right cylinders not firing


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thrasherg
Posts: 1837
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Location: Plano, TX
Motorcycle: 2004 GL1800, 2005 Honda Shadow 750, 2008 Yamaha R6 with RG500 engine, CRF450X, CRF230, CRF250X, XR200, CR500

right cylinders not firing

Postby thrasherg » Sat Jan 17, 2015 2:37 pm



Ladies & gentlemen,

a friend of mine just dropped his 1200 off and asked me to look at it. When we try to start it, it only runs on 2 cylinders. I removed the 4 carbs, completely cleaned them and fitted a carb overhaul kit. I am 100% certain they are put together correctly. I replaced both spark plugs and the fuel filter. I have confirmed the fuel pump works and is pumping fuel to both carbs on the right hand side. However when we try to start it, it always fires up and idles at about 500 RPM, but only the left sidse exhausts get warm. It clearly is not firing on the right hand side. What is common to those 2 cylinders and might cause an issue? I don't know if it's one ignition coil feeding both spark plugs on that side (But I doubt it)? after a while all 4 cylinders do start firing and it runs fairly well (Not 100%). There is good compression on both cylinders, so I am 99% sure it's a problem with the ignition side of things.

All suggestions gratefully received as I would like to get this bike out of my garage (It takes up a lot of space!!).

Gary



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oldishwinger
Posts: 171
Joined: Sun Jul 14, 2013 11:26 pm
Location: New Zealand
Motorcycle: 1986 GL1200 Aspencade

Re: right cylinders not firing

Postby oldishwinger » Sat Jan 17, 2015 4:30 pm

definitely check the coils and also spark plug leads the manual shows how to.

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HawkeyeGL1200
Posts: 918
Joined: Sat Jul 05, 2014 11:53 am
Location: Courtland, Va.
Motorcycle: 1984 GL1200 Interstate
1981 GL1100 Interstate

Re: right cylinders not firing

Postby HawkeyeGL1200 » Sat Jan 17, 2015 7:41 pm

Every time I've encountered a problem with BOTH cylinders on one side (typically the right for some reason... maybe because of the lean on the side stand) it has always been fuel related.

As I'm sure you already know, both the front cylinders share a coil and the rear cylinders also share a coil... so if it were the front pair or the rear pair, I may be inclined to start looking into spark, then fuel, but when a "side" isn't firing, it leads me to fuel... Of course it could have been two bad plugs... but you've already replaced those... in fact, it looks like you've already eliminated most of the typical causes of lack of fuel.. so I'm going to go out on a limb and ask how you tested the fuel pump output and if there is a chance that the pump isn't getting told to fire by the relay or the ECU (I can't remember the source for the voltage input to the fuel pump... but I do know that the pump doesn't "turn on" with the key switch. The engine must be rotating for the pump to be provided with the 12 volts it needs to move fuel... so that's where I'd start looking, because I believe you aren't getting enough fuel to sustain the engine ... mine did the same thing you describe the day the fuel pump died on me... of course mine was an easy fixer... all I had to do was plug in a new one..

When you resolve this, and I believe you will shortly, I'm be interested in knowing what you find as the cause...
I am wrong as often as I am right concerning what is wrong with someone else' motorcycle without having seen the machine in person. Guessing with limited information, as to the source of the trouble, is sketchy at best.

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thrasherg
Posts: 1837
Joined: Tue Oct 20, 2009 11:21 am
Location: Plano, TX
Motorcycle: 2004 GL1800, 2005 Honda Shadow 750, 2008 Yamaha R6 with RG500 engine, CRF450X, CRF230, CRF250X, XR200, CR500

Re: right cylinders not firing

Postby thrasherg » Sat Jan 17, 2015 11:23 pm

Thanks guys, I unscrewed the drain plugs on both right carbs and fuel pours out, so there is definitely fuel getting to the carbs. I disconnected the output of the fuel pump, start the engine and let it idle at 700RPM on the pump dumps out loads of fuel. It could be that both carbs have blocked jets, but unlikely as I just overhauled all 4 carbs.. Still think it is ignition related, but will check the fuel side a bit more.

Gary

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HawkeyeGL1200
Posts: 918
Joined: Sat Jul 05, 2014 11:53 am
Location: Courtland, Va.
Motorcycle: 1984 GL1200 Interstate
1981 GL1100 Interstate

Re: right cylinders not firing

Postby HawkeyeGL1200 » Sun Jan 18, 2015 6:59 am

The only explanation I can think of is you put in two bad plugs... which I don't believe.

Maybe a smart member will be able to help LOL

thrasherg wrote:Thanks guys, I unscrewed the drain plugs on both right carbs and fuel pours out, so there is definitely fuel getting to the carbs. I disconnected the output of the fuel pump, start the engine and let it idle at 700RPM on the pump dumps out loads of fuel. It could be that both carbs have blocked jets, but unlikely as I just overhauled all 4 carbs.. Still think it is ignition related, but will check the fuel side a bit more.

Gary
I am wrong as often as I am right concerning what is wrong with someone else' motorcycle without having seen the machine in person. Guessing with limited information, as to the source of the trouble, is sketchy at best.

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86pearlblue
Posts: 100
Joined: Sat Sep 22, 2012 6:04 pm
Location: Hartford, Connecticut
Motorcycle: 1986 gl1200a

Re: right cylinders not firing

Postby 86pearlblue » Sun Jan 18, 2015 9:12 am

a few things to check...
1) make sure the plugs are hooked to the proper coils.
2) check the crank position sensors. one might be bad (although that should also affect either front or rear, not side to side.)
3) check your timing belts. if the right side has skipped a tooth or if there's too much slack in it, it would cause some issues without smacking the pistons into the valves.

You could also check the rubber portions of the intakes and the gaskets on the heads for cracks etc. It could be sucking air instead of the fuel mix. A test for this would be, with the engine running, spray some WD-40 or starting fluid around the area. If the engine revs up, you have a leak.

As I write this, another thing occurred to me. You night check the vacuum hoses for leaks.

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HawkeyeGL1200
Posts: 918
Joined: Sat Jul 05, 2014 11:53 am
Location: Courtland, Va.
Motorcycle: 1984 GL1200 Interstate
1981 GL1100 Interstate

Re: right cylinders not firing

Postby HawkeyeGL1200 » Sun Jan 18, 2015 9:22 am

You make several excellent points, and I hadn't considered that the plug wires may be mispositioned.. this "thing" has been bugging the heck out of me this morning... as all my eggs were in the "fuel" basket ... I too, thought about vacuum leaks, but my (limited, granted) experience is that generally cracked or damaged vacuum leaks tend to lean out and raise RPM, rather than cause a cylinder not to fire.

One check I did think about it to pull the plugs (or get two more plugs) and plug them into the boots, ground them to the engine and turn the engine over to see if there's fire on that side. It won't tell you if the fire is occurring at the correct time to fire the cylinder(s) but it could eliminate wires as a culprit.. I have to admit to being stumped.

86pearlblue wrote:a few things to check...
1) make sure the plugs are hooked to the proper coils.
2) check the crank position sensors. one might be bad (although that should also affect either front or rear, not side to side.)
3) check your timing belts. if the right side has skipped a tooth or if there's too much slack in it, it would cause some issues without smacking the pistons into the valves.

You could also check the rubber portions of the intakes and the gaskets on the heads for cracks etc. It could be sucking air instead of the fuel mix. A test for this would be, with the engine running, spray some WD-40 or starting fluid around the area. If the engine revs up, you have a leak.

As I write this, another thing occurred to me. You night check the vacuum hoses for leaks.
I am wrong as often as I am right concerning what is wrong with someone else' motorcycle without having seen the machine in person. Guessing with limited information, as to the source of the trouble, is sketchy at best.

User avatar
thrasherg
Posts: 1837
Joined: Tue Oct 20, 2009 11:21 am
Location: Plano, TX
Motorcycle: 2004 GL1800, 2005 Honda Shadow 750, 2008 Yamaha R6 with RG500 engine, CRF450X, CRF230, CRF250X, XR200, CR500

Re: right cylinders not firing

Postby thrasherg » Sun Jan 18, 2015 5:39 pm

Thanks everyone, I pulled the carbs and checked them again, found nothing wrong so put them back in. Still wouldn't run on the right cylinders. Checked that I had the spark plugs correctly connected and they where!! unplugged the spark caps from the spark plugs and put another spark plug and started the engine with the spare spark plug where I could see the spark gap. No spark!! Removed the cap and checked it and it was open circuit!! Both caps on the right are open circuit!! Bought 4 new plug caps and changed them all, tried the spark plug again and now have a nice spark!! Plugged the caps back onto the original spark plugs and started the engine!! All 4 cylinders running!! I have never heard of 2 caps going bad at the same time, but there you go!! Very happy to have a nice smooth running engine again.. Thanks for all the suggestions.

Gary

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HawkeyeGL1200
Posts: 918
Joined: Sat Jul 05, 2014 11:53 am
Location: Courtland, Va.
Motorcycle: 1984 GL1200 Interstate
1981 GL1100 Interstate

Re: right cylinders not firing

Postby HawkeyeGL1200 » Sun Jan 18, 2015 5:50 pm

I'm curious if they are resistor caps and if the screws that hold the resistors and springs in them are tight?

AND I'm glad you fixed the problem...
I am wrong as often as I am right concerning what is wrong with someone else' motorcycle without having seen the machine in person. Guessing with limited information, as to the source of the trouble, is sketchy at best.

User avatar
thrasherg
Posts: 1837
Joined: Tue Oct 20, 2009 11:21 am
Location: Plano, TX
Motorcycle: 2004 GL1800, 2005 Honda Shadow 750, 2008 Yamaha R6 with RG500 engine, CRF450X, CRF230, CRF250X, XR200, CR500

Re: right cylinders not firing

Postby thrasherg » Mon Jan 19, 2015 5:55 pm

Hawkeye, the original caps on the bike where resistive, as I am running resistive spark plugs, I chose to use non-resistive caps to give a small boost to the ignition system.. Not hearing any interference on the radio, so it doesn't seem to have done any harm.. Just need to take the bike for a good test ride and if all is well, give it back to it's owner!! If only it would stop raining in this state (WA)!! I miss Texas..

I haven't tried to open up the old caps to see what the problem was! I don't think they where the original honda caps, as they have NGK written on them.

Gary




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