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Discussion Starter · #1 ·
Bike runs good at low rpm but when I open it up "full throttle" it sputters and carries on until i back off throttle. I believe its a fuel system problem but have very little knowledge on these old bikes. Where should I start, what are common problems with these bikes. All your opinions and stories are appreciated. Its a 1983 Silver Wing with a GL650. Thanks guys
 

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Interesting. Mine has a similar problem although It has only had a test run but definitely spluttered at higher revs. I have a small after market fuel filter fitted and I think it is a fuel starvation problem. I intend to fit a slightly bigger filter when its other problem is sorted. Are you running on a standard air filter and exhaust?
 

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Discussion Starter · #3 ·
Interesting. Mine has a similar problem although It has only had a test run but definitely spluttered at higher revs. I have a small after market fuel filter fitted and I think it is a fuel starvation problem. I intend to fit a slightly bigger filter when its other problem is sorted. Are you running on a standard air filter and exhaust?
Stock filter and exhaust took tank and air filter off tonight, air filter looked very dirty, petcock screen was clean as a whistle. I did notice a small fuel line leading to the passenger side carb (right cylinder carb) to the petcock was not attach to the carb nipple. I have two carbs that are separate i was wondering if one fed fuel at low rpm and if the other (right side carb) was high rpm. Didn't get a chance to test ride tonight, Ill let you know tomorrow night.
 

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Your bike has a vacuum petcock. The small line from the petcock to the carb is the vacuum line.
A dirt air filter will cause running problems. A short run with the air filter removed will trll you if that is one of your problems.
 

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'84 CX650E that is evolving into a GL500
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Except that running without the air filter can make an engine run like crap at all RPMs.....

Welcome to the forum. Please add your location to your profile and your bike's model and model year (NOT year first registered) to your signature (see Forum Settings link in my signature) so that you don't have to remember to tell us every time and we don't have to keep asking when you forget.

And welcome to the world of antique vehicle ownership. Your bike has had 39 years of Previous Owners who may or may not have done the maintenance necessary to keep it safe & reliable so it is highly recommended to download the Factory Shop Manual for your model (available through the CX Wiki - link in my signature) and go through all of the service procedures, regardless of whether your bike has reached the specified mileage. I also recommend looking on all rubber parts with suspicion because rubber does not age gracefully. Check the date codes on your tires and replace them if they are over 5 years old no matter how good they look & feel because old rubber simply cannot flow around the irregularities in the asphalt well enough to grip, especially if it is cool or wet. If your bike still has the original rubber brake line(s) (should be replaced every 2 or 3 fluid changes = 5 or 6 years) start shopping for modern stainless braided ones (they last practically forever and double the life of the fluid).

It is pretty standard for bikes to have a separate carb for each cylinder. They need to be balanced (AKA "synched") so that they both allow the same amount of air/fuel mixture into the engine but other than that and being controlled by the same cables they work more or less independently. The shop manual has a section about the carbs.

The vacuum line may have detached from the barb when you removed the tank. It should be a tight fit so that it doesn't leak and if it isn't that is another possible cause of your problem. The vacuum petcock has 2 valves, a manually controlled valve that works the same as a non-vacuum petcock, allowing you to select between ON, OFF and REServe and a vacuum valve that prevents fuel from entering the manual valve when the engine is not running. The vacuum valve needs a decent amount of vacuum to open fully so if the vacuum line is cracked or loose (it is one of those old rubber parts I mentioned above) the valve may allow enough fuel to reach the carbs at lower speeds but not at higher speeds.

Mike is not wrong about the effect of a dirty air filter either.

If the filter is visibly dirty it needs to be replaced and you should be able to get enough 1/4" vacuum line to replace it from any local auto parts place for a couple of $ so it would make sense to replace both.

BTW: There are 3 barbs on the vacuum petcock:
- The large barb is for the fuel line
- The small barb farthest from the body of the petcock is for the vacuum line
- The small barb between the other 2 is for the drain/vent line.

You already know about the first 2. The drain/vent line should run down behind the engine with the other end in the same bracket near the swingarm as the overflow lines (from the barbs on the bottoms of the carbs) so that if/when the diaphragm in the vacuum valve fails the fuel that escapes will be carried past the hot parts so it won't cause a fire (the overflow lines do the same in the event of a carb overflowing). If any of those lines are missing replacing it is highly recommended.
 

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Discussion Starter · #7 ·
Except that running without the air filter can make an engine run like crap at all RPMs.....

Welcome to the forum. Please add your location to your profile and your bike's model and model year (NOT year first registered) to your signature (see Forum Settings link in my signature) so that you don't have to remember to tell us every time and we don't have to keep asking when you forget.

And welcome to the world of antique vehicle ownership. Your bike has had 39 years of Previous Owners who may or may not have done the maintenance necessary to keep it safe & reliable so it is highly recommended to download the Factory Shop Manual for your model (available through the CX Wiki - link in my signature) and go through all of the service procedures, regardless of whether your bike has reached the specified mileage. I also recommend looking on all rubber parts with suspicion because rubber does not age gracefully. Check the date codes on your tires and replace them if they are over 5 years old no matter how good they look & feel because old rubber simply cannot flow around the irregularities in the asphalt well enough to grip, especially if it is cool or wet. If your bike still has the original rubber brake line(s) (should be replaced every 2 or 3 fluid changes = 5 or 6 years) start shopping for modern stainless braided ones (they last practically forever and double the life of the fluid).

It is pretty standard for bikes to have a separate carb for each cylinder. They need to be balanced (AKA "synched") so that they both allow the same amount of air/fuel mixture into the engine but other than that and being controlled by the same cables they work more or less independently. The shop manual has a section about the carbs.

The vacuum line may have detached from the barb when you removed the tank. It should be a tight fit so that it doesn't leak and if it isn't that is another possible cause of your problem. The vacuum petcock has 2 valves, a manually controlled valve that works the same as a non-vacuum petcock, allowing you to select between ON, OFF and REServe and a vacuum valve that prevents fuel from entering the manual valve when the engine is not running. The vacuum valve needs a decent amount of vacuum to open fully so if the vacuum line is cracked or loose (it is one of those old rubber parts I mentioned above) the valve may allow enough fuel to reach the carbs at lower speeds but not at higher speeds.

Mike is not wrong about the effect of a dirty air filter either.

If the filter is visibly dirty it needs to be replaced and you should be able to get enough 1/4" vacuum line to replace it from any local auto parts place for a couple of $ so it would make sense to replace both.

BTW: There are 3 barbs on the vacuum petcock:
- The large barb is for the fuel line
- The small barb farthest from the body of the petcock is for the vacuum line
- The small barb between the other 2 is for the drain/vent line.

You already know about the first 2. The drain/vent line should run down behind the engine with the other end in the same bracket near the swingarm as the overflow lines (from the barbs on the bottoms of the carbs) so that if/when the diaphragm in the vacuum valve fails the fuel that escapes will be carried past the hot parts so it won't cause a fire (the overflow lines do the same in the event of a carb overflowing). If any of those lines are missing replacing it is highly recommended.
Thanks for all the feedback, my vacuum line to carb was junk, replaced it and bike ran better but not like it should. After my test ride with new hose the right cylinder carb start dumping from overflow. Pulled the carbs but haven't torn them apart yet because I want a schematic and need a rebuild kit. Any ideas on were I can find that. Thanks a lot guys very much appreciated
 

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'84 CX650E that is evolving into a GL500
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Look in the FSM - you did download it, didn't you?

Also, Larry (LRCXed) has written a very good book on cleaning these carbs. The recommended carb kit is from Randakk's Cycle Shakk; It has all of the parts you will need in better than original quality and none of the stuff you don't (like thise aftermarket jets and needles that are never right that come in some cheaper kits).

BTW: It sounds like when you replaced the vacuum line the flow of fuel to the carbs increased and either revealed a stuck float valve or washed a piece of debris into the float valve. Before going much farther I would try cleaning the float valve's seat with a q-tip and some methanol or carb cleaner.
 

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Replace your O rings on the carb manifolds even if they look good.
 

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I've dealt with two bikes like that and it was plug wires that needed replacing.
 

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1982 GL500i
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I had a similar problem 11 years ago with my 82 GL500i. A previous owner apparently thought that lots of fuel would make lots of power, so he drilled out the main jets with a 1/8" drill bit. Idle was ok, but opening the throttle just made it run awful, and it wouldn't even do 25 mph from the excess fuel flow. I swapped out all of the jets from a spare carb set that had not been internally molested, and the bike ran perfectly. I only did a full-scale overhaul 3 years ago when Randaak made his GL500 & GL650 carb kits available.
Here is a link to the kit he has made for the CX/GL 650 carbs:
https://www.randakks.com/honda-cx500-randakk-master-carb-overhaul-kit-version-c.html
 

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'84 CX650E that is evolving into a GL500
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Um.... Randakk's kits for the CX family have been available for more than 10 years. I know because they weren't new when I installed one in Eccles that long ago.
 

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1982 GL500i
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I stand corrected Bob, I actually only purchased his GL500 Kit 3 years ago. I did use one of his GL1000 Kits when those came out 10 or so years ago, and one of the GL1100 Kits 2-3 Years ago as well. Sometimes I am lucky to remember when I found what vs. when I actually made use of them, lol! :rolleyes:
 

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'84 CX650E that is evolving into a GL500
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Randall Washington (Randakk) and Dick Smith (Dick in Raleigh) were good friends (Dick was Chopper Charles' Dad and was the one that convinced Charles to start the forum that this one is descended from). Not long after Randakk started selling his kits for the early GoldWings online Dick convinced him that there were enough of us with CX bikes that would want top quality kits for our bikes too.

I checked back in my maintenance logs and I installed the Randakk kit in my GL1000 carbs (that are still on my GL1100) in 2009 and the one in my CX650E carbs in 2009.
 
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