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Discussion Starter · #1 ·
I've been working on my GL650 and it has been running pretty decent. It seemed like every time I rode it, it ran a little better. Until last Sunday. Last Sunday, I decided to ride to my parents on the other side of town. On the way there, it just didn't seem to have any power. It would take off good, but acceleration seemed to be very sluggish. It also seemed to lack power while pulling, especially up hills. As I went up one hill, I had to keep gearing down and was only going about 45mph by the time I reached the top after running close to 70 at the bottom.



Yesterday I put some Seafoam in the tank and took it up the road. I was getting on it pretty hard when it lurched forward a couple of times and then took off. I thought maybe there had been a piece of trash that finally broke loose. After that it ran great.



Today, I took it out again and it was back to not running good. No power. But this time, there was nothing I could do to make it run better. Then it completely died and it took me a couple of minutes to figure out I was out of gas. The problem with that was that I had only traveled 70 miles on that tank. 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. I haven't taken the petcock off yet, but it doesn't seem to have an obstruction either



When the bike is running poorly, I can smell gas. I don't know if that means lean or rich, but the gas is going somewhere.



When I first got the bike, my friend "lightly" cleaned the carbs. I've already decided to get a copy of Larry's book and go through them the right way. But, is that where I need to start with this particular issue or could it be something else?



Any help would be appreciated.
 

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It does sound like carbs. But there are a couple of other things to check that can cause poor performance.



Inspect the vacuum hose from the right carb to the petcock. Make sure it does not have any splits, especially at the ends.



If you have not already done so, consider the main fuse modification. A main fuse with a hairline crack can be misleading.
 

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Discussion Starter · #3 ·
Inspect the vacuum hose from the right carb to the petcock. Make sure it does not have any splits, especially at the ends.


Thanks, Dave. I put new vacuum hose on it, but I just stuck it on with out the clamps. I didn't realize it was such a big deal, but I'll put something on it to hold it tight.



I will go ahead and do the fuse modification as well. Thanks for the tip.



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

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That dripping COULD be a tiny little spring-loaded pin on top of the needle valve that keeps the vibration of the running bike from giving the float a false signal that it needs more gas....Doing that main fuse fix will certainly not hurt anything, and even if ya don't put it in right away, you'll have it on hand for when it does. Don't ask me how I know this......Lol
 

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Discussion Starter · #6 ·
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.
 

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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.
 

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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.


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
 

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Discussion Starter · #9 ·
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.
 

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Discussion Starter · #10 ·
Even though the bike is running better than it was, the gas mileage is still in the toilet. I was planning to ride to work this morning, but when I got to the end of my road the bike died. Out of gas again with less than 90 miles on this tank full.



This weekend I will address the petcock and quite possibly the carbs. I know Larry suggests a ultrasonic cleaner, but will I be able to get adequate results without it? I'm not in a position right now to purchase even the cheaper one from Harbor Freight.



I will also do the fuse modification Dave suggested. Is there anything else I should look at while I'm in mechanic mode?
 

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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.


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.
 

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My only question, Eurovee is how many folks were actually in that pub on August 23, 1996 at 22:50? That wasn't a Sunday was it?



Sorry about the hijack, now back to our regular scheduled post.
 
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