Bike won’t get to idle after fuel line swap

[AlanP]

I have a 98 standard. While taking off the gas tank to service the air filter, I saw the fuel line at the petcock was pretty beat up and needed to be replaced. I purchased a new line from Honda, complete with T junction and the other 2 lines to the carbs, so I know it’s correct. Using the service manual and help from this forum, I followed all the instructions for removing the air box and tubes. I only replaced the two fuel lines and pretty sure I didn’t disturb any of the other hoses. As far as I can tell, the engine still has all the pollution control systems (I purchased the bike used from a dealer who imported it to Canada from Arizona, so it’s an American model). Everything went back together fairly easily (those darn airbox pipes!). The bike started and ran just fine, except for a noticeable drop in power at about 3k rpm. I never had that before so I took it all apart again to double check my work. After reinstalling the air box and pipes, I had to use a ratchet strap to get the pipes to seat properly on the carbs and I made sure the pipes were snug on the back side and not curled under. Now the bike will only start with full choke, no throttle but will only chug along below idle before it stalls. Any other setting of choke or throttle and it will not start at all. After some research here, i tested the petcock and connections. I put my finger over the end of the  vacuum line to see if there was a bit of suction as I turned the motor open. Seemed fairly strong. Next I used a straw to suck on the petcock vacuum input while the petcock was on open. Fuel started to flow out of the main port so that was working fine. I used fuel stabilizer over the winter, as I always do, and I can’t see that the stabilizer would affect the gas quality. Any and all ideas are appreciated. Thanks. Cheers...

[signart]

Something you can check real easy while waiting for someone else to chime in. Make sure you didn't get the tank vent hose pinched when installing the tank. You can try starting with the gas cap open to verify this.

[gordonv]

Could this be bad vacuum lines? Doesn't broken hoses do this?

[Lyle Laun]

Did you oil up a K&N filter ?

Regards
Lyle...

[AlanP]

Did you oil up a K&N filter ?

Regards
Lyle...

Yes, K&N. I’ve been maintaining it for years without a hitch. I cleaned up the little bit of oil that dripped out from the last time, as mentioned elsewhere.

[AlanP]

Something you can check real easy while waiting for someone else to chime in. Make sure you didn't get the tank vent hose pinched when installing the tank. You can try starting with the gas cap open to verify this.

Thanks. I’ll try that later today. I didn’t hook up the vent hose this time in case I had to take it all apart again.

[AlanP]

Could this be bad vacuum lines? Doesn't broken hoses do this?

That’s what I thought too, but all the lines under the airbox looked fine. 

[AlanP]

Well, i managed to get it started after it sat in the sun to warm up a bit. But it’s runnng very rough and will eventually stall. At least the throttle works so I can rev it up to 2.5k or so but it eventually dies again. I think I’m going to have to take it apart again and thoroughly inspect all the vacuum lines. Leaving the gas cap open didn’t help.

[gordonv]

Now the bike will only start with full choke, no throttle but will only chug along below idle before it stalls.

Has the bike been sitting? You mentioned fuel stabilizer. Do you have fresh fuel in the tank yet?

I'm thinking clogged carbs. Run some carb cleaner. Berryman B-12 is the best, but not available in Canada, so use Techron. Also buy your fuel from Chevron as much as you can.

[AlanP]

Has the bike been sitting? You mentioned fuel stabilizer. Do you have fresh fuel in the tank yet?

I'm thinking clogged carbs. Run some carb cleaner. Berryman B-12 is the best, but not available in Canada, so use Techron. Also buy your fuel from Chevron as much as you can.

No, it’s not been sitting since last year. I was riding it earlier this year and the only challenge was the lack of power around 3K rpm. Fresh gas and carb cleaner. We’re not privileged like you westerners, we don’t have chevron back here. 

[AlanP]

Took off the airbox and triple checked all the lines. Everything lines up with the shop manual picture.  I’m not sure the crankcase breather storage tank hose was connected to the airbox. Would that cause this problem?

[Lyle Laun]

Pull the K&N air filter and go for a ride to help eliminate a few things. I suspect your air filter has too much oil on it.

Lyle

[rug_burn]

Let's see-  sounds like you got a vacuum leak somewhere.   I'm real current working on those carbs, having done it as late as yesterday.   
1. First thing I'd do is give it a quick visual check -  the one oddball vacuum line going to the upper side of the #3 carb;  the important line going to the #6 intake tube vacuum stub; and the ones going to the #3 and #4 intake tubes.   And of course, check those vacuum caps also, they don't last forever.  I know my engine won't hardly run if the #6 vacuum line is off.   Also might want to check if the other ends of those tubes are connected where they should be.
2.  If this turns up nothing, I'd try to find the leak using a hose you hold to your ear, and can move around the other end to locate the leaks.   This may sound ridiculous, but it actually works great. 
3.  You might want to get a bunch of small mirrors and a flashlight with a beam you can make a spotlight or flood out to wide angle as needed.   I made the mirrors from a broken mirror with a glass cutter, and diamond hone to dull the edges.   I mounted a couple on iron wire handles so you can get them in tight places.     You can then take a good look in and around under the carbs and make sure everything is as it should be.  And you can verify that those rubber intake tubes aren't curled under during assembly

Something else that's possible is that moving things around like you did you may have developed a leak on the o-ring sealed 'intake-tube-to-head' joint.  Of course by this time you should have replaced these o-rings a few times by now, but you might want to check those.  I use American 'inch sized' .103" x-section o-rings here, because you can get a better seal with them.

I'd say:  Don't worry, it's probably just something loose that you missed, same thing's happened to me many times over the years.

[AlanP]

Put it all back together carefully and  ow it’s running fairly well but down on power and a little raspy. Idle is too low. I’m going to get the carb cleaner and run her on the highway. Thanks for the input, all.

[MarkT]

Another trick for looking for a vacuum leak or to determine the problem is a VL - Use a propane torch - squirt the gas around the intake manifold area while it's running.  If there's a serious leak the engine will speed up when it sucks in the gas.