Rough Idle, poor low speed performance, good above 2200RPM - issue resolved.

[nogrey]

Hey all. Just thought I’d post this issue I’ve been working through for some time. Rough idle, missing on one cylinder from idle through 2200 rpm then all good. I’ve had the carbs out 4 times for this issue. Tried using propane to find a vacuum issue. No change in idle from this test. I had already removed the carbs and cleaned them. Bike had been sitting for a time so a good carb cleaning was a given. Removed all the varnish from the carbs, reinstalled and the performance was better, but not where it should be. Still had rough idle and poor low speed performance. Should mention that this bike is completely stock except the two brothers pipes.  Replace the downdraft tube O rings and that made a pretty good difference, but still a poor idle and poor performance from 900 to 2200 RPM. Finally started removing spark plug wires and found that cylindar 6 was not combusting at all at idle (pulled plug caps 1 by 1). Removed the carbs (again) and disassembled carb 6 completely. Found significany slug of varnish (apparently something that had come through after the previous cleaning) and used carb cleaner to clean it out. Removed the slow jet and found it to be about half clogged. Used the Honda jet cleaning tool to clear the blockage. Cleaned again with carb cleaner. Blew the carb out with compressed air. Replaced the float valve, and the float bowl gasket (because it did not pass the vacuum test). Also cleaned the pilot screw orifice and replaced the gasket. Biggest find this time was when I removed the air cutoff valve to check the vacuum line. The vacuum line was fine, but the air cutoff valve had a leak. It would not hold vacuum at the vacuum port. I replace the cutoff valve. Reinstalled the carbs and viola! Idle as smooth glass! I’m thinking that the new seals helped, but the new cutoff valve was the clincher. Hope this can help someone else as I struggled with this for about a month.

[MnM Valk 97]

Thanks for the follow-up. I learn something new here every day. Love it!

[Jersey]

I had the same thing occur a few weeks ago rebuilding the carbs.  Expensive little buggers, but nice when it all works!! 

Thanks for passing this along.  I wonder how many miss checking the vacuum on these when they rebuild?

[kodiakfisher]

What is this air cutoff that you mention. I did a quick search in the maintenance manual and couldn't find what it is.

I am at least curious.

thanks,

[Jersey]

What is this air cutoff that you mention. I did a quick search in the maintenance manual and couldn't find what it is.

I am at least curious.

thanks,

It's Part #24  https://www.cmsnl.com/honda-gl1500cf-valkyrie-interstate-1999-x-usa-california_model1082/partslist/E++2002.html#.W-yRjOhKiUk

[Red Ballz]

I’m glad I saw this. I’m having just about the same issue right now. At idle, cylinder 6 is missing but as soon as I’m on the gas it seems to be just fine. There are no leaks. The carbs have been thoroughly cleaned. I’ve tried adjusting the pilot screw in and out. Moved spark plugs to different holes. I was going to hook up a compression tester tomorrow.

I guess I have another part to order.

[Bagger John - #3785]

I've got a similar situation going on with my '99 CA-model Tourer.

When I added I/S pods to the bike, I had to remove the tank, airbox and intake runners to allow the carbs to be moved rearward enough to remove the air deflector and replace it with the one from an I/S. During reassembly I replaced the vacuum caps, PAIR valve lines and intake O-rings with Redeye parts. The air filter element was also replaced.

Upon testing after everything was back together, I noticed that the idle adjustment needed to be touched up slightly to get the bike to idle at 900-1000RPM; it was a little lower than the 'before-surgery' point. A test ride showed a bit of roughness from 1700-2200RPM (indicated), but the bike idles fine and pulls very hard above 3000RPM.

Next up was a can of Berryman's B12 in a full tank of gas, followed by a carb sync. I got them all to within 1/4" vacuum of each other and the base (#3) carb. This seems to have helped slightly but the miss is still present. Not a complete cut-out, mind you, but you know the motor is down on power a bit.

How many tanks with Berryman's are sufficient to clean a varnished low-speed jet, assuming this is the problem? Or should I be looking at the air-cut valves next? Possibly the line from the #6 intake runner to the vacuum port of the petcock?

[nogrey]

I've got a similar situation going on with my '99 CA-model Tourer.

When I added I/S pods to the bike, I had to remove the tank, airbox and intake runners to allow the carbs to be moved rearward enough to remove the air deflector and replace it with the one from an I/S. During reassembly I replaced the vacuum caps, PAIR valve lines and intake O-rings with Redeye parts. The air filter element was also replaced.

Upon testing after everything was back together, I noticed that the idle adjustment needed to be touched up slightly to get the bike to idle at 900-1000RPM; it was a little lower than the 'before-surgery' point. A test ride showed a bit of roughness from 1700-2200RPM (indicated), but the bike idles fine and pulls very hard above 3000RPM.

Next up was a can of Berryman's B12 in a full tank of gas, followed by a carb sync. I got them all to within 1/4" vacuum of each other and the base (#3) carb. This seems to have helped slightly but the miss is still present. Not a complete cut-out, mind you, but you know the motor is down on power a bit.

How many tanks with Berryman's are sufficient to clean a varnished low-speed jet, assuming this is the problem? Or should I be looking at the air-cut valves next? Possibly the line from the #6 intake runner to the vacuum port of the petcock?

If I understand you correctly, this issue began after the IS pods and new air dam were installed and did not exist prior. So I’m thinking this problem was induced, and is not a clogged jet. When re-installing the air box, the most common failure that causes your described symptoms is one of the airbox downdraft tubes is mis-aligned. Usually on the back side of the carb where you can not see it. I would check those first. Since you have not de-smogged you’re going to need to use a mechanics mirror and a flashlight. Any leak there will cause your issue. Also, you mentioned the intake runners. If you are referring to the chrome downdraft tubes, then there is another possibility. The O rings are super easy to either nick, or even misalign. Just fixed a friends ‘97 that we’d gone through with the same issue. He came over and we started eyeballing things. I was just about to get out a can of carb cleaner and spraying connections when I saw part of an O ring protruding from the base of the downdraft tube on cylinder #3. Pulled it off and replaced it and viola! The difficult thing about these issues is any leak in the system can cause the same symptoms. If you haven’t had the carbs apart, I wouldn’t start there.

[Bagger John - #3785]

If I understand you correctly, this issue began after the IS pods and new air dam were installed and did not exist prior. So I’m thinking this problem was induced, and is not a clogged jet.

A bit of an update:

In the words of Pogo: "We have met the enemy, and he is us..."

Got the pods, intake valances (Kuryakyn) and linkage covers off the bike then started poking around with an inspection mirror. Intake runners all looked solid. Next up were the vacuum lines, and...oh, wait - what's THAT? The carbs currently on the bike are CA-model units, and one of the secondary evap lines (on the #1 carb, right next to the air dam) had somehow waltzed off its nipple.

Any fans of "My 600lb Life" on the board? You'd get a renewed sense of appreciation for Dr. Now and his gastric-bypass surgery procedures through an abdominal hole if you watched me reattaching the line with hemostats and other surgical tools. Suffice it to say that space is a little tight.

How the line came loose is a mystery. The only thing which comes to mind is interference from the air dam as I was positioning the carbs on the intake runners, and it was simply pulled off via friction.

A road test with the gal pal aboard last night showed the rough spot lower in the power band - like, right off idle - and a lot narrower in duration. This is exactly what I'd suspect upon syncing a carb with a vacuum leak. I'll take the right-side pod off again this week and sync #1 to #3, which should make the problem disappear entirely.

Question for the CA vs. non-CA sake of argument:

I love clean air and a healthy planet, but I also love motorcycles with a minimal amount of potential failure points. I'm going to get into the airbox area again next spring, when I install a Dan-Marc shutoff and convert the petcock to a manual setup.

Should I de-CA the emissions plumbing at that point? Meaning, the evap canister, valves and the secondary lines will go away and the 6 carb nipples will be plugged. My thoughts on the PAIR valve setup is that as long as it works and I can get spare parts I'll leave all of it intact, but a complete de-smogging will occur at the point I can't.

[nogrey]

Question for the CA vs. non-CA sake of argument:

I love clean air and a healthy planet, but I also love motorcycles with a minimal amount of potential failure points. I'm going to get into the airbox area again next spring, when I install a Dan-Marc shutoff and convert the petcock to a manual setup.

Should I de-CA the emissions plumbing at that point? Meaning, the evap canister, valves and the secondary lines will go away and the 6 carb nipples will be plugged. My thoughts on the PAIR valve setup is that as long as it works and I can get spare parts I'll leave all of it intact, but a complete de-smogging will occur at the point I can't.

A friend of mine purchased a CA bike. Everything had to be gone through. I didn’t even give it a second thought. Every bike that comes through my garage gets a de-smog. My reasons are more about reliability than anything. It has no effect on performance. Removing all the lines, pair valves nd vacuum valve really cleans up the engine. If you install a manual petcock you have eliminated all vacuum lines. That’s a lot of deteriorating rubber eliminated. Just my personal opinion, but I’d de-smog it at the first opportunity. BTW, I also remove the “octopus” that is the 6 fuel drain lines that attach to the bottom of each carb. I never use the drains unless I’m removing them and I do them after. Makes the engine super clean.