes sense).

He told me he removed the gas and I think he mentioned that he changed the shims. Idk if he decided to remove the cams to change them and the forgot to align the timing dots when putting the chain back on. If so, I wonder if there is damage on the head explaining the bad compression.

In the manual, it says that the timing dots on the cams should align with the arrows on the caps of cylinder 2 which I am not, like way off. Hoping someone can confirm that this could cause a no start issue before removing bolts

 

Spray some PB Blaster or Free All into each cylinder, reinstall the plugs and crank it for 10 seconds or so, if the rings are sticky that should help loosen them up. When I got my XJ cylinder 1 only showed 60 psi but after some PB Blaster, then some ATF and running the bike for a couple hours it now shows 150 psi.

 

Not sure if our bikes are that way, but one tick of timing doesnt always mean the valves are crashing into the piston, it just means they are CLOSER to smashing... You may be lucky and that is the case, or may be not lucky. Either way, fix the timing so it aligns, and try the oil in the cylinders trick.

 

@XJ650inTexas,

If I read your post right, looks like you have good compression on your cylinders now. It also reads that you have the bike running? Do you will think the timing if off if she is running? She should sound like a good sewing machine when it is running properly.

Glad that those rings loosened up for you and you have some good compression back. I have only had one bike in my rebuilding days that was so bad I had to break her open. That bike has missing spark plugs and sat outside. These engines are wonderful and almost bulletproof.

 

I'm not an expert on these XJ engines, but in the hot rod world you can buy timing sets to advance or retard the valve timing by 2° - 6° so the question would be how much (and with two cams, are they both off in the same direction). The PO said it ran? Is there any way you can contact and follow up on whether the cams were ever removed? Squirt some motor oil in each cylinder and retest the compression - if it jumps up you know it's the rings, if not it's the valvetrain.

 

Hey guys, got some good news! Went through the process of resetting the timing on the bike and got it running! Just need some basic maintenance before riding it