Blowing ignition fuse

Hi all,

I'm writing for the first time on the forum, though I read a lot of posts in the past year.

I have been experiencing a problem since I put everything back in place (or so I think) after doing that seemingly unavoidable shim job on the valves of my 1983 XJ550 Maxim.

Just so you know, before I got working on the valves, I had the ignition coils and the pickup coils removed and unplugged. I had then performed a compression test and the starter was turning just fine.

After the valve job, I installed the pickup coils, a pair of new ignition coils from XJ4Ever (thanks a lot for that!) and screwed everything else in place. I was ready to crank the engine, but nothing happened. The key turned to "on", the kill switch set at "run" and the neutral light lit (hand on the clutch and kick stand up as well), but the starter was not turning. My investigation led me to a blown ignition fuse (the rear-most one in the old fuse box).

Since I didn't have a spare one, I swapped it with a good one (I think the turn signal one). It blew up too as soon as I turned the key. I tested the two terminals where the ignition fuse goes with my voltmeter (was I wrong in doing so?), and it read about 12 volts.

Now. The only three things I remember unplugging and replugging besides de pickup and ignition coils are

1. the blue wire that goes from the neutral switch near the chain to a blue wire underneath the tool box ;
2. the black wire that comes out of the pickup coils terminal at TCI and plugs into a black wire underneath the tool box ;
3. the two ground wires that attach to the frame at one of the ignition coils mounting brackets.

I checked on the forum for blowing fuses, but all I could find was a thread about a MAIN fuse blowing. Even though it's similar to my situation, I don't see how the info could help me.

The guy on the forum suspected a blown TCI, but, in the end, it was a wrong connection (human error) that was causing the problem.

Should I test the TCI as it's described in the thread? I read somewhere it's risky. Is that right?

I know I could probably find the error by testing every circuit but, although I have the electrical diagram, I am not really savvy when it comes to circuits and I'm afraid I could cause more problems by doing so, when the cause of the malfunction is probably right under my nose.

To whom will read this, I give my thanks. I just hope I can address this issue before it begins to freeze up here in Quebec, so my bike can be ready to ride in spring.

 

I am trying to post the link to that thread I am mentioning, but it seems the forum won't let me.

 

Look for a pinched wire. Sounds like a dead short.

 

Thank you for your answer.

It seemed pretty crowded underneath the tool box/TCI harness when I screwed it back in place.

I'll check into that.

 

You can use the brute force method of disconnecting / connecting items until you find an item that when disconnected the fuse no longer blows, but I would suggest using an ohm meter to find the problem:

First, with the ignition fuse removed determine which side is the input and output for the ignition fuse. You can do this by turning the key on and checking for 12V on the two ignition fuse terminals in respect to chassis ground. The one that measures 12V is the input side. Turn the key off and disconnect the negative lead of the battery.

Switch the DMM to 200 ohm scale and connect the positive lead to the output side of the ignition fuse terminal, connect the negative lead to chassis ground - kill switch set to run.

You will likely at this point note a reading that is near zero ohms, which would be why the fuse is blowing. Note a normal reading here should be about 100 ohms, or the resistance of the side stand relay coil. All other sources (excepting the starter solenoid - see below) powered by the ignition fuse will have a fairly high input resistance

If your initial starting point is near 100 ohms just skip to the next step. If the reading is near zero ohms turn the kill switch off, the reading should go to open, if not your looking for a harness issue - pinched wire etc. before the kill switch.

Assuming the reading was near zero with the kill switch set to run start to isolate ignition circuit components by disconnecting them one at a time looking for the meter to display either the 100 ohms of the side stand relay or an open condition. There is not much here - the two ignition coils, the TCI, the side stand relay, and the starter cutoff relay. The solenoid is also a suspect but only with power applied and when the safety circuit is not deployed as that is the point where the starter cutoff relay will send 12V to the starter solenoid. It would only be suspect if your ohm readings are near 100 ohms with everything connected.

If you still have a low reading near zero with everything disconnected then you are looking for a harness issue on the output side of the kill switch.

 

Spam filter, you will be OK after 5 posts for pictures and links

 

Ok thanks!

 

Thank you very much. I will try all of that this weekend and post the result afterwards.

 

Does she still have the OEM fuse box?
Your Fuse Box -- A Ticking Bomb??? By: Rick Massey

HOW TO: Install an aftermarket fuse box

Also: Read This First

 

Yep
If I manage to get the bike running ok, the next thing on my list is changing the that old thing for a new box like the one you indicated. I think it's the one Chacal advertises in his catalog. Am I right?

HCP22571KIT Aftermarket COMPLETE FUSEBOX UPGRADE KIT, featuring the glow-when-blown style of push-in ATO fuses.
https://www.facebook.com/VintageYam...383213023074/2004383213023074/?type=3&theater

 

Start with the fuse box. It's the first major electrical component after the battery.

 

Hey Rooster (and others),

I finally got the time to run the tests you suggested. Here are the results for each step.

My reading was oscillating between 0.2 and 0.4 ohms.​

It did go to open.​

Here is what I got with the following parts disconnected on at a time :

• Right ignition coil : 1100 ohms
• Left ignition coil : 0.4 ohms
• TCI (both terminals) : 0.4 ohms
• Side stand relay : 0.6 ohms
• Starter cutoff relay : 0.6 ohms

​

Since I got neither an open circuit nor a 100 ohms resistance, should I look into that last option? The resistance with the right coil disconnected is by far higher than the others. Should I treat that as an open circuit?

Thanks again for your time.

 

Also worth mentioning : I was unable to get any reading other than O.L. while testing the secondary resistance on the two new ignition coils I just installed. The primary resistances, at the connectors, were right on specs.

 

Thanks for the advice. I'll include one with my next shipment.

 

That's a good reading with the right ignition coil disconnected. The low resistance that goes to 1100 ohms when disconnected implies that the primary winding is shorted to the internal metal mounting bar. Just disconnect that ignition coil and measure from the ignition coil primary winding R/W wire to chassis and it should be open - if it is shorted at the R/W wire that is your problem.

What brand new ignition coil?

As far as secondary resistance be sure to adjust your meter scale to the proper setting, particularly if you are measuring through the caps. The resistance with caps will exceed 20 Kohm so you would need to select the 200 Kohm setting. Note also some books show primary to secondary measurements which is incorrect. The secondary is checked from cap to cap.

 

Just to clear this up I had called that incorrectly earlier. The 100 ohm reading is only going to happen if you have the side stand up closing the switch and connecting the low side of the side stand relay to ground.

The 1100 reading is a consistent reading for the TCI when checking from +12V to rtn, so that is a good reading.

I also just reread where you got the ignition coils from Len, but I still feel the most likely short would be internal to the coil. It might be a possibility that the case was damaged during the mounting process?? Anyways, no way should the coil read shorted to chassis as it is doing when it is connected.

 

I performed the resistance test you suggested (along with other tests) on both ignition coils. Here is what I got.

Left hand coil :

• Primary (between grey and R/W wires) : 2.4 ohms
• Secondary (between the plug wires) : 11.5k ohms
• R/W wire to mounting point on chassis : open

Right hand coil :

• Primary (between grey and R/W wires) : 2.4 ohms
• Secondary (between the plug wires) : 11.8k ohms
• R/W wire to mounting point on chassis : 0.4 ohms

The last circuit seems to be the culprit. The case of the coil doesn't seem cracked, but the reading is clear. I'll see if I can get the thing replaced.

Again, thank you very much. I'll let you know when I get the bike to run properly.

 

Hey guys,

I have a (not so positive) update to post.

Len offered to replace the defective ignition coils with better ones and I took the opportunity to order a replacement fusebox (as k-moe suggested). I installed those nice parts and tested positively for sparks on all four, but could not get the bike to start.

This spring I bought and installed a new battery AND ordered from Len everything I need to take my carbs to the church of clean. Which I did!

Today, I put everything back together and was disappointed to ear the starter turn without ever getting the engine to start. Reading on spark plugs (mine were fairly new), I found that I should not use resistor plugs along with the resistor plug caps I bought from Len and I thought AH AH!... But switching to NGK D8EA didn't improve my situation.

So here I am. I bought a bike that was running poorly, fiddled with it (valve clearance, carbs, coils, electrical system ...) hoping to get it to run better, but only managed to dig my hole deeper, it would seem.

After two summers trying to find the culprit, I have to say I don't know where to look next. The TCI maybe? Do you guys have any recomendations?

Thanks for reading.

 

So the carbs were taken to church but did you bench sync and wet set afterwards?

http://www.xj4ever.com/setting fuel levels.pdf

The battery is new but was it fully charged?

Did you prime the carbs before trying to start it? Have you verified the petcock is working and flows on prime?

Did it fire just a little when trying to start?

Were the plugs getting wet?

 

Thank you for your time and consideration Rooster. It's much appreciated.

Here are my answers to your questions :

So the carbs were taken to church but did you bench sync and wet set afterwards?

Yes. I bench sinked them using two pieces of copper wire and this method : https://xjbikes.com/forums/threads/how-to-bench-synch-your-carbs.6366/ .
The term "sliver of light" was interpreted as "the tiniest ray of light". After a few tries at cranking, I began playing a little with the idle speed screw just around the point of contact with the throttle shaft arm.

If by wet set you mean setting the fuel level in each carb using the clear tube method, then yes. Before re-racking them, each carb was set at 2mm below the lip of the carb body.​

The battery is new but was it fully charged?

Yes. Bought it this spring and charged it overnight on 2 Amps before reinstalling it.​

Did you prime the carbs before trying to start it? Have you verified the petcock is working and flows on prime?

The petcock works (I saw and tasted some fuel coming out of it). Before my first attempt at cranking, I set the petcock to Prime and blead each carb to make sure that fuel had reached each bowls.​

Did it fire just a little when trying to start?

It stutters, intermittently makes soft "pop pop" sounds and sometimes a loud bang (wich I understand is unburnt fuel finally exploding inside the exhaust).​

Were the plugs getting wet?

The brand new plugs I inserted were just lightly browned with soot after a few crankings. They were not wet, nore did I ever pulled out a wet plug. After a lot of cranking, they always come out with a dry, mat black coating on the tip.​

 

Verify that you have the plug wires routed to the correct cylinders. Left pair go to the outboard cylinders. Right pair go to the inboard cylinders.

She wants to run, and will. We just have to figure out what detail still needs a bit of work.

 

Thanks k-moe. Your positive, yet pragmatic attitude warms my heart. I hope you're right (soooo much).

I'll make sure to check on those wires and post a reply ASAP.

Do I risk anything by trying to reverse those connections (left to inboard, right to outboard) just in case another connection was inverted up the circuit?

 

The spark timing will be off, which will prevent the engine from running, and may be the issue you have now. Otherwise there won't be any damage done so long as the coils have a path to ground through the sparkplugs.

The primary side of the coils have color-coded wires. The orange and red/white pair go to the left coil (outboard cylinders). The grey and red/white pair go to the right coil (inboard cylinders). Either wire of a pair can be hooked to either terminal on their respective coils.

 

OMG IT FIRED UP!!

Thank you so much for that insight! I think I tried to reverse the connections since I couldn't get it to run after intalling the coils. I must have forgoten to put it back to normal afterwards...

So it did fire up, but I it does not run better than when I bought it though. The choke (enrichment circuit) still has to remain on, to the point it will rev high (5 to 7k). But, if I kill the choke, it kills the engine.

1) Is this unusual after a carb rebuild?

2) Do you think adjusting each mixture screw (to get highest rev, then tune rev down with idle speed screw, repeat with next carb) will solve this?

3) Since I never got the bike to run properly, I don't even know how it's suppose to behave. When I fire it up using choke, should start to rev around 2k and then slowly drop to +/- 1.1k ?

Thanks again! This really made my day (week, summer, and so on...)

 

If it runs with enrichment but not without, adjust your idle screw first. Then you can make adjustments to the pilot screws, with or without colortune plug, your choice. Vacuum balancing the carbs is also required. Rebuilding the carbs will change everything.

 

This will vary depending on the ambient air temperature, but in general:

Starting with full enrichment the bike should start fairly easily and idle around 1100 RPM.
As the engine warms the idle speed will increase, eventually topping out at around 2200 RPM.
Gradually reducing the enrichemnt will lower the idle speed.
Cutting off enrichemnt before the engine is fully warm will cause the engine to stall, either at idle or under initial load depending on how warm it is.

Idle speed should be set with the engine fully warm, and you'll need to find a balance between having not-too high of an idle when stopping during a long ride, and not having too low an idle when cold so that cold starts aren't a huge hassle. I generally aim for an idle speed of around 1200-1500 RPM when fully hot (after a long ride).

 

Thanks guys. I managed to get it to idle using the idle speed

Indeed it does! When the bike is warm, I can deffinitly feel the difference when riding. Even though I feel like I could get it to turn smoother, I'm super happy with the result I have now.

I tried to fiddle with de mixture screws (don't have colortune yet), but could not get a noticeable variation in sound, rhythm or else while doing so. Although, I did not went farther than 3 1/2 turns or below 1 1/2 turns. The bike still has wishy-washy starts. The best I found I could do is to put enrichment about half-way through and a give a tinsy bit of throtle while pressing on the starter button.

Far from being an expert, my feeling is that then engine lakcs air when cold. It seems like opening the butterfly valves just a little during startup helps balancing the enriched mixture. I would like to open those using the idle speed screw, but then my idle, speed, when warm, would be too high. Any thoughts?

As for vacuum balancing and colortune, I'm unsure weaher I want to buy both kits or ask a mechanics to do the tuning. If I'm not mistaken, it's not so complicated to do yourself, so It's more about the spending. Can tu tell me how much I should spend to get a trustable instrument for vaccum balancing? I can see some at 50$ and others at 600$, all of varying types.

 

https://fortnine.ca/en/motion-pro-syncpro-carburetor-tuner

$150.99 Canadian price with free shipping for purchases greater than $50.
About the cost of 2 shop labour hours.

 

You can always inexpensively make your own device for vacuum balancing/sync'ing the carbs. I have used about 6 feet of clear plastic tubing that just fits over the nipples on the carb to head boots. I use automatic transmission fluid in it. I clamp the tubing to a board to stabilize it and make it easier to see and handle. A couple of feet of fluid in the tubing and attach to carbs 1 & 2 and with the bike running adjust until the fluid is level in both sides. If the carbs are way off and it sucks the ATF into the carbs it is no big deal, the bike will just smoke and clear away the mosquitos for awhile. Balance 1 to 2 then 3 to 4 then 2 to 3 remembering that #3 is the "master", everything else will adjust to it. Adjust overall idle speed as needed. All is all, you will have about $6 invested. If you want to get real fancy you can use 2 pieces of tubing and hook up 1 & 2 plus 3 & 4 at the same time. You still have to move things around to do 2 to 3 though. It is not as pretty as the Motion Pro device, but I am cheap.

 

You can make something like this but instead make it maybe 4 ft high in order to use colored water or transmission fluid. Just use a board, tubing, appropriate vacuum connectors and something like coaxial cable staples to affix tubing to the board. Nothing fancy but you can then sync all four carbs at once.
https://www.xjbikes.com/forums/threads/homemade-manometer.126761/

Edit, don't forget the vacuum restrictors that help keep the fluid from going crazy.
https://www.autozone.com/fittings-a...-16in-hard-vacuum-tubing-connector/369702_0_0