Misfire and coil down when wet

Hi All,

Went out today on my XJ700 Maxim X and all was well for 109 miles until I hit an heavy rain storm, after a few miles in the heavy rain I lost power and thought I was running onto reserve but moving the pet cock to reserve made no difference. I then headed for the nearest gas station still thinking / hoping I may be just nearly out of gas. Once full of gas I still had the misfire, I then thought it maybe got water in the electrics and went onto to spray WD40 all around the coils and and spark plugs but had no improvement and continued home on 2 cylinders, on the way home it dried out and I was hoping it would be soon OK but was still on 2 cylinders when I got home.

Once home I checked it out and found it was 2 & 3 plugs which have no spark, put new plugs in, checked all connections but still only runs on 2 but now find when it hits 3000rpm all 4 kick in and revs out OK, soon as it drops below 3000rpm back onto 1 & 4 firing only.

Water seemed to trigger the problem off but I'm not sure if there's some other failure with the electrics, could it the coil for 2 & 3 that's failing, or something to do with the pick up coils.

Any help and advice will be greatly appreciated

 

Pickup coil is sealed off under your left crankcase cover, unless it isnt sealed properly or it was damaged while open then thats probably not the issue.

Water leaching up your spark plug wires and shorting your coil is most likely your issue here. I just went through a very similar mess myself, check your service manual for the test specs for the coil, get a multimeter and test em, only way to know for sure if the coil is good. Im betting your secondary reading is out of spec (when you take the reading across the ignition leads)

 

I solved my issue with a new coil and by cleaning up all the connections that have to do with ignition

 

If the coils check good it would be wise to inspect the plug wires and coil housings for cracking. That is where the water gets in and causes the spark to jump to ground before it can reach the plugs. The coils can be covered with epoxy, and new wires can be spliced in to the ends of the old; or you can use a dremel to cut away the coil housing where the wires are moulded in and replace the whole wire. Atermarket coils and wires are another option.

If you go the route of repairing the cracks, just be sure to thoroughly clean the coils with solvent so the epoxy will adhere.

 

Thanks for the replies Guys which probably confirms what I think, had a look on ebay for a coil, but as I'm in the UK your looking a $100 plus to buy and get one shipped to the UK, I'm wondering if a coil from a XJ900 Diversion would do the job

 

Based on the partzilla cross reference, it shares a coil part number with '84 & '85 fj600 and '86 & '87 fz600

http://www.partzilla.com/parts/detail/yamaha/YP-33M-82320-60-00.html

 

That's handy to know, thanks info

 

Try E-bay Germany. Shipping would be less, and they seem to have gotten more XJs per-capita than just about anywhere else.

 

Started it up last night after 24hrs to dry out and started up ok on 4 but I've always found it a little hesitant to pick up from tickover, I'm now wondering if it's the coil that's at fault,

 

Our engines tend to be cold blooded, but warm up quickly when all is well. Have you checked the primary and secondary resistances of the coils?

 

No I haven't, how would I do that?

I am on the look out for another coil and will just change it if I get one

 

Measure the secondary resistance between the plug wires on the same coil, and the primary resistance between the two smaller wire terminals that the wiring harness plugs into.

From Len's catalog:

XJ700-X water-cooled models:

Pick-up coils:
120 ohms +/- 20% = 96 ohms to 144 ohms acceptable range


Ignition Coils:

Primary side (input from main wiring harness):
2.7 ohms +/- 10% = 2.43 ohms - 2.97 ohms acceptable range

Secondary side (spark plug wires, without their end caps):
12K ohms +/- 20% = 9,600 ohms - 14,400 ohms acceptable range


Spark plug caps:
1985 XN/XNC models: 10K +/- 20% = 8,000 to 12,000 ohms per cap acceptable range
1986 SX/SXC models: 15K +/- 20% = 12,000 to 18,000 ohms per cap acceptable range


Spark plugs:
1985 XN/XNC models: 0 ohms per plug
1986 SX/SXC models: 5K ohms per plug

One way or another you have to attend to the water intrusion issue, and a used coil is no guarantee of that problem being solved.

 

Managed to spend a couple of hours on the Maxim today, as I said before once dry the bike started OK on all 4 but since buying the bike it always needed a few revs to get going otherwise it would bog down.
I took the coils off and it was soon apparent what the problem was, the coil for 2 & 3 had a crack in the case, see photo below. I'd managed to get a pair of spare coils off ebay to fit a FZ600 which arrived through the post yesterday, once the coil was swopped I fired it up and it felt better straight away, I'm now thinking the Guy I bought it from probably sold it because he couldn't sort this problem out as it had new plugs & plug caps and he'd also had the carbs stripped and ultrasonically cleaned. Took her out for a spin and she now runs much better pulling away from tickover no problem.

 

I'm not sure what you guys think, but given the location so close to the engine where there seems to be a lot of heat generated I'm not surprised the case has cracked

 

Heat and age kill plastics.

 

Exactly. Ever stepped into your garage in the middle of winter and thought...damn it's cold out here. Imagine what it does to that plastic. Very few if anything man made last forever. Imo 30 year old coils that still function is pretty damn good.

Gary H.

 

It is currently quite warm weather for over here in West Yorkshire, UK. Yesterday it was around 23 / 24c or 75 f and I find the water cooled XJ700 maxim X gives off a lot of heat, since I modified the temp sensor to a cooler one the fan kicks in and stops the temp gauge moving past the centre point which is good, but all the heat rises up and over heats me. Seems odd as I also have a air cooled XJ900S diversion which doesn't emit hardly any heat.

Is this normal for the XJ700 water cooled as I'm wondering if the thermostat is working OK

 

You will notice the heat from a water cooled bike more as it has a fan that is pushing the hot air directly toward you. BTW 75ºF is quite cool for the part of North America where I live; in fact I think that was the overnight low last night.

If you want to allay your concerns get a meat thermometer and set it between the radiator fins. That will tell you the actual temperature of the coolant at the radiator.