free website stats program 1993 Sportster weak spark | Page 2 | Harley Davidson Forums

1993 Sportster weak spark

Not real familiar with the Sportster but I had one here last week that was running bad. 05 Custom. Long story short it was the CPS. Now, does that year / model have one?
 
GscottB said:
I found very weak spark
Click to expand...

What do you mean by weak spark? Is it failing to jump the gap when it should. You can have 50,000 available volts jump a .025" gap and it can look weak to the eye. Your eye can't measure the duration of the spark.
Are you using an adjustable spark gap tool tester to determine what is weak or not.

The 1993 Sportster must be dual fire, so the secondary spark plug gaps are in series. It's like having just 1 plug with a gap of .064" (.032" + .032"). One bad spark plug wire reduces the spark in both plugs, not just the one that is bad.
 
Red Fish, CPS Cam position sensor, yes - That is the second thing I replaced.
Hoople - Adjustable Spark gap tester - yes, that is the first thing tested. I started at 3/8 inch and spark was a very very thin line of almost no color (orange if any). I got the same thing at 1/4 inch. And it seemed to be intermittent. What times I have tested, run the motor after replacing sensor, full choke, it had a misfire and a bit of a back fire. I don't have a tack, but full choke is what, probably 1500-2000 RPM? When I replaced the sensor, I marked the case and tried to place the new one in the same position. It may need timed. I am just about convinced my problem now is the module, which I have a new one for installation. I just don't want to destroy it. It just seems odd that both the sensor and module went bad at same time. Could my melted sensor have destroyed my module? Could a bad module have destroyed my sensor? Just looking for all the input I can get to try and nail this.
PS - every (motor) I own, from weed eater, boat motors, to 1963 roto tiller produces a large blue spark at 5/16 inch. This weak spark I'm seeing couldn't possibly be 50K volts, could it?
 
Well - still not running. New coil, sensor, module, battery - will still run only on full choke. Call me stupid, I'm gonna look into the carb now, even though I rebuilt and lined tank in May. If I find the problem in the carb/intake, I still don't get it - why such a weak spark? All components test out, resistance in wire harness, etc. Some $450 later, I guess I better open up the carb. What do other folks spark look like? I'm getting barely visible spark at 1/4 inch. Plug wires test at 5 and 6k ohms. 12.5+ volts at coil. When I try and twist throttle while on full choke, it stalls. Accelerator pump? Any help?
 
take the breather off and hit the throttle a few times. You should see a tube sticking up and shooting spray when you hit the throttle. If no spray, the accel. pump is bad. Carb kit is about $39.00.
 
Well, it's been a long time but thought I'd update if anyone can use my experience. I finally got it running decent a few weeks ago. Problem is I don't know what fixed it! Replaced in this order:
Plugs - Coil - Sensor - Module - Battery - Plug wires - Carb rebuild.
I had suspensions of intake leak even though I tried the either method. It was difficult because it would run only at high RPM. The way the carb is secured with the breather makes it tricky. Being so frustrated with it, plug wires and carb rebuild were the last things that seemed to have fixed it. Old plug wires tested out with the ohms test and carb was rebuilt just months before problem started.
Only problem left is it has a bit of popping on de-accelerating that it didn't have before. Keep in mind this is an 883 to 1200 conversion with K&N air cleaner mod and straight pipes. I still need to time it (I can't see the mark through inspection plug with oil spray). I don't have the numbers of the jets at hand but the low speed was over size and the high speed was stock. But! it runs decent!
 
To help with checking the timing a clear timing plug is available which will allow you to check the timing and keep the oil in as it does throw a lot of spray without it

Brian
 
GscottB said:
Well, it's been a long time but thought I'd update if anyone can use my experience. I finally got it running decent a few weeks ago. Problem is I don't know what fixed it! Replaced in this order:
Plugs - Coil - Sensor - Module - Battery - Plug wires - Carb rebuild.
I had suspensions of intake leak even though I tried the either method. It was difficult because it would run only at high RPM. The way the carb is secured with the breather makes it tricky. Being so frustrated with it, plug wires and carb rebuild were the last things that seemed to have fixed it. Old plug wires tested out with the ohms test and carb was rebuilt just months before problem started.
Only problem left is it has a bit of popping on de-accelerating that it didn't have before. Keep in mind this is an 883 to 1200 conversion with K&N air cleaner mod and straight pipes. I still need to time it (I can't see the mark through inspection plug with oil spray). I don't have the numbers of the jets at hand but the low speed was over size and the high speed was stock. But! it runs decent!
Click to expand...
If you have stock ignition you should be OK, as far as the decel popping, have you considered some type of baffles in the straight pipes? Straight pipes are notorious for de cel popping, there is nothing in the pipes to keep the un burned gases in check and No back pressure to help with exhaust scavenging, it is quite possible you could be sucking in some un burned exhaust this will compromise intake fill and give you a weird combustion mixture JMO
 
Thanks for the replies. I'll keep carb in mind for the future. But it needs to be darn near dark outside to see spark, so I thought ignition.
Fin: I have the clear timing plug (I called it inspection plug). I may have got a glimpse of the mark once or twice.
Jack: Didn't know about baffles. I'll have to look into that. But It didn't pop before my trouble/s.
 
You must log in or register to reply here.
Back
Top