Leaking fuel into exhuast pipe... rough idle.

[maxystaxi]

In the past two days the 75 GL1000 was having a hard time idling. Its rough and basically dies at 1000 RPMs. At higher RPMs it seems to be steady and with the occasional misfire. I've noticed fuel leaking from the right exhaust pipe. Also Cylinder #1 is cooler to the touch than the other cylinders. I've been reading that it can be either the ignition system (coil,wire,cap) or a stuck float in carb 1. All the plugs are new and have only about 5 miles on them. I've rechecked all the gaps on the plugs (D8EA @ 0.026") as well.

What should I be looking for first? This bike is new-to-me and I'm a novice at this stuff. I also don't have a lot of test equipment or tools for bike calibrations.

 

[slabghost]

Rap on carb #1 with the plastic handle of screwdriver. Turn off the fuel. Pull the plug wire from 1 and hook it to a known good plug and ground it to the block. Remove the air filter box cover and look for puddled fuel in the plenum. Fire it up and check for spark on plug one.. No fuel in plenum, good spark, hook up the plug wire and run the bike untill it sputters still with fuel off. Turn the fuel on momentarily ( a few seconds ) and run it again until it sputters then turn the fuel on and see if it smooths out and cylinder 1 gets hot.

 

[bronko37]

All these issues to me point at the carb. The fact that you have fuel coming out of the exhaust points at the floats. If this bike has been sitting for any length of time its time to pull the carb rack and give it a thorough cleaning. Doesnt sound like a ignition issue, yet. Definitely a fuel delivery problem.

 

[maxystaxi]

slabghost » Thu Apr 30, 2015 10:36 am[/url]":1vciczvf]
Rap on carb #1 with the plastic handle of screwdriver. Turn off the fuel. Pull the plug wire from 1 and hook it to a known good plug and ground it to the block. Remove the air filter box cover and look for puddled fuel in the plenum. Fire it up and check for spark on plug one.. No fuel in plenum, good spark, hook up the plug wire and run the bike untill it sputters still with fuel off. Turn the fuel on momentarily ( a few seconds ) and run it again until it sputters then turn the fuel on and see if it smooths out and cylinder 1 gets hot.

There is fuel in the plenum.

Seems to be a fuel/carb issue then?

 

[Steve83]

Yup...carb problem for sure. Try slabghost's suggestions first.

 

[dan filipi]

When I had stock carbs it nearly became routine maintenance shutting the gas off to empty the bowls which repositions the floats.
Not saying it's required by all but it's a good first check and costs nothing.

 

[maxystaxi]

dan filipi » Thu Apr 30, 2015 11:06 am[/url]":3dlgy1a7]
When I had stock carbs it nearly became routine maintenance shutting the gas off to empty the bowls which repositions the floats.
Not saying it's required by all but it's a good first check and costs nothing.

Is there a trick to capture the fuel from the bowls? Maybe a baby funnel with fuel line attached to it?

 

[slabghost]

Shut the gas off and run it. That will empty the bowls and open the needle valve more fully than usual. When you turn the fuel back on it may flush whatever is blocking the needle from sealing out of there.

 

[maxystaxi]

slabghost » Thu Apr 30, 2015 11:13 am[/url]":188k3exe]
Shut the gas off and run it. That will empty the bowls and open the needle valve more fully than usual. When you turn the fuel back on it may flush whatever is blocking the needle from sealing out of there.

Well I did the spark plug test and I have spark on cylinder one. I even swapped the spark plugs, caps and even swapped the wires between cylinder 1&2. I drained all the bowls and even shot some seafoam spray up into the bowls allowing any gunk or crud to flow back out. I tapped on the sides of carb 1. I allowed the fuel to flow back into the bowls. I shut off the fuel and allowed the bowls to empty.

Nothing... same issue.

I've never taken apart a complex carb such as this nor do I have any of the tools to synchronize them. I called the local shop that has some experience with the old honda's and he's booked for over a month.

I'm sure I can make my way through randakk's rebuild video. But what else am I going to need to make sure this is corrected?

 

[slabghost]

Here is an excellent how to on these carbs. Whether you are just cleaning the jets and passages or doing a full rebuild. Read through this before you get started.
viewtopic.php?f=69&t=2127

 

[mcgovern61]

My opinion, STOP running the engine! Gas leaking into the plenum (and exhaust pipes) also means gas leaking into the oil! Gas in the oil will wash out the bearings and can wipe them out!! (You most likely need to change your oil at this point!)

I would pull the carbs and clean them.

 

[slabghost]

Excellent point. Check the oil for gas smell ASAP. Good catch Gerry.

 

[bronko37]

maxystaxi » Thu Apr 30, 2015 5:09 pm[/url]":2ti7r925]

slabghost » Thu Apr 30, 2015 11:13 am[/url]":2ti7r925]
Shut the gas off and run it. That will empty the bowls and open the needle valve more fully than usual. When you turn the fuel back on it may flush whatever is blocking the needle from sealing out of there.

Well I did the spark plug test and I have spark on cylinder one. I even swapped the spark plugs, caps and even swapped the wires between cylinder 1&2. I drained all the bowls and even shot some seafoam spray up into the bowls allowing any gunk or crud to flow back out. I tapped on the sides of carb 1. I allowed the fuel to flow back into the bowls. I shut off the fuel and allowed the bowls to empty.

Nothing... same issue.

I've never taken apart a complex carb such as this nor do I have any of the tools to synchronize them. I called the local shop that has some experience with the old honda's and he's booked for over a month.

I'm sure I can make my way through randakk's rebuild video. But what else am I going to need to make sure this is corrected?

Get the video. Get the kit. Take your time and make sure everything is perfect before re assembly. You will need some carb cleaner and several bottles of Brake cleaner. Also you will need a steady supply of compressed air.

 

[zman]

Ignore all the complicated stuff, If your NOT leaking from the center of the plenum then it is your float needles more then likely,remove the faux tank, disconnect the throttle cables, remove air cleaner and air cleaner housing, loosen and remove the manifolds, the fuel lines, vacuum line if you have any, push the carbs over to the right and remove the 2 air chamber tops,springs and slides, mark them with sharpy to the corresponding carbs and keep them safe, be gentle with them they don't like to be nicked or scratched. gently pull rack out the left side, lift/tilt sort of like picking a lock they need to be just right to come through.
There are a bunch of tutorials out there on disassembly for you to reference, what your doing is more then likely new float needles and adjustment, and blow out the passageways just to be sure they are all clear.
Once the rack is off you can fill them on the bench and find where you are leaking from and once your done bench fill them to be sure they are fixed then drain each bowl into a measuring cup to be sure each bowl has the proper amount of fuel.
If it is from the center plenum seal it will be a little more involved but if it is just the floats needing adjusting you do not need to disassemble the whole rack.

 

[ekvh]

Here's what works for me. Could be three areas, float valves, oring between carb and plenum, and the plenum gasket between the plenum halves. To check, bike or carbs level, dry the carbs off, remove the slides and caps, dry the venturi throats off, and turn the gas on. Watch for leaks. To narrow down the leak faster, cut and fit a piece of paper in the plenum base to see where it occurs first. If it's the plenum gasket, it will get wet in the center along the seam. If it comes from the sides, you now know which carb/carbs leak. Dry they off again and repeat this time watching in the opening for the slides. If it is coming from the brass jets, it's a float valve. If it comes down the venturi from the plenum side, it's the fat o-ring that seals the fuel port between the plenum and carbs. All easy fixes, but carbs have to come off. Do yourself a favor and rig a test source of a liter of fuel from six feet above the rack and test it before reinstalling on the bike.

If your float gaskets are aftermarket, they are likely junk. Another issue is cheap bowl gaskets which fit nicely dry, but swell and interfere with the floats when gas hits them. You can see this if you're paying attention when you first remove the bowl. Good materials like Randakks don't swell.

 

[maxystaxi]

Thank you all for the advice.

As I'm looking around the carbs to get them ready to be pulled I noticed that the carb 1 button has been repaired at one time from a PO. This is the carb I suspect to be the issue. Does the carb button, if cracked, produce the same issues I'm getting?

https://drive.google.com/file/d/0B8OSlI ... sp=sharing

 

[bronko37]

maxystaxi » Fri May 01, 2015 7:32 am[/url]":fc82x6m5]
Thank you all for the advice.

As I'm looking around the carbs to get them ready to be pulled I noticed that the carb 1 button has been repaired at one time from a PO. This is the carb I suspect to be the issue. Does the carb button, if cracked, produce the same issues I'm getting?

https://drive.google.com/file/d/0B8OSlI ... sp=sharing

If that button is cracked it will reduce the vacuum in that cap which could slow the lift on the piston. However the bike would still run ok and that does not explain any of the flooding issues. My bike had a big hole in the button before I repaired it and the bike ran great still.

 

[ekvh]

Not that I can see. That just controls the slide moving up and down which pulls the needle out of the main jet. You have a leak from one of the three places. The checks are a lot easier than just guessing. I have had all three fail on various sets.

 

[mcgovern61]

Do yourself a favor and rig a test source of a liter of fuel from six feet above the rack and test it before reinstalling on the bike.

This is great advice! Just as an FYI, I use a lawn mower gas tank and some gas hose with a shut off valve to test my carbs off the bike. Very effective and easy to work with. I have also found that I did not even need the six feet to find leaks. I had my carbs up on a table with the tank two feet above that (tank was on a chair that was up on the same table).

 

[brianinpa]

mcgovern61 » Fri May 01, 2015 9:00 am[/url]":1qjol1z5]

Do yourself a favor and rig a test source of a liter of fuel from six feet above the rack and test it before reinstalling on the bike.

This is great advice! Just as an FYI, I use a lawn mower gas tank and some gas hose with a shut off valve to test my carbs off the bike. Very effective and easy to work with. I have also found that I did not even need the six feet to find leaks. I had my carbs up on a table with the tank two feet above that (tank was on a chair that was up on the same table).

Gerry,

Can you post a picture of your set-up?