2 exhaust pipes hot 2 cold, found solutions!

[BRycraft]

On my 82 GS850GLZ which I am finishing restoring, it was running fine then all of a sudden it was backfiring and wouldn't idle. After finding #3#4 pipes hot and #1#2 pipes cold I swapped wires and no help at first then problem jumped after a short while. Using a spark tester all leads were sparking (so it appeared), plugs were new, compression is very good, valves adjused properly, new fuel tank and petcock, inline filter, & carbs were professionally serviced. I pulled the coils and found specs in limits, 4 oms primary and 12K secondary, then I checked the NGK boots that come off the ends of the wires and on the boots themselves found stamped 5K ohms, when I did a ohm test 2 of them were reading well over 10K while the other 2 were closer to 5K ohms. Since the plug wires on the coils were molded into the coils I decided on replacing them with Dynatek's DC1-1, new wires and plugs. When I rechecked the spark using the spark tester they glowed bright orange compared to the small orange glow that I assumed was normal earlier as I never used one of these testers before so I had no real reference as what normal glow was, so either the coils were starting to fail even though they checked in the normal spec range or a combo of them the suspect wires and out of spec boots was part of my problem. After it started and ran for a few minutes smoothly it started acting like 2 of the cylinders were not firing and this time #1#2 were hot and #3#4 were not, i sprayed some carb cleaner in the carbs and then they all were getting hot then it started acting up again and wouldn't idle, then only 1 pipe was cold, I was about to lose what was left of my mind, what could be happening? Yesterday I decided to pull the carbs something I didn't want to do and checked all the floats, a couple were misadjusted which I tended to, I cleaned the needle valves and screens anyway, and pulled and cleaned the slides as they appeared to stick slightly when released after they were pushed up. I put it all back together and decided to replace the inline fuel filter I had installed when this all went together the first time, even though it was clear, this was one of thoes $2 filters that are clear plastic and looks like a top or martini glass, anyway when I pulled the hoses off the filter I was disturbed by what had happened, the ends of the filter that were inside the hoses were melted and deformed, the supply tubes were closed up more then 1/2 way restricting fuel big time. This filter was not laying on the engine but it was touching the top of the carbs and the filter body was unharmed, there isn't much room for a filter between petcock and carb inlet on this bike, but thought extra precaution wouldn't hurt. Somehow there was enough heat generated in that area do deform the ends of this type filter and restrict gas flow. What was happening was after it sat long enough for the fuel to fill the floats it would run just till 1 or more of the bowls would starve for fuel and whichever carb was more dominant was the one that would draw more fuel leaving the others very lean.
So I thought I would leave this thread for those who may think things are working properly when they may not be and not to over look the obvious.
This was driving me nuts, I put a lot into this bike and for 19 miles it had run very good when it all of a sudden gave me fits. Here the filter I installed which looked good was actually the primary problem. I dont regret replacing the coils because the glow on that spark tester is by far much brighter then before. I hope this helps someone else who may be having 1 or more of the problems I was having, any of which will kill the performance of a motor in a hurry.

Bill

[nabrams]

This is a great post. It's a perfect illustration fo using the "assume nothing" approach and the need to methodically check all the basic issues: Spark, fuel flow, compression, etc.

[bmac]

Bill, just out of curiosity did you reinstall a new filter or eliminate totally.



bmac

[BRycraft]

Removed Filter

I ended up removing the filter all together. I also tried a metal one that the inside filter element is replaceable but it is too long and large in diameter to sit properly without hitting the carbs or tank itself, which is how I ended up with the martini glass, it was the shortest and fit, or so I thought.

I can send anyone a pic of the filter if they want to see what happened, how it deformed inside the rubber hose while the body itself remained unharmed I will never know, just in the wrong place at wrong time I guess.

Bill

[Tieftoener]

Great information - thanks so much for taking the time to write it all down. These posts are so informative and helpful. Hopefully, it'll stick in my mind - unfortunately, I'm running out of glue

[flyingace]

Thanks for posting the results of your labors. We all learn something from it. I never imagined that restricted fuel flow would only effect 2 cylinders and not all of them.

[ruddy]

Thanks for sharing your experiences with us. We all benefit when members do this. The overwhelming opinion of this forum seems to be decidedly anti fuel filter. Your experience is yet another example.

[BRycraft]

anti-fuel filter

I have to agree with the anti-filter statement, I really thought that another filter would help keep my carbs clear of debris but the trouble it cost was just not worth it, and had I not decided to go ahead and remove it, I was actually gonna replace it with another one, when I got them I got 2, one for a spare like most supplies I get I like getting a spare, had I not gotten the spare I might not have pulled it figuring it is clear and has to be ok, I could even see gas flowing into it when I turned on the petcock.(BTW) I have a non vacuum operated petcock which is why after I shut it down and started it back up it would run fine because fuel was filling the low bowls as it sat, something a vacuum petcock would not do unless it was in prime position. Guess the amount of gas I was seeing wasn't enough to supply the carbs running. Ya figure the gas goes into the fuel port between #2#3 carbs before it makes it to #1#4, and those 2 cylinders would normally be the starving ones should the volume of fuel reaching them is diminished as #2#3 were taking most of it, at least that was my impression of why it happened. I appreciate everyones kind comments and glad my work is appreciated, however I have gained as much knowledge reading everyone elses threads, so I like to bring something to the table as anyone else I assume what makes this such a awesome site. Since I had recently seen several threads on similiar problems others were writing about I felt this was important to get out since my troubleshooting methods and or results might help someone else.

[Jethro]

Bingo. Additional in-line fuel filters are nothing but trouble. The 5 of them that are already on your bike is enough, ask the Suzuki engineers if you don't believe me.

The problem with them is that you need to use 5/16" fuel line. If you don't, your bike will be fuel starved, without a doubt, weather you know it or not. So now what if you add a fuel filter to that line? A 5/16" outside diameter filter will equal about a 1/4" inside diameter of the fuel filter. You are restricting flow- again weather you know it or not.

[BRycraft]

Restricted Flow

You bring up a valid point, I took my inside dial caliper and was shocked at the readings, even though the supply hose diameter is 5/16"ID the ID of the petcock port opening is about 13/64ths, the difference in the wall thickness, the ID of this particular fuel filter is only 9/64ths, so the diameter of the filter opening isn't even 1/2 the size of the petcock opening, and it is a 5/16th filter. Even before it deformed itself I was restricting fuel already.
That wasn't something I never gave consideration, I relied on the fact that it was sold as a 5/16" filter.
Thanks for bringing that up.

Bill