Spark advance and stock compression
Harley Ignition & Harley ElectricsDiscuss Spark advance and stock compression in the Harley Tech & Harley How-to forums; Hey guys
I have another one for you. I had a feverish need to reward the bike for its get up and go yesterday so I decided to pick up ...
Hey guys
I have another one for you. I had a feverish need to reward the bike for its get up and go yesterday so I decided to pick up the first of the parts needed for the upcoming overhaul. I decided to stay away from the fully programable, adjustable, tweakable, screw-up able ignition systems Donnie recomends in Techline and go for the biggest and baddest of the screaming eagle plug-in modules and coils. I just installed them and fortunately for me it's raining so I can ask advice before I ride. The instructions say this system is for higher than stock compression, which will be fine when I get the headwork and 95 inch kit. At the moment though I am still stock. It warns that the spark advance on the unit when used with stock compression "MAY" lead to power loss (gulp) and hotter than normal exhaust emissions. My 3 questions. Is that true? If so why? And, can I hurt the bike by riding it with this ignition until I move to the higher compression set-up. I can and will pull it off if there's a risk. But if it's good to go then go I will.
Keep the coils in, pull the module out until you upgrade. The key word here is " SPARK ADVANCE" Twin cams run hot to begin with. Again wait till you upgrade or you may loose the gains that you already made by tweeking the carb. So to answer your three questions, yup , because {advance} and it sure can!
03, The advantage to having an adjustable ignition system is that you can adjust it for any combination that you may have. Just think, in the future if you plan on making more upgrades the plug-in module may not be enough! Just remember this is a street bike and there is a point you don't want to go beyond!
03,, remember, the higher the compression the more likely detonation may occur,, soo, we retard the overall advance and even slow the rate of advance...
For instance, I run 28* with a "medium rate" of advance in my 120" with 10.5 to 1 comp... In a stock 74 or 80" with say 8 to 1 we could get away with 32-35* at a fairly fast rate of advance...
So, what the instructions are saying with out really saying it, is that the unit has a slower rate of advance and probably a low overall advance,,, that is why your pipes may blue along with overheating and loss of power, it would be "de-tuning" your stock set-up but properly tuned for a hot-rod... I wouldn't run it like that... Capice..??
Thanks
I'll pull the module. I don't want to do anything to hurt the bike. It is my only bike and I ride a lot. Your warning about not going beyond a certain point is interesting. I do depend on the bike. Laconia is only weeks away and I'll probably hit it for a day or two. The run from here is about seven hundred miles and I do it in a day. The bike loves a good long run like that, although my body barely survives it. Should I reconsider the bore and headwork and just stay where I am with a milder ignition? Maybe I should be looking for a basket case harley and attempt a complete rebuild on a project bike. That is something I've always dreamed about.
There's basically three types of modules, plug-in fixed, selectable and adjustable. With the first one you get what you get. With a selectable they allow you specific set options ie, lets say four advance curves, four rev limits etc, etc. With an adjustable module the skies the limit, you can adjust it anywhere you want.
03,Where are you staying, I'll be going up to Laconia for the first weekend. The 9th- 11th and maybe even the 12th. Go with the big bore kit and heads! If you have the finances to do a project bike, build the biggest,baddest motor that you can and keep your other bike reliable with streetable modifications.
This is some very interesting info.I did the '95 upgrade with flat-top pistons.I also did the cams. I used the SE ignition ,which was designed for the stage 2 big bore, as recommended in the SE book.After riding a little and the bike is hot,it backfires when I start it.After getting advice from several forums like this, I decided to put the stock module back in.Backfire now gone.Now did I waste my money on this module, or is my timing off a little and the advanced curve ignition pushing it over the edge and causing it to backfire?
I can't help you on that jimib but I'm sure the lads here will. Hey Frisco, I think we may pass on an interstate. At this point I can't get away from work until the 14th. My plan is to haul ass down on that date and stay in North Conway. Stayed at the North Conway Grand last year. The hotels there actually CUT the price during bike week and have free hot breakfasts, covered secure bike parking and a bike wash station. The ride in to Weirs is a nice little run to start and end your day. There is still a chance I can get away for the first weekend, If so I'll update you. I decided to go with the Dyno programmable ignition. Its price puts it between the Screaming Eagle I just bought and the Crane Fireball Donny recomends. I'll return the SE in the morning and have them order me up the Dyno for the weekend.
03, ya got me mixed up with myt, I'm not the one that may go to Laconia,, but meetin up sometime to talk motorsickles and drink whisky would just alright by me...
Just on Friday I burned up my THIRD Dyna, luckily I was close to home and a bud with a trailer, I have heard good things about the Dyna 2000i however... Sugar Butt is now runnin the same Crane HI-4 that I ran in the shovel for three years, no probs...
I would suggest the most adjustable ignition,,, ya can't screw it up unless you're stupid and I don't think you're stupid...Like mty says, do your upgrade AND get a basket, have fun, hell ya only go round once...
Jimib,,,, It would appear that the ignition may be at fault for your backfiring... If it is adjustable you can fix it, if not then that's a good reason to get the most adjustable ignition huh...
I don't like electronic ignitions, I've burned up 4 now, 1 CompuFire, 3 Dyna's... After Fridays prob I put points back in the 120", runs fine... When an elec ignition drops, you're toast,,, never been dropped by points, however when I do those two sickles that I "threw together" just to get registered before the turn of the year, I'll probably try another elect ignition...
Spark advance and stock compression 
Linear Mode
