'83 XJ750K turning over but not cranking

Hey All,

Just joined the community after buying my first motorcycle, a 1983 XJ750K. The previous owners have done a number on her, most relevant to this topic is that the entire wiring of the bike is a hack job.

On to the topic at hand, my current battery is a WPS CB14L-A2 12V 14Ah (I know my Haynes books says I should have a 12A). Removed the battery to put some distilled water in and when I reinstalled the battery the bike would turn over but not crank.

A friend came over to help and at first the only problem was a loose wire on the ignition relay. Fixed that and the bike cranked. Came back two days later and the bike wouldn't start. I figured the relay went bad so I bought an identical replacement to what the PO installedn (Radioshack part #275-0226, 30A at 12VDC auto relay). When I installed the relay, I'm not 100% sure I put the wires back on as before (I took notes and pictures but still not confidant since some of the numbers were blurry when uninstalling the old relay). So if someone knew the correct configuration, I'd really appreciate it.

Through multiple attempts of starting the bike, I took a toll on the battery. Bought a Battery Tender Plus and recharged the battery. Took the battery to Autozone and they ran the free diagnostic test, came back good. So I'm pretty confident it's not the battery.

So now I'm at a loss as how to move forward, what to investigate or what to fix. Any ideas or help?

I don't have a lot of technical know-how, especially in the electrical department. But I do have a multimeter to help me troubleshoot.

Sorry if I rambled, just trying to give all the background info I could. Thanks!

 

That relay isn't up to the job.

Get a starter relay.

 

Any ideas how my bike used to crank with what appears to be the exact same relay?

 

It is possible the relay is not good even if it's new.

 

When you say good, do you mean not fit for the installation or not a functioning part?

Thanks

 

Yes. It cranked until the under sized relay burned up.

Your new relay may have burned up instantly, or you might have wired it wrong. Either way it's a dead end. Get a proper solenoid so you can move on to the next problem.

The relay you have is for some lights or a horn, not a high current device like a starter. I can't even imagine how it was connected because the wire that should going to the starter is larger than the terminals on the relay.

 

Thanks MiCarl

Not to beat a dead horse, but this relay isn't routed to the starter, it goes to the ignition coils, does that make a difference?

 

andrewrmac,

Welcome. You need a manual(s). Having the bike might make you impatient once it starts. IMO remove the rear wheel and leave it off until you have your bike road worthy. Running and riding your bike in its current condition will not bode well for you nor the bike. It's a good steed. These bikes are well built and very durable. The members here will help you bring it back. IMO the information here is not to encourage "show" bikes unless you chose to go that far. However, it will learn you how to make your bike a solid daily rider and to maintain it in good form. Again, welcome and good luck with the build.

Gary

 

Agree with the above, you need a manual. I'm guessing you're actually meaning the safety circuit relay. It could either be wired wrong or maybe part of the safety circuit (sidestand switch/clutch switch/neutral switch, most likely sidestand) is bad, but make sure you know what you're looking at first job :wink: Then make sure the wiring is correct to it.

Also agree with wheel/s off! you need to pull the back wheel to replace (not check, replace ) the brake shoes anyhow. Have a read of the links in my sig to find out about 30yr old brakes and tires, your insurance broker will thank you :lol:

Welcome to the forums & best of luck with your bike.

 

Thanks Gary, I agree, I don't want to put a bike on the road that is unsafe for me or others.

I do have a Haynes manual, but I get really backwards since the XJ750K isn't spoken to a far amount of the time in the book.

What state is considered road worthy? Is there a post buried somewhere that walks through the major and minor things to check out and repair before putting the bike on the road? It rode for three weeks and then this fiasco started, so I feel like I'm not too far away from that.

 

Read my post too Couple of links in my sig re safety

The wiring diagrams should show your model & what wires go where, if you can't read them I'll look at mine & tell you what colours are supposed to go where

EDIT-: Not awfully clear in the diagram, could be side stand relay or starting circuit cut off. My bet is the latter (this would have 2 red/white wires & a black/yellow and light blue. This look right?

EDIT 2-: If that's the colours you have, then from looking at the diagram & a relay I have here, that'd mean red/whites go to 87 and 30, and black/yellow & light blue go to 85/86.

Would appreciate if somebody could confirm I got this right?

 

a-mac,

IMO road worthy in short is having everything properly connected /fastened and functioning within specifications for how it was designed (including mods). At this point your bike will function at its best and will give you the most enjoyment. This site is thorough and exact. The members here know these bikes. They don't "rig" stuff here, they fix it. These are old bikes and as such most of the required maintenance hasn't been kept like some of things mentioned above. You'll spend a fist full to bring it back but once you've done that and know how to maintain it (which you'll learn) the reward is priceless...literally. Where to start? IMO you need to get that wiring sorted before you fry something. Use your book to familiarize yourself with what goes where and get that back right. You also need to remove the oil filler cap and take a whif. If it smells like gas you will need to change your oil and check some other things before you try to crank it again.
Hope this helps.

Gary

 

Before you get too far into Troubleshooting, ... Check.
Be sure the RELAY --> IS <-- a Safety Circuit Relay.

I don't have a Safety Circuit Relay to check which Terminals are Trigger and Load.

But the difference is something like this:

Power:

| (+) ^ (+) |

| (-) - (-) |

Safety:

| (+) ^ (-) |

| (+) - (-) |

The Triggering current and Load terminals are completely different.

IF, ... a Generic Power Relay is used where a Safety Relay belongs, ... the Bike acts like its possessed.

 

Thanks 750E-II_29Rbloke

Are you also using the Haynes manual? If so, which diagram are you using, the XJ650 J and K one?

Well of the four wires going to the relay, two are solid red and two are solid black so let me trace them out and tell you where they land on the relay...

87 - black wire coming from battery positive terminal (also an in-line 30A fuse in that line, does that make sense?)

86 - black wire going to bolt holding the 1&4 ignition coil to the frame, so I'm assuming that's a ground

85 - red wire that is spliced to a red/white wire that dives into the wiring harness..... and found an open ended red/white wire that has continuity with my original wire, there is also continuity with the three 10A fuses found under the seat (does this make sense to anybody??)

30 - red wire that splits into the two red/white wires going to the ignition coils

So judging from the XJ650 J and K wiring diagram I am looking at, the red/white lines from the ignition coils are coming off the starting circuit cut-off relay, do you agree? I cannot discern from the wiring diagram how each wire should connect to the relay, any ideas?

----

Just a couple side question, when you say replace the back brake shoe, is that the same thing as the brake shoe kit I found on bikebandit? Should I also get a couple of those tension springs? Last question, where can I buy stainless steel brake lines?

 

My Haynes diagram I referred to for your bike is for XJ750K and MK. (you have a 750 K right as per 1st post?)

That harness has been chopped about

 

DELETED-: NOW IRRELEVANT

 

But I have the US 1983 XJ750K, there's a short chapter in my Haynes that says for the U.S. version the lighting and electrical system are different and simplified from the UK counterparts, and says to use the 650 Maxim electrical diagrams instead. I'm figuring the XJ650K is the correct diagram of all the 650 options, thoughts?

And it makes me sad that my bike is so chopped, I didn't even know what I was looking at when I bought the bike, much less how extra difficult it would be to troubleshoot.

 

But let me take a step back, what other systems can I investigate in hopes of ruling them out as the problem?

 

The safety circuits all look very similar, and function in the same basic way in that open safety circuit switches will result in the s/c relay opening & cutting power from the starter solenoid. I'd say somebody lost their ignition live & added the permanent live with 30A fuse that you have, but it's a shame it's chopped about.

Perhaps they tried to remove one or more safety circuits?

So the red/white that's linked with the fuses etc, does that go live with ignition on and kill switch to run?

EDIT-: I'm tearing my hair out now, that wiring doesn't make any sense whatever! Why can't people just accept Yamaha knew what they were doing!?! GRRRRRRRR!!! :evil: [/Rant] feel for you with that vipers nest, would be a lot easier to fix hands-on than down a keyboard

 

DELETED-: IRRELEVANT

 

Gary, I will check this when I get home from work. I have already changed the oil once, had to drop the aftermarket exhaust as it routes the exhaust all under the oil pan.

I will put more time going over the overall wiring on the bike, but any ideas which wiring diagram I should use since I have the '83 US edition?

 

When you said it wouldn't crank I assumed you were working with the starter relay.

Crank = starter turns engine.

I don't believe there should be a relay on the coils. The safety circuits all involve the ignition module (TCI).

You can get wiring diagrams HERE.

 

Hang on, so the engine IS spinning over on the starter then? just not firing up?

DISREGARD ANYTHING I'VE SAID ABOUT CHANGING THE WIRES ROUND THEN!!! 8O if it's cranking but no start you need to check for spark first off :wink:

 

Hmmmm....I agree with Bloke, this is a head scratcher. We really need to see what you have there. You have four wires, two black, two red. One black is 30A straight main (nothing is tied into it); other is ground; one red is tied into ignition; other is tied into coils; there is a aftermarket safety circuit relay and there is power across the three 10A fuses at the box, correct? Man, I'd sure hate to tell you something wrong but based on the wiring diagram for your bike in addition to that being the wrong safety relay I think that straight feed (black 30A) to your switch will prevent the direct current your regulator/rectifier returns to your battery from happening. Reason I say that is the original thick red 30A main is connected to the ignition switch not the starter switch and the return dc from the regulator/rectifier is tied into it. Your bike will recharge around 2200rpms. When you start and run your bike under that you are running off the battery alone. IMO if you get the correct relay and are able to start your bike with that straight wiring to the switch it will not recharge your battery. It'll start and run until it drains the battery which won't take long. Hang in there, all is not lost.

Gary

 

Thanks Rick

Radio Shack just describe it as an "Auto Relay".

I'm afraid I don't follow your nomenclature for visually describing the differences between the power and safety relay. What do the + and ^ and - mean? Should I be able to visually determine if the relay is a safety or power relay?

I apologize for being slow on the uptake with this and I really appreciate your help.

 

I'm not so sure you can just swap the Yamaha "Safety Cutout Relay" with a generic one from the auto parts.

Relay ID and functional guide (original Yamaha relays, anyway http://xjbikes.com/Forums/viewtopic/t=27543.html

 

Guys, I can't thank you enough for helping me out on this one. I won't be able to get to all the questions tonight, I'll pick things back up tomorrow.

I apologize, I don't have the lingo down like I thought. When I turn the key to on, the neutral light comes on and the headlight comes on. When try to start the bike, there's an audible sound somewhere between chugga-chugga and scratching.

Is there a way (other than audibly) to determine if the starter is turning the engine?

I don't find a diagram for a US XJ750K in this list, am I missing something?

Okay, I didn't change the wires.

This is how I checked for spark: I put the negative terminal of the multimeter on the negative terminal of the battery, popped off one of the spark plug cap assemblies and put the multimeter positive terminal into the plug cap assembly. I put the multimeter onto VDC on 20. When I tried to start the bike, the numbers jumped all over the place, sometimes as high as 18.X or so. Is that the correct process? Do I have spark? What's the best way to check for spark on the 2 and 3 spark plug since the plug cap assemblies are longer than my multimeter terminals?

 

Checking for spark is best done by simply taking a plug out of the motor, then with it in its cap rest it next to the engine and crank the engine a few times. I prefer doing this in dim light so I can really 'see' the spark and determine if it's 'fat' or 'weak' or MIA.

If you're hearing a chug-chug then 'eeeek' sound, well I'd say your engine is turning over, but it should chug-chug-chug for a good long time before 'eeeeking' otherwise the battery isn't strong enough which will prevent starting as there isn't enough juice left over for a vigorous spark. If your still not sure and want to be, you can put your finger over an open spark plug hole and the compression will push it off when turning over, or you can remove the left front cover and see the pick-ups spinning around which are attached to the crank.

Based on personal experience, first eliminate all other possibilities before you start rearranging wires. Do this without documenting where they were at your peril!!

 

What he said ^

Sounds like the motor is turning over, and there's something happening at the plug leads (but don't use a multimeter again for testing for spark it may hurt it & you may get a jolt too).

Let us know what the spark looks like on each lead, when tested as described by mercuryman (and if the plugs are anything other than new already, I'd advise getting new ones as fouled plugs can cause no-start too)

 

Sorry, I didn't check the list. Maybe someone knows the differences between the J and K. I checked and they do use a different wiring harness.

I expect the differences are minor. The J diagram will probably get you a long way there.

 

My diagrams are listed as
*XJ750 RH/RJ/RK
*XJ750 K & MK
*XJ750 J
*XJ750(UK)

according to that Haynes chapter, "these models are no longer fitted with the XJ750 J's sophisticated computer...... uses more conventional instruments similar to those described in Chapter 6 for 650 Maxim...."

This doesn't mean use the diagram for the 650, it means the instruments & lights will just look similar to that model by the way! Your XJ750 K & MK diagram IS for your bike

It's not worded very well that old Haynes is it!

 

Thanks MercuryMan,

So I don't have a socket big enough to remove the sparkplug (does 21 mm sound right to you?) so I tried the test just looking into the cap while cranking with the lights off, I can see very dim sparking going on in each of the caps. So I will replace my sparkplugs once I can get the right tool for the job, I really didn't feel like risking it with my crescent wrench and stripping the plug.

I did try adding more di-electric grease to the plug terminal to promote contact to no avail. I also noticed that there was some soot on the plug terminals, does that mean I was too heavy handed last time I put on some di-electric grease or did they run dry?

I removed the left front cover and yes the pick-ups spin (finally some good news!).

Tomorrow's goals: buy socket for spark plugs, do real spark plug test, and buy new spark plugs.

EDIT: 13/16" was the correct size for the spark plug

 

Ah ha! Good catch!

 

Went to O'Reilly auto parts, bought four bright and shiny NGK 8P7ES spark plugs, brought them home to do the spark test... and the terminals were too big to fit in my plug cap assembly! What the hey?

I pulled one of the old spark plugs and it's a NGK B8ES model. Here's a picture to compare the two. I'm pretty sure I've got textbook carbon fouling on the old spark plugs.

http://xjbikes.com/coppermine/displayim ... pos=0.html

Here's my question, do I return the 8P7ES plugs and buy four more B8ES plugs? I'm guessing I don't have to swap out the plug cap assemblies back to OEM.

:?

 

Shhh i'll share this secret just with you.........


http://m.youtube.com/#/watch?v=O4X_bdJo ... 4X_bdJox8w



Unscrew the little cap on the top.

 

The diagram on page 269 of the Haynes manual is for the 83 XJ750K. If you have already figured this out please disregard this post.

 

Wow what a rookie mistake!

 

I appreciate the double confirmation, thanks!

 

EDIT: When testing for spark before, I just held the plug in the air and didn't rest the plug against the engine. What a difference following directions make! There is weak spark! I've pulled off the battery since I'd drained it down to 12.1 volts.

Here is a video for how to check for spark for anyone in the future who has never done it before: http://www.youtube.com/watch?v=cdif7gaWDLc
I cannot take credit for the video, he then goes on to perform a compression test

End edit

Welp, checked for spark with the new plugs, no spark on any of the plug caps.

Checked starter motor solenoid, there is an audible click and the resistance goes to zero across the terminals when I disconnect the starter motor lead and press the starter button.

Started the ignition coil resistance tests, got the correct resistance for both coils on the primary coil check. Then things got weird... for the second coil check, I could only see infinite resistance between the 1 and 4 coil, and 21.1 Kohms of resistance between the 2 and 3 coil. But when I would swap over to the continuity check for the 2 and 3 coil, it wouldn't beep at me.

Is there something wrong with my ignition coils? These little guys are super expensive on bikebandit (need to check prices with chacal) so if there are other tests I could do, I'd greatly appreciate the head's up....

 

"So I don't have a socket big enough to remove the sparkplug (does 21 mm sound right to you?) so I tried the test just looking into the cap while cranking with the lights off, I can see very dim sparking going on in each of the caps."

This has me puzzled.....without earthing the lead there won't be a spark. I fail to see how you saw a spark peering into the cap? I should also mention that the engine should not be run without the lead(s) being properly grounded. This will harm your electrical system.

 

If you're getting iffy readings for your coils & no spark I'd suggest unscrewing the leads out of the coils & unscrewing the caps out of the leads & then checking each lead, cap and coil independently. (you should find continuity though each lead, & I think the caps have 5k ohm resistors) it could be you have bad plug leads or caps. Given that you said you saw sparking inside the caps earlier I'd suggest the caps/leads my be "leaking" anyway & as they're reasonably cheap to replace I'd fit new ones provided the coils check out OK when tested sans-leads

Another check you could do is for voltage across the coils + and - wiring connectors. you should see 12v for a second or so just as you switch the ignition on (TCI cuts earth after that, when not cranking, to protect the coils)

It is also possible you damaged the coils by cranking with no plugs connected but I'd check every other possibility first.
Those old plugs are pretty well fouled & fit for the bin

 

x10 what they ^ said. I simply would not try to crank it w/o having a plug in the cap and grounding. The risk of damage to electrical systems is too great. When you turn off the inside lighting and hold the plug next to the engine while cranking the spark across the plug is easily visible...or not.

Hope this helps.

Gary

 

You can find used coils on cheapBay unless you just want to be sure and upgrade to better coils.

If you were checking your secondary resistance between bare plug wires (unscrew the plug caps) and you got infinite resistance then that coil is shot.

Have you tried the plug in cap against motor test for spark?

 

Surely you mean the WIRES OR the coil are shot? would be silly to condemn a coil without at least confirming the readings directly at the coil.

I think he said there was no spark when testing with the new plugs.

 

I suppose the wires could be bad, but you can only check primary resistance on XJ coils at the coil and not secondary resistance, since the plug wires are molded into the cases of the coil. More often than not if the coil is fine then it's the connection between the plug wire and the cap that isn't conducting properly, and usually just because it needs to have fresh wire exposed and be re-attached to the plug cap. I'm sure these OE coil wires fail, but so far my experience has been either the coil or the connection is the problem.

 

Agreed, it is usually the wire to cap connection that's the cause of any "coil" problems, I did think the wires unscrewed from XJ coils though. One of mine was loose & it seemed to screw back in :? maybe my coils aren't stock, can't see Yamaha using different ones just for my model... I'll have to go look now if the weather allows me lol

 

You're right adrian, I was attempting the test without grounding the plug, with the plug grounded I got spark.

 

All!

I only had enough time this morning to go check for spark the right way this morning. This evening I will come back and still perform all the tests on the coils/wires that you suggested... I read fitz's post about the process, and how I want to be in charge of it, not the bike, so I think that just because there is a spark doesn't mean I shouldn't investigate the whole system while I've already got it under the microscope.

Thanks!

 

Well, that's good to hear you have a spark. Good idea to make sure everything's in spec too, as you say, you're in amongst it anyway.

Not wishing to hijack but on the removing wires from coils thing, mine do unscrew from the coils but Chacal has this to say...

Spark Plug Wire Splicer:

pw1) Aftermarket NGK-brand SPARK PLUG WIRE SPLICER. This handy little device allows you to cut off a bad original plug wire and splice in a replacement piece, which is really handy, since the plug wires on the original factory coils are basically non-replaceable......so if a plug wire goes bad, the whole coil is basically junk! Not real clever factory engineering, but there you have it.

This splicer allows you to extend or replace a damaged or bad plug wire, just like you would splice into a piece of electrical wire. Watertight, screw-on design is made from a high-impact plastic material and adds no resistance (0 ohms) to the circuit. Very handy and practical solution!
HCP2789 Aftermarket SPARK PLUG WIRE SPLICER, fits up to 8mm plug wire. Each:
$ 6.50
HCP2789SET4 Aftermarket SPARK PLUG WIRE SPLICERS, fits up to 8mm plug wire, set of 4:
$ 22.95

I must have different coils too! 8O those splicers are a cool thing though if a wire was to go bad...