Another potential ignition issue...Pleae confirm

TimHixson · #1 11th June 2012

Ok, I have an 89 Sportster 883 That is pretty stock. It has never left me stranded, but I think my ignition module may be bad or failing. It starts and runs decent, but breaks up some where around 4000-5000 rpms consistantly. My main problem is after riding for 30-45 minutes it starts missing out, and is rather inconsistant. I have read all the threads with "ignition" in the title, and it sure seems like it might be getting hot and acting up.

Please correct me if I am wrong, but a bad coil will completely stop working when it gets hot correct? I think it is the module.

Anyone have something else I can check? I have the repair manual and have checked out all the battery wires and the VOES thingy.

antsap · #2 11th June 2012

Hi Tim,

Does it do this when you get up over 4000, and then if you drop below is behaves, and you can repeat it in close succession? If so, then I don't think its an over heating coil or anything like that.

Take these suggestions with a grain of salt (I'm an ironhead guy), but to me it sounds more like a rev limiter kicking in, or even potentially high speed jetting issues with the carb.

Scuba10jdl · #3 11th June 2012

If it starts missing out once the bike is warm at any RPM, it's very well could be the ignition module or coil. If it only starts missing when you get into the high RPM and not below, I would take a look into your main jet.

antsap · #4 11th June 2012

Hey Tim,

Did anything change recently (parts / settings etc), or did the problem sort of creep out of the blue on you?

Did the bike sit for a while before being run with the problem surfacing immediately, or were you riding it fine one day, then the next it started mis-behaving and such?

Whatever info you can provide might help us with a better diagnosis for you.
Hope you figure it out soon and get back (safely) on the road!

TimHixson · #5 11th June 2012

Thanks for the replys guys. The missing out after riding happens at all rpms, but the breaking up above 4k is there all the time. I have only had this bike for about a year, and it has done this the whole time. I bought it in barley running condition. The previous owner had the stock cv carb assembled wrong with the needle on top of the spring support instead of under it. It would idle, but die when you touched the throttle. Now it runs decent, but the missing out is pretty inconsistant.

I did the normal cleaning the carb stuff, and I put a filter between the tank and carb to help rule out a carb issue.

Long story short, I pretty much bought it acting like this.

sportsterdoc · #6 11th June 2012

If the coil secondary partially shorts, it will give a weaker spark. If the primary or secondary coil opens, it will give no spark. How do your plugs look? How strong a spark? Have you measured the coil resistance? Ignition modules usually fail from heat and sometimes recover, after cooling off. I have not heard of a module do what you are describing (now is the time for others to jump in)

Is your petcock / petcock filter clean? You could have a clean carb and starve it for fuel from the tank...or the bowl level could be low, or the fuel cap vent blocked.

steelworker · #7 11th June 2012

The battery cables and crimped end connectors would have been the first thing I'd check (increased vibes at high revs making a bad connection worse), but you've done that.

You can test the module (which I'm assuming is located in the nosecone?) using a hairdryer. Sounds like you're only getting the problem when the engine is hot, so if you heat the module/pickup with a hairdryer when the engine is cold and it plays up straight away, then you've found the problem.

A bad coil tends to show up under load (i.e. hard acceleration). You can test the coil's resistance against the specification in your manual.

Another thing you could check is the routing of your fuel hose. I once got chatting with a bloke outside my local indie, who'd just brought his bike in to check out a misfire he was getting when the engine warmed up. His (clear) fuel hose was looped down between, and touching, the barrels, and I could see air bubbles forming in the bottom of the loop and rising up to the carb. The fuel was vapourising in the hose.

TimHixson · #8 11th June 2012

I am pretty sure it is electrical. It is not falling on it's face as if it were running out of fuel. It is sputtering like it is dropping a cylinder. The plugs are new and look good when I pull them. I will run an ohm check on the coil and module per the manual.

I have the fuel line routed away from the heads/jugs pretty good with an inline filter that is clear. I have not seen any bubbles in it and it is always full of fuel. I have taken the petcock and carb apart and cleaned everything.

The battery is strong, and it cranks fine, but I will probably take the battery out and clean/check the cables again.

The bike is stock, so I assume the ingition module and stuff are just the way it came from the factory.

sportsterdoc · #9 11th June 2012

Take a look at the timing (which includes looking at the ignition module)
After removing the cover over the nose cone mounted module, leave it off for a while and see if the cooling has any affect.

TimHixson · #10 11th June 2012

Quote:

Originally Posted by sportsterdoc

Take a look at the timing (which includes looking at the ignition module)
After removing the cover over the nose cone mounted module, leave it off for a while and see if the cooling has any affect.

That is a good point. I have not checked the timing at all. It reminded me that I do get a backfire out the exhaust once in a while when I start it after a short ride. I will look at that also.

Thanks everyone.