new coil, new mystery

schtipp · Posted: July 15, 2009, 12:07 am Post subject: new coil, new mystery

i got the dual tower high output coil from mike. seems like the bike got leaner. starts harder. idles worse. lots of popping. seems to have more power in the mid range on up. i cleaned the carbs twice. tried to fatten up the mix with the idle mix screws. didn't seem to help. bike is an 81 special 2

schtipp · Posted: July 15, 2009, 12:08 am Post subject: Re: new coil, new mystery

is this all just coincidence or is there a connection between the coils and my lean primary

schtipp · Posted: July 15, 2009, 12:31 am Post subject: Re: new coil, new mystery

has anyone else put on the green monster? how did it effect your bike? do i have to clean these a third time?

pamcopete · Posted: July 15, 2009, 5:39 am Post subject: Re: new coil, new mystery

schtipp,

Non of those symptoms are associated with installing the green coil.

-Are you running the stock TCI or the PAMCO?
-Have you tried replacing the original coil, if it is still working?
-Have you cleaned the contacts in your kill switch?
-Is the vacuum hose connected to the pet c***?

It's possible that you disturbed the sediment in the tank when you removed it to install the coil. If you do not have an in line fuel filter, then that sediment may have gotten into the carbs. Try draining the bowls.

The Green Monster coil produces a very high 75,000 volts. You must install it in the recomended way using the included standoffs to keep the towers away from the gas tank and the possibility of arcing. This results in the towers exiting on the left side:

You should also use resistors spark plugs in adition to the resistor caps because of the very high voltage. Like, NGK BPR7ES, the resistor version of the standard BP7ES would be a good placeto start.

TeeCat · Posted: July 15, 2009, 5:59 am Post subject: Re: new coil, new mystery

Quote::

It's possible that you disturbed the sediment in the tank when you removed it to install the coil. If you do not have an in line fuel filter, then that sediment may have gotten into the carbs. Try draining the bowls.

schtipp... also, as was recommended to me by nudude here, keep a button-sized rare earth magnet just in front of the petcock(s). This will essentially negate the possibility of metallic residue finding its way into your fuel siphons and, along with Pete's recommendations, help you to rule out a fuel delivery issue.

TC

schtipp · Posted: July 15, 2009, 8:12 am Post subject: Re: new coil, new mystery

ok i did clean the kill switch , the ignition switch, all harness connectors associated with ignition, resoldered the entire cdi board, replaced the transistor with the tip 120 from radio shack as stated in one thread on here. the old coil is shot. i checked the timing with stroboscopic and its right on as is the advance. also checked that the cam is properly timed to the crank. checked valve lash. checked battery voltage. checked charging voltages. checked reg/ rect. i do however have a theory. as i lie awake distraut over my poor bike i thought about when my troubles started. the day i got the coil, but the day before that i layed it down in a turn on a slippery road(raining hard). i think that the bike being on its side and grinding across the asphalt may have stirred up sediment that had settled in the tank and in the bowls. i cleaned the carbs twice since then and the pet c88k once but it looks like today i'll do the primary cicuit again. gonna use a small wire to really poke around in the three holes today. thanks for posting guys, I needed the sanity check also needed some other people to let me know i'm heading in the right direction. by the way. i had on this joe rocket jacket with the pads in it. its trendier than i like but it saved me a lot of skin.

schtipp · Posted: July 15, 2009, 8:17 am Post subject: Re: new coil, new mystery

i like the magnet thing. i'm gonna do that. also i will try the restister plugs if my troubles extend after another cleaning session. how pronounced of a difference should the idle mix screws make? will they normally take you through the full range from wicked lean to uber fat? mine didn't seem to do much, stayed lean all the way to 6 turns out.

pamcopete · Posted: July 15, 2009, 8:32 am Post subject: Re: new coil, new mystery

Well, I know that the TIP120 has been mentioned here to repair the TCI, but that transistor is totally unsuited for the application. It only has a V(ceo) of 60 volts. The primary of the coil spikes all the way up to 400 + volts and requires a transistor with a V(ceo) of at least 400 volts.

These two transistors would be better suited for the application, and in fact, their spec sheet makes specific refference to the ignition application. They each have a V(ceo) of 400 Volts and a power rating of 175 watts as compared to the TIP power rating of of only 65 watts:

STMicro BU931 in the TO-218 case
otorola MJH10012 in the TO-218 case

schtipp · Posted: July 15, 2009, 11:07 am Post subject: Re: new coil, new mystery

pete, sounds bad. does this mean that the tip 120 will burn up on me shortly. it's working for now, i'ld hate to take a chance at messing up my board to change it again. if you think it's a must i will. let me know... i re cleaned the pilot circuit in the carbs today. took a twist tie wire and poked around each of the three little holes. still the same results. got it to stay running. 6 turns out on the idle mix screws. wants to die when you goose the throttle. hard to pull out, have to keep the rpms over 2k or it stalls. i took it for a thirty minute drive. plugs are pretty ashy looking on the finger, stayed pretty white on the porcelain under the electrode i think i'm going to order some bigger jets. i just don't get it. the only change has been the coil, and some daytona bars from mike. do you guys think it's the bars? Laughing

pamcopete · Posted: July 15, 2009, 12:07 pm Post subject: Re: new coil, new mystery

schtipp,

The circuitry in the TCI is probaly designed to clamp the voltage on the primary to something less than 400 V, like 360V perhaps. That means that you have 360 volts across the primary to produce the out put, so the effect of using the TIP 120 is a smaller output voltage because it will break down at a lower voltage. The reason that it survives is because of the very short duration of the voltage excursion.

The condition of your spark plug is consistant with a low voltage to the plugs.

If you are really brave, you could remove the caps from both plug wires and position the ends of the wires in close proximity to each other. Start with 10 mm. If the coil will jump a 10mm gap, that is equivalent to 30K volts. Then try 15mm which is equivalent to 45Kv. Thats more than enough voltage, so no need to go further.

Do not hold the wires in your hands when doing this test. Tape them down end to end on the seat or on a piece of unpainted wood.

schtipp · Posted: July 15, 2009, 11:16 pm Post subject: Re: new coil, new mystery

took the bike to work today. ran poorly. checked the plugs there though and the right carb must have had something open up. it was actually rich. now i dialed that one in pretty close but the other side is being a sl**at least i know that this is all a big carb nightmare. it only took a week of eliminating everything else to do it and i'm still going to have to clean the left one again. anyway it's a labor of love. thanks guys for the solid input. this case is closed Very Happy

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