Why resistor spark plugs?

[pregrid]

The title says it all. I understand why we run resistor spark plugs in our cages with radios and all the computer what nots but on these ancient motorcycles wouldn't a non-resistor plug deliver more spark? I'm having starting issues and I'm working in several directions but this has bugged me for a while. I'm running a pamco, Mike's Ultimate high output coil, 5K caps and NGK BPR7ES plugs. I'm just wonderin' if the non resistor plugs wouldn't give a hotter spark? Ideas??

 

[oldbiker]

with the pamco you generally get a set of plugs its worth checking on petes, or mikesxs web site just to get it right hope this helps regards oldbiker

 

[XSLeo]

With the Pamco and Ultimate coil I doubt your problem is ignition related.
With the resister plugs the resistance keeps the spark from jumping the gap until the spark voltage builds up higher than the standard plug can. It also makes the spark last a bit longer. This makes for a larger longer lasting spark. Always a good thing.
If you are getting that nice hot spark at the right time then it can't be ignition related.
Check your timing, if a bit advanced it can make it harder to start. On your 79 it should have two marks with the F between them. Set your idle timing over to the right line to retard the timing a bit.
If you have this right, don't worry about your ignition. Start looking in the carbs. Is the enrichener working right? The idle circuits clear?
Leo

 

[speez]

running R's makes the spark last longer, not as strong but longer, longer burns more fuel, you can try to run stock plugs and see if they are good for you,

 

[CDNTX650]

id get rid of the resistor plugs. dont need em if you have the caps. one or the other man.

 

[pregrid]

id get rid of the resistor plugs. dont need em if you have the caps. one or the other man.

that's what I was thinkin'. Guess I'll have to try them and see what happens.

Thanks for the answers guys. I'm lookin' for reliable starting, something I don't have yet. Kicked the shit out of it this afternoon and it just wouldn't start. Got spark, I know that. Battery is fully charged. New VMs. Finally got it to start by twisting the throttle as I was kicking it. Thought I was not supposed to do that. Never had to before. Damn thing's got a little over 200 miles on it and it's never been this fickle. Fuckin' old bikes anyway!

 

[TwoJugs]

The resistance in the spark system helps to let the voltage build before it can jump the plug gap. then when it does there is more voltage built in the coil to discharge. Better spark. Not sure what the formula is on how much resistance to add though. I would stay with what ever they recommend as far as wires and plugs. If you are having problems and they are operating as they should then you can remove that from the equation. If you start to tinker where it doesn't need help you can chase your tail longer.

 

[pregrid]

I believe your right Jugs. I think I may have it nailed down. This things been running rich since the beginning even tho the carbs were set up by Mike Morris (although in fairness he does send a tutorial on tuning them and I'm sure every bike requires different setups). So after taking the carbs apart to make sure they were clean and the float levels had not changed I dropped the needles one notch and opened up the air bleeds to 2 1/2 turns out. Before I put them back on I set the slide height down so as to have starting point. That last adjustment may have affected the starting. Got it fired up and had to hold the throttle just to idle even when warm. Got the idle set properly and after sitting overnight she fired up on one kick this mornrng. Gonna go for a ride to try and get a plug reading (previously the were really black after a good run).

This thread was started 'cause I have a tendency to over think things. Stay tuned and thanks to everyone, I LOVE this place.

 

[pregrid]

Just went for a putt, after several hours of cooling down she started on the second kick (with choke on), idles higher with the choke than it ever did, no biggie. Went just 5 miles or so, enough to get it to operating temp, ran tits. Wants to idle high or try to die so I've gotta adress that (maybe screw the air screws in a little) but the proof is in the spark plugs and I'm happy. Keep in mind this is just dropping the needles one notch and moving the air bleeds from one turn out to two. Got a little more tweaking to do (and put several more miles on it and read the plugs again) but I'm happy. Left plug is before (with only 50 miles on it), right is after (also a new plug to start). Oh, both are resistor plugs. Thanks again for all the input!

 

[XSLeo]

CDNTX650, on a stock TCI coil with 15kv ouput I agree, the resister caps, or the resister plugs, not both. On the ultimate coil with 82kv output both will be fine. Plenty of spark. You can even open the plug gap some too.
With my green Monster coil with 75 kv output I opened the plug gap to .038 to .040. Works fine.
Leo