1982 Yamaha XJ650L Turbo Seca - No start after riding and running fine.

Hello, as the title states I have a 1982 Yamaha XJ650L Turbo Seca. I just replaced the turbo with a rebuilt one from XJ4Ever, shoutout to Len for that. The bike was running beautifully for almost a couple weeks. Took it out for a ride yesterday, then parked it. Went to start it an hour later, it progressively idled more and more rough, had to restart it a couple times because it died while idling, and now, it cranks but no start. Starter fluid has no effect.

I took two different spark plugs off while cranking the motor, one had intermittent spark, the other, no spark at all. I'm suspecting that is the issue, what could be the potential underlying cause? I've checked fuses, they look good. Is it the ignition box on the side of the bike?

As a side note, I went to start it after work today and it fired up very very briefly and then died. Maybe a second's worth. When it fired up, it made a weird hum noise. Not sure what that was or if it's even related.

Thanks in advance for any input, let me know if more information is needed. Hopefully somebody has had a similar experience.

 

Having done some research, as I was unfamiliar with the ignition system on this bike, I found this in the forums:

"The ignition system actually begins at the left end of your CRANKSHAFT, since the rotational position of the crankshaft determines the position of the pistons and of the camshafts. Obviously, since the purpose of the entire ignition system is to deliver a high-voltage spark at the plugs at exactly the proper instant----meaning, as the piston approaches Top Dead Center of the compression stroke----then the ignition system must "know" what the position of the crankshaft is in order to transfer that information (via electrical signals) to the major components: the PICK-UP COILS, then onto the TCI UNIT, to the IGNITION COILS, via the PLUG WIRES and through the PLUG CAPS and finally, onto the SPARK PLUGS."

It seems like I have some work cut out for me. I know the spark plugs, the plug wires, and the caps have been replaced within the last 2 years. That leaves the pick up coils, the tci unit, and the ignition coils. The post I read stated that failure of the pickup coils is possible, but rare. Not totally writing it off, but this leaves the tci unit, and ignition coils. Am I to suspect this is an issue with 1 or both ignition coils? Obviously speculating does nothing beyond helping me know where to look, as I will likely have to start testing voltages, ore just haphazardly replace parts and hope that it fixes the issue. At the moment I'm simply trying to gather information so I know how to best move forward.

 

Testing the coils is the easy next step, IMO

 

Looks like there may be a trip to harbor freight in order to buy a multimeter...

"XJ650 models:

Pick-up coils:
1980-81 XJ650 Maxim and Midnight Maxim: 700 ohms +/- 20% = 560 ohms to 840 ohms acceptable range
1982 XJ650RJ Seca (non-yics engines): 700 ohms +/- 20% = 560 ohms to 840 ohms acceptable range
1982-84 XJ650 Maxim: 650 ohms +/- 20% = 520 ohms to 780 ohms acceptable range
1982 XJ650RJC Seca (yics engine): 650 ohms +/- 20% = 520 ohms to 780 ohms acceptable range
1982-83 XJ650 Turbo: 120 ohms +/- 20% = 96 ohms to 144 ohms acceptable range


Ignition Coils:

Primary side (input from main wiring harness):
2.5 ohms +/- 10% = 2.25 ohms - 2.75 ohms acceptable range

Secondary side (spark plug wires, without their end caps):
11K ohms +/- 20% = 8,800 ohms - 13,200 ohms acceptable range


Spark plug caps:
5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range

Spark plugs:
0 ohms per plug"

Any other suggestions beyond what is stated in this quoted post?

 

Having a decent multimeter is going to be very useful. Note that the cheapest-of-the-cheap multimeters may not be able to accurately measure low ohms (less than 25 ohms), and you can get "bit" by this issue when checking the primary side of the ignition coils.

The brief start and then cutting off, along with your observation of intermittent/no spark on some of the plugs, would lead me to suspect that either the plugs (cheap) or the ignition coils (much more expensive) may be the problem. Also note that on the end of each spark plug wire is the hard plastic RESISTIVE CAP, and those can go bad, too. The resistance of those caps should be measured individually; they can be removed from the spark plug wire by "unscrewing" them from the end of the plug wire. It also is a good idea to snip 1/8" off the end of the plug wire (while you have the caps off for testing) to make sure you don't have any corrosion issues in the plug wires themselves.

 

Wasted spark system so how you do that is important. You may not have spark or it might be intermittent if you pull 1 and 4 and test, or 2 and 3 and test unless you ground the wire or plug of the cylinder that is not being tested as well as the cylinder being tested for that coil pair.

And don't forget battery voltage as the XJ series the starter will appear to be working fine, but the reality is the battery voltage has dropped significantly lowering the available voltage to the primary of the ignition coil - low voltage to the primary equals low voltage on the secondary, which means a weak spark that may be visible externally but non-existent under compression. Battery voltage needs to stay above 10 volts when cranking

 

So am I to gather that a multimeter from harbor freight will be inadequate? I can check other hardware stores.

The spark plug caps were replaced but I will test them for electrical resistance. About snipping the plug wire, will I be able to just reinsert the caps after doing that?

That is interesting...I have a 0.75 amp charger I'll plug into my battery and ensure it is fully charged. It is worth noting that this issue arose when I had the bike on the center stand, while running, to observe rotation of the rear tire to inspect for it being out of round. I had to restart it a couple times. Perhaps having to restart it too many times without getting the rpm high enough drained my batter too low that it now supplies inadequate voltage to the ignition system?

 

Maybe, I'm not familiar with their products, but multimeters (besides specialty versions) are somewhat of a commodity item, meaning.......the more you pay, the better quality/performing item you'll get.

I use a Klein MM700 for everyday use, it can measure primary ignition coil resistance pretty accurately (within 0.2 ohms)....I've had it verified against an Agilent Keysight 4-wire meter, a real professional ($2500+) meter.... you can find the Klein meter (new) on eBay, etc. for around $70 or so. The Klein won't accurately measure extremely low ohms (like measuring the alternator stator windings or starter motor armature windings).....but nothing on the consumer side (or "electrician" side) will, you'll need a pro or specialty meter to do that.

The plug wire "screws" into the end of the spark plug cap, the "terminal" inside the plug cap looks just like a pointed-end drywall screw, and the tip of that terminal punctures the center of the spark plug wire (meaning: the actual wire, not just the insulation) and "screws" into the wire.

 

Alright. Update! First of all, thank you for the responses. Secondly, I solved the initial issue I was experiencing when I started this thread. It was an electrical issue with my ignition fuse and the way it connected. Replaced it with an inline fuse holder and all was well. Got the bike out, rode it, and after about an hour of riding it slowly started to miss, and began to bog down until eventually dying, and I couldn’t restart it. That being said, it will run when I spray starter fluid in the surge tank. So I now suspect an issue with fuel delivery.

I pulled the fuel tank, and fuel line running from the petcock. Drained it, and some debris came out with fuel. I then drained the fuel tank. Rinsed it with seafoam as well, drained that. Added fuel, reconnected, put it all back together, and still no start. Am I to suspect this is an issue with the fuel pump at this point? I’m sorry to switch the subject of the thread…

 

Another update. I am now noticing that my fuel pump only comes on when I attempt to start the bike with the kickstand down. This was my process for verifying:

With the petcock set to OFF, key on, right hand ignition switch set to RUN, the kickstand down, and the trans in 1st gear, I press the start button. I can feel and audibly hear the fuel pump, and I have an inline fuel filter after the petcock with a clear housing. I watch the fuel level drop, as the petcock is closed and does not replenish the fuel level inside the clear filter housing.

Next, I open the petcock to replenish the fuel level inside fuel filter housing, then close the petcock. Place the trans in neutral, and repeat the same process, with the kickstand still down. Now, the starter roars to life, but the fuel level inside the filter housing does not drop. What possibly could be causing the fuel pump to power on, ONLY when I have the kickstand down with the bike in gear? I am very perplexed at this…

 

I discovered the typical in-line fuel filter is too restrictive for the Seca Turbo.
Try running without the filter.

 

Interesting. I’ll try it. Should I be worried about debris from the fuel tank potentially entering the fuel system or engine? I’ve rinsed the tank out (with gasoline) but I’m sure more will find its way into the fuel lines. You think maybe a fuel filter with a mesh screen would allow better fuel flow than a typical cotton style filter? It would make sense if this filter that’s in there now has clogged and is restricting fuel flow…

 

It looks like the fuel pump should power on any time the start button is depressed, and after the starter button is released then the fuel pump relay is kept energized by two phases of the stator through two steering diodes.

Is it possible low battery voltage could be an issue during starting? I am not sure of that one but I know the Yamaha relays I have tested have a pull in voltage of just over 6 volts, but I have no clue how much voltage is required to keep the fuel pump operational

 

It is possible…although I have a low amp battery charger and I’ve been keeping it plugged in when parked. I did notice something interesting though, when I can actually get the engine to fire up, albeit very briefly, by placing my hand on the pump I do feel it activate, only after the engine fires. Kinda odd but it seems as though it’s working…?

The previous owner had some work done to this bike before I got it, which included evidently installing a new fuel pump. It is not a Yamaha pump. I found it to be a Napa fuel pump rated for 14 psi and 25gph. In addition to that, they installed the fuel filter. But they chose a bizarre way to run the fuel line leading from the petcock to the fuel pump. The line runs off the petcock, turns straight downward for about 1ft. The fuel filter is mounted near the bottom of this downward slope. It then travels all the way back up to connect to the fuel pump. I am going to shorten the line, and run it so the line follows a slight downward grade all the way to the pump, instead of plummeting down and then having to travel back up to the pump.

If none of this works I’ll begin looking at replacing various components of the fuel system, or maybe all of it from the petcock to the check valve.

 

So I've completed re-routing the fuel line from the petcock. The path it follows is satisfactory, but I'm noticing that when I open the petcock, the line experiences no fuel flow. However, when I disconnect the outlet end of the filter, fuel flows freely through the filter and out the end. Any idea what would be causing this? Is this fuel system vented to allow fuel flow? And if it is, could I have a clogged vent hose somewhere?

 

I have since replaced the fuel pump and discarded the fuel filter. The bike ran fine for about 30min and then left me stranded again, just like it did the first time. Really curious as to what’s going on. It runs and rides out great. Get into the turbo, feels good, then it it suddenly starts misfiring, then over the course of about 2 minutes, starves out to the point of dying. I’m suspecting either the fuel pressure regulator allowing too much fuel, or carb issues? The carburetors were supposedly cleaned and sync’d but I’m not sure of details. It just seems odd that it runs and rides so well for a short period of time then suddenly doesn’t. Then after it sits for a little while, it starts right up and does the same thing all over again.

 

The gas cap VENT system may be plugged. Try riding it w/o the gas cap on (or, loosen/remove it when it starts running poorly) and see if the issue goes away.

Another possible issue is the TCI or pick-up coils having issues (loose/bad solder joint), although fuel-related issues seem to be the more probable cause.

 

You make a good point. I have tested the fuel flow by removing the cap to the tank and running the motor, but I have yet to try actually riding the bike out on the road that way. I know that fuel flows freely out of the tank with the petcock opened, and the fuel cap on. I tested that by disconnecting the hose from the system and watching it pour into a solo cup. Maybe that isn’t enough of a test for the ventilation of the fuel cap. But I will try that for sure and report back. I really hope it isn’t the regulator. I already spent $1,000 on a new turbo. Another $800 for a new regulator does not set well with me But at least I know the turbo works…very well

 

Okay, and just to be clear, it's not the REGULATOR that I was referring to, but the TCI (also called the igniter unit).........heat can cause electrical devices (pick-up coils, TCI, even ignition coils and the regulator!) to work okay at low temps but as they warm up or get hot they can fail (and that's a particularly frustrating situation to diagnose.........). Hopefully it's a fuel related issues, those are much easier to diagnose.

One thing to check for is that when the engine dies, I would immediately open a fuel bowl drains screw (take the proper tool to do so along with you on the ride) and open a bowl drain screw (or 2) and verify whether the bowl is full of fuel (of course, turn the engine off first, and also take some type of small container (cup, can) to catch the fuel so it doesn't pour out onto a hot engine.

 

Yeah I apologize, I didn’t acknowledge what you said about the TCI. When I referred to the regulator it was just me assuming what could be the issue based on what was next in the fuel system, I was not factoring in the TCI. Hopefully that is not the issue! Increasing temps seems like a probable cause, but I’d have my work cut out for me nailing down what it’s specifically affecting.

As for draining the bowl, I will prep for and try that as well. If the carb bowl is near empty…would you suspect the pressure regulator? I’ve already gutted the fuel line check valve and it did not run well that way. I’ve since put it back together. And the fuel pump is new. It is not OEM, but it is a 14psi, 25gph rated pump.

 

Moving forward, I’m going to get the bike running again, because it will for about 20 minutes for it begins to misfire then slowly die. When this occurs I will attempt to drain one or more float bowls in the carburetor.

In addition to that, I was going to look into installing an inline fuel pressure gauge just before the fuel line check valve. This could be especially useful if I find that one or more of the carburetor float bowls have little to no fuel.

Yesterday my dad and I spent some time testing two relays. The fuel pump relay, and the starter circuit/ignition cutoff relay. The pump relay itself seems to have tested fine, but the starter circuit relay had an Ohm reading that jumped all over the place. Would this relay being faulty be a potential cause of the issue I’m experiencing? I was under the impression the starter circuit cutoff relay would only affect just that…

 

Update time! So I’ve installed this fuel pressure gauge, lo and behold, the fuel pump is in fact not operating when everything is hot. And to add to that, I noticed smoke coming from one of the wiring harnesses on the bike. It is the one that the voltage regulator connects to. And 2 of the connections were beginning to melt. I feel I am making progress on the actual problem, but as for what is causing the pump to shut off, and if it’s related to these melting connections? I have no idea. Any thoughts on this? See photo below for melted connections. Where it melted was the male harness, with the wiring that runs to the rest of the bike. Not the harness with wiring that runs to the regulator itself.

 

I’ll also add, the connection to the 20amp main fuse was hot. And was even beginning to warp itself.

 

Update. The pump does not appear to be shutting off, as measured voltage to the pump was still 12 when the bike is running approx. 1,500 rpm. I am led to conclude I have a faulty pressure regulator. I am looking into the Holley 12-887. It looks promising, but my only concern is how the pressure is adjusted by a set screw on the unit itself, vs being adjusted automatically by manifold pressure. Would this flood my carburetors or cause other issues?

 

I would do this before buying a new FPR.
It needs to maintain 2.8 psi without the motor running so make sure you get a gauge with a small scale.
0-15 psi is what I have.

 

Yeah I installed one, 0-15 psi. Fuel pressure dwindles over the course of the bike running for about 20 minutes, and activating the pump with the bike off it produces almost no pressure. Voltage is being supplied to the pump, and it’s a brand new pump. I suspect the regulator, but I may have to deep dive a little more before buying the new regulator.

 

One easy thing to try is to gut the innerds from the fuel check valve. These are known to stick closed.
You just have to remember to shut the gas on and off manually.
Just one more thing to eliminate

 

Another trick with these bikes
When you’re diagnosing the fuel system you don’t need the motor running.
With the bike on the sidestand and in gear, if you press the starter button you will hear the fuel pump running but nothing else

 

I did also try that…twice actually. Bike still ran poorly. I guess I can try it again?

Yeah that as well. I can feel the pump come on but it will read no pressure on my gauge at all. I think I’m gonna be going for, yet another, new pump and this time the Holley 12-887 bypass fuel pressure regulator. If that doesn’t work I’m gonna be running out of ideas on how to address the issue.

 

One thing that seems odd is that fuel does not seem to gravity feed to the pump at all. It will flow freely out of the tank when the inlet side of the pump is disconnected though. Not sure I like the thought of the pump running dry even briefly but I don’t really understand why it doesn’t seem to gravity feed to the pump.

 

With a new Carter fuel pump and the Holley 12-887 regulator it seems to stay running, but I am noticing that the revs hang when it’s warmed up. The seem to want to hover around 2k rpm. Would this indicate a lean condition or rich condition?