Coil resistance values, resistor caps

[ron2830]

Need some more advice from all the XSperts here. Disconnected coils and resistance is about 1.4 ohms on primaries, 37K on one set of plug wires 31K on the other. This is with the resistor caps in place which if my math is correct add a total of 10K across the pairs, so 27K and 21K if I removed the caps.

Question, this seems to be quite a bit higher than specs in manual, are my plug wires failing? If so I will replace them per the tech tip on the site. Any suggestion on where to get wires with proper boots, etc, suppose I should try to find solid copper, no radio on board.

2nd question, are the resistors in the caps needed for any purpose other than radio interference, I may just remove them and replace with a piece of round copper ground wire the same length.

Thanks again to all for my many inquiries.

Ron

[randy]

Ron,

To diagnose the high resistance problem, unscrew the caps from the wire and clip 1/4" off the wire, then replace the caps. You should see a dramatic difference. If not, the ends inside the coils are corroded.

Yes, you can ditch the resistors.

You can use any solid core plug wire of the 7mm-8mm variety

[ron2830]

Not sure how to get to the wire to trim it, do the boots just pull off after removing the caps and resistors? I don't want to damage the existing wires if they are fine.

[Ken Talbot]

The plug caps simply uncrew from the wires. If they are a bit corroded and worn, it may seem like the cap is just spinning and not coming off. When that happens, keep spinning and just yank them off. Once apart, it will be really obvious where the problem can be.

[ron2830]

Thanks Ken, figured it out. Anyplace to get replacement boots and caps, looks like the pointed end that embeds into the wire is broken on one.

[TopCatGr58]

Hey Ron,

Check out MikesXS, he sells 650 parts, but the plug caps are fairly universal. He has some with NO RESISTANCE, as well as ones with the 5K resistance. Most are 90 degree style. You can also get them from Dennis Kirk, I haven't seen them on BikeBandit, but I can't remember if I really looked hard for them!?

In the tech tips IIRC, there are some photo guides on figuring out the naming structure for the NGK plug caps, so you know what style, angle, resistance, etc. to order/look for!
T.C.

[TopCatGr58]

Tech Tip NOW POSTED!

Okay,

Just found out that there wasn't a tech tip! I found the post I had made earlier, and copied it into the tech tips, Maintanence section, Electrical, easy to find now!
T.C.

[ron2830]

thanks to all, you may have saved me some work and money. I think my wires are fine, with the caps removed I checked resistance directly on the bare wires (clipped them as suggested to get clean metal) and now have about 15.2K across both sets. Three of the caps/boots have about 7.2K from the spark plug side to the wire side the other is 16.8K! A bad resistor I suspect. Plan to remove the resistors tomorrow clean everything up and check again. Without the resistors I should see a short between these two points, am I right?

[ron2830]

Diassembled two of the caps to remove the resistors and found lots of corrosion on the springs that keep tension on the resistor. Two other caps wont come apart. Someone else has tried to remove them, the slot is gone for the screwdriver tip to remove them, I have tried several methods, the the brass is soft and I already mangled one of the clips the grabs the spark plug threads. Any suggestions? Source for replacements or equivalent? Thanks.

[DiverRay]

Go down to the local auto parts store that carries NGK spark plugs. They can order the caps for you. I got mine in about 2 days, $20 for all 4 NEW caps.
Ray

[TopCatGr58]

Ahem, Ron,

Take a look at my replies just above yours! The "NEW" tech tip lists sources as well!
T.C.

[ron2830]

Any part numbers for the NGK caps? I suppose they can match them up if I take these in. Also Topcat, for the life of me I can't find your new tech tip, is added to one of the existing tips.

[TopCatGr58]

Hey Ron,

Instead of clicking on the Tech Tips in the left column, go to the MAIN FORUM page, and scroll down the page, you'll see the tips.

Here's the direct link:NGK Spark Plug Caps Tip

Depending on the style determines the description/combo of letters/numbers NGK uses for their plugs!
T.C.

[ron2830]

Thanks to all, got the new caps at local Yamaha dealer, all four for about $12. I think these were for 12mm plugs but they fit fine, I the only difference seems to be the rubber boots, just a little tighter fit around the plug. Easy to install, now I have about 25K ohms across #1 and # 4 and #2 and # 3. Would there be any advantage to removing the caps to get down to 15 K ? Also is there any chance the RF interference would cause any issues in the ignition unit?

Great forum, you guys are all a great help.

[mro]

Ahem, Ron,
Take a look at my replies just above yours! The "NEW" tech tip lists sources as well!
T.C.

Hey TC,
you just type too fast for some of us to fallow.



mro