XJ550 Maxim Engine stops when warm.

I had to replace the coils because one was cracked and the other one was toast. Since replacing the coils with Dynatek 3 ohm mini's when the engine warms up it bogs down until it cuts out. Once that happens it has to cool back down before restarting. I've felt the coils after this happens and they don't feel hot to the touch, and they test good on both the primary and secondary.

I don't want to suspect the TCI just yet because I can't really test if its good or not, and I haven't tested the pick up coils because I haven't found the connector yet for it since I'm new to this bike. Am I right to be looking at the pick up coils first? I should mention I'm to inclined to mess with the regulator rectifier yet because the previous own hardwired it into the harness for some reason rather than leaving it as a regular connection.

 

just to rule out a simple fix, pop the gas cap when it happens. if the vent is plugged it can do that

 

Popping the gas cap had no effect. Couldn't restart it afterwards either. I'm now more leaning towards a bad R/R that's causing the battery to not charge at all. It explains the inability to start it after it shuts down because I know a low battery will turn the starter over, but won't necessarily have the power to fire the ignition coils.

If it is indeed the R/R then that means I either have to directly wire another one back in, or I'll have to find a replacement male connector for the wiring harness. Either way I'm going to have to dig up a wiring diagram unless the 3 white wires aren't specific to one another.

Nothing quite like undoing someone else's wiring job, even if it was spliced/soldered and shrink wrapped correctly.

 

Basic bump, problem has reared its ugly head again after replacing R/R, and stator with new ones from Ricks Motorsports. Leaning towards rotor needing to be replaced, something else I'm missing in the electrical system which can't be much at this point, or something wrong with the carbs which seem unlikely.

 

Symptoms of a warm XJ engine stalling is tight valves. Engine gets hot and valves get tight and don't seal = no power and stalling out.
How long has it been since you checked clearances?
I bought a bike from a guy with same problem , run for about 5 min or less and quit. Replaced all the tight valve shims and runs like a top to this day. Thankfully it didn't burn any valves.
If you think your charging system is not working right before you spend any money get yourself a meter and test the voltages at the battery.

 

the left connector on the tci unit is where you test the pick up coils from you will see 4 wires there. unplug the connector. you will see an orange wire and a gray wire the black wire is a common wire to the tci from the pickups there is also a black wire with a bullet connector the bullet is not the wire you want

set meter to 2 k ohms orange to black will read .650k ohms which is 650 ohms test the gray wire the same way to the black wire same reading.
your pick ups are located in the side of the engine left side under the crank shaft cover. it is in front of your shifter.
the cover you have to remove to do a valve shim check
left when you sit on bike

Do the valve clearances even if the pick ups are bad

when a system fails on your bike such as the ignition coils test the whole system to ensure you have found every thing in your case of the ignition coils another 5 minutes time for the pick ups

 

Valve clearances. Check them.

 

Pickups tested at 654, and 645. Looks like I'll be doing a valve clearance check this weekend.

 

Got to Cylinder 1 Exhaust today before work and found the .18mm failed to fit. Didn't have time to write it down but believe .13mm was the one that finally made it. Tomorrow I'll go at it again and write down all the measurements and shim sizes, but if the first one was any indication I'll be doing some shim replacing.

 

Only 1 valve was in spec. Here are the values. I'll work on finding which shim numbers I need sometime tonight and verify. If I've read correctly the shims are 29mm diameter?

Exhaust:
E1 .13mm 255
E2 .18mm okay
E3 .13mm 260 or 250 PO placed numbers up instead of down.
E4 .10mm 260

Intake:
I1 .10mm 260
I2 .10mm 260
I3 .10mm 265
I4 .06mm 270

 

I can see why when it warmed up it would stall out. Those are some tight valves for sure.

 

Looking at the chart you need these some you can swap

E1. 250
E2 --
E3. -- Verify shim thickness with a micrometer then check chart to be sure.
E4. 250

I.1 255
I2. 255
I3. 260
I4. 265

Then verify clearances once you swap shims. I always Crank the engine over several times to squeeze any oil out from under the shims before I re-check.

 

So, I managed to crack into the system tonight. The mystery shim on E3 took a 255 replacement. Now comes the problem, the I1 255 and I4 265 replacements were both to tight, neither .13 or .12mm would fit but .10mm would so I decided to error on the side of caution for fear of running too tight again and went with a I1 at 250 and I4 at 260. Now they both clear at .15mm but since I didn't have a clearance gauge higher than that except for .18mm I'm unsure on if they have a wider clearance than spec.

Just as a safety precaution, what kinds of troubles could I be looking at having slightly to loose shims vs what I already seen for to tight?

 

stack your feeler blades
if you add .05 to .10 you get 15 if you had .11 because you could not measure it and end up with .16 its good by this standard from fsm

notice that .006 is good for 0.15 and 0.16
when you convert .006 to mm it is 0.152
.16mm= .00629 inch
.15mm=.0059 inch
so your valves wont open as far as you would like it will be in spec soon.
better a valve does not open fully than opens to much
your talking .0001 inch that is one ten thousandth of an inch

 

Once again it stalled out around 20 minutes in this time. So the valves were part of the problem. Next thing I'm going to try on the list is replacing the headlight with a less powerful one. If that fails I may just tear it all down and do my first ever engine and carb rebuild.

 

I am going to make a suggestion. Before you tear everything down, I think it would be wise to find out exactly why it's shutting off. When it stops running check for spark, the fuel. Spray some starting fluid in the air box to see if it fires if you have spark. Something is going away like battery voltage, spark is dieing out because of an electrical failure, or your fuel is not getting into the carbs. Narrow down the issue because it may not have anything to do with what you are planning on doing. Just trying to save you from a headache.

 

Does the '81 550 have a sidestand safety switch?

 

Reading back in this thread, I see you are suspecting the charging system. Did you ever get a multi meter and measure your battery voltage?
Voltage at rest
Voltage while cranking
Voltage at idle
Voltage at 1500 rpm
Voltage at 3000 rpm

These readings will give a good picture of your charging system. Should be 12.8 at rest to start with. Then all the way up to over 14 volts on the top end.

You were talking about the wattage of your head light. Can you post the wattage?
Also are you running any other accessories?

Fuel related.
If I suspected my fuel is restricted. I would do two things first. Double check the vacuum hose to the petcock. If it is getting hot and collapsing from vacuum that will shut off your fuel flow. I have seen people use clear vinyl hose and it collapses under vacuum from the heat off the engine. Another thing is to pull the petcock out of the tank and inspect the sock on the topside. It may be part way clogged from debris in the tank.

Spark related.
Throw a old plug in one of the wires when it quits. Lay the plug in the head and crank it over to see if you still have spark.

 

yes, he should remove the relay under the seat to bypass it.

did you check out and or replace the alternator brushes? how long are they? 17mm is new, 11 mm is replacment. good photo in this link
http://www.xjbikes.com/forums/threads/im-going-crazy.66888/page-4#post-466203

 

Alternator brushes are brand new, and when I replaced the rotor after I found it had visible wear marks it also tested within spec. Today as I ran the bike again I pulled the vacuum like from the petcock and noticed an improvement, but not much. The battery itself is a new one, and at 3k rpm I get 14.3 volts on it.

I'll pull the tank when I get a chance and check the screen on the petcock. The coils are Dynatek 3ohm minis and the next time the bike dies on me I'm going to get the primary and secondary readings immediately afterwards to see if maybe part of the problem isn't heat related for them.

 

Went through and did an electrical test today on the system, except for the pickup coils which I tested earlier. Here are the results.

Coils:
Coil 1 Primary = 3.3ohms, Secondary 11.07kohms.
Coil 2 Primary = 3.3ohms, Secondary 10.93kohms.

Battery voltage = 12.18v

Diode testing on regulator/rectifier came back with failures on black lead/black wire on all 3 diodes.

Rotor ohms readings bounced around, but readings were typically within the 5.1 to 5.3 ohm with low extreme at 4.2 and high extreme at 5.8 ohms.

Conclusions so far that I can make are that the rotor I originally tested and found to be good has failed and took the new regulator/rectifier a long for the ride.

 

Do you think the voltage is dropping enough to loose your ignition system. The TCI does not work so well under 10 volts and quits at about 9 or slightly less

 

That's the current suspicion I have. Right now I have the battery on a 1.5amp trickle charger, and last night I went from the Sylvania H6024 XV headlight(specs are 53/63w) to a standard H6024(40/60w) headlight. In the past I had a SR185 that had all kinds of charging problems until I discovered the PO for it had replaced the light in it with a much to powerful one.

Also have a new rectifier and rotor coming in the next week or so. With any luck this will solve at least one problem.

 

And you plugged the open vacuum line and set the petcock to prime??

That's a good voltage indicating the charging system is working.

Bad diodes on a system putting out 14.3 volts?? What kind of reading did you get on the diodes to make you think three of them are bad?

 

Actually I goofed, had the multimeter on Ohms instead of diode. Diode tests all come back as .45 volts for color crossing, and 0 for color matching. Ohms readings on the black were 8.5 Mohms, 5M ohms, and 3.6 Mohms for black lead to black wire and red lead to white wires.

 

If you are getting 14.3 volts then I would say its not a charging system problem.
Concentrate on fuel delivery to the carbs next.

 

Tested the charging on the battery today after letting it trickle charge to full over night. Starting voltage was 13.38v. Started, let her warm, and read voltage across battery at 3krpm. Voltage was above 15v. Immediately shut her down. Rotor and Rectifier are getting changed for certain now.

 

Did this fix the issue?