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View Full Version : Engine stalling sputtering and backfiring irratically and then going back to normal



Grinnling
04-10-2014, 10:38 PM
Ok so I get my bike back from the shit head mechanic after he "fixed" a stalling problem I was having, and now Rees a sporadically spark issue it seams the timing is going in and out of wack and I have no idea why. At one point i lost spark in one of the cylinders and was running one down. And like a stroke of slut magic it came back to life at about 50-60 mph and everything went back to normal and ran fine. A lot of people are thinking its electrical a lot are thinking water in the gasoline and I'm thinking someone fucked with the carburetor a little to much, original issue was just a spontaneous stall out that would instantly kill the motor, now it's running rough and there appears to be some sort of goblin giggling somewhere near the bottom end. Now it seams to be set off but stop and go traffic so far atleast. I'm letting some dry gas clean out the tank right now and I'm gonna start it up tomorrow to see if that clears it up. But I'm wondering if anyone has any other thoughts on the subject. The bike is a 1986 sportster 883, I'm trying to get some second opinions on the problem and to see if anyone would be able to help me figure it out for trouble shooting purposes.

Sky
04-11-2014, 6:13 AM
Loose nut behind the handlebars?
When you say "lost spark" that means electrical. But if you mean "lost combustion" or "dead cylinder", well that could be mechanical too. Or fuel delivery, or a combo.
Suck, squeeze, bang, Blow. In the right amount, at the right time. Good luck

dexxx
04-11-2014, 8:39 AM
Does it happen at any consistent times? i.e. low end, high end, warming up, hard throttle, or just randomly? The same cylinder everytime? both cylinder? alternate cylinders? If it's the same cylinder every time you can rule out the carb, and check leaks and spark plug could be fouling/almost dead. If its both cylinders then check carb float might be getting stuck or your coil may be going bad.

Wiring is always a potential problem, could be bad ground hitting the frame randomly or wiring getting/losing bad connection as your riding, but that would be more like the stalling you WERE having than the cylinder dying out like you have NOW

Answer the questions above first then we can help more

Grinnling
04-11-2014, 4:00 PM
It's happened twice and both times as of right now have been triggered by low end speed.

I probably mean losing combustion as I'm not sure how to check the carb To make sure fuel is getting to engine I am going to try pulling the plugs because for some reason this bike kills spark plugs like lionidas kills Persians.

and I didn't think to check either time which cylinder it was but when it happens again I will check

RustyShackleford66
04-11-2014, 5:20 PM
What did your mechanic do to it when he fixed it? What did he tell you he found?

What type of ignition is it?

I would drain the fuel and replace with fresh, check all electrical connections starting at the battery and then ignition switch, and coil. Check for chafed insulation. Replace the plugs.
It doesn't sound like a carburation issue to me. I wouldn't start playing with the carburetor yet.

7884
04-11-2014, 6:29 PM
sounds like a leak. Put it neutral and start it up. pull one spark plug off, if its stilling running put it back on and do the other. Shuts off check for leaks around that cylinder. without changing spark plugs

Grinnling
04-11-2014, 7:50 PM
What did your mechanic do to it when he fixed it? What did he tell you he found?

What type of ignition is it?

I would drain the fuel and replace with fresh, check all electrical connections starting at the battery and then ignition switch, and coil. Check for chafed insulation. Replace the plugs.
It doesn't sound like a carburation issue to me. I wouldn't start playing with the carburetor yet.

Well when he fixed it he said he replaced the intake gasket and rejetted the carb, he said he found an intake leak,

It's an electric push button ignition.

And I'll check the wires at those points and Im going to check the plugs too when I get a chance tomorrow.

RustyShackleford66
04-12-2014, 11:48 AM
Don't "check the plugs" REPLACE THEM!

You might want to look and see if the wires on the back side of your kill switch are shorting out on the handle bars. Remove the switch housing and check for bare or pinched wires.

Frog
04-12-2014, 11:26 PM
I would start by looking at what he did to the bike. If stock wasn't the Keihin butterfly in use in '86? Was your stalling problem when sitting at lights?

More info on what you mean by "killing spark plugs" or whatever terminology you used.

flathead
04-13-2014, 5:47 AM
well maybe a lose wire, coil has a small crack, try looking at the cheapest fix first that would be lose wires. then check coil, points/ecm. plugs, plug wires, drain gas from carb bowl. check connection at the battery. you got this fix it and buy yourself a beer

Saltytonk
04-13-2014, 9:29 AM
I'm very lost by your choice of words.... first when it was asked "what ignition are you running?" it was not about your starter switch. Your ignition system is what gives spark to your coil and the timing thereof. It sounds like your ignition is crapping out. If indeed it is an electronic ignition ...it could be the pickup sensor in the nose cone.. Look in the cone ..see if the sensor is melted. It will be obvious if it is. Start there.

Grinnling
04-13-2014, 3:01 PM
I would start by looking at what he did to the bike. If stock wasn't the Keihin butterfly in use in '86? Was your stalling problem when sitting at lights?

More info on what you mean by "killing spark plugs" or whatever terminology you used.

They get a lot of excessive build up on the plugs.

And When I bought the bike it had an s and s super e installed on it. He said that he rejetted the carb back to the factory setting from s and s. because the jets were oversize which i didnt really understand because the bike ran fine before.

A majority of the stalling and backfiring has occured at low speed and every stop light feels like its going to die. Intact as I rode today I have a steep decline at the end of my street that I can coast down and gain speed. And it stalled completely, Im going to assume its the stock ignition system, and coil. And when you say nose cone what do you mean?

Im going to check the wires on the handle bars tonight after I get another ride in, today the rough idle was significantly less then the previous ride but I want to check and see if it was just a fluke I also have a video of it at idle and photos of the plugs which I will upload shortly

Saltytonk
04-13-2014, 6:05 PM
On the right side of the engine case right below the cylinders and right between them is a "cone" with a round cover. This cover is known as an ignition or points cover. The right side case is the cam chest. This is where your timing gears are located Behind the round cover is either your pickup sensor or depending on year and if an after market ignition is installed the entire system.

The cam chest on a sportster contains 4 gears. This is why you will often hear sportsters refered to as quad cams. These gears time your engine to open the valves at the right time.

I'm sorry you are having trouble with your bike.
And I hope you get it Running. But you should really get aquatinted with how an internal combustion engine works and the terminology of parts and systems on your bike.
Google , YouTube and search functions on forums such as right here on chopcult along with service manuals are your friend.
I'm not trying to be a dick. Just pointing you in the right direction.

poorbiker
04-13-2014, 7:22 PM
Salty is right, get a manual and read brother.
Its almost impossible to diagnose online however I would be surprised if it turns out to be anything other than electrical, probably ignition, maybe a shorted wire and or coil or ign. wires. A simple volt meter with ohm/contitunity feature and again beginners dc automotive electrical trouble shooting book will really pay for itself in the long run........hope you figure it out............

Frog
04-13-2014, 9:43 PM
I can't help with the "E" carb because I've never used one. Gotta love affair going on with my Keihin CV at the moment. Check your float adjustment and any other adjustables such as enrichers/chokes, fuel/air mix and recheck the jets he put in. If it has an enricher sometimes they don't work properly and cause an overly rich situation.

Kinda hard to screw up the jet sizes when putting back to stock but who knows. Check what he did. You might have to play with the jets to get it just right. The plug fouling, if not oil, still points to the carb IMO. I suppose a weak spark could do it but I'm still leaning toward the carb as the problem. Especially when it stalls going downhill.

Losing one cylinder sure points at electrical though and maybe you have two problems. Damn I hope not cause finding one problem is bad enough.

Borrow a buddies carb that should work with that bike and bolt her up. You never know. I let a Bud borrow my CV once to help in troubleshooting a running issue. My carb on his bike acted the same way his carb on his bike. We kinda ruled out the carb.

willbilly
04-15-2014, 12:35 PM
sounds like ign moldule,had that problem and thought mines was carb turned out to be ign moldule,also had loose wire on coil same thing in and out problems good luck eltric problems are a pain to me it sounds like a eltric problem forsure,sportys are bad on ign moldules buy one with a warrenty

RandomSavage
04-30-2014, 10:08 PM
I know on the newer sportys, they have the same exact problem. Its the crankcase or crankshaft position sensor. 50 dollar part. I had the same problem, but not sure about your older model.

Grinnling
05-01-2014, 10:02 PM
Allright so the mechanic cracked the whole thing open and low and behold found the wrong pre jet in it it was running real lean and the idle screw was untouched from the previous mechanic when they swapped jets. So the new mechanic rejetted the bike back to what it needed to be

Saltytonk
05-02-2014, 6:16 AM
I don't know how one could know if the idle screw had been adjusted or not. And the idle screw sets the idle speed.
The air mix screw sets the air - fuel mixture .

Have you ran the bike yet? I doubt very seriously that this would cause your bike to stall or run on one cylinder. You also said that the plugs had excessive buildup and were fouling.
A lean condition will not cause your plugs to have excessive buildup.....they will burn up rather than build up.

I would guess you have multiple problems going on.

Grinnling
05-03-2014, 3:07 AM
Well I'm not sure what was going on all I know is now the bike is running reliably and hasn't given me anymore trouble so whatever joe did fixed it. And I've learned not to look a gift horse in the mouth. :P