Rookie Question...

Good day all. I'm new to this group but have been learning a lot from your discussions. I have what I believe will be a quick question for you. I recently bought an 82 XJ550 and decided to change the plugs as it seems to hesitate and although it runs pretty well it's a little rough. Thought I'd start with the simple stuff. Anyway...I started it up after changing the plugs and it runs exactly as it did with the old ones. I decided to pull the cable off each plug one at a time and see if there was any noticeable difference to how the engine ran. 1, 2 and 3 caused rougher running but plug 4 had no change on the engine sound at all. What are all the possible causes for this? I'm hoping it's just a bad cable to plug 4 as I planned to change those soon anyway. Thanks for your help!

 

first off do not pull wires while engine is running.
take the plug cap(boot) off it unscrews ,cut the plug wire back about 3/8" lube the wire a little and screw back in.
if you want to test for spark you take your spare plug pull a wire put plug on ground to motor and turn it over to see a spark.

so what have you done for maintaince on your bike.
is it beeing driven daily?

 

Take one of your old spark plugs put it in the number 4 cable. Then hold it against the head and check for a spark. You will need to clean the carbs. Where are you in Ontario?

 

Good point XJ 550. I wish I could type faster.

 

When it was running....he should have felt #4 pipe....for warmth or coldness.....to see it is firing

 

Start here:
http://www.xjbikes.com/forums/threads/the-information-overload-hour.27544/
Do you know the previous owner well enough to trust them (absolutely trust them) with your life?

Seriously, XJ's are great bikes, recommissioning one takes due diligence, and a commitment of some loonies, twoonies and time. Read that link above all the way through, keep asking questions here and your riding life will have just gotten a little better!

 

And don't forget plug caps are 5k ohms
At $5 each they are an affordable fix

 

550 10k ohms

HCP13604 Aftermarket 10K ohm CERAMIC RESISTOR, can be used to replace the

original internal plug cap 10K resistor on all T-131, T-135, and T-140 plug

caps on XJ550, XJ700-X, and XJ750-X models.

 

Stumpy, you've been reading my posts!

 

Yes but for Canada all Yamaha 550-750xj ngk specifies 5k ohm for all models as our models used resistor plugs.US models that did not use resistor plugs so that may be why they have required the 10k ohm so total remains the same.

 

makes sense to me, but not from a manufacturing stand point.

 

I haven't owned the bike long enough (about a month) to have done much maintenance to it. I had to replace the clutch cable. I've inquired with some fb bike friends of mine and they seem to think it's more of a carb issue than electrical. I'm doing a Seafoam cleanse and riding as often as possible to try and clear the crud which I assume is bunging up the works. Sprayed WD40 on the air intakes between carbs and manifold with no effect on idle so I think I'm leak free there. My next step is to try a carb sync and see if that helps. The rough (and it's not THAT rough) running only happens at idle and a little stuttery up to 3k. Runs great at speed but does "pop" a bit when decelerating. I have never cleaned carbs but will attempt it if necessary. I seem to be going through oil fast as well but there's no puddles on the ground. Exhaust is a little hazy blue on startup but you almost have to look for it to notice it.

 

I've been riding it every few days or so since buying it a month ago. Prior to that I believe it sat for about a year.

 

I'm in Belleville.

 

[QUOTE="Steve Latter, post: 474672, member: 18513".. I decided to pull the cable off each plug one at a time and see if there was any noticeable difference to how the engine ran. 1, 2 and 3 caused rougher running but plug 4 had no change on the engine sound at all. What are all the possible causes for this? I'm hoping it's just a bad cable to plug 4 as I planned to change those soon anyway. Thanks for your help![/QUOTE]

Hang on, pulling any plug should mean that teh bike goes to two cylinders as you are removing the return path to the coil which feeds 1 & 4 or 2 & 3 right ?

 

Hang on, pulling any plug should mean that teh bike goes to two cylinders as you are removing the return path to the coil which feeds 1 & 4 or 2 & 3 right ?[/QUOTE]
both sides of the wire are "ground". coils work on hysteresis. it puts potential to both ends of the wire

 

sort of, when the magnetic field collapses and puts either a + or - charge on the tip of the plug, normally it goes to the other plug and makes two sparks. so far so good. now pull one cap off and the +/- still goes to the wires, when it comes to the plug that is connected there is still a DIFFERENCE OF POTENTIAL (DOP) from the tip to the tang and it sparks.
say both plugs are connected the tip is at -20,000 the tang is at +20,000.....spark.
only one plug connected, the tip is at -20,000 the tang at 0......still sparks, but not as good, but good enough to work

 

Got it, I think..