GL650 Not Running Good

Okay. I put zip ties around both ends of the vacuum line and tightened it down good. But while I was out today, I also picked up a couple of new spark plugs and installed them. The old ones looked kinda sooty. I just fired it up and took it for a ride around a good test ride loop (Phil's neighborhood) and it ran great.



Now I'm in need of some education. If the vacuum line was the problem, I would assume that it was keeping the diaphragm from opening in the petcock and starving it for fuel. But what happened to my fuel? Why did it drop below 20mpg while it was running bad? Do I have a misunderstanding of the cause and effect? Would the vacuum line cause a problem that would result in it flooding? Or did I back into a solution with the spark plugs? Or is it an intermittent problem waiting to resurface?



BTW, the air filter is new.



I appreciate everyone's help.

I was going to suggest that your problem may be electrical and to check to see if the plugs were sparking. when you said above that the bike was working bad and then would surge a couple of times and then worked ok it made me think electrical.

It sounded like one cylinder was cutting in and out.



You could try sticking the old plugs back in to confirm if that was the problem.



Also you said the carb was dripping when the bike sat,,this would indicate that the petcock may not be operating properly,,only it is not causing fuel starvation,,it may be operating as a normal petcock and letting fuel through without the bike running.

donboze said:

Now I'm in need of some education. If the vacuum line was the problem, I would assume that it was keeping the diaphragm from opening in the petcock and starving it for fuel. But what happened to my fuel? Why did it drop below 20mpg while it was running bad? Do I have a misunderstanding of the cause and effect? Would the vacuum line cause a problem that would result in it flooding? Or did I back into a solution with the spark plugs? Or is it an intermittent problem waiting to resurface?





When I got home I took the inline filter off to see if there was trash in it, but I didn't see anything. I also opened the petcock and drained some fuel into a can and it flowed freely



When I park the bike, if I don't turn off the petcock the right carb will be dripping a small amount of fuel





I appreciate everyone's help.

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Well, something aint right with that vacuum fuel tap, because if you blocked off the vac.hose (in a normally functioning tap) no fuel would flow because the diaphragms arn`t being opened....



If, both the vacuum and fuel diaphragms had holes in them the engine would draw fuel into the engine through the vac.hose causing rough running, and poor mpg.



But, in a normally functioning and set-up vac tap a perished fuel diaphragm would cause fuel to dribble out of the vent/drain hose....



Also, you say you opened the fuel tap and fuel was seen to flow freely. Was this with the engine running, because if it wasn`t this also points to something amiss with the tap.



Are you sure the `overflowing right carb` isn`t the vac.tap drain hose? They exit under the engine in about the same place.



I think it`s time to open up the vac.tap and see whats going on in there. You shouldn`t be able to smell petrol...



You can dissasemble the tap without removing it from the tank (got to take tank off though): with the tap turned to `off` no fuel will flow even with the diaphragms etc removed.



There are 2/3 ways to convert the tap to manual operation if you decide you wanna go that route depending on what you find

Eurovee, good point on the petcock (fuel tap). When I said that fuel was running through it freely, the bike was not running. In fact the tank wasn't even on the bike. I had it on a stool letting fuel run back into a gas can. So there is obviously something wrong with the petcock. Are there parts available or would it be better to convert it to manual?



Yesterday it ran good. Today it was intermittent again. It would run good for a few miles and then poorly for a few miles. But it wasn't the sluggishness from before. It seemed to be just rough running (missing?). Could it be possible that it is pulling fuel through the vacuum line causing this symptom?



And by the way, when I first joined this forum I ran across the bike in your avatar. Did you post a build thread? Anyway, very nice. I love the creativity.

donboze said:

So there is obviously something wrong with the petcock. Are there parts available or would it be better to convert it to manual?



It seemed to be just rough running (missing?). Could it be possible that it is pulling fuel through the vacuum line causing this symptom?



And by the way, when I first joined this forum I ran across the bike in your avatar. Did you post a build thread? Anyway, very nice. I love the creativity.

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The poor mileage you`re getting may or may not be due to the vac.tap, but it`s definately suspect so that would be one of the first things i`d look at.

I get about about 180 - 190 miles on my GL650 before going onto reserve, then about another 30 miles after that..



There are rebuild kits available to fix the vac tap, they are about 25 of our english pounds. I`d rather take the opportunity when faced with a problematic vac tap to save 25 of my english pounds and convert to manual which`ll be more reliable and may give better starting performance when the bikes been left for a while (that CX quirk of running on one cyclinder after being stood a week or so). Plus i`m a right tight fecker and i`d rather use my improvisation skills to fix something than pay extortionate prices for 2 discs of rubber worth 50p.

Actually i`m not that stingy - i once bought a round of drinks in a pub - 23rd August 1996 it was, about 22.50 hours if i remember correctly.



Anyway,if conditions are right (or should that be wrong!) it`s perfectly possible for fuel to be drawn into the engine via the vac hose, it`d be unusual, but possible.

As i say though, a leaking fuel diaphragm should be evident by fuel dribbling out the vent/drain hose, unless a previous owner has tinkered with the tap and maybe blocked off the drain hose to `fix` it! Another reason to take a look-see.



There were a few Suzuki`s in the 80`s which had a vac tap with only one diaphragm - fuel on one side and vacuum (the engine) on the other.

When the diaphragm perished fuel could flow down into the vac hose/inlet/engine and rest in the cylinder.

When you fired the bike up if you were unlucky you`d get hydraulic lock and sometimes major engine damage!

That`s why our CX`s have two diaphragms.......



You can read some info on the vac taps here (scroll down to the bottom) and click on `CX-Periment` at the page top to see the build blog of the creation in my avatar.