Author Topic: Carbeuration Issues? (Read 3429 times)

SRwitt · « **on:** June 30, 2005, 10:19:53 PM »

Hello all, Im Shawn im new here and have some questions. I just bought a 91 B400 about a month ago. For the first couple of weeks it ran great. Then one night it started sputtering and stalling like I was running out of fuel. I was cruising at lower rpms so i figured it could be loading up with fuel and flooding out. I revved it a few times and it would clear out. The next day on my way home from work it went way over rich and was blowing large amounts of black smoke.

I get it home pull things apart, clean the air filter, and pulled off the float bowls. All 4 bowls seemed fairly clean, but when I got to the #4 carb the pilot? jet i believe was laying in the bowl. I screwed that back in place and put it together tried firing it up and it ran better, but would not rev very quickly, wouldnt run below under about 4k rpms and was still blowing a little black smoke. Now last night i started it up and let it run for a few and was checking for heat off of the header. After 3 or 4 minutes of running, I could grab the thing on the #4 tube and hold it.

Tonight after reading suggestions from other users in another topic I checked my spark plugs and made sure all were sparking. They all have spark but, the #1 plug is really wet compared to the others soaked most of the way up the threads, #2 is wet at the tip and a little up the threads, #3 is wet at the tip but doesnt look like it has seen much fuel, #4 was almost bone dry.

So i guess that #1 and 2 are running rich and #3 and 4 are starving of fuel. Is a thorough carb cleaning in order, or what type of problems may I have?

Thank you
Shawn

gsxr400 racer · « **Reply #1 on:** July 01, 2005, 02:15:08 AM »

Just change your plugs see how it runs with new NGK'S . Then get back to use if it fouls plugs again you got a carb problem , start with new orings and a good cleaning and carb sync!

SRwitt · « **Reply #2 on:** July 01, 2005, 10:43:04 AM »

The plugs that are in it now are new, I forgot to mention that. I changed the plugs when the problem first appeared.

TheKillerB · « **Reply #3 on:** July 01, 2005, 01:19:40 PM »

Pull your fuel hose off and see if fuel runs out of the petcock. It's possible the petcock is shot. They operate on vacuum and with age, the diaphragm tears and fuel ends up getting sucked down the vacuum line and straight into the #1 cyclinder, causing it too run very rich. This is not uncommon for these bikes at their age.

SRwitt · « **Reply #4 on:** July 01, 2005, 02:59:09 PM »

Ive had the tank off numerous times since my issues began, only a small amount of fuel leaks out, probably whats already past the valve after that it doesn't leak any fuel that i've noticed.

I'm looking at going to get a vacuum guage to try and sync the carbs if anyone thinks that would be a good place to start along with a thorough cleaning?

I still don't have a service manual as of yet, just all of the microfiches. The link that is posted on these forums to the manual won't work for me. Anyone have a link to the actual service manual?

Also when synching the carbs do i just match the vacuum on all of them or are there set numbers i should be looking for?

PitterB4 · « **Reply #5 on:** July 01, 2005, 04:35:12 PM »

Cleaning/synching is a great place to start. Like someone else mentioned, new O-rings would help too.

Synching - just follow the instructions. It's pretty easy. You just want them all to be the same - no particular value. You match the right 2 cylinders to each other, then the left 2 and then the two halves to each other.

SRwitt · « **Reply #6 on:** July 01, 2005, 04:42:04 PM »

Ok i found the thread idle screw & balancing on the forum. I saw the homemade carb sync tool and was wondering, do i need a tool like this whether store bought or made or will a simple dial readout vacuum guage be sufficient? Is there something I'm missing about the fluid based ones or will either the dial or mercury/oil ones work the same?

todius · « **Reply #7 on:** July 08, 2005, 05:27:50 PM »

The simple dial vacuum guage works just as well (if not better), but it helps to have 4 of them so that you can monitor the vacuum on all 4 carbs at the same time. I have a set of 4 dial-type guages from JCWhitney that I use to synch my carbs.

http://www.jcwhitney.com/autoparts/Product/showCustom-0/Pr-p_Product.CATENTRY_ID:2004169/c-10101/Nty-1/p-2004169/Ntx-mode+matchallpartial/N-10101/tf-Browse/s-10101/Ntk-AllTextSearchGroup?Ntt=carburetor%20synchronizer

SRwitt · « **Reply #8 on:** July 09, 2005, 02:57:13 PM »

Thank you for the reply about the guages. However the bike is already in the shop but i will keep the link for future reference.

Shawn

b4cruz · « **Reply #9 on:** July 09, 2005, 04:31:16 PM »

Quote from: "todius"

4 dial-type guages from JCWhitney that I use to synch my carbs.

I like the 4 gauges best. Its the same retail price as the mercury type tool which needs to be refilled. And mercury is bad. My home made tool works great and is cheap, but it is frustrating because resetting the oil in the tubes takes sometime if the carbs are really out of ballance and one sucks the oil all the way out of the other. Next time I need to clean and reballance and re-Oring or re-jet I think I will buy the 4 gauges.

SRwitt · « **Reply #10 on:** July 10, 2005, 01:01:27 PM »

Yeah I noticed that about the homemade one. I made one last weekend and the oil still hasn't settled yet. Hopefully its not a carb issue with my bike I'm still waiting on the shop to call me and tell me the damage.