Carb/running issue, where do I start?

[Slick]

OK there is a little history on the carb problems I was having HERE http://www.fjowners.com/index.php?topic=3647.0

I recently bought 4 of these http://cgi.ebay.com/ebaymotors/Yamaha-FJ1100-FJ1200-Carburetor-Repair-Kits-Carb-/150628953501?pt=Motorcycles_Parts_Accessories&hash=item23122f6d9d

When I installed them I also played around with the carb sync.(Which I may regret doing) I had read on the forums that some people have rough sync'd their carbs just by holding them up to the light. Well when I took mine out I noticed that the carbs were not too sync'd if I went by that. So I did make some adjustments (not too much) before putting it all back together, Well when I first started the bike it ran BEAUTIFUL. Snappy throttle, crisp sound. I took it for a ride and it seem to be running great. Then it started bogging like it was running out of gas, then stalled and would not start. I let her sit for about 15 min and she started only to ride another 15min until repeating the same symptoms. I got the bike all the way home that way and that has been where she sit.


Today I went out to see what I could get into. I started the bike and it was back firing bad. I rev'ed it for a min or so and seen some smoke coming out from the carb area. I turned the bike off and tried to see where the smoke is coming from. I cant tell anymore than from the bottom of the carb area. I dont know if its the bottoms of the carbs, or the area under the carbs. So also I was wondering how long these needles and jjets have been clogged, and if the bike was tuned WITH dirty jets/needles. I came up with an idea. I have a Temp gun and was thinking if all the cylinders were running in sync then the header temp should be the same across all 4 pipes, RIGHT? Well mine vary GREATLY. These are the temps at the same location(at the top, by engine) on each header after the bike ran for minutes.

Cyl:

#4 - 132 F
#3 - 147 F
#2 - 266 F
#1 - 254 F

Something has got to be wrong here. So where do I start?

[Dan Filetti]

There are smarter people that will chime in here, but I would say that #1 and #2 are lean, and #3 and #4 are rich...

Dan

[SlowOldGuy]

Well, I'm too lazy to read 3 pages of posts.

Did you clean the carbs?
Did you clean them well?
Are you sure?

If you answer no to any of these questions, then clean the carbs, clean them well and be sure they are clean.

DavidR.

[SkyFive]

You can sync the carbs with one automotive vacum guage. Take a vacum reading on #3 at a specific engine speed, 2000 rpm's works good, and adjust the other three, one at a time of course, using the same engine speed to the same vacum reading that you got on #3.

Check the fuel level if your unsure of your float condition/bouyancy, the manual says with the engine running but it's much easier to confirm on the work bench than on the bike.

Pre-sync with a drill bit as a guage, almost any size will work.

Read your plugs for mixture adjustments and I do this after a long ride so it will be more accurate. I found a old post on this website that suggested turning all the mixture screws in 1/4 turn at a time until the engine almost stalls then turn them all out a total of 3/4 turn. I havent tried this but it sounds like good advice. Mine were nearly perfect at 2 turns out.

I have a infrared thermometer, I tried taking a measurement on the engine/exhaust but due to reflectivity and heating variations of the metal parts I don't believe it would be accurate enough for adjusting your carbs.

[carsick]

There are smarter people that will chime in here, but I would say that #1 and #2 are lean, and #3 and #4 are rich...

Dan

Hey Dan, try running with your choke on at night (wait, is yer gixxer FI?) and see what extra fuel does to your exhaust pipe temps... more gas cools the combustion chamber but heats the hell out of the exhaust if it's within the mixture range that can be burnt. Skyfive makes another excellent point, if pipes are shiny an IR thermometer can be all over the place, but usually low. Your listed temps seem low, are they stock doublewall pipes or aftermarket singlewall?  The runs good then not sounds like rust and crap from the tank jamming up your carb's many finely calibrated super small orifices, and/or allowing the needle seats to leak fuel creating a high bowl level and mighty rich conditions.

[andyb]

A plug read will tell you more about the mixture than pipe temps will.  EGT would be useful, but isn't necessary unless you're trying to squeeze that last bit out.

You can do a bench synch all day long, but it's not worth a damn unless the valve lash is really close all the way across.  Been there, done that.  Got the tools and did it properly and was absolutely shocked at the difference.  Doing it off the bike is good for getting things close enough to run, but not good enough to ride.

[Dan Filetti]

Try running with your choke on at night (wait, is yer gixxer FI?) and see what extra fuel does to your exhaust pipe temps... more gas cools the combustion chamber but heats the hell out of the exhaust if it's within the mixture range that can be burnt. 

Ah, I miss-read the original post, I thought he was measuring HEAD temp, [not headER temp].   Still, I'm admittedly fairly ignorant on this subject, not even sure if this is a viable method of measuring anything of value.

Oh, and yeah the Gixxer is FI, but that's not perfect either, I'm trying to figure out a flutter it's recdntly picked up...

Dan

[Mark Olson]

your gas tank is still dirty with rust and it has plugged up your carbs again.  you have not posted about doing anything with the tank yet.

at the least install a inline gas filter from the tank to the carbs and be careful not to kink the gas line or you will run out of fuel.
pull the carbs and clean them again after fuel filter is installed. carbs are very touchy about dirty fuel.

[SlowOldGuy]

I have yet to see a fuel filter that will stop rust particles from getting to the carbs.  You must fix the source of the rust (tank) to prevent it form getting to the carbs.  POR-15 works great.

DavidR.

[Mark Olson]

yeah I know , thats why I said "at the least"