F4 fuel problem (Full Version)

CBR Forum >> General >> General Tech

F4 fuel problem

  

Aweasel -> F4 fuel problem (6/24/2008 5:39:06 PM)

I just cleaned the carbs on my 99 F4, they were varnished and whatnot and I''''''''m pretty sure I did a decent job cleaning because each pilot jet would shoot a needle stream if I put carb cleaner through a hose and into it, main jets were no problem either. Put it back together and it''''''''s a pain to get to start and idle without opening the choke on it all the way and adjusting the throttle position open a little. So I take it apart again down to the carbs and fill a spray bottle with gasoline to shoot into each stack. Sure enough it''''''''ll run this way, actually runs wide open with no problem if I keep the gas flowing.

Problem is:

The vacuum needle/air delivery whatever you want to call it in the stacks flutter when I give it throttle when fuel is hooked up the right way(out tank, into pump, out to t-hose, into carbs, etc.) and eventually it will cut out no matter what choke setting if I try to give it throttle, a little before it dies out I am able to rev up to 4-5k but it''''''''ll stumble and then eventually cuts out.

I''''''''m thinking there''''''''s a fuel delivery problem, either the pump is crap or there is a blockage in the carbs but I''''''''m not sure how to check the pump, it pumps gas through the t-hose but it''''''''s kinda sloppy, not uniform and it''''''''s more like a pulsing than a stream(understandable), probably half a second between pulses. Again, not sure what it should look like as I''''''''ve never messed with carbs nor have I ever worked on a motorcycle.

I''''''''ve got down to the carbs and am ready to take them off if need be to dry them out and re-install them, I installed them with a sheen of carb cleaner still in the bowls and throughout. Any insight, if any videos or further explanation of my problem here would help the diagnosis it wouldn''''''''t be a problem.

Thanks in advance

  
justasquid -> RE: F4 fuel problem (6/24/2008 9:52:35 PM)

Did the bike run fine before you tore it apart?


Your fuel pump sounds fine. These are very low pressure.. 1.5-2 psi and it will have a pulse to it. they are not high pressure so you wont see a stream that shoots out. They don''t require much to fill the carburators.

The fluttering you see is normal if the engine is cutting out. That is vaccum operated so unless your engine is running smooth and firing all the time, it will flutter with every pulse that is not firing.

I would suspect you have something clogged in your carburators. I would guess your idle jet ( air screw) may be gunked up. I would re-clean everything again. You may also want to check your floats to make sure they are working and the needle and seat are in good condition.

If you are running this with the air box off or the lid off, try and put everything back on including all of your vaccum lines.

Again, if the decision was made to tear into the bike because of the way it was running. Try to describe exactly what it was doing.

Aweasel -> RE: F4 fuel problem (6/25/2008 3:39:31 AM)

I bought the bike in non-running condition, the prev-owner said the carbs needed cleaned and he showed me by putting fuel into the stacks, it ran this way so I figured ok and picked it up for a super low price. The bike runs this way with and without the air box and all that jazz on it.

everything in the carbs looked and felt fine after a good cleaning and inspection just before I installed everything. Right off the bat after I had all the lines, throttle, and fuel hooked back up the bike was hell to get to start and it finally ran for a little with no problem and would even rev up no problem but then it started acting up again within a little leading me to believe maybe something was stuck somewhere in the carbs and then lodged itself in the jets, I''d really hate to have to take those damn things out again, I just know one of em will split in two forcing me to order new ones. That''s my luck

what exactly would I do to make sure the floats are working? I know they are held up by that small spring action thing(sorry, can''t remember the name of it) and those were working fine when I reinstalled everything.

Aweasel -> RE: F4 fuel problem (6/25/2008 2:31:18 PM)

ok, so I took off the carbs again, picked up 2 cans of carb cleaner(I don''t hold back lol) and took out the jets again, they were still clean so I gave them another quick shot, blew some air through them. Reinstalled them and turned the carbs over. I took off the stacks and sprayed the crap out of the the jets there. Reinstalled the carbs(dunno why so many people have a problem with these things, first timer here and had em off, cleaned, and reinstalled in about 1 hour start to finish) buttoned everything up but this time I drained the tank and put in a fresh gallon of 93 octane. Went to start, no dice, just crank. I figure I flooded it from trying so often so what I did was turn the fuel off, hooked the battery up to my car and cranked at WOT for, and I''m not shitting you at least 4 solid minutes of non stop cranking with choke fully open. The bike kept popping and shooting bursts of flame but sure enough it fired up and ran...for those of you that come up on this thread through a search, don''t forget to turn the fuel back on. I closed the choke after about a minute and backedthe idle down to about 1200. Runs like a ****in champ. I''m stoked as hell. Picked up this bike for an insane deal and got it back to it''s previous glory for less than 20 bux. Now, time to get a jacket, some gloves, and a tire haha.

Thanks for the help guys

  

Page: [1]

Return to CBR Forum home page or view the Full Version of this page.