#1 cylinder firing intermitently.

1985 XJ700 Maxim

I have compression, I'm pretty sure I have spark...and I seem to have fuel...why don't I have ignition?

 

With the wasted spark setup these bikes use, pretty much anything that affects cylinder 1's ignition will also affect cylinder 4.

Exceptions to this are a shorted plug wire (which would likely be pretty obvious, especially if you run it in the dark and look for arcing) and the plug itself. Have you tried swapping plugs between 1 and 4 to see whether the problem switches cylinders? You could also try swapping wires between 1 and 4 to test them.

If the problem doesn't follow the plugs or wires, then the problem's probably in the #1 carb. A bit of starter fluid into the #1 carb throat might help confirm of disprove this theory as well.

 

Thank you for the response.

I guess more information would be helpful.

I just bought the bike for my old lady. It has been sitting for about three years. It doesn't wan to to idle and as mentioned #1 cylinder fire intermitently.

I haven't really done much of anything with it yet but will try moving the plug to see what happens and let you know.

 

Take a Spare Spark Plug.
Unplug the Spark Plug Cap from the Number-1 Plug.

Plug-in the Spare Plug.
Ground the Spare Plug and run the Engine.
Look to see if the Spare Plug is Firing.

 

Ok I just went out and swapped #1 and #4 spark plugs. With them swapped #1 and #4 cylinder were not firing. Both plugs are pretty black. I'm now pretty sure I need to replace the spark plugs and go from there.

It;s the middle of the night and plenty dark and there was no "light show" around the plug wires anywhere so i don't think any of them are "leaking"

By the way...why does it list me as a biker wannabe? I've been riding for 27 years. Is it just cuz I'm new to this forum?

 

Yes to the second question...

For the first question (if it was a question), I'd say yes'ish... New plugs would be good so you can be more confident there's nothing wrong with them, but you may be able to just clean them and then swap them with 2/3 so you have a known good pair of plugs to test with.

You may find, though, that, even with new plugs, neither of 1/4 are firing. If that's the case, wires, caps, or the coil itself are the most likely culprit, with other possibilities being the TCI box, the harness, oxidized connectors, and the VR pickup under the timing cover.

Let us know what you find with better plugs and we can give some more troubleshooting steps from there.

Cheers,
Paul

 

Actually, there is one other thing you can check quickly (if you have a multimeter).

Measure the resistance from the contact of the number one spark plug cap to the number four cap. It should be, at a guess, around 22K Ohms. If it's a lot higher, or open, then the problem is the coil, wires, or caps. The caps unscrew from the wires - in case you find a problem with the overall resistance and want to narrow down where the problem is. The caps by themselves are probably 5K Ohms (again, a guess, since I'm not that familiar with the coils on the 700).

 

I do have a multimeter, I'll try that tomorrow. Won't have the cash on hand to get new plugs until Monday so I'll have all weekend to do other tests and whatnot.

Another question that feels like a stupid one. Where is the fuse block? I've had both seats off and both side covers, even had the tank off. But no sign of a fuse block anywhere.

While I'm asking...the fuel indicator light on the tach, I know it's supposed to come on when the fuel gets down to certain level. Well it didn't and I ended up pushing this thing home the other day. While I had the tank off I jumped the poles int he plug for the fuel sensor and the light came on. Now I know this means either a bad connection at the plug or at the sensor, or that the sensor itself is somehow failing. My question is whether these bikes are known for the sensor failing.

 

On the 750's, the fuse box is a little plastic box under the seat. Again, though, don't know that much about the 700's.

 

A little up date. I went out and ohmed the coils. #2-#3 coil ohmed out at almost 22k exactly. the #1-#4 coil ohmed at 31.5k this was with the plug caps on. I'll do it again without the plug caps but I think it's pretty safe to assume that coil is failing.

I'd liek to get an idea of what a replacement will cost. I know the coils for my GoldWing run about $65 each. Comparable?

I found the fuse box, it's behind the idiot light panel...really stupid place to put it in my opinion so it will most likely be relocated in the not to distant future.

Thanks again for the help guys.

 

Ok so I just did a little bit of shopping online for a new coil and...DAMN!

So anyone got a good used one layin around?

 

I think it's more likely that the coil itself is OK, since they're pretty much open or not.

Wires are a likely culprit, though (escpecially their connections to the coil in the housing). The caps are also likely.

Nice thing is that suitable NGK caps are available from most motorcycle shops for about $4 a piece. Probably LB05F for 1/4.

Not sure if NOS coils are still available for the 700. For the 750's/650's they're long gone. Best bet may be some good used ones. Dyna makes some suitable aftermarkets, but some fabrication is needed to mount them to the frame.

There are also some articles elsewhere on this site about how to Dremel your coils apart and replace the wires.

Cheers,
Paul

 

If they're interchangable with an 82 XJ750 (check on Motogrid for P/N's) then I have a good used one "laying around". Let me know what you find first about the caps, etc.

Cheers,
Paul

 

Heya Paul,


I decided to ohm test the coil through the wires without the plug caps. And I'm glad i did. The coil tested at just over 13 ohms without the caps. I tested each cap and they were both at 9.5ohms which is an extra 4.5 ohms from where they shoud be which is exactly enough to push 22ohms to 31ohms.

I also noticed that the P/N for the caps is different from the caps on the cylinders without issues. T-133 for the good ones T-134 for the bad ones.

I'm thinking PO was an idiot. After all he sold me the bike which cosmetically is gorgeous and the only problem with it is the one I'm dealing with now, for $225.

I rummaged around in my GoldWing spares for plug caps because they are 4.9 ohm caps....unfortunately I only have one that is going bad because it tests out at 5.9 ohm.

So I'm gonna have to pick up two new plug caps...way better than a new coil!

God I love my multimeter, and I really love the fact that I'm finally starting to learn how to use it! And I love web forums with people willing to give good advice!

If you hadn't suggested getting an ohm reading I prolly never would have thought to do it.

 

I think the 700's don't need a Fuse Block.

Your Fuses are Under The Plastic between the Instruments.
You have the new style Fuses too ... I think!

 

Yup right on both counts.

 

Went out to tinker a bit today. Found that the low fuel indicator light wasn't working because a wire had come lose from the sensor inside the tank. soldered it back and it's working fine now.

What kind of job is it to replace the wires? DO they just screw out of the coil like they do out of the plug caps?

 

Search archives:

Coil Surgery

 

I found that thread...

Going to leave that as a last resort.

 

I havent been able to find them, locally, but ... you might try using some New Wire and four of those "Spark Plug Wire Splice" barrels.

Clip the Wires as close to the Coil as the Splice will permit and then run you some New Wires.

 

I have been wondering about those - does anyone have real life experience with the splicers? Seems to me if you connected them then sealed them well it should work fine.

 

I bought a couple, just in case, but didn't use them (ended up replacing the coils instead). The NGK splicers, though, are about 2" long, and non-flexible, so installing them may require some rerouting of the wires.

Too bad nobody (at least, that I know of) makes a screw-on coil terminal (i.e. something that would allow you to cut off the stock wires short, screw on a terminal, and then use replaceable wires from there out).

(note that these coils probably can not be run from a TCI box)

 

It's my thought, that a coil is a coil. And a coil from a "wasted spark" system is a coil from a wasted spark system.

So my question is, asside from mounting issues is there any reasont hat a coil from another four cylinder bike couldn't be used.

I ask this because I have a spare set of coils from a GoldWing. Replacing the wires on them is a breeze as the wires connect to the coil in much the same manner as the NGK splicer.

Any thoughts on this?

 

I'm afraid that a coil is not a coil.

Stock coils have 2.5 Ohms primary resistance. The Saturn coils I'm running have .5 Ohms primary resistance. Besides resistance of the primary, the primary's inductance, and to a lesser extent the resistance and inductance of the secondary also come into play to calculate the correct dwell time for the coil.

I can run the Saturn coils because I'm using a Microsquirt ECU in place of my TCI box. It has current-limited driver transistors, and it allows me to set the dwell to whatever interval I need.

If I would have tried to drive these coils from the TCI box, I'd have been overdwelling them considerably, and would have burned up the coils, the TCI, or both.

One other thing to consider is that the XJ coils are regular inductance coils designed for Kettering-type dwell, but many other bikes use CDI ignition, which requires a rather different type of coil. In CDI, the control module charges up a large capacitor with a couple hundred volts, then discharges that into the coil when firing to step up the voltage to the 50KV or so needed to fire the plugs.

So, unless the Gold Wing coils are pretty close in primary and secondary characteristics, and its ignition is not CDI, it would not be a good idea to swap them in.

 

Thank you for the insight. The GoldWing does indeed employ a CDI system. So that idea gets scrapped.

What if I swapped out the TCI box for the igniters from the GoldWing? Probably a dumb question but seeing as how I'm not real sure what the difference between the igniters and a TCI box is I had to ask it.

 

I've been riding for about 27 years. But it's only been the last few years that I've actually worked on then. So please bear with me and my dumb questions.

I've had my GoldWing stripped down to the frame three times now and it's still going. So I'm not completely inept. Just don't have much a of a background.

 

No problem with the questions... happy to answer.

There would be a few reasons why swapping control units would probably not work:

1. The TCI unit is designed to work with specific pickup coils (under the left-end timing cover) to sense crank position. It's unlikely that the Gold Wing module would be happy with the XJ signal.

2. The TCI unit expects a particular reluctor tooth shape (again, under the left-end timing cover) to indicate dwell and firing points. Even if you could swap pickups, you probably couldn't swap reluctors without some metal fabrication work.

3. The timing advance curve needed by the engine is hard-coded into the control module. While the XJ would probably run with a Gold Wing advance curve, it woudn't run as well as it does with its own.

However, with all that said, is there anything wrong with your stock coils? I had thought you found the problem to be the caps.

Cheers,
Paul

 

Yeah, T'm just thinking ahead a little. The caps on the #2 and #3 cylinders are longer than the 1 and 4 cylinders. I did not ohm test the 2 and 3 cylinder caps. Bu I do know they have differnt p/n's. I'm thinking I may have to get longer caps for 1 and 4. If I do the wires will not be long enough because of the angle of the spark plugs.

So I may need longer wires. I'm not real happy with what I've read about using the splicers, nor am I thrilled about cutting open the coils. For what it's worth the coils on this Maxim are different, at least in shape from the one's in the write up about coil surgery. So I am really leary of attempting that.

I'm also working with little to no money, so using something I already have on hand is really appealing.

The check I was expecting to arrive today didn't so I'm still in a holding pattern even on the new plugs and caps.

For what's it's worth though, I had some ignition issues on my Wing. and needed to build same new plug wires. I had no money to work with at the time. The Wing utilizes the same type of stranded core plug wire that the XJ's use. All I had on hand was some 4 awg amp hook up wire. with that heavy of gauge I knew it was capable of handling the load, and the insulation was just as thick as the insulation on the existing plug wires.

So I used it to build new wires. And it worked. No "light show" and no noticeable ill effects on the ignition, and I had these nice bright shiny red plug wires!.

I eventually went back to the original type wires because I got a replacement set of coils with wires attached. It if happens that I have to add wire I will probably use the amp wire again because I have it on hand and it will look pretty good on the red Maxim.

 

When I built my wire set, I used new caps througout. The 1/4 caps are NGK LB05F. The 2/3 caps are NGK VB05F. They're both 5K resistor caps, but the LB05F is 90 degrees and the VB is 120 degrees. This should be the case for your bike as well. A pair of the LB05F's should be fine to replace the outer caps. Again, about $4 or $5 a piece from a motorcycle shop (I think my local shop actually charged less than $4).

Sorry to say, but 4 gauge amp wire for ignition is a bad idea. The insulation on plug wires is designed for 50KV or more. The insulation on the amp wire is designed for 600V. It will break down eventually. Flexibility of the 4 gauge is a second issue, but the main problem is heat. Plug wires have silicone or teflon jacketing that's designed to handle 500 degree heat sitting on top of an engine. Regular electrical wire is generally insulated with PVC, which can't take much over 150 degrees or so before it melts.

 

Well I should have known it was too good to be true. In truth I didn't have the amp wires on the Wing for very long at all.

 

Update;

I finally got the new plugs in. made a world of difference.

Couple questions though. I'm hearing a pretty loud whine from the transmission. Now I know this is normal for my GoldWing, but is it normal for the Maxim? It's probably twice if not three times as loud as the whine from my Wing.

It doesn't want to idle with out a at least a little choke. I'm thinking idle jets may be clogged or mixture setting is off. Maybe idle set to low?

Gonna try Seafoam first and go from there.

 

There is a definite whine to the shaft drive bikes. I love the sound.

 

Well the whine is coming it seems from the crank, not sure if that's normal or not.

And it definitely will not idle without being choked. I've got a full tank of gas in it with a dose of Seafoam now I just have to run it and see if that help smooth it out a bit.

Any insight into the idle issue would be greatly appreciated.