View Full Version : Electrical gremlin...
03-26-2008, 07:00 PM
Maybe someone has had this issue and can point me at a good starting place. When starting my bike, it spits and pops terribly out of the front exhaust. It's been kinda doing it for the last 2+ years, but seems like it's getting worse and harder to start. It's a track bike, so most of the electronics (headlight, brake, signals, etc. have been long since removed).
I rebuilt the engine and went to 100mm pistons over a year ago. Same issue before and after the rebuild. I thought maybe one of the exhaust valves were sticking slightly open or something crazy like that. So, last month I installed my ported/polished heads that were collecting dust. So, completely new top end. Same issue!
I talked to Ed with AF1 about it possibly being a coil failure but he said that he's never seen it happen. I did have a short in my voltage regulator early last year due to an exposed wire, but fixed that. It's got spark, fuel and all the good stuff. Anyone have any idea what could be causing this?
BTW - When it gets hot, it seems to be ok.
03-26-2008, 09:38 PM
Geez, 1/4 Chicken. Here's my best guess based on what you have offered.
You said it spits and pops out of the front exhaust only during warmup.
I am going to assume:
1) the rear exhaust note is normal
2) the front intake note is normal
3) the front and rear plug colors are the same after a hard run / chop.
Here's my thoughts:
It is wet fouling the front plug(s) only during warmup because the spark is weaker there, or the fuel is richer there compared to the rear hole.
If you agree, you could take these diagnostic steps to isolate a possible bad component:
1) switch the front cylinder coil(s) to the rear cylinder and vice-versa.
2) switch the front cylinder injector to the rear cylinder and vice-versa.
If the problem follows a component, well, I guess you would know what to do...
03-27-2008, 01:12 PM
The plugs all look good. I just put the bike back together and the plugs were neither fouled or wet. It "seems" to spit & pop from the front and up through the throttle bodies if I happen to have the tank up. I'm going to try the coil swap this weekend to see if that tells me anything.
I may try the wire mod for the regulator while I'm at it. Since it's better when warm, my mind went directly to a faulty regulator/coil. I'm going to pick up a volt meter today and see if I can diagnose the power to find any drops or weak spots on cold start up.
03-27-2008, 10:38 PM
The whole electrical system runs off of the battery. It is the tank, so to speak. The charging system just tries to keep that tank full.
If you still have the stock meter on board, you may be able to monitor system voltage while riding. Expect troubles if it drops below maybe 11 VDC.
Other than that, you just mentioned that the front intake makes abnormal sounds too. This is big news, more than just weird noises out the exhaust.
By the way, on 2 wire ignition coils, (like you have,) you don't have to mount them to test them during a front - rear swap. Just switch the primary leads and the secondary leads at the same time.
Also, first check the plug boots and wires: Unscrew each plug boot from each wire. Look for signs of arcing / burning where the boots screw into the core wire. Clip the wires fresh if in doubt. Measure the resistance of each boot core - they will be about 5K ohms if they are resistor type and less if not, but each of the 4 boots should be close to the same, +/- 10%. (reference.)
Seal them up with die-electric silicone grease at both connections.
Keep me posted - I'll gladly take you to the next step if you can give me solid info and results.
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